/*! JointJS v2.1.2 (2018-05-08) - JavaScript diagramming library


This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
(function(root, factory) {

    if (typeof define === 'function' && define.amd) {

        // For AMD.

        define(['backbone', 'lodash', 'jquery'], function(Backbone, _, $) {

            Backbone.$ = $;

            return factory(root, Backbone, _, $);
        });

    } else if (typeof exports !== 'undefined') {

        // For Node.js or CommonJS.

        var Backbone = require('backbone');
        var _ = require('lodash');
        var $ = Backbone.$ = require('jquery');

        module.exports = factory(root, Backbone, _, $);

    } else {

        // As a browser global.

        var Backbone = root.Backbone;
        var _ = root._;
        var $ = Backbone.$ = root.jQuery || root.$;

        root.joint = factory(root, Backbone, _, $);
        root.g = root.joint.g;
        root.V = root.Vectorizer = root.joint.V;
    }

}(this, function(root, Backbone, _, $) {

(function() {

    /**
     * version: 0.3.0
     * git://github.com/davidchambers/Base64.js.git
     */

    var object = typeof exports != 'undefined' ? exports : this; // #8: web workers
    var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

    function InvalidCharacterError(message) {
        this.message = message;
    }

    InvalidCharacterError.prototype = new Error;
    InvalidCharacterError.prototype.name = 'InvalidCharacterError';

    // encoder
    // [https://gist.github.com/999166] by [https://github.com/nignag]
    object.btoa || (
        object.btoa = function(input) {
            var str = String(input);
            for (
                // initialize result and counter
                var block, charCode, idx = 0, map = chars, output = '';
                // if the next str index does not exist:
                //   change the mapping table to "="
                //   check if d has no fractional digits
                str.charAt(idx | 0) || (map = '=', idx % 1);
                // "8 - idx % 1 * 8" generates the sequence 2, 4, 6, 8
                output += map.charAt(63 & block >> 8 - idx % 1 * 8)
            ) {
                charCode = str.charCodeAt(idx += 3 / 4);
                if (charCode > 0xFF) {
                    throw new InvalidCharacterError("'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.");
                }
                block = block << 8 | charCode;
            }
            return output;
        });

    // decoder
    // [https://gist.github.com/1020396] by [https://github.com/atk]
    object.atob || (
        object.atob = function(input) {
            var str = String(input).replace(/=+$/, '');
            if (str.length % 4 == 1) {
                throw new InvalidCharacterError("'atob' failed: The string to be decoded is not correctly encoded.");
            }
            for (
                // initialize result and counters
                var bc = 0, bs, buffer, idx = 0, output = '';
                // get next character
                // eslint-disable-next-line no-cond-assign
                buffer = str.charAt(idx++);
                // character found in table? initialize bit storage and add its ascii value;
                ~buffer && (bs = bc % 4 ? bs * 64 + buffer : buffer,
                    // and if not first of each 4 characters,
                    // convert the first 8 bits to one ascii character
                bc++ % 4) ? output += String.fromCharCode(255 & bs >> (-2 * bc & 6)) : 0
            ) {
                // try to find character in table (0-63, not found => -1)
                buffer = chars.indexOf(buffer);
            }
            return output;
        });

}());

(function() {

    if (typeof Uint8Array !== 'undefined' || typeof window === 'undefined') {
        return;
    }

    function subarray(start, end) {
        return this.slice(start, end);
    }

    function set_(array, offset) {

        if (arguments.length < 2) {
            offset = 0;
        }
        for (var i = 0, n = array.length; i < n; ++i, ++offset) {
            this[offset] = array[i] & 0xFF;
        }
    }

    // we need typed arrays
    function TypedArray(arg1) {

        var result;
        if (typeof arg1 === 'number') {
            result = new Array(arg1);
            for (var i = 0; i < arg1; ++i) {
                result[i] = 0;
            }
        } else {
            result = arg1.slice(0);
        }
        result.subarray = subarray;
        result.buffer = result;
        result.byteLength = result.length;
        result.set = set_;
        if (typeof arg1 === 'object' && arg1.buffer) {
            result.buffer = arg1.buffer;
        }

        return result;
    }

    window.Uint8Array = TypedArray;
    window.Uint32Array = TypedArray;
    window.Int32Array = TypedArray;
})();

/**
 * make xhr.response = 'arraybuffer' available for the IE9
 */
(function() {

    if (typeof XMLHttpRequest === 'undefined') {
        return;
    }

    if ('response' in XMLHttpRequest.prototype ||
        'mozResponseArrayBuffer' in XMLHttpRequest.prototype ||
        'mozResponse' in XMLHttpRequest.prototype ||
        'responseArrayBuffer' in XMLHttpRequest.prototype) {
        return;
    }

    Object.defineProperty(XMLHttpRequest.prototype, 'response', {
        get: function() {
            return new Uint8Array(new VBArray(this.responseBody).toArray());
        }
    });
})();

// https://tc39.github.io/ecma262/#sec-array.prototype.includes
if (!Array.prototype.includes) {
    Object.defineProperty(Array.prototype, 'includes', {
        value: function(searchElement, fromIndex) {

            // 1. Let O be ? ToObject(this value).
            if (this == null) {
                throw new TypeError('"this" is null or not defined');
            }

            var o = Object(this);

            // 2. Let len be ? ToLength(? Get(O, "length")).
            var len = o.length >>> 0;

            // 3. If len is 0, return false.
            if (len === 0) {
                return false;
            }

            // 4. Let n be ? ToInteger(fromIndex).
            //    (If fromIndex is undefined, this step produces the value 0.)
            var n = fromIndex | 0;

            // 5. If n ≥ 0, then
            //  a. Let k be n.
            // 6. Else n < 0,
            //  a. Let k be len + n.
            //  b. If k < 0, let k be 0.
            var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

            function sameValueZero(x, y) {
                return x === y || (typeof x === 'number' && typeof y === 'number' && isNaN(x) && isNaN(y));
            }

            // 7. Repeat, while k < len
            while (k < len) {
                // a. Let elementK be the result of ? Get(O, ! ToString(k)).
                // b. If SameValueZero(searchElement, elementK) is true, return true.
                // c. Increase k by 1.
                if (sameValueZero(o[k], searchElement)) {
                    return true;
                }
                k++;
            }

            // 8. Return false
            return false;
        }
    });
}

// https://tc39.github.io/ecma262/#sec-array.prototype.find
if (!Array.prototype.find) {
    Object.defineProperty(Array.prototype, 'find', {
        value: function(predicate) {
            // 1. Let O be ? ToObject(this value).
            if (this == null) {
                throw new TypeError('"this" is null or not defined');
            }

            var o = Object(this);

            // 2. Let len be ? ToLength(? Get(O, "length")).
            var len = o.length >>> 0;

            // 3. If IsCallable(predicate) is false, throw a TypeError exception.
            if (typeof predicate !== 'function') {
                throw new TypeError('predicate must be a function');
            }

            // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
            var thisArg = arguments[1];

            // 5. Let k be 0.
            var k = 0;

            // 6. Repeat, while k < len
            while (k < len) {
                // a. Let Pk be ! ToString(k).
                // b. Let kValue be ? Get(O, Pk).
                // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
                // d. If testResult is true, return kValue.
                var kValue = o[k];
                if (predicate.call(thisArg, kValue, k, o)) {
                    return kValue;
                }
                // e. Increase k by 1.
                k++;
            }

            // 7. Return undefined.
            return undefined;
        }
    });
}

// Production steps of ECMA-262, Edition 6, 22.1.2.1
if (!Array.from) {
    Array.from = (function () {
        var toStr = Object.prototype.toString;
        var isCallable = function (fn) {
            return typeof fn === 'function' || toStr.call(fn) === '[object Function]';
        };
        var toInteger = function (value) {
            var number = Number(value);
            if (isNaN(number)) { return 0; }
            if (number === 0 || !isFinite(number)) { return number; }
            return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
        };
        var maxSafeInteger = Math.pow(2, 53) - 1;
        var toLength = function (value) {
            var len = toInteger(value);
            return Math.min(Math.max(len, 0), maxSafeInteger);
        };

        // The length property of the from method is 1.
        return function from(arrayLike/*, mapFn, thisArg */) {
            // 1. Let C be the this value.
            var C = this;

            // 2. Let items be ToObject(arrayLike).
            var items = Object(arrayLike);

            // 3. ReturnIfAbrupt(items).
            if (arrayLike == null) {
                throw new TypeError('Array.from requires an array-like object - not null or undefined');
            }

            // 4. If mapfn is undefined, then let mapping be false.
            var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
            var T;
            if (typeof mapFn !== 'undefined') {
                // 5. else
                // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
                if (!isCallable(mapFn)) {
                    throw new TypeError('Array.from: when provided, the second argument must be a function');
                }

                // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
                if (arguments.length > 2) {
                    T = arguments[2];
                }
            }

            // 10. Let lenValue be Get(items, "length").
            // 11. Let len be ToLength(lenValue).
            var len = toLength(items.length);

            // 13. If IsConstructor(C) is true, then
            // 13. a. Let A be the result of calling the [[Construct]] internal method
            // of C with an argument list containing the single item len.
            // 14. a. Else, Let A be ArrayCreate(len).
            var A = isCallable(C) ? Object(new C(len)) : new Array(len);

            // 16. Let k be 0.
            var k = 0;
            // 17. Repeat, while k < len… (also steps a - h)
            var kValue;
            while (k < len) {
                kValue = items[k];
                if (mapFn) {
                    A[k] = typeof T === 'undefined' ? mapFn(kValue, k) : mapFn.call(T, kValue, k);
                } else {
                    A[k] = kValue;
                }
                k += 1;
            }
            // 18. Let putStatus be Put(A, "length", len, true).
            A.length = len;
            // 20. Return A.
            return A;
        };
    }());
}

// https://tc39.github.io/ecma262/#sec-array.prototype.findIndex
if (!Array.prototype.findIndex) {
    Object.defineProperty(Array.prototype, 'findIndex', {
        value: function(predicate) {
            // 1. Let O be ? ToObject(this value).
            if (this == null) {
                throw new TypeError('"this" is null or not defined');
            }

            var o = Object(this);

            // 2. Let len be ? ToLength(? Get(O, "length")).
            var len = o.length >>> 0;

            // 3. If IsCallable(predicate) is false, throw a TypeError exception.
            if (typeof predicate !== 'function') {
                throw new TypeError('predicate must be a function');
            }

            // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
            var thisArg = arguments[1];

            // 5. Let k be 0.
            var k = 0;

            // 6. Repeat, while k < len
            while (k < len) {
                // a. Let Pk be ! ToString(k).
                // b. Let kValue be ? Get(O, Pk).
                // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
                // d. If testResult is true, return k.
                var kValue = o[k];
                if (predicate.call(thisArg, kValue, k, o)) {
                    return k;
                }
                // e. Increase k by 1.
                k++;
            }

            // 7. Return -1.
            return -1;
        }
    });
}

if (!String.prototype.includes) {
    String.prototype.includes = function(search, start) {
        'use strict';
        if (typeof start !== 'number') {
            start = 0;
        }

        if (start + search.length > this.length) {
            return false;
        } else {
            return this.indexOf(search, start) !== -1;
        }
    };
}

if (!String.prototype.startsWith) {
    String.prototype.startsWith = function(searchString, position){
        return this.substr(position || 0, searchString.length) === searchString;
    };
}

Number.isFinite = Number.isFinite || function(value) {
    return typeof value === 'number' && isFinite(value);
};

//The following works because NaN is the only value in javascript which is not equal to itself.
Number.isNaN = Number.isNaN || function(value) {
    return value !== value;
}


// Geometry library.
// -----------------

var g = (function() {

    var g = {};

    // Declare shorthands to the most used math functions.
    var math = Math;
    var abs = math.abs;
    var cos = math.cos;
    var sin = math.sin;
    var sqrt = math.sqrt;
    var min = math.min;
    var max = math.max;
    var atan2 = math.atan2;
    var round = math.round;
    var floor = math.floor;
    var PI = math.PI;
    var random = math.random;
    var pow = math.pow;

    g.bezier = {

        // Cubic Bezier curve path through points.
        // @deprecated
        // @param {array} points Array of points through which the smooth line will go.
        // @return {array} SVG Path commands as an array
        curveThroughPoints: function(points) {

            console.warn('deprecated');

            return new Path(Curve.throughPoints(points)).serialize();
        },

        // Get open-ended Bezier Spline Control Points.
        // @deprecated
        // @param knots Input Knot Bezier spline points (At least two points!).
        // @param firstControlPoints Output First Control points. Array of knots.length - 1 length.
        // @param secondControlPoints Output Second Control points. Array of knots.length - 1 length.
        getCurveControlPoints: function(knots) {

            console.warn('deprecated');

            var firstControlPoints = [];
            var secondControlPoints = [];
            var n = knots.length - 1;
            var i;

            // Special case: Bezier curve should be a straight line.
            if (n == 1) {
                // 3P1 = 2P0 + P3
                firstControlPoints[0] = new Point(
                    (2 * knots[0].x + knots[1].x) / 3,
                    (2 * knots[0].y + knots[1].y) / 3
                );

                // P2 = 2P1 – P0
                secondControlPoints[0] = new Point(
                    2 * firstControlPoints[0].x - knots[0].x,
                    2 * firstControlPoints[0].y - knots[0].y
                );

                return [firstControlPoints, secondControlPoints];
            }

            // Calculate first Bezier control points.
            // Right hand side vector.
            var rhs = [];

            // Set right hand side X values.
            for (i = 1; i < n - 1; i++) {
                rhs[i] = 4 * knots[i].x + 2 * knots[i + 1].x;
            }

            rhs[0] = knots[0].x + 2 * knots[1].x;
            rhs[n - 1] = (8 * knots[n - 1].x + knots[n].x) / 2.0;

            // Get first control points X-values.
            var x = this.getFirstControlPoints(rhs);

            // Set right hand side Y values.
            for (i = 1; i < n - 1; ++i) {
                rhs[i] = 4 * knots[i].y + 2 * knots[i + 1].y;
            }

            rhs[0] = knots[0].y + 2 * knots[1].y;
            rhs[n - 1] = (8 * knots[n - 1].y + knots[n].y) / 2.0;

            // Get first control points Y-values.
            var y = this.getFirstControlPoints(rhs);

            // Fill output arrays.
            for (i = 0; i < n; i++) {
                // First control point.
                firstControlPoints.push(new Point(x[i], y[i]));

                // Second control point.
                if (i < n - 1) {
                    secondControlPoints.push(new Point(
                        2 * knots [i + 1].x - x[i + 1],
                        2 * knots[i + 1].y - y[i + 1]
                    ));

                } else {
                    secondControlPoints.push(new Point(
                        (knots[n].x + x[n - 1]) / 2,
                        (knots[n].y + y[n - 1]) / 2)
                    );
                }
            }

            return [firstControlPoints, secondControlPoints];
        },

        // Solves a tridiagonal system for one of coordinates (x or y) of first Bezier control points.
        // @deprecated
        // @param rhs Right hand side vector.
        // @return Solution vector.
        getFirstControlPoints: function(rhs) {

            console.warn('deprecated');

            var n = rhs.length;
            // `x` is a solution vector.
            var x = [];
            var tmp = [];
            var b = 2.0;

            x[0] = rhs[0] / b;

            // Decomposition and forward substitution.
            for (var i = 1; i < n; i++) {
                tmp[i] = 1 / b;
                b = (i < n - 1 ? 4.0 : 3.5) - tmp[i];
                x[i] = (rhs[i] - x[i - 1]) / b;
            }

            for (i = 1; i < n; i++) {
                // Backsubstitution.
                x[n - i - 1] -= tmp[n - i] * x[n - i];
            }

            return x;
        },

        // Divide a Bezier curve into two at point defined by value 't' <0,1>.
        // Using deCasteljau algorithm. http://math.stackexchange.com/a/317867
        // @deprecated
        // @param control points (start, control start, control end, end)
        // @return a function that accepts t and returns 2 curves.
        getCurveDivider: function(p0, p1, p2, p3) {

            console.warn('deprecated');

            var curve = new Curve(p0, p1, p2, p3);

            return function divideCurve(t) {

                var divided = curve.divide(t);

                return [{
                    p0: divided[0].start,
                    p1: divided[0].controlPoint1,
                    p2: divided[0].controlPoint2,
                    p3: divided[0].end
                }, {
                    p0: divided[1].start,
                    p1: divided[1].controlPoint1,
                    p2: divided[1].controlPoint2,
                    p3: divided[1].end
                }];
            };
        },

        // Solves an inversion problem -- Given the (x, y) coordinates of a point which lies on
        // a parametric curve x = x(t)/w(t), y = y(t)/w(t), ﬁnd the parameter value t
        // which corresponds to that point.
        // @deprecated
        // @param control points (start, control start, control end, end)
        // @return a function that accepts a point and returns t.
        getInversionSolver: function(p0, p1, p2, p3) {

            console.warn('deprecated');

            var curve = new Curve(p0, p1, p2, p3);

            return function solveInversion(p) {

                return curve.closestPointT(p);
            };
        }
    };

    var Curve = g.Curve = function(p1, p2, p3, p4) {

        if (!(this instanceof Curve)) {
            return new Curve(p1, p2, p3, p4);
        }

        if (p1 instanceof Curve) {
            return new Curve(p1.start, p1.controlPoint1, p1.controlPoint2, p1.end);
        }

        this.start = new Point(p1);
        this.controlPoint1 = new Point(p2);
        this.controlPoint2 = new Point(p3);
        this.end = new Point(p4);
    };

    // Curve passing through points.
    // Ported from C# implementation by Oleg V. Polikarpotchkin and Peter Lee (http://www.codeproject.com/KB/graphics/BezierSpline.aspx).
    // @param {array} points Array of points through which the smooth line will go.
    // @return {array} curves.
    Curve.throughPoints = (function() {

        // Solves a tridiagonal system for one of coordinates (x or y) of first Bezier control points.
        // @param rhs Right hand side vector.
        // @return Solution vector.
        function getFirstControlPoints(rhs) {

            var n = rhs.length;
            // `x` is a solution vector.
            var x = [];
            var tmp = [];
            var b = 2.0;

            x[0] = rhs[0] / b;

            // Decomposition and forward substitution.
            for (var i = 1; i < n; i++) {
                tmp[i] = 1 / b;
                b = (i < n - 1 ? 4.0 : 3.5) - tmp[i];
                x[i] = (rhs[i] - x[i - 1]) / b;
            }

            for (i = 1; i < n; i++) {
                // Backsubstitution.
                x[n - i - 1] -= tmp[n - i] * x[n - i];
            }

            return x;
        }

        // Get open-ended Bezier Spline Control Points.
        // @param knots Input Knot Bezier spline points (At least two points!).
        // @param firstControlPoints Output First Control points. Array of knots.length - 1 length.
        // @param secondControlPoints Output Second Control points. Array of knots.length - 1 length.
        function getCurveControlPoints(knots) {

            var firstControlPoints = [];
            var secondControlPoints = [];
            var n = knots.length - 1;
            var i;

            // Special case: Bezier curve should be a straight line.
            if (n == 1) {
                // 3P1 = 2P0 + P3
                firstControlPoints[0] = new Point(
                    (2 * knots[0].x + knots[1].x) / 3,
                    (2 * knots[0].y + knots[1].y) / 3
                );

                // P2 = 2P1 – P0
                secondControlPoints[0] = new Point(
                    2 * firstControlPoints[0].x - knots[0].x,
                    2 * firstControlPoints[0].y - knots[0].y
                );

                return [firstControlPoints, secondControlPoints];
            }

            // Calculate first Bezier control points.
            // Right hand side vector.
            var rhs = [];

            // Set right hand side X values.
            for (i = 1; i < n - 1; i++) {
                rhs[i] = 4 * knots[i].x + 2 * knots[i + 1].x;
            }

            rhs[0] = knots[0].x + 2 * knots[1].x;
            rhs[n - 1] = (8 * knots[n - 1].x + knots[n].x) / 2.0;

            // Get first control points X-values.
            var x = getFirstControlPoints(rhs);

            // Set right hand side Y values.
            for (i = 1; i < n - 1; ++i) {
                rhs[i] = 4 * knots[i].y + 2 * knots[i + 1].y;
            }

            rhs[0] = knots[0].y + 2 * knots[1].y;
            rhs[n - 1] = (8 * knots[n - 1].y + knots[n].y) / 2.0;

            // Get first control points Y-values.
            var y = getFirstControlPoints(rhs);

            // Fill output arrays.
            for (i = 0; i < n; i++) {
                // First control point.
                firstControlPoints.push(new Point(x[i], y[i]));

                // Second control point.
                if (i < n - 1) {
                    secondControlPoints.push(new Point(
                        2 * knots [i + 1].x - x[i + 1],
                        2 * knots[i + 1].y - y[i + 1]
                    ));

                } else {
                    secondControlPoints.push(new Point(
                        (knots[n].x + x[n - 1]) / 2,
                        (knots[n].y + y[n - 1]) / 2
                    ));
                }
            }

            return [firstControlPoints, secondControlPoints];
        }

        return function(points) {

            if (!points || (Array.isArray(points) && points.length < 2)) {
                throw new Error('At least 2 points are required');
            }

            var controlPoints = getCurveControlPoints(points);

            var curves = [];
            var n = controlPoints[0].length;
            for (var i = 0; i < n; i++) {

                var controlPoint1 = new Point(controlPoints[0][i].x, controlPoints[0][i].y);
                var controlPoint2 = new Point(controlPoints[1][i].x, controlPoints[1][i].y);

                curves.push(new Curve(points[i], controlPoint1, controlPoint2, points[i + 1]));
            }

            return curves;
        };
    })();

    Curve.prototype = {

        // Returns a bbox that tightly envelops the curve.
        bbox: function() {

            var start = this.start;
            var controlPoint1 = this.controlPoint1;
            var controlPoint2 = this.controlPoint2;
            var end = this.end;

            var x0 = start.x;
            var y0 = start.y;
            var x1 = controlPoint1.x;
            var y1 = controlPoint1.y;
            var x2 = controlPoint2.x;
            var y2 = controlPoint2.y;
            var x3 = end.x;
            var y3 = end.y;

            var points = new Array(); // local extremes
            var tvalues = new Array(); // t values of local extremes
            var bounds = [new Array(), new Array()];

            var a, b, c, t;
            var t1, t2;
            var b2ac, sqrtb2ac;

            for (var i = 0; i < 2; ++i) {

                if (i === 0) {
                    b = 6 * x0 - 12 * x1 + 6 * x2;
                    a = -3 * x0 + 9 * x1 - 9 * x2 + 3 * x3;
                    c = 3 * x1 - 3 * x0;

                } else {
                    b = 6 * y0 - 12 * y1 + 6 * y2;
                    a = -3 * y0 + 9 * y1 - 9 * y2 + 3 * y3;
                    c = 3 * y1 - 3 * y0;
                }

                if (abs(a) < 1e-12) { // Numerical robustness
                    if (abs(b) < 1e-12) { // Numerical robustness
                        continue;
                    }

                    t = -c / b;
                    if ((0 < t) && (t < 1)) tvalues.push(t);

                    continue;
                }

                b2ac = b * b - 4 * c * a;
                sqrtb2ac = sqrt(b2ac);

                if (b2ac < 0) continue;

                t1 = (-b + sqrtb2ac) / (2 * a);
                if ((0 < t1) && (t1 < 1)) tvalues.push(t1);

                t2 = (-b - sqrtb2ac) / (2 * a);
                if ((0 < t2) && (t2 < 1)) tvalues.push(t2);
            }

            var j = tvalues.length;
            var jlen = j;
            var mt;
            var x, y;

            while (j--) {
                t = tvalues[j];
                mt = 1 - t;

                x = (mt * mt * mt * x0) + (3 * mt * mt * t * x1) + (3 * mt * t * t * x2) + (t * t * t * x3);
                bounds[0][j] = x;

                y = (mt * mt * mt * y0) + (3 * mt * mt * t * y1) + (3 * mt * t * t * y2) + (t * t * t * y3);
                bounds[1][j] = y;

                points[j] = { X: x, Y: y };
            }

            tvalues[jlen] = 0;
            tvalues[jlen + 1] = 1;

            points[jlen] = { X: x0, Y: y0 };
            points[jlen + 1] = { X: x3, Y: y3 };

            bounds[0][jlen] = x0;
            bounds[1][jlen] = y0;

            bounds[0][jlen + 1] = x3;
            bounds[1][jlen + 1] = y3;

            tvalues.length = jlen + 2;
            bounds[0].length = jlen + 2;
            bounds[1].length = jlen + 2;
            points.length = jlen + 2;

            var left = min.apply(null, bounds[0]);
            var top = min.apply(null, bounds[1]);
            var right = max.apply(null, bounds[0]);
            var bottom = max.apply(null, bounds[1]);

            return new Rect(left, top, (right - left), (bottom - top));
        },

        clone: function() {

            return new Curve(this.start, this.controlPoint1, this.controlPoint2, this.end);
        },

        // Returns the point on the curve closest to point `p`
        closestPoint: function(p, opt) {

            return this.pointAtT(this.closestPointT(p, opt));
        },

        closestPointLength: function(p, opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            var localOpt = { precision: precision, subdivisions: subdivisions };

            return this.lengthAtT(this.closestPointT(p, localOpt), localOpt);
        },

        closestPointNormalizedLength: function(p, opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            var localOpt = { precision: precision, subdivisions: subdivisions };

            var cpLength = this.closestPointLength(p, localOpt);
            if (!cpLength) return 0;

            var length = this.length(localOpt);
            if (length === 0) return 0;

            return cpLength / length;
        },

        // Returns `t` of the point on the curve closest to point `p`
        closestPointT: function(p, opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            // does not use localOpt

            // identify the subdivision that contains the point:
            var investigatedSubdivision;
            var investigatedSubdivisionStartT; // assume that subdivisions are evenly spaced
            var investigatedSubdivisionEndT;
            var distFromStart; // distance of point from start of baseline
            var distFromEnd; // distance of point from end of baseline
            var minSumDist; // lowest observed sum of the two distances
            var n = subdivisions.length;
            var subdivisionSize = (n ? (1 / n) : 0);
            for (var i = 0; i < n; i++) {

                var currentSubdivision = subdivisions[i];

                var startDist = currentSubdivision.start.distance(p);
                var endDist = currentSubdivision.end.distance(p);
                var sumDist = startDist + endDist;

                // check that the point is closest to current subdivision and not any other
                if (!minSumDist || (sumDist < minSumDist)) {
                    investigatedSubdivision = currentSubdivision;

                    investigatedSubdivisionStartT = i * subdivisionSize;
                    investigatedSubdivisionEndT = (i + 1) * subdivisionSize;

                    distFromStart = startDist;
                    distFromEnd = endDist;

                    minSumDist = sumDist;
                }
            }

            var precisionRatio = pow(10, -precision);

            // recursively divide investigated subdivision:
            // until distance between baselinePoint and closest path endpoint is within 10^(-precision)
            // then return the closest endpoint of that final subdivision
            while (true) {

                // check if we have reached required observed precision
                var startPrecisionRatio;
                var endPrecisionRatio;

                startPrecisionRatio = (distFromStart ? (abs(distFromStart - distFromEnd) / distFromStart) : 0);
                endPrecisionRatio = (distFromEnd ? (abs(distFromStart - distFromEnd) / distFromEnd) : 0);
                if ((startPrecisionRatio < precisionRatio) || (endPrecisionRatio) < precisionRatio) {
                    return ((distFromStart <= distFromEnd) ? investigatedSubdivisionStartT : investigatedSubdivisionEndT);
                }

                // otherwise, set up for next iteration
                var divided = investigatedSubdivision.divide(0.5);
                subdivisionSize /= 2;

                var startDist1 = divided[0].start.distance(p);
                var endDist1 = divided[0].end.distance(p);
                var sumDist1 = startDist1 + endDist1;

                var startDist2 = divided[1].start.distance(p);
                var endDist2 = divided[1].end.distance(p);
                var sumDist2 = startDist2 + endDist2;

                if (sumDist1 <= sumDist2) {
                    investigatedSubdivision = divided[0];

                    investigatedSubdivisionEndT -= subdivisionSize; // subdivisionSize was already halved

                    distFromStart = startDist1;
                    distFromEnd = endDist1;

                } else {
                    investigatedSubdivision = divided[1];

                    investigatedSubdivisionStartT += subdivisionSize; // subdivisionSize was already halved

                    distFromStart = startDist2;
                    distFromEnd = endDist2;
                }
            }
        },

        closestPointTangent: function(p, opt) {

            return this.tangentAtT(this.closestPointT(p, opt));
        },

        // Divides the curve into two at point defined by `t` between 0 and 1.
        // Using de Casteljau's algorithm (http://math.stackexchange.com/a/317867).
        // Additional resource: https://pomax.github.io/bezierinfo/#decasteljau
        divide: function(t) {

            var start = this.start;
            var controlPoint1 = this.controlPoint1;
            var controlPoint2 = this.controlPoint2;
            var end = this.end;

            // shortcuts for `t` values that are out of range
            if (t <= 0) {
                return [
                    new Curve(start, start, start, start),
                    new Curve(start, controlPoint1, controlPoint2, end)
                ];
            }

            if (t >= 1) {
                return [
                    new Curve(start, controlPoint1, controlPoint2, end),
                    new Curve(end, end, end, end)
                ];
            }

            var dividerPoints = this.getSkeletonPoints(t);

            var startControl1 = dividerPoints.startControlPoint1;
            var startControl2 = dividerPoints.startControlPoint2;
            var divider = dividerPoints.divider;
            var dividerControl1 = dividerPoints.dividerControlPoint1;
            var dividerControl2 = dividerPoints.dividerControlPoint2;

            // return array with two new curves
            return [
                new Curve(start, startControl1, startControl2, divider),
                new Curve(divider, dividerControl1, dividerControl2, end)
            ];
        },

        // Returns the distance between the curve's start and end points.
        endpointDistance: function() {

            return this.start.distance(this.end);
        },

        // Checks whether two curves are exactly the same.
        equals: function(c) {

            return !!c &&
                    this.start.x === c.start.x &&
                    this.start.y === c.start.y &&
                    this.controlPoint1.x === c.controlPoint1.x &&
                    this.controlPoint1.y === c.controlPoint1.y &&
                    this.controlPoint2.x === c.controlPoint2.x &&
                    this.controlPoint2.y === c.controlPoint2.y &&
                    this.end.x === c.end.x &&
                    this.end.y === c.end.y;
        },

        // Returns five helper points necessary for curve division.
        getSkeletonPoints: function(t) {

            var start = this.start;
            var control1 = this.controlPoint1;
            var control2 = this.controlPoint2;
            var end = this.end;

            // shortcuts for `t` values that are out of range
            if (t <= 0) {
                return {
                    startControlPoint1: start.clone(),
                    startControlPoint2: start.clone(),
                    divider: start.clone(),
                    dividerControlPoint1: control1.clone(),
                    dividerControlPoint2: control2.clone()
                };
            }

            if (t >= 1) {
                return {
                    startControlPoint1: control1.clone(),
                    startControlPoint2: control2.clone(),
                    divider: end.clone(),
                    dividerControlPoint1: end.clone(),
                    dividerControlPoint2: end.clone()
                };
            }

            var midpoint1 = (new Line(start, control1)).pointAt(t);
            var midpoint2 = (new Line(control1, control2)).pointAt(t);
            var midpoint3 = (new Line(control2, end)).pointAt(t);

            var subControl1 = (new Line(midpoint1, midpoint2)).pointAt(t);
            var subControl2 = (new Line(midpoint2, midpoint3)).pointAt(t);

            var divider = (new Line(subControl1, subControl2)).pointAt(t);

            var output = {
                startControlPoint1: midpoint1,
                startControlPoint2: subControl1,
                divider: divider,
                dividerControlPoint1: subControl2,
                dividerControlPoint2: midpoint3
            };

            return output;
        },

        // Returns a list of curves whose flattened length is better than `opt.precision`.
        // That is, observed difference in length between recursions is less than 10^(-3) = 0.001 = 0.1%
        // (Observed difference is not real precision, but close enough as long as special cases are covered)
        // (That is why skipping iteration 1 is important)
        // As a rule of thumb, increasing `precision` by 1 requires two more division operations
        // - Precision 0 (endpointDistance) - total of 2^0 - 1 = 0 operations (1 subdivision)
        // - Precision 1 (<10% error) - total of 2^2 - 1 = 3 operations (4 subdivisions)
        // - Precision 2 (<1% error) - total of 2^4 - 1 = 15 operations requires 4 division operations on all elements (15 operations total) (16 subdivisions)
        // - Precision 3 (<0.1% error) - total of 2^6 - 1 = 63 operations - acceptable when drawing (64 subdivisions)
        // - Precision 4 (<0.01% error) - total of 2^8 - 1 = 255 operations - high resolution, can be used to interpolate `t` (256 subdivisions)
        // (Variation of 1 recursion worse or better is possible depending on the curve, doubling/halving the number of operations accordingly)
        getSubdivisions: function(opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            // not using opt.subdivisions
            // not using localOpt

            var subdivisions = [new Curve(this.start, this.controlPoint1, this.controlPoint2, this.end)];
            if (precision === 0) return subdivisions;

            var previousLength = this.endpointDistance();

            var precisionRatio = pow(10, -precision);

            // recursively divide curve at `t = 0.5`
            // until the difference between observed length at subsequent iterations is lower than precision
            var iteration = 0;
            while (true) {
                iteration += 1;

                // divide all subdivisions
                var newSubdivisions = [];
                var numSubdivisions = subdivisions.length;
                for (var i = 0; i < numSubdivisions; i++) {

                    var currentSubdivision = subdivisions[i];
                    var divided = currentSubdivision.divide(0.5); // dividing at t = 0.5 (not at middle length!)
                    newSubdivisions.push(divided[0], divided[1]);
                }

                // measure new length
                var length = 0;
                var numNewSubdivisions = newSubdivisions.length;
                for (var j = 0; j < numNewSubdivisions; j++) {

                    var currentNewSubdivision = newSubdivisions[j];
                    length += currentNewSubdivision.endpointDistance();
                }

                // check if we have reached required observed precision
                // sine-like curves may have the same observed length in iteration 0 and 1 - skip iteration 1
                // not a problem for further iterations because cubic curves cannot have more than two local extrema
                // (i.e. cubic curves cannot intersect the baseline more than once)
                // therefore two subsequent iterations cannot produce sampling with equal length
                var observedPrecisionRatio = ((length !== 0) ? ((length - previousLength) / length) : 0);
                if (iteration > 1 && observedPrecisionRatio < precisionRatio) {
                    return newSubdivisions;
                }

                // otherwise, set up for next iteration
                subdivisions = newSubdivisions;
                previousLength = length;
            }
        },

        isDifferentiable: function() {

            var start = this.start;
            var control1 = this.controlPoint1;
            var control2 = this.controlPoint2;
            var end = this.end;

            return !(start.equals(control1) && control1.equals(control2) && control2.equals(end));
        },

        // Returns flattened length of the curve with precision better than `opt.precision`; or using `opt.subdivisions` provided.
        length: function(opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision; // opt.precision only used in getSubdivisions() call
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            // not using localOpt

            var length = 0;
            var n = subdivisions.length;
            for (var i = 0; i < n; i++) {

                var currentSubdivision = subdivisions[i];
                length += currentSubdivision.endpointDistance();
            }

            return length;
        },

        // Returns distance along the curve up to `t` with precision better than requested `opt.precision`. (Not using `opt.subdivisions`.)
        lengthAtT: function(t, opt) {

            if (t <= 0) return 0;

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            // not using opt.subdivisions
            // not using localOpt

            var subCurve = this.divide(t)[0];
            var subCurveLength = subCurve.length({ precision: precision });

            return subCurveLength;
        },

        // Returns point at requested `ratio` between 0 and 1 with precision better than `opt.precision`; optionally using `opt.subdivisions` provided.
        // Mirrors Line.pointAt() function.
        // For a function that tracks `t`, use Curve.pointAtT().
        pointAt: function(ratio, opt) {

            if (ratio <= 0) return this.start.clone();
            if (ratio >= 1) return this.end.clone();

            var t = this.tAt(ratio, opt);

            return this.pointAtT(t);
        },

        // Returns point at requested `length` with precision better than requested `opt.precision`; optionally using `opt.subdivisions` provided.
        pointAtLength: function(length, opt) {

            var t = this.tAtLength(length, opt);

            return this.pointAtT(t);
        },

        // Returns the point at provided `t` between 0 and 1.
        // `t` does not track distance along curve as it does in Line objects.
        // Non-linear relationship, speeds up and slows down as curve warps!
        // For linear length-based solution, use Curve.pointAt().
        pointAtT: function(t) {

            if (t <= 0) return this.start.clone();
            if (t >= 1) return this.end.clone();

            return this.getSkeletonPoints(t).divider;
        },

        // Default precision
        PRECISION: 3,

        scale: function(sx, sy, origin) {

            this.start.scale(sx, sy, origin);
            this.controlPoint1.scale(sx, sy, origin);
            this.controlPoint2.scale(sx, sy, origin);
            this.end.scale(sx, sy, origin);
            return this;
        },

        // Returns a tangent line at requested `ratio` with precision better than requested `opt.precision`; or using `opt.subdivisions` provided.
        tangentAt: function(ratio, opt) {

            if (!this.isDifferentiable()) return null;

            if (ratio < 0) ratio = 0;
            else if (ratio > 1) ratio = 1;

            var t = this.tAt(ratio, opt);

            return this.tangentAtT(t);
        },

        // Returns a tangent line at requested `length` with precision better than requested `opt.precision`; or using `opt.subdivisions` provided.
        tangentAtLength: function(length, opt) {

            if (!this.isDifferentiable()) return null;

            var t = this.tAtLength(length, opt);

            return this.tangentAtT(t);
        },

        // Returns a tangent line at requested `t`.
        tangentAtT: function(t) {

            if (!this.isDifferentiable()) return null;

            if (t < 0) t = 0;
            else if (t > 1) t = 1;

            var skeletonPoints = this.getSkeletonPoints(t);

            var p1 = skeletonPoints.startControlPoint2;
            var p2 = skeletonPoints.dividerControlPoint1;

            var tangentStart = skeletonPoints.divider;

            var tangentLine = new Line(p1, p2);
            tangentLine.translate(tangentStart.x - p1.x, tangentStart.y - p1.y); // move so that tangent line starts at the point requested

            return tangentLine;
        },

        // Returns `t` at requested `ratio` with precision better than requested `opt.precision`; optionally using `opt.subdivisions` provided.
        tAt: function(ratio, opt) {

            if (ratio <= 0) return 0;
            if (ratio >= 1) return 1;

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            var localOpt = { precision: precision, subdivisions: subdivisions };

            var curveLength = this.length(localOpt);
            var length = curveLength * ratio;

            return this.tAtLength(length, localOpt);
        },

        // Returns `t` at requested `length` with precision better than requested `opt.precision`; optionally using `opt.subdivisions` provided.
        // Uses `precision` to approximate length within `precision` (always underestimates)
        // Then uses a binary search to find the `t` of a subdivision endpoint that is close (within `precision`) to the `length`, if the curve was as long as approximated
        // As a rule of thumb, increasing `precision` by 1 causes the algorithm to go 2^(precision - 1) deeper
        // - Precision 0 (chooses one of the two endpoints) - 0 levels
        // - Precision 1 (chooses one of 5 points, <10% error) - 1 level
        // - Precision 2 (<1% error) - 3 levels
        // - Precision 3 (<0.1% error) - 7 levels
        // - Precision 4 (<0.01% error) - 15 levels
        tAtLength: function(length, opt) {

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            var localOpt = { precision: precision, subdivisions: subdivisions };

            // identify the subdivision that contains the point at requested `length`:
            var investigatedSubdivision;
            var investigatedSubdivisionStartT; // assume that subdivisions are evenly spaced
            var investigatedSubdivisionEndT;
            //var baseline; // straightened version of subdivision to investigate
            //var baselinePoint; // point on the baseline that is the requested distance away from start
            var baselinePointDistFromStart; // distance of baselinePoint from start of baseline
            var baselinePointDistFromEnd; // distance of baselinePoint from end of baseline
            var l = 0; // length so far
            var n = subdivisions.length;
            var subdivisionSize = 1 / n;
            for (var i = (fromStart ? (0) : (n - 1)); (fromStart ? (i < n) : (i >= 0)); (fromStart ? (i++) : (i--))) {

                var currentSubdivision = subdivisions[i];
                var d = currentSubdivision.endpointDistance(); // length of current subdivision

                if (length <= (l + d)) {
                    investigatedSubdivision = currentSubdivision;

                    investigatedSubdivisionStartT = i * subdivisionSize;
                    investigatedSubdivisionEndT = (i + 1) * subdivisionSize;

                    baselinePointDistFromStart = (fromStart ? (length - l) : ((d + l) - length));
                    baselinePointDistFromEnd = (fromStart ? ((d + l) - length) : (length - l));

                    break;
                }

                l += d;
            }

            if (!investigatedSubdivision) return (fromStart ? 1 : 0); // length requested is out of range - return maximum t
            // note that precision affects what length is recorded
            // (imprecise measurements underestimate length by up to 10^(-precision) of the precise length)
            // e.g. at precision 1, the length may be underestimated by up to 10% and cause this function to return 1

            var curveLength = this.length(localOpt);

            var precisionRatio = pow(10, -precision);

            // recursively divide investigated subdivision:
            // until distance between baselinePoint and closest path endpoint is within 10^(-precision)
            // then return the closest endpoint of that final subdivision
            while (true) {

                // check if we have reached required observed precision
                var observedPrecisionRatio;

                observedPrecisionRatio = ((curveLength !== 0) ? (baselinePointDistFromStart / curveLength) : 0);
                if (observedPrecisionRatio < precisionRatio) return investigatedSubdivisionStartT;
                observedPrecisionRatio = ((curveLength !== 0) ? (baselinePointDistFromEnd / curveLength) : 0);
                if (observedPrecisionRatio < precisionRatio) return investigatedSubdivisionEndT;

                // otherwise, set up for next iteration
                var newBaselinePointDistFromStart;
                var newBaselinePointDistFromEnd;

                var divided = investigatedSubdivision.divide(0.5);
                subdivisionSize /= 2;

                var baseline1Length = divided[0].endpointDistance();
                var baseline2Length = divided[1].endpointDistance();

                if (baselinePointDistFromStart <= baseline1Length) { // point at requested length is inside divided[0]
                    investigatedSubdivision = divided[0];

                    investigatedSubdivisionEndT -= subdivisionSize; // sudivisionSize was already halved

                    newBaselinePointDistFromStart = baselinePointDistFromStart;
                    newBaselinePointDistFromEnd = baseline1Length - newBaselinePointDistFromStart;

                } else { // point at requested length is inside divided[1]
                    investigatedSubdivision = divided[1];

                    investigatedSubdivisionStartT += subdivisionSize; // subdivisionSize was already halved

                    newBaselinePointDistFromStart = baselinePointDistFromStart - baseline1Length;
                    newBaselinePointDistFromEnd = baseline2Length - newBaselinePointDistFromStart;
                }

                baselinePointDistFromStart = newBaselinePointDistFromStart;
                baselinePointDistFromEnd = newBaselinePointDistFromEnd;
            }
        },

        translate: function(tx, ty) {

            this.start.translate(tx, ty);
            this.controlPoint1.translate(tx, ty);
            this.controlPoint2.translate(tx, ty);
            this.end.translate(tx, ty);
            return this;
        },

        // Returns an array of points that represents the curve when flattened, up to `opt.precision`; or using `opt.subdivisions` provided.
        // Flattened length is no more than 10^(-precision) away from real curve length.
        toPoints: function(opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision; // opt.precision only used in getSubdivisions() call
            var subdivisions = (opt.subdivisions === undefined) ? this.getSubdivisions({ precision: precision }) : opt.subdivisions;
            // not using localOpt

            var points = [subdivisions[0].start.clone()];
            var n = subdivisions.length;
            for (var i = 0; i < n; i++) {

                var currentSubdivision = subdivisions[i];
                points.push(currentSubdivision.end.clone());
            }

            return points;
        },

        // Returns a polyline that represents the curve when flattened, up to `opt.precision`; or using `opt.subdivisions` provided.
        // Flattened length is no more than 10^(-precision) away from real curve length.
        toPolyline: function(opt) {

            return new Polyline(this.toPoints(opt));
        },

        toString: function() {

            return this.start + ' ' + this.controlPoint1 + ' ' + this.controlPoint2 + ' ' + this.end;
        }
    };

    var Ellipse = g.Ellipse = function(c, a, b) {

        if (!(this instanceof Ellipse)) {
            return new Ellipse(c, a, b);
        }

        if (c instanceof Ellipse) {
            return new Ellipse(new Point(c.x, c.y), c.a, c.b);
        }

        c = new Point(c);
        this.x = c.x;
        this.y = c.y;
        this.a = a;
        this.b = b;
    };

    Ellipse.fromRect = function(rect) {

        rect = new Rect(rect);
        return new Ellipse(rect.center(), rect.width / 2, rect.height / 2);
    };

    Ellipse.prototype = {

        bbox: function() {

            return new Rect(this.x - this.a, this.y - this.b, 2 * this.a, 2 * this.b);
        },

        clone: function() {

            return new Ellipse(this);
        },

        /**
         * @param {g.Point} point
         * @returns {number} result < 1 - inside ellipse, result == 1 - on ellipse boundary, result > 1 - outside
         */
        normalizedDistance: function(point) {

            var x0 = point.x;
            var y0 = point.y;
            var a = this.a;
            var b = this.b;
            var x = this.x;
            var y = this.y;

            return ((x0 - x) * (x0 - x)) / (a * a ) + ((y0 - y) * (y0 - y)) / (b * b);
        },

        // inflate by dx and dy
        // @param dx {delta_x} representing additional size to x
        // @param dy {delta_y} representing additional size to y -
        // dy param is not required -> in that case y is sized by dx
        inflate: function(dx, dy) {
            if (dx === undefined) {
                dx = 0;
            }

            if (dy === undefined) {
                dy = dx;
            }

            this.a += 2 * dx;
            this.b += 2 * dy;

            return this;
        },


        /**
         * @param {g.Point} p
         * @returns {boolean}
         */
        containsPoint: function(p) {

            return this.normalizedDistance(p) <= 1;
        },

        /**
         * @returns {g.Point}
         */
        center: function() {

            return new Point(this.x, this.y);
        },

        /** Compute angle between tangent and x axis
         * @param {g.Point} p Point of tangency, it has to be on ellipse boundaries.
         * @returns {number} angle between tangent and x axis
         */
        tangentTheta: function(p) {

            var refPointDelta = 30;
            var x0 = p.x;
            var y0 = p.y;
            var a = this.a;
            var b = this.b;
            var center = this.bbox().center();
            var m = center.x;
            var n = center.y;

            var q1 = x0 > center.x + a / 2;
            var q3 = x0 < center.x - a / 2;

            var y, x;
            if (q1 || q3) {
                y = x0 > center.x ? y0 - refPointDelta : y0 + refPointDelta;
                x = (a * a / (x0 - m)) - (a * a * (y0 - n) * (y - n)) / (b * b * (x0 - m)) + m;

            } else {
                x = y0 > center.y ? x0 + refPointDelta : x0 - refPointDelta;
                y = ( b * b / (y0 - n)) - (b * b * (x0 - m) * (x - m)) / (a * a * (y0 - n)) + n;
            }

            return (new Point(x, y)).theta(p);

        },

        equals: function(ellipse) {

            return !!ellipse &&
                    ellipse.x === this.x &&
                    ellipse.y === this.y &&
                    ellipse.a === this.a &&
                    ellipse.b === this.b;
        },

        intersectionWithLine: function(line) {

            var intersections = [];
            var a1 = line.start;
            var a2 = line.end;
            var rx = this.a;
            var ry = this.b;
            var dir = line.vector();
            var diff = a1.difference(new Point(this));
            var mDir = new Point(dir.x / (rx * rx), dir.y / (ry * ry));
            var mDiff = new Point(diff.x / (rx * rx), diff.y / (ry * ry));

            var a = dir.dot(mDir);
            var b = dir.dot(mDiff);
            var c = diff.dot(mDiff) - 1.0;
            var d = b * b - a * c;

            if (d < 0) {
                return null;
            } else if (d > 0) {
                var root = sqrt(d);
                var ta = (-b - root) / a;
                var tb = (-b + root) / a;

                if ((ta < 0 || 1 < ta) && (tb < 0 || 1 < tb)) {
                    // if ((ta < 0 && tb < 0) || (ta > 1 && tb > 1)) outside else inside
                    return null;
                } else {
                    if (0 <= ta && ta <= 1) intersections.push(a1.lerp(a2, ta));
                    if (0 <= tb && tb <= 1) intersections.push(a1.lerp(a2, tb));
                }
            } else {
                var t = -b / a;
                if (0 <= t && t <= 1) {
                    intersections.push(a1.lerp(a2, t));
                } else {
                    // outside
                    return null;
                }
            }

            return intersections;
        },

        // Find point on me where line from my center to
        // point p intersects my boundary.
        // @param {number} angle If angle is specified, intersection with rotated ellipse is computed.
        intersectionWithLineFromCenterToPoint: function(p, angle) {

            p = new Point(p);

            if (angle) p.rotate(new Point(this.x, this.y), angle);

            var dx = p.x - this.x;
            var dy = p.y - this.y;
            var result;

            if (dx === 0) {
                result = this.bbox().pointNearestToPoint(p);
                if (angle) return result.rotate(new Point(this.x, this.y), -angle);
                return result;
            }

            var m = dy / dx;
            var mSquared = m * m;
            var aSquared = this.a * this.a;
            var bSquared = this.b * this.b;

            var x = sqrt(1 / ((1 / aSquared) + (mSquared / bSquared)));
            x = dx < 0 ? -x : x;

            var y = m * x;
            result = new Point(this.x + x, this.y + y);

            if (angle) return result.rotate(new Point(this.x, this.y), -angle);
            return result;
        },

        toString: function() {

            return (new Point(this.x, this.y)).toString() + ' ' + this.a + ' ' + this.b;
        }
    };

    var Line = g.Line = function(p1, p2) {

        if (!(this instanceof Line)) {
            return new Line(p1, p2);
        }

        if (p1 instanceof Line) {
            return new Line(p1.start, p1.end);
        }

        this.start = new Point(p1);
        this.end = new Point(p2);
    };

    Line.prototype = {

        bbox: function() {

            var left = min(this.start.x, this.end.x);
            var top = min(this.start.y, this.end.y);
            var right = max(this.start.x, this.end.x);
            var bottom = max(this.start.y, this.end.y);

            return new Rect(left, top, (right - left), (bottom - top));
        },

        // @return the bearing (cardinal direction) of the line. For example N, W, or SE.
        // @returns {String} One of the following bearings : NE, E, SE, S, SW, W, NW, N.
        bearing: function() {

            var lat1 = toRad(this.start.y);
            var lat2 = toRad(this.end.y);
            var lon1 = this.start.x;
            var lon2 = this.end.x;
            var dLon = toRad(lon2 - lon1);
            var y = sin(dLon) * cos(lat2);
            var x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dLon);
            var brng = toDeg(atan2(y, x));

            var bearings = ['NE', 'E', 'SE', 'S', 'SW', 'W', 'NW', 'N'];

            var index = brng - 22.5;
            if (index < 0)
                index += 360;
            index = parseInt(index / 45);

            return bearings[index];
        },

        clone: function() {

            return new Line(this.start, this.end);
        },

        // @return {point} the closest point on the line to point `p`
        closestPoint: function(p) {

            return this.pointAt(this.closestPointNormalizedLength(p));
        },

        closestPointLength: function(p) {

            return this.closestPointNormalizedLength(p) * this.length();
        },

        // @return {number} the normalized length of the closest point on the line to point `p`
        closestPointNormalizedLength: function(p) {

            var product = this.vector().dot((new Line(this.start, p)).vector());
            var cpNormalizedLength = min(1, max(0, product / this.squaredLength()));

            // cpNormalizedLength returns `NaN` if this line has zero length
            // we can work with that - if `NaN`, return 0
            if (cpNormalizedLength !== cpNormalizedLength) return 0; // condition evaluates to `true` if and only if cpNormalizedLength is `NaN`
            // (`NaN` is the only value that is not equal to itself)

            return cpNormalizedLength;
        },

        closestPointTangent: function(p) {

            return this.tangentAt(this.closestPointNormalizedLength(p));
        },

        equals: function(l) {

            return !!l &&
                    this.start.x === l.start.x &&
                    this.start.y === l.start.y &&
                    this.end.x === l.end.x &&
                    this.end.y === l.end.y;
        },

        intersectionWithLine: function(line) {

            var pt1Dir = new Point(this.end.x - this.start.x, this.end.y - this.start.y);
            var pt2Dir = new Point(line.end.x - line.start.x, line.end.y - line.start.y);
            var det = (pt1Dir.x * pt2Dir.y) - (pt1Dir.y * pt2Dir.x);
            var deltaPt = new Point(line.start.x - this.start.x, line.start.y - this.start.y);
            var alpha = (deltaPt.x * pt2Dir.y) - (deltaPt.y * pt2Dir.x);
            var beta = (deltaPt.x * pt1Dir.y) - (deltaPt.y * pt1Dir.x);

            if (det === 0 || alpha * det < 0 || beta * det < 0) {
                // No intersection found.
                return null;
            }

            if (det > 0) {
                if (alpha > det || beta > det) {
                    return null;
                }

            } else {
                if (alpha < det || beta < det) {
                    return null;
                }
            }

            return [new Point(
                this.start.x + (alpha * pt1Dir.x / det),
                this.start.y + (alpha * pt1Dir.y / det)
            )];
        },

        // @return {point} Point where I'm intersecting a line.
        // @return [point] Points where I'm intersecting a rectangle.
        // @see Squeak Smalltalk, LineSegment>>intersectionWith:
        intersect: function(shape, opt) {

            if (shape instanceof Line ||
                shape instanceof Rect ||
                shape instanceof Polyline ||
                shape instanceof Ellipse ||
                shape instanceof Path
            ) {
                var intersection = shape.intersectionWithLine(this, opt);

                // Backwards compatibility
                if (intersection && (shape instanceof Line)) {
                    intersection = intersection[0];
                }

                return intersection;
            }

            return null;
        },

        isDifferentiable: function() {

            return !this.start.equals(this.end);
        },

        // @return {double} length of the line
        length: function() {

            return sqrt(this.squaredLength());
        },

        // @return {point} my midpoint
        midpoint: function() {

            return new Point(
                (this.start.x + this.end.x) / 2,
                (this.start.y + this.end.y) / 2
            );
        },

        // @return {point} my point at 't' <0,1>
        pointAt: function(t) {

            var start = this.start;
            var end = this.end;

            if (t <= 0) return start.clone();
            if (t >= 1) return end.clone();

            return start.lerp(end, t);
        },

        pointAtLength: function(length) {

            var start = this.start;
            var end = this.end;

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            var lineLength = this.length();
            if (length >= lineLength) return (fromStart ? end.clone() : start.clone());

            return this.pointAt((fromStart ? (length) : (lineLength - length)) / lineLength);
        },

        // @return {number} the offset of the point `p` from the line. + if the point `p` is on the right side of the line, - if on the left and 0 if on the line.
        pointOffset: function(p) {

            // Find the sign of the determinant of vectors (start,end), where p is the query point.
            p = new g.Point(p);
            var start = this.start;
            var end = this.end;
            var determinant = ((end.x - start.x) * (p.y - start.y) - (end.y - start.y) * (p.x - start.x));

            return determinant / this.length();
        },

        rotate: function(origin, angle) {

            this.start.rotate(origin, angle);
            this.end.rotate(origin, angle);
            return this;
        },

        round: function(precision) {

            var f = pow(10, precision || 0);
            this.start.x = round(this.start.x * f) / f;
            this.start.y = round(this.start.y * f) / f;
            this.end.x = round(this.end.x * f) / f;
            this.end.y = round(this.end.y * f) / f;
            return this;
        },

        scale: function(sx, sy, origin) {

            this.start.scale(sx, sy, origin);
            this.end.scale(sx, sy, origin);
            return this;
        },

        // @return {number} scale the line so that it has the requested length
        setLength: function(length) {

            var currentLength = this.length();
            if (!currentLength) return this;

            var scaleFactor = length / currentLength;
            return this.scale(scaleFactor, scaleFactor, this.start);
        },

        // @return {integer} length without sqrt
        // @note for applications where the exact length is not necessary (e.g. compare only)
        squaredLength: function() {

            var x0 = this.start.x;
            var y0 = this.start.y;
            var x1 = this.end.x;
            var y1 = this.end.y;
            return (x0 -= x1) * x0 + (y0 -= y1) * y0;
        },

        tangentAt: function(t) {

            if (!this.isDifferentiable()) return null;

            var start = this.start;
            var end = this.end;

            var tangentStart = this.pointAt(t); // constrains `t` between 0 and 1

            var tangentLine = new Line(start, end);
            tangentLine.translate(tangentStart.x - start.x, tangentStart.y - start.y); // move so that tangent line starts at the point requested

            return tangentLine;
        },

        tangentAtLength: function(length) {

            if (!this.isDifferentiable()) return null;

            var start = this.start;
            var end = this.end;

            var tangentStart = this.pointAtLength(length);

            var tangentLine = new Line(start, end);
            tangentLine.translate(tangentStart.x - start.x, tangentStart.y - start.y); // move so that tangent line starts at the point requested

            return tangentLine;
        },

        translate: function(tx, ty) {

            this.start.translate(tx, ty);
            this.end.translate(tx, ty);
            return this;
        },

        // @return vector {point} of the line
        vector: function() {

            return new Point(this.end.x - this.start.x, this.end.y - this.start.y);
        },

        toString: function() {

            return this.start.toString() + ' ' + this.end.toString();
        }
    };

    // For backwards compatibility:
    Line.prototype.intersection = Line.prototype.intersect;

    // Accepts path data string, array of segments, array of Curves and/or Lines, or a Polyline.
    // Path created is not guaranteed to be a valid (serializable) path (might not start with an M).
    var Path = g.Path = function(arg) {

        if (!(this instanceof Path)) {
            return new Path(arg);
        }

        if (typeof arg === 'string') { // create from a path data string
            return new Path.parse(arg);
        }

        this.segments = [];

        var i;
        var n;

        if (!arg) {
            // don't do anything

        } else if (Array.isArray(arg) && arg.length !== 0) { // if arg is a non-empty array
            n = arg.length;
            if (arg[0].isSegment) { // create from an array of segments
                for (i = 0; i < n; i++) {

                    var segment = arg[i];

                    this.appendSegment(segment);
                }

            } else { // create from an array of Curves and/or Lines
                var previousObj = null;
                for (i = 0; i < n; i++) {

                    var obj = arg[i];

                    if (!((obj instanceof Line) || (obj instanceof Curve))) {
                        throw new Error('Cannot construct a path segment from the provided object.');
                    }

                    if (i === 0) this.appendSegment(Path.createSegment('M', obj.start));

                    // if objects do not link up, moveto segments are inserted to cover the gaps
                    if (previousObj && !previousObj.end.equals(obj.start)) this.appendSegment(Path.createSegment('M', obj.start));

                    if (obj instanceof Line) {
                        this.appendSegment(Path.createSegment('L', obj.end));

                    } else if (obj instanceof Curve) {
                        this.appendSegment(Path.createSegment('C', obj.controlPoint1, obj.controlPoint2, obj.end));
                    }

                    previousObj = obj;
                }
            }

        } else if (arg.isSegment) { // create from a single segment
            this.appendSegment(arg);

        } else if (arg instanceof Line) { // create from a single Line
            this.appendSegment(Path.createSegment('M', arg.start));
            this.appendSegment(Path.createSegment('L', arg.end));

        } else if (arg instanceof Curve) { // create from a single Curve
            this.appendSegment(Path.createSegment('M', arg.start));
            this.appendSegment(Path.createSegment('C', arg.controlPoint1, arg.controlPoint2, arg.end));

        } else if (arg instanceof Polyline && arg.points && arg.points.length !== 0) { // create from a Polyline
            n = arg.points.length;
            for (i = 0; i < n; i++) {

                var point = arg.points[i];

                if (i === 0) this.appendSegment(Path.createSegment('M', point));
                else this.appendSegment(Path.createSegment('L', point));
            }
        }
    };

    // More permissive than V.normalizePathData and Path.prototype.serialize.
    // Allows path data strings that do not start with a Moveto command (unlike SVG specification).
    // Does not require spaces between elements; commas are allowed, separators may be omitted when unambiguous (e.g. 'ZM10,10', 'L1.6.8', 'M100-200').
    // Allows for command argument chaining.
    // Throws an error if wrong number of arguments is provided with a command.
    // Throws an error if an unrecognized path command is provided (according to Path.segmentTypes). Only a subset of SVG commands is currently supported (L, C, M, Z).
    Path.parse = function(pathData) {

        if (!pathData) return new Path();

        var path = new Path();

        var commandRe = /(?:[a-zA-Z] *)(?:(?:-?\d+(?:\.\d+)? *,? *)|(?:-?\.\d+ *,? *))+|(?:[a-zA-Z] *)(?! |\d|-|\.)/g;
        var commands = pathData.match(commandRe);

        var numCommands = commands.length;
        for (var i = 0; i < numCommands; i++) {

            var command = commands[i];
            var argRe = /(?:[a-zA-Z])|(?:(?:-?\d+(?:\.\d+)?))|(?:(?:-?\.\d+))/g;
            var args = command.match(argRe);

            var segment = Path.createSegment.apply(this, args); // args = [type, coordinate1, coordinate2...]
            path.appendSegment(segment);
        }

        return path;
    };

    // Create a segment or an array of segments.
    // Accepts unlimited points/coords arguments after `type`.
    Path.createSegment = function(type) {

        if (!type) throw new Error('Type must be provided.');

        var segmentConstructor = Path.segmentTypes[type];
        if (!segmentConstructor) throw new Error(type + ' is not a recognized path segment type.');

        var args = [];
        var n = arguments.length;
        for (var i = 1; i < n; i++) { // do not add first element (`type`) to args array
            args.push(arguments[i]);
        }

        return applyToNew(segmentConstructor, args);
    },

    Path.prototype = {

        // Accepts one segment or an array of segments as argument.
        // Throws an error if argument is not a segment or an array of segments.
        appendSegment: function(arg) {

            var segments = this.segments;
            var numSegments = segments.length;
            // works even if path has no segments

            var currentSegment;

            var previousSegment = ((numSegments !== 0) ? segments[numSegments - 1] : null); // if we are appending to an empty path, previousSegment is null
            var nextSegment = null;

            if (!Array.isArray(arg)) { // arg is a segment
                if (!arg || !arg.isSegment) throw new Error('Segment required.');

                currentSegment = this.prepareSegment(arg, previousSegment, nextSegment);
                segments.push(currentSegment);

            } else { // arg is an array of segments
                if (!arg[0].isSegment) throw new Error('Segments required.');

                var n = arg.length;
                for (var i = 0; i < n; i++) {

                    var currentArg = arg[i];
                    currentSegment = this.prepareSegment(currentArg, previousSegment, nextSegment);
                    segments.push(currentSegment);
                    previousSegment = currentSegment;
                }
            }
        },

        // Returns the bbox of the path.
        // If path has no segments, returns null.
        // If path has only invisible segments, returns bbox of the end point of last segment.
        bbox: function() {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            var bbox;
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                if (segment.isVisible) {
                    var segmentBBox = segment.bbox();
                    bbox = bbox ? bbox.union(segmentBBox) : segmentBBox;
                }
            }

            if (bbox) return bbox;

            // if the path has only invisible elements, return end point of last segment
            var lastSegment = segments[numSegments - 1];
            return new Rect(lastSegment.end.x, lastSegment.end.y, 0, 0);
        },

        // Returns a new path that is a clone of this path.
        clone: function() {

            var segments = this.segments;
            var numSegments = segments.length;
            // works even if path has no segments

            var path = new Path();
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i].clone();
                path.appendSegment(segment);
            }

            return path;
        },

        closestPoint: function(p, opt) {

            var t = this.closestPointT(p, opt);
            if (!t) return null;

            return this.pointAtT(t);
        },

        closestPointLength: function(p, opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            var localOpt = { precision: precision, segmentSubdivisions: segmentSubdivisions };

            var t = this.closestPointT(p, localOpt);
            if (!t) return 0;

            return this.lengthAtT(t, localOpt);
        },

        closestPointNormalizedLength: function(p, opt) {

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            var localOpt = { precision: precision, segmentSubdivisions: segmentSubdivisions };

            var cpLength = this.closestPointLength(p, localOpt);
            if (cpLength === 0) return 0; // shortcut

            var length = this.length(localOpt);
            if (length === 0) return 0; // prevents division by zero

            return cpLength / length;
        },

        // Private function.
        closestPointT: function(p, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var closestPointT;
            var minSquaredDistance = Infinity;
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                var subdivisions = segmentSubdivisions[i];

                if (segment.isVisible) {
                    var segmentClosestPointT = segment.closestPointT(p, { precision: precision, subdivisions: subdivisions });
                    var segmentClosestPoint = segment.pointAtT(segmentClosestPointT);
                    var squaredDistance = (new Line(segmentClosestPoint, p)).squaredLength();

                    if (squaredDistance < minSquaredDistance) {
                        closestPointT = { segmentIndex: i, value: segmentClosestPointT };
                        minSquaredDistance = squaredDistance;
                    }
                }
            }

            if (closestPointT) return closestPointT;

            // if no visible segment, return end of last segment
            return { segmentIndex: numSegments - 1, value: 1 };
        },

        closestPointTangent: function(p, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var closestPointTangent;
            var minSquaredDistance = Infinity;
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                var subdivisions = segmentSubdivisions[i];

                if (segment.isDifferentiable()) {
                    var segmentClosestPointT = segment.closestPointT(p, { precision: precision, subdivisions: subdivisions });
                    var segmentClosestPoint = segment.pointAtT(segmentClosestPointT);
                    var squaredDistance = (new Line(segmentClosestPoint, p)).squaredLength();

                    if (squaredDistance < minSquaredDistance) {
                        closestPointTangent = segment.tangentAtT(segmentClosestPointT);
                        minSquaredDistance = squaredDistance;
                    }
                }
            }

            if (closestPointTangent) return closestPointTangent;

            // if no valid segment, return null
            return null;
        },

        // Checks whether two paths are exactly the same.
        // If `p` is undefined or null, returns false.
        equals: function(p) {

            if (!p) return false;

            var segments = this.segments;
            var otherSegments = p.segments;

            var numSegments = segments.length;
            if (otherSegments.length !== numSegments) return false; // if the two paths have different number of segments, they cannot be equal

            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                var otherSegment = otherSegments[i];

                // as soon as an inequality is found in segments, return false
                if ((segment.type !== otherSegment.type) || (!segment.equals(otherSegment))) return false;
            }

            // if no inequality found in segments, return true
            return true;
        },

        // Accepts negative indices.
        // Throws an error if path has no segments.
        // Throws an error if index is out of range.
        getSegment: function(index) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (!numSegments === 0) throw new Error('Path has no segments.');

            if (index < 0) index = numSegments + index; // convert negative indices to positive
            if (index >= numSegments || index < 0) throw new Error('Index out of range.');

            return segments[index];
        },

        // Returns an array of segment subdivisions, with precision better than requested `opt.precision`.
        getSegmentSubdivisions: function(opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            // works even if path has no segments

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            // not using opt.segmentSubdivisions
            // not using localOpt

            var segmentSubdivisions = [];
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                var subdivisions = segment.getSubdivisions({ precision: precision });
                segmentSubdivisions.push(subdivisions);
            }

            return segmentSubdivisions;
        },

        // Insert `arg` at given `index`.
        // `index = 0` means insert at the beginning.
        // `index = segments.length` means insert at the end.
        // Accepts negative indices, from `-1` to `-(segments.length + 1)`.
        // Accepts one segment or an array of segments as argument.
        // Throws an error if index is out of range.
        // Throws an error if argument is not a segment or an array of segments.
        insertSegment: function(index, arg) {

            var segments = this.segments;
            var numSegments = segments.length;
            // works even if path has no segments

            // note that these are incremented comapared to getSegments()
            // we can insert after last element (note that this changes the meaning of index -1)
            if (index < 0) index = numSegments + index + 1; // convert negative indices to positive
            if (index > numSegments || index < 0) throw new Error('Index out of range.');

            var currentSegment;

            var previousSegment = null;
            var nextSegment = null;

            if (numSegments !== 0) {
                if (index >= 1) {
                    previousSegment = segments[index - 1];
                    nextSegment = previousSegment.nextSegment; // if we are inserting at end, nextSegment is null

                } else { // if index === 0
                    // previousSegment is null
                    nextSegment = segments[0];
                }
            }

            if (!Array.isArray(arg)) {
                if (!arg || !arg.isSegment) throw new Error('Segment required.');

                currentSegment = this.prepareSegment(arg, previousSegment, nextSegment);
                segments.splice(index, 0, currentSegment);

            } else {
                if (!arg[0].isSegment) throw new Error('Segments required.');

                var n = arg.length;
                for (var i = 0; i < n; i++) {

                    var currentArg = arg[i];
                    currentSegment = this.prepareSegment(currentArg, previousSegment, nextSegment);
                    segments.splice((index + i), 0, currentSegment); // incrementing index to insert subsequent segments after inserted segments
                    previousSegment = currentSegment;
                }
            }
        },

        isDifferentiable: function() {

            var segments = this.segments;
            var numSegments = segments.length;

            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                // as soon as a differentiable segment is found in segments, return true
                if (segment.isDifferentiable()) return true;
            }

            // if no differentiable segment is found in segments, return false
            return false;
        },

        // Checks whether current path segments are valid.
        // Note that d is allowed to be empty - should disable rendering of the path.
        isValid: function() {

            var segments = this.segments;
            var isValid = (segments.length === 0) || (segments[0].type === 'M'); // either empty or first segment is a Moveto
            return isValid;
        },

        // Returns length of the path, with precision better than requested `opt.precision`; or using `opt.segmentSubdivisions` provided.
        // If path has no segments, returns 0.
        length: function(opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return 0; // if segments is an empty array

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision; // opt.precision only used in getSegmentSubdivisions() call
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var length = 0;
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                var subdivisions = segmentSubdivisions[i];
                length += segment.length({ subdivisions: subdivisions });
            }

            return length;
        },

        // Private function.
        lengthAtT: function(t, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return 0; // if segments is an empty array

            var segmentIndex = t.segmentIndex;
            if (segmentIndex < 0) return 0; // regardless of t.value

            var tValue = t.value;
            if (segmentIndex >= numSegments) {
                segmentIndex = numSegments - 1;
                tValue = 1;
            }
            else if (tValue < 0) tValue = 0;
            else if (tValue > 1) tValue = 1;

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var subdivisions;
            var length = 0;
            for (var i = 0; i < segmentIndex; i++) {

                var segment = segments[i];
                subdivisions = segmentSubdivisions[i];
                length += segment.length({ precisison: precision, subdivisions: subdivisions });
            }

            segment = segments[segmentIndex];
            subdivisions = segmentSubdivisions[segmentIndex];
            length += segment.lengthAtT(tValue, { precisison: precision, subdivisions: subdivisions });

            return length;
        },

        // Returns point at requested `ratio` between 0 and 1, with precision better than requested `opt.precision`; optionally using `opt.segmentSubdivisions` provided.
        pointAt: function(ratio, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            if (ratio <= 0) return this.start.clone();
            if (ratio >= 1) return this.end.clone();

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            var localOpt = { precision: precision, segmentSubdivisions: segmentSubdivisions };

            var pathLength = this.length(localOpt);
            var length = pathLength * ratio;

            return this.pointAtLength(length, localOpt);
        },

        // Returns point at requested `length`, with precision better than requested `opt.precision`; optionally using `opt.segmentSubdivisions` provided.
        // Accepts negative length.
        pointAtLength: function(length, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            if (length === 0) return this.start.clone();

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var lastVisibleSegment;
            var l = 0; // length so far
            for (var i = (fromStart ? 0 : (numSegments - 1)); (fromStart ? (i < numSegments) : (i >= 0)); (fromStart ? (i++) : (i--))) {

                var segment = segments[i];
                var subdivisions = segmentSubdivisions[i];
                var d = segment.length({ precision: precision, subdivisions: subdivisions });

                if (segment.isVisible) {
                    if (length <= (l + d)) {
                        return segment.pointAtLength(((fromStart ? 1 : -1) * (length - l)), { precision: precision, subdivisions: subdivisions });
                    }

                    lastVisibleSegment = segment;
                }

                l += d;
            }

            // if length requested is higher than the length of the path, return last visible segment endpoint
            if (lastVisibleSegment) return (fromStart ? lastVisibleSegment.end : lastVisibleSegment.start);

            // if no visible segment, return last segment end point (no matter if fromStart or no)
            var lastSegment = segments[numSegments - 1];
            return lastSegment.end.clone();
        },

        // Private function.
        pointAtT: function(t) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            var segmentIndex = t.segmentIndex;
            if (segmentIndex < 0) return segments[0].pointAtT(0);
            if (segmentIndex >= numSegments) return segments[numSegments - 1].pointAtT(1);

            var tValue = t.value;
            if (tValue < 0) tValue = 0;
            else if (tValue > 1) tValue = 1;

            return segments[segmentIndex].pointAtT(tValue);
        },

        // Helper method for adding segments.
        prepareSegment: function(segment, previousSegment, nextSegment) {

            // insert after previous segment and before previous segment's next segment
            segment.previousSegment = previousSegment;
            segment.nextSegment = nextSegment;
            if (previousSegment) previousSegment.nextSegment = segment;
            if (nextSegment) nextSegment.previousSegment = segment;

            var updateSubpathStart = segment;
            if (segment.isSubpathStart) {
                segment.subpathStartSegment = segment; // assign self as subpath start segment
                updateSubpathStart = nextSegment; // start updating from next segment
            }

            // assign previous segment's subpath start (or self if it is a subpath start) to subsequent segments
            if (updateSubpathStart) this.updateSubpathStartSegment(updateSubpathStart);

            return segment;
        },

        // Default precision
        PRECISION: 3,

        // Remove the segment at `index`.
        // Accepts negative indices, from `-1` to `-segments.length`.
        // Throws an error if path has no segments.
        // Throws an error if index is out of range.
        removeSegment: function(index) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) throw new Error('Path has no segments.');

            if (index < 0) index = numSegments + index; // convert negative indices to positive
            if (index >= numSegments || index < 0) throw new Error('Index out of range.');

            var removedSegment = segments.splice(index, 1)[0];
            var previousSegment = removedSegment.previousSegment;
            var nextSegment = removedSegment.nextSegment;

            // link the previous and next segments together (if present)
            if (previousSegment) previousSegment.nextSegment = nextSegment; // may be null
            if (nextSegment) nextSegment.previousSegment = previousSegment; // may be null

            // if removed segment used to start a subpath, update all subsequent segments until another subpath start segment is reached
            if (removedSegment.isSubpathStart && nextSegment) this.updateSubpathStartSegment(nextSegment);
        },

        // Replace the segment at `index` with `arg`.
        // Accepts negative indices, from `-1` to `-segments.length`.
        // Accepts one segment or an array of segments as argument.
        // Throws an error if path has no segments.
        // Throws an error if index is out of range.
        // Throws an error if argument is not a segment or an array of segments.
        replaceSegment: function(index, arg) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) throw new Error('Path has no segments.');

            if (index < 0) index = numSegments + index; // convert negative indices to positive
            if (index >= numSegments || index < 0) throw new Error('Index out of range.');

            var currentSegment;

            var replacedSegment = segments[index];
            var previousSegment = replacedSegment.previousSegment;
            var nextSegment = replacedSegment.nextSegment;

            var updateSubpathStart = replacedSegment.isSubpathStart; // boolean: is an update of subpath starts necessary?

            if (!Array.isArray(arg)) {
                if (!arg || !arg.isSegment) throw new Error('Segment required.');

                currentSegment = this.prepareSegment(arg, previousSegment, nextSegment);
                segments.splice(index, 1, currentSegment); // directly replace

                if (updateSubpathStart && currentSegment.isSubpathStart) updateSubpathStart = false; // already updated by `prepareSegment`

            } else {
                if (!arg[0].isSegment) throw new Error('Segments required.');

                segments.splice(index, 1);

                var n = arg.length;
                for (var i = 0; i < n; i++) {

                    var currentArg = arg[i];
                    currentSegment = this.prepareSegment(currentArg, previousSegment, nextSegment);
                    segments.splice((index + i), 0, currentSegment); // incrementing index to insert subsequent segments after inserted segments
                    previousSegment = currentSegment;

                    if (updateSubpathStart && currentSegment.isSubpathStart) updateSubpathStart = false; // already updated by `prepareSegment`
                }
            }

            // if replaced segment used to start a subpath and no new subpath start was added, update all subsequent segments until another subpath start segment is reached
            if (updateSubpathStart && nextSegment) this.updateSubpathStartSegment(nextSegment);
        },

        scale: function(sx, sy, origin) {

            var segments = this.segments;
            var numSegments = segments.length;

            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                segment.scale(sx, sy, origin);
            }

            return this;
        },

        segmentAt: function(ratio, opt) {

            var index = this.segmentIndexAt(ratio, opt);
            if (!index) return null;

            return this.getSegment(index);
        },

        // Accepts negative length.
        segmentAtLength: function(length, opt) {

            var index = this.segmentIndexAtLength(length, opt);
            if (!index) return null;

            return this.getSegment(index);
        },

        segmentIndexAt: function(ratio, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            if (ratio < 0) ratio = 0;
            if (ratio > 1) ratio = 1;

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            var localOpt = { precision: precision, segmentSubdivisions: segmentSubdivisions };

            var pathLength = this.length(localOpt);
            var length = pathLength * ratio;

            return this.segmentIndexAtLength(length, localOpt);
        },

        toPoints: function(opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;

            var points = [];
            var partialPoints = [];
            for (var i = 0; i < numSegments; i++) {
                var segment = segments[i];
                if (segment.isVisible) {
                    var currentSegmentSubdivisions = segmentSubdivisions[i];
                    if (currentSegmentSubdivisions.length > 0) {
                        var subdivisionPoints = currentSegmentSubdivisions.map(function(curve) {
                            return curve.start;
                        });
                        Array.prototype.push.apply(partialPoints, subdivisionPoints);
                    } else {
                        partialPoints.push(segment.start);
                    }
                } else if (partialPoints.length > 0) {
                    partialPoints.push(segments[i - 1].end);
                    points.push(partialPoints);
                    partialPoints = [];
                }
            }

            if (partialPoints.length > 0) {
                partialPoints.push(this.end);
                points.push(partialPoints);
            }
            return points;
        },

        toPolylines: function(opt) {

            var polylines = [];
            var points = this.toPoints(opt);
            if (!points) return null;
            for (var i = 0, n = points.length; i < n; i++) {
                polylines.push(new Polyline(points[i]));
            }

            return polylines;
        },

        intersectionWithLine: function(line, opt) {

            var intersection = null;
            var polylines = this.toPolylines(opt);
            if (!polylines) return null;
            for (var i = 0, n = polylines.length; i < n; i++) {
                var polyline = polylines[i];
                var polylineIntersection = line.intersect(polyline);
                if (polylineIntersection) {
                    intersection || (intersection = []);
                    if (Array.isArray(polylineIntersection)) {
                        Array.prototype.push.apply(intersection, polylineIntersection);
                    } else {
                        intersection.push(polylineIntersection);
                    }
                }
            }

            return intersection;
        },

        // Accepts negative length.
        segmentIndexAtLength: function(length, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var lastVisibleSegmentIndex = null;
            var l = 0; // length so far
            for (var i = (fromStart ? 0 : (numSegments - 1)); (fromStart ? (i < numSegments) : (i >= 0)); (fromStart ? (i++) : (i--))) {

                var segment = segments[i];
                var subdivisions = segmentSubdivisions[i];
                var d = segment.length({ precision: precision, subdivisions: subdivisions });

                if (segment.isVisible) {
                    if (length <= (l + d)) return i;
                    lastVisibleSegmentIndex = i;
                }

                l += d;
            }

            // if length requested is higher than the length of the path, return last visible segment index
            // if no visible segment, return null
            return lastVisibleSegmentIndex;
        },

        // Returns tangent line at requested `ratio` between 0 and 1, with precision better than requested `opt.precision`; optionally using `opt.segmentSubdivisions` provided.
        tangentAt: function(ratio, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            if (ratio < 0) ratio = 0;
            if (ratio > 1) ratio = 1;

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            var localOpt = { precision: precision, segmentSubdivisions: segmentSubdivisions };

            var pathLength = this.length(localOpt);
            var length = pathLength * ratio;

            return this.tangentAtLength(length, localOpt);
        },

        // Returns tangent line at requested `length`, with precision better than requested `opt.precision`; optionally using `opt.segmentSubdivisions` provided.
        // Accepts negative length.
        tangentAtLength: function(length, opt) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            opt = opt || {};
            var precision = (opt.precision === undefined) ? this.PRECISION : opt.precision;
            var segmentSubdivisions = (opt.segmentSubdivisions === undefined) ? this.getSegmentSubdivisions({ precision: precision }) : opt.segmentSubdivisions;
            // not using localOpt

            var lastValidSegment; // visible AND differentiable (with a tangent)
            var l = 0; // length so far
            for (var i = (fromStart ? 0 : (numSegments - 1)); (fromStart ? (i < numSegments) : (i >= 0)); (fromStart ? (i++) : (i--))) {

                var segment = segments[i];
                var subdivisions = segmentSubdivisions[i];
                var d = segment.length({ precision: precision, subdivisions: subdivisions });

                if (segment.isDifferentiable()) {
                    if (length <= (l + d)) {
                        return segment.tangentAtLength(((fromStart ? 1 : -1) * (length - l)), { precision: precision, subdivisions: subdivisions });
                    }

                    lastValidSegment = segment;
                }

                l += d;
            }

            // if length requested is higher than the length of the path, return tangent of endpoint of last valid segment
            if (lastValidSegment) {
                var t = (fromStart ? 1 : 0);
                return lastValidSegment.tangentAtT(t);
            }

            // if no valid segment, return null
            return null;
        },

        // Private function.
        tangentAtT: function(t) {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null; // if segments is an empty array

            var segmentIndex = t.segmentIndex;
            if (segmentIndex < 0) return segments[0].tangentAtT(0);
            if (segmentIndex >= numSegments) return segments[numSegments - 1].tangentAtT(1);

            var tValue = t.value;
            if (tValue < 0) tValue = 0;
            else if (tValue > 1) tValue = 1;

            return segments[segmentIndex].tangentAtT(tValue);
        },

        translate: function(tx, ty) {

            var segments = this.segments;
            var numSegments = segments.length;

            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                segment.translate(tx, ty);
            }

            return this;
        },

        // Helper method for updating subpath start of segments, starting with the one provided.
        updateSubpathStartSegment: function(segment) {

            var previousSegment = segment.previousSegment; // may be null
            while (segment && !segment.isSubpathStart) {

                // assign previous segment's subpath start segment to this segment
                if (previousSegment) segment.subpathStartSegment = previousSegment.subpathStartSegment; // may be null
                else segment.subpathStartSegment = null; // if segment had no previous segment, assign null - creates an invalid path!

                previousSegment = segment;
                segment = segment.nextSegment; // move on to the segment after etc.
            }
        },

        // Returns a string that can be used to reconstruct the path.
        // Additional error checking compared to toString (must start with M segment).
        serialize: function() {

            if (!this.isValid()) throw new Error('Invalid path segments.');

            return this.toString();
        },

        toString: function() {

            var segments = this.segments;
            var numSegments = segments.length;

            var pathData = '';
            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                pathData += segment.serialize() + ' ';
            }

            return pathData.trim();
        }
    };

    Object.defineProperty(Path.prototype, 'start', {
        // Getter for the first visible endpoint of the path.

        configurable: true,

        enumerable: true,

        get: function() {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null;

            for (var i = 0; i < numSegments; i++) {

                var segment = segments[i];
                if (segment.isVisible) return segment.start;
            }

            // if no visible segment, return last segment end point
            return segments[numSegments - 1].end;
        }
    });

    Object.defineProperty(Path.prototype, 'end', {
        // Getter for the last visible endpoint of the path.

        configurable: true,

        enumerable: true,

        get: function() {

            var segments = this.segments;
            var numSegments = segments.length;
            if (numSegments === 0) return null;

            for (var i = numSegments - 1; i >= 0; i--) {

                var segment = segments[i];
                if (segment.isVisible) return segment.end;
            }

            // if no visible segment, return last segment end point
            return segments[numSegments - 1].end;
        }
    });

    /*
        Point is the most basic object consisting of x/y coordinate.

        Possible instantiations are:
        * `Point(10, 20)`
        * `new Point(10, 20)`
        * `Point('10 20')`
        * `Point(Point(10, 20))`
    */
    var Point = g.Point = function(x, y) {

        if (!(this instanceof Point)) {
            return new Point(x, y);
        }

        if (typeof x === 'string') {
            var xy = x.split(x.indexOf('@') === -1 ? ' ' : '@');
            x = parseFloat(xy[0]);
            y = parseFloat(xy[1]);

        } else if (Object(x) === x) {
            y = x.y;
            x = x.x;
        }

        this.x = x === undefined ? 0 : x;
        this.y = y === undefined ? 0 : y;
    };

    // Alternative constructor, from polar coordinates.
    // @param {number} Distance.
    // @param {number} Angle in radians.
    // @param {point} [optional] Origin.
    Point.fromPolar = function(distance, angle, origin) {

        origin = (origin && new Point(origin)) || new Point(0, 0);
        var x = abs(distance * cos(angle));
        var y = abs(distance * sin(angle));
        var deg = normalizeAngle(toDeg(angle));

        if (deg < 90) {
            y = -y;

        } else if (deg < 180) {
            x = -x;
            y = -y;

        } else if (deg < 270) {
            x = -x;
        }

        return new Point(origin.x + x, origin.y + y);
    };

    // Create a point with random coordinates that fall into the range `[x1, x2]` and `[y1, y2]`.
    Point.random = function(x1, x2, y1, y2) {

        return new Point(floor(random() * (x2 - x1 + 1) + x1), floor(random() * (y2 - y1 + 1) + y1));
    };

    Point.prototype = {

        // If point lies outside rectangle `r`, return the nearest point on the boundary of rect `r`,
        // otherwise return point itself.
        // (see Squeak Smalltalk, Point>>adhereTo:)
        adhereToRect: function(r) {

            if (r.containsPoint(this)) {
                return this;
            }

            this.x = min(max(this.x, r.x), r.x + r.width);
            this.y = min(max(this.y, r.y), r.y + r.height);
            return this;
        },

        // Return the bearing between me and the given point.
        bearing: function(point) {

            return (new Line(this, point)).bearing();
        },

        // Returns change in angle from my previous position (-dx, -dy) to my new position
        // relative to ref point.
        changeInAngle: function(dx, dy, ref) {

            // Revert the translation and measure the change in angle around x-axis.
            return this.clone().offset(-dx, -dy).theta(ref) - this.theta(ref);
        },

        clone: function() {

            return new Point(this);
        },

        difference: function(dx, dy) {

            if ((Object(dx) === dx)) {
                dy = dx.y;
                dx = dx.x;
            }

            return new Point(this.x - (dx || 0), this.y - (dy || 0));
        },

        // Returns distance between me and point `p`.
        distance: function(p) {

            return (new Line(this, p)).length();
        },

        squaredDistance: function(p) {

            return (new Line(this, p)).squaredLength();
        },

        equals: function(p) {

            return !!p &&
                this.x === p.x &&
                this.y === p.y;
        },

        magnitude: function() {

            return sqrt((this.x * this.x) + (this.y * this.y)) || 0.01;
        },

        // Returns a manhattan (taxi-cab) distance between me and point `p`.
        manhattanDistance: function(p) {

            return abs(p.x - this.x) + abs(p.y - this.y);
        },

        // Move point on line starting from ref ending at me by
        // distance distance.
        move: function(ref, distance) {

            var theta = toRad((new Point(ref)).theta(this));
            var offset = this.offset(cos(theta) * distance, -sin(theta) * distance);
            return offset;
        },

        // Scales x and y such that the distance between the point and the origin (0,0) is equal to the given length.
        normalize: function(length) {

            var scale = (length || 1) / this.magnitude();
            return this.scale(scale, scale);
        },

        // Offset me by the specified amount.
        offset: function(dx, dy) {

            if ((Object(dx) === dx)) {
                dy = dx.y;
                dx = dx.x;
            }

            this.x += dx || 0;
            this.y += dy || 0;
            return this;
        },

        // Returns a point that is the reflection of me with
        // the center of inversion in ref point.
        reflection: function(ref) {

            return (new Point(ref)).move(this, this.distance(ref));
        },

        // Rotate point by angle around origin.
        // Angle is flipped because this is a left-handed coord system (y-axis points downward).
        rotate: function(origin, angle) {

            origin = origin || new g.Point(0, 0);

            angle = toRad(normalizeAngle(-angle));
            var cosAngle = cos(angle);
            var sinAngle = sin(angle);

            var x = (cosAngle * (this.x - origin.x)) - (sinAngle * (this.y - origin.y)) + origin.x;
            var y = (sinAngle * (this.x - origin.x)) + (cosAngle * (this.y - origin.y)) + origin.y;

            this.x = x;
            this.y = y;
            return this;
        },

        round: function(precision) {

            var f = pow(10, precision || 0);
            this.x = round(this.x * f) / f;
            this.y = round(this.y * f) / f;
            return this;
        },

        // Scale point with origin.
        scale: function(sx, sy, origin) {

            origin = (origin && new Point(origin)) || new Point(0, 0);
            this.x = origin.x + sx * (this.x - origin.x);
            this.y = origin.y + sy * (this.y - origin.y);
            return this;
        },

        snapToGrid: function(gx, gy) {

            this.x = snapToGrid(this.x, gx);
            this.y = snapToGrid(this.y, gy || gx);
            return this;
        },

        // Compute the angle between me and `p` and the x axis.
        // (cartesian-to-polar coordinates conversion)
        // Return theta angle in degrees.
        theta: function(p) {

            p = new Point(p);

            // Invert the y-axis.
            var y = -(p.y - this.y);
            var x = p.x - this.x;
            var rad = atan2(y, x); // defined for all 0 corner cases

            // Correction for III. and IV. quadrant.
            if (rad < 0) {
                rad = 2 * PI + rad;
            }

            return 180 * rad / PI;
        },

        // Compute the angle between vector from me to p1 and the vector from me to p2.
        // ordering of points p1 and p2 is important!
        // theta function's angle convention:
        // returns angles between 0 and 180 when the angle is counterclockwise
        // returns angles between 180 and 360 to convert clockwise angles into counterclockwise ones
        // returns NaN if any of the points p1, p2 is coincident with this point
        angleBetween: function(p1, p2) {

            var angleBetween = (this.equals(p1) || this.equals(p2)) ? NaN : (this.theta(p2) - this.theta(p1));

            if (angleBetween < 0) {
                angleBetween += 360; // correction to keep angleBetween between 0 and 360
            }

            return angleBetween;
        },

        // Compute the angle between the vector from 0,0 to me and the vector from 0,0 to p.
        // Returns NaN if p is at 0,0.
        vectorAngle: function(p) {

            var zero = new Point(0,0);
            return zero.angleBetween(this, p);
        },

        toJSON: function() {

            return { x: this.x, y: this.y };
        },

        // Converts rectangular to polar coordinates.
        // An origin can be specified, otherwise it's 0@0.
        toPolar: function(o) {

            o = (o && new Point(o)) || new Point(0, 0);
            var x = this.x;
            var y = this.y;
            this.x = sqrt((x - o.x) * (x - o.x) + (y - o.y) * (y - o.y)); // r
            this.y = toRad(o.theta(new Point(x, y)));
            return this;
        },

        toString: function() {

            return this.x + '@' + this.y;
        },

        update: function(x, y) {

            this.x = x || 0;
            this.y = y || 0;
            return this;
        },

        // Returns the dot product of this point with given other point
        dot: function(p) {

            return p ? (this.x * p.x + this.y * p.y) : NaN;
        },

        // Returns the cross product of this point relative to two other points
        // this point is the common point
        // point p1 lies on the first vector, point p2 lies on the second vector
        // watch out for the ordering of points p1 and p2!
        // positive result indicates a clockwise ("right") turn from first to second vector
        // negative result indicates a counterclockwise ("left") turn from first to second vector
        // note that the above directions are reversed from the usual answer on the Internet
        // that is because we are in a left-handed coord system (because the y-axis points downward)
        cross: function(p1, p2) {

            return (p1 && p2) ? (((p2.x - this.x) * (p1.y - this.y)) - ((p2.y - this.y) * (p1.x - this.x))) : NaN;
        },


        // Linear interpolation
        lerp: function(p, t) {

            var x = this.x;
            var y = this.y;
            return new Point((1 - t) * x + t * p.x, (1 - t) * y + t * p.y);
        }
    };

    Point.prototype.translate = Point.prototype.offset;

    var Rect = g.Rect = function(x, y, w, h) {

        if (!(this instanceof Rect)) {
            return new Rect(x, y, w, h);
        }

        if ((Object(x) === x)) {
            y = x.y;
            w = x.width;
            h = x.height;
            x = x.x;
        }

        this.x = x === undefined ? 0 : x;
        this.y = y === undefined ? 0 : y;
        this.width = w === undefined ? 0 : w;
        this.height = h === undefined ? 0 : h;
    };

    Rect.fromEllipse = function(e) {

        e = new Ellipse(e);
        return new Rect(e.x - e.a, e.y - e.b, 2 * e.a, 2 * e.b);
    };

    Rect.prototype = {

        // Find my bounding box when I'm rotated with the center of rotation in the center of me.
        // @return r {rectangle} representing a bounding box
        bbox: function(angle) {

            if (!angle) return this.clone();

            var theta = toRad(angle || 0);
            var st = abs(sin(theta));
            var ct = abs(cos(theta));
            var w = this.width * ct + this.height * st;
            var h = this.width * st + this.height * ct;
            return new Rect(this.x + (this.width - w) / 2, this.y + (this.height - h) / 2, w, h);
        },

        bottomLeft: function() {

            return new Point(this.x, this.y + this.height);
        },

        bottomLine: function() {

            return new Line(this.bottomLeft(), this.bottomRight());
        },

        bottomMiddle: function() {

            return new Point(this.x + this.width / 2, this.y + this.height);
        },

        center: function() {

            return new Point(this.x + this.width / 2, this.y + this.height / 2);
        },

        clone: function() {

            return new Rect(this);
        },

        // @return {bool} true if point p is insight me
        containsPoint: function(p) {

            p = new Point(p);
            return p.x >= this.x && p.x <= this.x + this.width && p.y >= this.y && p.y <= this.y + this.height;
        },

        // @return {bool} true if rectangle `r` is inside me.
        containsRect: function(r) {

            var r0 = new Rect(this).normalize();
            var r1 = new Rect(r).normalize();
            var w0 = r0.width;
            var h0 = r0.height;
            var w1 = r1.width;
            var h1 = r1.height;

            if (!w0 || !h0 || !w1 || !h1) {
                // At least one of the dimensions is 0
                return false;
            }

            var x0 = r0.x;
            var y0 = r0.y;
            var x1 = r1.x;
            var y1 = r1.y;

            w1 += x1;
            w0 += x0;
            h1 += y1;
            h0 += y0;

            return x0 <= x1 && w1 <= w0 && y0 <= y1 && h1 <= h0;
        },

        corner: function() {

            return new Point(this.x + this.width, this.y + this.height);
        },

        // @return {boolean} true if rectangles are equal.
        equals: function(r) {

            var mr = (new Rect(this)).normalize();
            var nr = (new Rect(r)).normalize();
            return mr.x === nr.x && mr.y === nr.y && mr.width === nr.width && mr.height === nr.height;
        },

        // @return {rect} if rectangles intersect, {null} if not.
        intersect: function(r) {

            var myOrigin = this.origin();
            var myCorner = this.corner();
            var rOrigin = r.origin();
            var rCorner = r.corner();

            // No intersection found
            if (rCorner.x <= myOrigin.x ||
                rCorner.y <= myOrigin.y ||
                rOrigin.x >= myCorner.x ||
                rOrigin.y >= myCorner.y) return null;

            var x = max(myOrigin.x, rOrigin.x);
            var y = max(myOrigin.y, rOrigin.y);

            return new Rect(x, y, min(myCorner.x, rCorner.x) - x, min(myCorner.y, rCorner.y) - y);
        },

        intersectionWithLine: function(line) {

            var r = this;
            var rectLines = [ r.topLine(), r.rightLine(), r.bottomLine(), r.leftLine() ];
            var points = [];
            var dedupeArr = [];
            var pt, i;

            var n = rectLines.length;
            for (i = 0; i < n; i ++) {

                pt = line.intersect(rectLines[i]);
                if (pt !== null && dedupeArr.indexOf(pt.toString()) < 0) {
                    points.push(pt);
                    dedupeArr.push(pt.toString());
                }
            }

            return points.length > 0 ? points : null;
        },

        // Find point on my boundary where line starting
        // from my center ending in point p intersects me.
        // @param {number} angle If angle is specified, intersection with rotated rectangle is computed.
        intersectionWithLineFromCenterToPoint: function(p, angle) {

            p = new Point(p);
            var center = new Point(this.x + this.width / 2, this.y + this.height / 2);
            var result;

            if (angle) p.rotate(center, angle);

            // (clockwise, starting from the top side)
            var sides = [
                this.topLine(),
                this.rightLine(),
                this.bottomLine(),
                this.leftLine()
            ];
            var connector = new Line(center, p);

            for (var i = sides.length - 1; i >= 0; --i) {
                var intersection = sides[i].intersection(connector);
                if (intersection !== null) {
                    result = intersection;
                    break;
                }
            }
            if (result && angle) result.rotate(center, -angle);
            return result;
        },

        leftLine: function() {

            return new Line(this.topLeft(), this.bottomLeft());
        },

        leftMiddle: function() {

            return new Point(this.x , this.y + this.height / 2);
        },

        // Move and expand me.
        // @param r {rectangle} representing deltas
        moveAndExpand: function(r) {

            this.x += r.x || 0;
            this.y += r.y || 0;
            this.width += r.width || 0;
            this.height += r.height || 0;
            return this;
        },

        // Offset me by the specified amount.
        offset: function(dx, dy) {

            // pretend that this is a point and call offset()
            // rewrites x and y according to dx and dy
            return Point.prototype.offset.call(this, dx, dy);
        },

        // inflate by dx and dy, recompute origin [x, y]
        // @param dx {delta_x} representing additional size to x
        // @param dy {delta_y} representing additional size to y -
        // dy param is not required -> in that case y is sized by dx
        inflate: function(dx, dy) {

            if (dx === undefined) {
                dx = 0;
            }

            if (dy === undefined) {
                dy = dx;
            }

            this.x -= dx;
            this.y -= dy;
            this.width += 2 * dx;
            this.height += 2 * dy;

            return this;
        },

        // Normalize the rectangle; i.e., make it so that it has a non-negative width and height.
        // If width < 0 the function swaps the left and right corners,
        // and it swaps the top and bottom corners if height < 0
        // like in http://qt-project.org/doc/qt-4.8/qrectf.html#normalized
        normalize: function() {

            var newx = this.x;
            var newy = this.y;
            var newwidth = this.width;
            var newheight = this.height;
            if (this.width < 0) {
                newx = this.x + this.width;
                newwidth = -this.width;
            }
            if (this.height < 0) {
                newy = this.y + this.height;
                newheight = -this.height;
            }
            this.x = newx;
            this.y = newy;
            this.width = newwidth;
            this.height = newheight;
            return this;
        },

        origin: function() {

            return new Point(this.x, this.y);
        },

        // @return {point} a point on my boundary nearest to the given point.
        // @see Squeak Smalltalk, Rectangle>>pointNearestTo:
        pointNearestToPoint: function(point) {

            point = new Point(point);
            if (this.containsPoint(point)) {
                var side = this.sideNearestToPoint(point);
                switch (side){
                    case 'right': return new Point(this.x + this.width, point.y);
                    case 'left': return new Point(this.x, point.y);
                    case 'bottom': return new Point(point.x, this.y + this.height);
                    case 'top': return new Point(point.x, this.y);
                }
            }
            return point.adhereToRect(this);
        },

        rightLine: function() {

            return new Line(this.topRight(), this.bottomRight());
        },

        rightMiddle: function() {

            return new Point(this.x + this.width, this.y + this.height / 2);
        },

        round: function(precision) {

            var f = pow(10, precision || 0);
            this.x = round(this.x * f) / f;
            this.y = round(this.y * f) / f;
            this.width = round(this.width * f) / f;
            this.height = round(this.height * f) / f;
            return this;
        },

        // Scale rectangle with origin.
        scale: function(sx, sy, origin) {

            origin = this.origin().scale(sx, sy, origin);
            this.x = origin.x;
            this.y = origin.y;
            this.width *= sx;
            this.height *= sy;
            return this;
        },

        maxRectScaleToFit: function(rect, origin) {

            rect = new Rect(rect);
            origin || (origin = rect.center());

            var sx1, sx2, sx3, sx4, sy1, sy2, sy3, sy4;
            var ox = origin.x;
            var oy = origin.y;

            // Here we find the maximal possible scale for all corner points (for x and y axis) of the rectangle,
            // so when the scale is applied the point is still inside the rectangle.

            sx1 = sx2 = sx3 = sx4 = sy1 = sy2 = sy3 = sy4 = Infinity;

            // Top Left
            var p1 = rect.topLeft();
            if (p1.x < ox) {
                sx1 = (this.x - ox) / (p1.x - ox);
            }
            if (p1.y < oy) {
                sy1 = (this.y - oy) / (p1.y - oy);
            }
            // Bottom Right
            var p2 = rect.bottomRight();
            if (p2.x > ox) {
                sx2 = (this.x + this.width - ox) / (p2.x - ox);
            }
            if (p2.y > oy) {
                sy2 = (this.y + this.height - oy) / (p2.y - oy);
            }
            // Top Right
            var p3 = rect.topRight();
            if (p3.x > ox) {
                sx3 = (this.x + this.width - ox) / (p3.x - ox);
            }
            if (p3.y < oy) {
                sy3 = (this.y - oy) / (p3.y - oy);
            }
            // Bottom Left
            var p4 = rect.bottomLeft();
            if (p4.x < ox) {
                sx4 = (this.x - ox) / (p4.x - ox);
            }
            if (p4.y > oy) {
                sy4 = (this.y + this.height - oy) / (p4.y - oy);
            }

            return {
                sx: min(sx1, sx2, sx3, sx4),
                sy: min(sy1, sy2, sy3, sy4)
            };
        },

        maxRectUniformScaleToFit: function(rect, origin) {

            var scale = this.maxRectScaleToFit(rect, origin);
            return min(scale.sx, scale.sy);
        },

        // @return {string} (left|right|top|bottom) side which is nearest to point
        // @see Squeak Smalltalk, Rectangle>>sideNearestTo:
        sideNearestToPoint: function(point) {

            point = new Point(point);
            var distToLeft = point.x - this.x;
            var distToRight = (this.x + this.width) - point.x;
            var distToTop = point.y - this.y;
            var distToBottom = (this.y + this.height) - point.y;
            var closest = distToLeft;
            var side = 'left';

            if (distToRight < closest) {
                closest = distToRight;
                side = 'right';
            }
            if (distToTop < closest) {
                closest = distToTop;
                side = 'top';
            }
            if (distToBottom < closest) {
                closest = distToBottom;
                side = 'bottom';
            }
            return side;
        },

        snapToGrid: function(gx, gy) {

            var origin = this.origin().snapToGrid(gx, gy);
            var corner = this.corner().snapToGrid(gx, gy);
            this.x = origin.x;
            this.y = origin.y;
            this.width = corner.x - origin.x;
            this.height = corner.y - origin.y;
            return this;
        },

        topLine: function() {

            return new Line(this.topLeft(), this.topRight());
        },

        topMiddle: function() {

            return new Point(this.x + this.width / 2, this.y);
        },

        topRight: function() {

            return new Point(this.x + this.width, this.y);
        },

        toJSON: function() {

            return { x: this.x, y: this.y, width: this.width, height: this.height };
        },

        toString: function() {

            return this.origin().toString() + ' ' + this.corner().toString();
        },

        // @return {rect} representing the union of both rectangles.
        union: function(rect) {

            rect = new Rect(rect);
            var myOrigin = this.origin();
            var myCorner = this.corner();
            var rOrigin = rect.origin();
            var rCorner = rect.corner();

            var originX = min(myOrigin.x, rOrigin.x);
            var originY = min(myOrigin.y, rOrigin.y);
            var cornerX = max(myCorner.x, rCorner.x);
            var cornerY = max(myCorner.y, rCorner.y);

            return new Rect(originX, originY, cornerX - originX, cornerY - originY);
        }
    };

    Rect.prototype.bottomRight = Rect.prototype.corner;

    Rect.prototype.topLeft = Rect.prototype.origin;

    Rect.prototype.translate = Rect.prototype.offset;

    var Polyline = g.Polyline = function(points) {

        if (!(this instanceof Polyline)) {
            return new Polyline(points);
        }

        if (typeof points === 'string') {
            return new Polyline.parse(points);
        }

        this.points = (Array.isArray(points) ? points.map(Point) : []);
    };

    Polyline.parse = function(svgString) {

        if (svgString === '') return new Polyline();

        var points = [];

        var coords = svgString.split(/\s|,/);
        var n = coords.length;
        for (var i = 0; i < n; i += 2) {
            points.push({ x: +coords[i], y: +coords[i + 1] });
        }

        return new Polyline(points);
    };

    Polyline.prototype = {

        bbox: function() {

            var x1 = Infinity;
            var x2 = -Infinity;
            var y1 = Infinity;
            var y2 = -Infinity;

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty

            for (var i = 0; i < numPoints; i++) {

                var point = points[i];
                var x = point.x;
                var y = point.y;

                if (x < x1) x1 = x;
                if (x > x2) x2 = x;
                if (y < y1) y1 = y;
                if (y > y2) y2 = y;
            }

            return new Rect(x1, y1, x2 - x1, y2 - y1);
        },

        clone: function() {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return new Polyline(); // if points array is empty

            var newPoints = [];
            for (var i = 0; i < numPoints; i++) {

                var point = points[i].clone();
                newPoints.push(point);
            }

            return new Polyline(newPoints);
        },

        closestPoint: function(p) {

            var cpLength = this.closestPointLength(p);

            return this.pointAtLength(cpLength);
        },

        closestPointLength: function(p) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return 0; // if points array is empty
            if (numPoints === 1) return 0; // if there is only one point

            var cpLength;
            var minSqrDistance = Infinity;
            var length = 0;
            var n = numPoints - 1;
            for (var i = 0; i < n; i++) {

                var line = new Line(points[i], points[i + 1]);
                var lineLength = line.length();

                var cpNormalizedLength = line.closestPointNormalizedLength(p);
                var cp = line.pointAt(cpNormalizedLength);

                var sqrDistance = cp.squaredDistance(p);
                if (sqrDistance < minSqrDistance) {
                    minSqrDistance = sqrDistance;
                    cpLength = length + (cpNormalizedLength * lineLength);
                }

                length += lineLength;
            }

            return cpLength;
        },

        closestPointNormalizedLength: function(p) {

            var cpLength = this.closestPointLength(p);
            if (cpLength === 0) return 0; // shortcut

            var length = this.length();
            if (length === 0) return 0; // prevents division by zero

            return cpLength / length;
        },

        closestPointTangent: function(p) {

            var cpLength = this.closestPointLength(p);

            return this.tangentAtLength(cpLength);
        },

        // Returns a convex-hull polyline from this polyline.
        // Implements the Graham scan (https://en.wikipedia.org/wiki/Graham_scan).
        // Output polyline starts at the first element of the original polyline that is on the hull, then continues clockwise.
        // Minimal polyline is found (only vertices of the hull are reported, no collinear points).
        convexHull: function() {

            var i;
            var n;

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return new Polyline(); // if points array is empty

            // step 1: find the starting point - point with the lowest y (if equality, highest x)
            var startPoint;
            for (i = 0; i < numPoints; i++) {
                if (startPoint === undefined) {
                    // if this is the first point we see, set it as start point
                    startPoint = points[i];

                } else if (points[i].y < startPoint.y) {
                    // start point should have lowest y from all points
                    startPoint = points[i];

                } else if ((points[i].y === startPoint.y) && (points[i].x > startPoint.x)) {
                    // if two points have the lowest y, choose the one that has highest x
                    // there are no points to the right of startPoint - no ambiguity about theta 0
                    // if there are several coincident start point candidates, first one is reported
                    startPoint = points[i];
                }
            }

            // step 2: sort the list of points
            // sorting by angle between line from startPoint to point and the x-axis (theta)

            // step 2a: create the point records = [point, originalIndex, angle]
            var sortedPointRecords = [];
            for (i = 0; i < numPoints; i++) {

                var angle = startPoint.theta(points[i]);
                if (angle === 0) {
                    angle = 360; // give highest angle to start point
                    // the start point will end up at end of sorted list
                    // the start point will end up at beginning of hull points list
                }

                var entry = [points[i], i, angle];
                sortedPointRecords.push(entry);
            }

            // step 2b: sort the list in place
            sortedPointRecords.sort(function(record1, record2) {
                // returning a negative number here sorts record1 before record2
                // if first angle is smaller than second, first angle should come before second

                var sortOutput = record1[2] - record2[2];  // negative if first angle smaller
                if (sortOutput === 0) {
                    // if the two angles are equal, sort by originalIndex
                    sortOutput = record2[1] - record1[1]; // negative if first index larger
                    // coincident points will be sorted in reverse-numerical order
                    // so the coincident points with lower original index will be considered first
                }

                return sortOutput;
            });

            // step 2c: duplicate start record from the top of the stack to the bottom of the stack
            if (sortedPointRecords.length > 2) {
                var startPointRecord = sortedPointRecords[sortedPointRecords.length-1];
                sortedPointRecords.unshift(startPointRecord);
            }

            // step 3a: go through sorted points in order and find those with right turns
            // we want to get our results in clockwise order
            var insidePoints = {}; // dictionary of points with left turns - cannot be on the hull
            var hullPointRecords = []; // stack of records with right turns - hull point candidates

            var currentPointRecord;
            var currentPoint;
            var lastHullPointRecord;
            var lastHullPoint;
            var secondLastHullPointRecord;
            var secondLastHullPoint;
            while (sortedPointRecords.length !== 0) {

                currentPointRecord = sortedPointRecords.pop();
                currentPoint = currentPointRecord[0];

                // check if point has already been discarded
                // keys for insidePoints are stored in the form 'point.x@point.y@@originalIndex'
                if (insidePoints.hasOwnProperty(currentPointRecord[0] + '@@' + currentPointRecord[1])) {
                    // this point had an incorrect turn at some previous iteration of this loop
                    // this disqualifies it from possibly being on the hull
                    continue;
                }

                var correctTurnFound = false;
                while (!correctTurnFound) {

                    if (hullPointRecords.length < 2) {
                        // not enough points for comparison, just add current point
                        hullPointRecords.push(currentPointRecord);
                        correctTurnFound = true;

                    } else {
                        lastHullPointRecord = hullPointRecords.pop();
                        lastHullPoint = lastHullPointRecord[0];
                        secondLastHullPointRecord = hullPointRecords.pop();
                        secondLastHullPoint = secondLastHullPointRecord[0];

                        var crossProduct = secondLastHullPoint.cross(lastHullPoint, currentPoint);

                        if (crossProduct < 0) {
                            // found a right turn
                            hullPointRecords.push(secondLastHullPointRecord);
                            hullPointRecords.push(lastHullPointRecord);
                            hullPointRecords.push(currentPointRecord);
                            correctTurnFound = true;

                        } else if (crossProduct === 0) {
                            // the three points are collinear
                            // three options:
                            // there may be a 180 or 0 degree angle at lastHullPoint
                            // or two of the three points are coincident
                            var THRESHOLD = 1e-10; // we have to take rounding errors into account
                            var angleBetween = lastHullPoint.angleBetween(secondLastHullPoint, currentPoint);
                            if (abs(angleBetween - 180) < THRESHOLD) { // rouding around 180 to 180
                                // if the cross product is 0 because the angle is 180 degrees
                                // discard last hull point (add to insidePoints)
                                //insidePoints.unshift(lastHullPoint);
                                insidePoints[lastHullPointRecord[0] + '@@' + lastHullPointRecord[1]] = lastHullPoint;
                                // reenter second-to-last hull point (will be last at next iter)
                                hullPointRecords.push(secondLastHullPointRecord);
                                // do not do anything with current point
                                // correct turn not found

                            } else if (lastHullPoint.equals(currentPoint) || secondLastHullPoint.equals(lastHullPoint)) {
                                // if the cross product is 0 because two points are the same
                                // discard last hull point (add to insidePoints)
                                //insidePoints.unshift(lastHullPoint);
                                insidePoints[lastHullPointRecord[0] + '@@' + lastHullPointRecord[1]] = lastHullPoint;
                                // reenter second-to-last hull point (will be last at next iter)
                                hullPointRecords.push(secondLastHullPointRecord);
                                // do not do anything with current point
                                // correct turn not found

                            } else if (abs(((angleBetween + 1) % 360) - 1) < THRESHOLD) { // rounding around 0 and 360 to 0
                                // if the cross product is 0 because the angle is 0 degrees
                                // remove last hull point from hull BUT do not discard it
                                // reenter second-to-last hull point (will be last at next iter)
                                hullPointRecords.push(secondLastHullPointRecord);
                                // put last hull point back into the sorted point records list
                                sortedPointRecords.push(lastHullPointRecord);
                                // we are switching the order of the 0deg and 180deg points
                                // correct turn not found
                            }

                        } else {
                            // found a left turn
                            // discard last hull point (add to insidePoints)
                            //insidePoints.unshift(lastHullPoint);
                            insidePoints[lastHullPointRecord[0] + '@@' + lastHullPointRecord[1]] = lastHullPoint;
                            // reenter second-to-last hull point (will be last at next iter of loop)
                            hullPointRecords.push(secondLastHullPointRecord);
                            // do not do anything with current point
                            // correct turn not found
                        }
                    }
                }
            }
            // at this point, hullPointRecords contains the output points in clockwise order
            // the points start with lowest-y,highest-x startPoint, and end at the same point

            // step 3b: remove duplicated startPointRecord from the end of the array
            if (hullPointRecords.length > 2) {
                hullPointRecords.pop();
            }

            // step 4: find the lowest originalIndex record and put it at the beginning of hull
            var lowestHullIndex; // the lowest originalIndex on the hull
            var indexOfLowestHullIndexRecord = -1; // the index of the record with lowestHullIndex
            n = hullPointRecords.length;
            for (i = 0; i < n; i++) {

                var currentHullIndex = hullPointRecords[i][1];

                if (lowestHullIndex === undefined || currentHullIndex < lowestHullIndex) {
                    lowestHullIndex = currentHullIndex;
                    indexOfLowestHullIndexRecord = i;
                }
            }

            var hullPointRecordsReordered = [];
            if (indexOfLowestHullIndexRecord > 0) {
                var newFirstChunk = hullPointRecords.slice(indexOfLowestHullIndexRecord);
                var newSecondChunk = hullPointRecords.slice(0, indexOfLowestHullIndexRecord);
                hullPointRecordsReordered = newFirstChunk.concat(newSecondChunk);

            } else {
                hullPointRecordsReordered = hullPointRecords;
            }

            var hullPoints = [];
            n = hullPointRecordsReordered.length;
            for (i = 0; i < n; i++) {
                hullPoints.push(hullPointRecordsReordered[i][0]);
            }

            return new Polyline(hullPoints);
        },

        // Checks whether two polylines are exactly the same.
        // If `p` is undefined or null, returns false.
        equals: function(p) {

            if (!p) return false;

            var points = this.points;
            var otherPoints = p.points;

            var numPoints = points.length;
            if (otherPoints.length !== numPoints) return false; // if the two polylines have different number of points, they cannot be equal

            for (var i = 0; i < numPoints; i++) {

                var point = points[i];
                var otherPoint = p.points[i];

                // as soon as an inequality is found in points, return false
                if (!point.equals(otherPoint)) return false;
            }

            // if no inequality found in points, return true
            return true;
        },

        isDifferentiable: function() {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return false;

            var n = numPoints - 1;
            for (var i = 0; i < n; i++) {

                var a = points[i];
                var b = points[i + 1];
                var line = new Line(a, b);

                // as soon as a differentiable line is found between two points, return true
                if (line.isDifferentiable()) return true;
            }

            // if no differentiable line is found between pairs of points, return false
            return false;
        },

        length: function() {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return 0; // if points array is empty

            var length = 0;
            var n = numPoints - 1;
            for (var i = 0; i < n; i++) {
                length += points[i].distance(points[i + 1]);
            }

            return length;
        },

        pointAt: function(ratio) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty
            if (numPoints === 1) return points[0].clone(); // if there is only one point

            if (ratio <= 0) return points[0].clone();
            if (ratio >= 1) return points[numPoints - 1].clone();

            var polylineLength = this.length();
            var length = polylineLength * ratio;

            return this.pointAtLength(length);
        },

        pointAtLength: function(length) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty
            if (numPoints === 1) return points[0].clone(); // if there is only one point

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            var l = 0;
            var n = numPoints - 1;
            for (var i = (fromStart ? 0 : (n - 1)); (fromStart ? (i < n) : (i >= 0)); (fromStart ? (i++) : (i--))) {

                var a = points[i];
                var b = points[i + 1];
                var line = new Line(a, b);
                var d = a.distance(b);

                if (length <= (l + d)) {
                    return line.pointAtLength((fromStart ? 1 : -1) * (length - l));
                }

                l += d;
            }

            // if length requested is higher than the length of the polyline, return last endpoint
            var lastPoint = (fromStart ? points[numPoints - 1] : points[0]);
            return lastPoint.clone();
        },

        scale: function(sx, sy, origin) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return this; // if points array is empty

            for (var i = 0; i < numPoints; i++) {
                points[i].scale(sx, sy, origin);
            }

            return this;
        },

        tangentAt: function(ratio) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty
            if (numPoints === 1) return null; // if there is only one point

            if (ratio < 0) ratio = 0;
            if (ratio > 1) ratio = 1;

            var polylineLength = this.length();
            var length = polylineLength * ratio;

            return this.tangentAtLength(length);
        },

        tangentAtLength: function(length) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty
            if (numPoints === 1) return null; // if there is only one point

            var fromStart = true;
            if (length < 0) {
                fromStart = false; // negative lengths mean start calculation from end point
                length = -length; // absolute value
            }

            var lastValidLine; // differentiable (with a tangent)
            var l = 0; // length so far
            var n = numPoints - 1;
            for (var i = (fromStart ? (0) : (n - 1)); (fromStart ? (i < n) : (i >= 0)); (fromStart ? (i++) : (i--))) {

                var a = points[i];
                var b = points[i + 1];
                var line = new Line(a, b);
                var d = a.distance(b);

                if (line.isDifferentiable()) { // has a tangent line (line length is not 0)
                    if (length <= (l + d)) {
                        return line.tangentAtLength((fromStart ? 1 : -1) * (length - l));
                    }

                    lastValidLine = line;
                }

                l += d;
            }

            // if length requested is higher than the length of the polyline, return last valid endpoint
            if (lastValidLine) {
                var ratio = (fromStart ? 1 : 0);
                return lastValidLine.tangentAt(ratio);
            }

            // if no valid line, return null
            return null;
        },

        intersectionWithLine: function(l) {
            var line = new Line(l);
            var intersections = [];
            var points = this.points;
            for (var i = 0, n = points.length - 1; i < n; i++) {
                var a = points[i];
                var b = points[i+1];
                var l2 = new Line(a, b);
                var int = line.intersectionWithLine(l2);
                if (int) intersections.push(int[0]);
            }
            return (intersections.length > 0) ? intersections : null;
        },

        translate: function(tx, ty) {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return this; // if points array is empty

            for (var i = 0; i < numPoints; i++) {
                points[i].translate(tx, ty);
            }

            return this;
        },

        // Return svgString that can be used to recreate this line.
        serialize: function() {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return ''; // if points array is empty

            var output = '';
            for (var i = 0; i < numPoints; i++) {

                var point = points[i];
                output += point.x + ',' + point.y + ' ';
            }

            return output.trim();
        },

        toString: function() {

            return this.points + '';
        }
    };

    Object.defineProperty(Polyline.prototype, 'start', {
        // Getter for the first point of the polyline.

        configurable: true,

        enumerable: true,

        get: function() {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty

            return this.points[0];
        },
    });

    Object.defineProperty(Polyline.prototype, 'end', {
        // Getter for the last point of the polyline.

        configurable: true,

        enumerable: true,

        get: function() {

            var points = this.points;
            var numPoints = points.length;
            if (numPoints === 0) return null; // if points array is empty

            return this.points[numPoints - 1];
        },
    });

    g.scale = {

        // Return the `value` from the `domain` interval scaled to the `range` interval.
        linear: function(domain, range, value) {

            var domainSpan = domain[1] - domain[0];
            var rangeSpan = range[1] - range[0];
            return (((value - domain[0]) / domainSpan) * rangeSpan + range[0]) || 0;
        }
    };

    var normalizeAngle = g.normalizeAngle = function(angle) {

        return (angle % 360) + (angle < 0 ? 360 : 0);
    };

    var snapToGrid = g.snapToGrid = function(value, gridSize) {

        return gridSize * round(value / gridSize);
    };

    var toDeg = g.toDeg = function(rad) {

        return (180 * rad / PI) % 360;
    };

    var toRad = g.toRad = function(deg, over360) {

        over360 = over360 || false;
        deg = over360 ? deg : (deg % 360);
        return deg * PI / 180;
    };

    // For backwards compatibility:
    g.ellipse = g.Ellipse;
    g.line = g.Line;
    g.point = g.Point;
    g.rect = g.Rect;

    // Local helper function.
    // Use an array of arguments to call a constructor (function called with `new`).
    // Adapted from https://stackoverflow.com/a/8843181/2263595
    // It is not necessary to use this function if the arguments can be passed separately (i.e. if the number of arguments is limited).
    // - If that is the case, use `new constructor(arg1, arg2)`, for example.
    // It is not necessary to use this function if the function that needs an array of arguments is not supposed to be used as a constructor.
    // - If that is the case, use `f.apply(thisArg, [arg1, arg2...])`, for example.
    function applyToNew(constructor, argsArray) {
        // The `new` keyword can only be applied to functions that take a limited number of arguments.
        // - We can fake that with .bind().
        // - It calls a function (`constructor`, here) with the arguments that were provided to it - effectively transforming an unlimited number of arguments into limited.
        // - So `new (constructor.bind(thisArg, arg1, arg2...))`
        // - `thisArg` can be anything (e.g. null) because `new` keyword resets context to the constructor object.
        // We need to pass in a variable number of arguments to the bind() call.
        // - We can use .apply().
        // - So `new (constructor.bind.apply(constructor, [thisArg, arg1, arg2...]))`
        // - `thisArg` can still be anything because `new` overwrites it.
        // Finally, to make sure that constructor.bind overwriting is not a problem, we switch to `Function.prototype.bind`.
        // - So, the final version is `new (Function.prototype.bind.apply(constructor, [thisArg, arg1, arg2...]))`

        // The function expects `argsArray[0]` to be `thisArg`.
        // - This means that whatever is sent as the first element will be ignored.
        // - The constructor will only see arguments starting from argsArray[1].
        // - So, a new dummy element is inserted at the start of the array.
        argsArray.unshift(null);

        return new (Function.prototype.bind.apply(constructor, argsArray));
    }

    // Local helper function.
    // Add properties from arguments on top of properties from `obj`.
    // This allows for rudimentary inheritance.
    // - The `obj` argument acts as parent.
    // - This function creates a new object that inherits all `obj` properties and adds/replaces those that are present in arguments.
    // - A high-level example: calling `extend(Vehicle, Car)` would be akin to declaring `class Car extends Vehicle`.
    function extend(obj) {
        // In JavaScript, the combination of a constructor function (e.g. `g.Line = function(...) {...}`) and prototype (e.g. `g.Line.prototype = {...}) is akin to a C++ class.
        // - When inheritance is not necessary, we can leave it at that. (This would be akin to calling extend with only `obj`.)
        // - But, what if we wanted the `g.Line` quasiclass to inherit from another quasiclass (let's call it `g.GeometryObject`) in JavaScript?
        // - First, realize that both of those quasiclasses would still have their own separate constructor function.
        // - So what we are actually saying is that we want the `g.Line` prototype to inherit from `g.GeometryObject` prototype.
        // - This method provides a way to do exactly that.
        // - It copies parent prototype's properties, then adds extra ones from child prototype/overrides parent prototype properties with child prototype properties.
        // - Therefore, to continue with the example above:
        //   - `g.Line.prototype = extend(g.GeometryObject.prototype, linePrototype)`
        //   - Where `linePrototype` is a properties object that looks just like `g.Line.prototype` does right now.
        //   - Then, `g.Line` would allow the programmer to access to all methods currently in `g.Line.Prototype`, plus any non-overriden methods from `g.GeometryObject.prototype`.
        //   - In that aspect, `g.GeometryObject` would then act like the parent of `g.Line`.
        // - Multiple inheritance is also possible, if multiple arguments are provided.
        // - What if we wanted to add another level of abstraction between `g.GeometryObject` and `g.Line` (let's call it `g.LinearObject`)?
        //   - `g.Line.prototype = extend(g.GeometryObject.prototype, g.LinearObject.prototype, linePrototype)`
        //   - The ancestors are applied in order of appearance.
        //   - That means that `g.Line` would have inherited from `g.LinearObject` that would have inherited from `g.GeometryObject`.
        //   - Any number of ancestors may be provided.
        // - Note that neither `obj` nor any of the arguments need to actually be prototypes of any JavaScript quasiclass, that was just a simplified explanation.
        // - We can create a new object composed from the properties of any number of other objects (since they do not have a constructor, we can think of those as interfaces).
        //   - `extend({ a: 1, b: 2 }, { b: 10, c: 20 }, { c: 100, d: 200 })` gives `{ a: 1, b: 10, c: 100, d: 200 }`.
        //   - Basically, with this function, we can emulate the `extends` keyword as well as the `implements` keyword.
        // - Therefore, both of the following are valid:
        //   - `Lineto.prototype = extend(Line.prototype, segmentPrototype, linetoPrototype)`
        //   - `Moveto.prototype = extend(segmentPrototype, movetoPrototype)`

        var i;
        var n;

        var args = [];
        n = arguments.length;
        for (i = 1; i < n; i++) { // skip over obj
            args.push(arguments[i]);
        }

        if (!obj) throw new Error('Missing a parent object.');
        var child = Object.create(obj);

        n = args.length;
        for (i = 0; i < n; i++) {

            var src = args[i];

            var inheritedProperty;
            var key;
            for (key in src) {

                if (src.hasOwnProperty(key)) {
                    delete child[key]; // delete property inherited from parent
                    inheritedProperty = Object.getOwnPropertyDescriptor(src, key); // get new definition of property from src
                    Object.defineProperty(child, key, inheritedProperty); // re-add property with new definition (includes getter/setter methods)
                }
            }
        }

        return child;
    }

    // Path segment interface:
    var segmentPrototype = {

        // Redirect calls to closestPointNormalizedLength() function if closestPointT() is not defined for segment.
        closestPointT: function(p) {

            if (this.closestPointNormalizedLength) return this.closestPointNormalizedLength(p);

            throw new Error('Neither closestPointT() nor closestPointNormalizedLength() function is implemented.');
        },

        isSegment: true,

        isSubpathStart: false, // true for Moveto segments

        isVisible: true, // false for Moveto segments

        nextSegment: null, // needed for subpath start segment updating

        // Return a fraction of result of length() function if lengthAtT() is not defined for segment.
        lengthAtT: function(t) {

            if (t <= 0) return 0;

            var length = this.length();

            if (t >= 1) return length;

            return length * t;
        },

        // Redirect calls to pointAt() function if pointAtT() is not defined for segment.
        pointAtT: function(t) {

            if (this.pointAt) return this.pointAt(t);

            throw new Error('Neither pointAtT() nor pointAt() function is implemented.');
        },

        previousSegment: null, // needed to get segment start property

        subpathStartSegment: null, // needed to get closepath segment end property

        // Redirect calls to tangentAt() function if tangentAtT() is not defined for segment.
        tangentAtT: function(t) {

            if (this.tangentAt) return this.tangentAt(t);

            throw new Error('Neither tangentAtT() nor tangentAt() function is implemented.');
        },

        // VIRTUAL PROPERTIES (must be overriden by actual Segment implementations):

        // type

        // start // getter, always throws error for Moveto

        // end // usually directly assigned, getter for Closepath

        bbox: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        clone: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        closestPoint: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        closestPointLength: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        closestPointNormalizedLength: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        closestPointTangent: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        equals: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        getSubdivisions: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        isDifferentiable: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        length: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        pointAt: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        pointAtLength: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        scale: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        tangentAt: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        tangentAtLength: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        translate: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        serialize: function() {

            throw new Error('Declaration missing for virtual function.');
        },

        toString: function() {

            throw new Error('Declaration missing for virtual function.');
        }
    };

    // Path segment implementations:
    var Lineto = function() {

        var args = [];
        var n = arguments.length;
        for (var i = 0; i < n; i++) {
            args.push(arguments[i]);
        }

        if (!(this instanceof Lineto)) { // switching context of `this` to Lineto when called without `new`
            return applyToNew(Lineto, args);
        }

        if (n === 0) {
            throw new Error('Lineto constructor expects 1 point or 2 coordinates (none provided).');
        }

        var outputArray;

        if (typeof args[0] === 'string' || typeof args[0] === 'number') { // coordinates provided
            if (n === 2) {
                this.end = new Point(+args[0], +args[1]);
                return this;

            } else if (n < 2) {
                throw new Error('Lineto constructor expects 1 point or 2 coordinates (' + n + ' coordinates provided).');

            } else { // this is a poly-line segment
                var segmentCoords;
                outputArray = [];
                for (i = 0; i < n; i += 2) { // coords come in groups of two

                    segmentCoords = args.slice(i, i + 2); // will send one coord if args.length not divisible by 2
                    outputArray.push(applyToNew(Lineto, segmentCoords));
                }
                return outputArray;
            }

        } else { // points provided
            if (n === 1) {
                this.end = new Point(args[0]);
                return this;

            } else { // this is a poly-line segment
                var segmentPoint;
                outputArray = [];
                for (i = 0; i < n; i += 1) {

                    segmentPoint = args[i];
                    outputArray.push(new Lineto(segmentPoint));
                }
                return outputArray;
            }
        }
    };

    var linetoPrototype = {

        clone: function() {

            return new Lineto(this.end);
        },

        getSubdivisions: function() {

            return [];
        },

        isDifferentiable: function() {

            if (!this.previousSegment) return false;

            return !this.start.equals(this.end);
        },

        scale: function(sx, sy, origin) {

            this.end.scale(sx, sy, origin);
            return this;
        },

        translate: function(tx, ty) {

            this.end.translate(tx, ty);
            return this;
        },

        type: 'L',

        serialize: function() {

            var end = this.end;
            return this.type + ' ' + end.x + ' ' + end.y;
        },

        toString: function() {

            return this.type + ' ' + this.start + ' ' + this.end;
        }
    };

    Object.defineProperty(linetoPrototype, 'start', {
        // get a reference to the end point of previous segment

        configurable: true,

        enumerable: true,

        get: function() {

            if (!this.previousSegment) throw new Error('Missing previous segment. (This segment cannot be the first segment of a path; OR segment has not yet been added to a path.)');

            return this.previousSegment.end;
        }
    });

    Lineto.prototype = extend(segmentPrototype, Line.prototype, linetoPrototype);

    var Curveto = function() {

        var args = [];
        var n = arguments.length;
        for (var i = 0; i < n; i++) {
            args.push(arguments[i]);
        }

        if (!(this instanceof Curveto)) { // switching context of `this` to Curveto when called without `new`
            return applyToNew(Curveto, args);
        }

        if (n === 0) {
            throw new Error('Curveto constructor expects 3 points or 6 coordinates (none provided).');
        }

        var outputArray;

        if (typeof args[0] === 'string' || typeof args[0] === 'number') { // coordinates provided
            if (n === 6) {
                this.controlPoint1 = new Point(+args[0], +args[1]);
                this.controlPoint2 = new Point(+args[2], +args[3]);
                this.end = new Point(+args[4], +args[5]);
                return this;

            } else if (n < 6) {
                throw new Error('Curveto constructor expects 3 points or 6 coordinates (' + n + ' coordinates provided).');

            } else { // this is a poly-bezier segment
                var segmentCoords;
                outputArray = [];
                for (i = 0; i < n; i += 6) { // coords come in groups of six

                    segmentCoords = args.slice(i, i + 6); // will send fewer than six coords if args.length not divisible by 6
                    outputArray.push(applyToNew(Curveto, segmentCoords));
                }
                return outputArray;
            }

        } else { // points provided
            if (n === 3) {
                this.controlPoint1 = new Point(args[0]);
                this.controlPoint2 = new Point(args[1]);
                this.end = new Point(args[2]);
                return this;

            } else if (n < 3) {
                throw new Error('Curveto constructor expects 3 points or 6 coordinates (' + n + ' points provided).');

            } else { // this is a poly-bezier segment
                var segmentPoints;
                outputArray = [];
                for (i = 0; i < n; i += 3) { // points come in groups of three

                    segmentPoints = args.slice(i, i + 3); // will send fewer than three points if args.length is not divisible by 3
                    outputArray.push(applyToNew(Curveto, segmentPoints));
                }
                return outputArray;
            }
        }
    };

    var curvetoPrototype = {

        clone: function() {

            return new Curveto(this.controlPoint1, this.controlPoint2, this.end);
        },

        isDifferentiable: function() {

            if (!this.previousSegment) return false;

            var start = this.start;
            var control1 = this.controlPoint1;
            var control2 = this.controlPoint2;
            var end = this.end;

            return !(start.equals(control1) && control1.equals(control2) && control2.equals(end));
        },

        scale: function(sx, sy, origin) {

            this.controlPoint1.scale(sx, sy, origin);
            this.controlPoint2.scale(sx, sy, origin);
            this.end.scale(sx, sy, origin);
            return this;
        },

        translate: function(tx, ty) {

            this.controlPoint1.translate(tx, ty);
            this.controlPoint2.translate(tx, ty);
            this.end.translate(tx, ty);
            return this;
        },

        type: 'C',

        serialize: function() {

            var c1 = this.controlPoint1;
            var c2 = this.controlPoint2;
            var end = this.end;
            return this.type + ' ' + c1.x + ' ' + c1.y + ' ' + c2.x + ' ' + c2.y + ' ' + end.x + ' ' + end.y;
        },

        toString: function() {

            return this.type + ' ' + this.start + ' ' + this.controlPoint1 + ' ' + this.controlPoint2 + ' ' + this.end;
        }
    };

    Object.defineProperty(curvetoPrototype, 'start', {
        // get a reference to the end point of previous segment

        configurable: true,

        enumerable: true,

        get: function() {

            if (!this.previousSegment) throw new Error('Missing previous segment. (This segment cannot be the first segment of a path; OR segment has not yet been added to a path.)');

            return this.previousSegment.end;
        }
    });

    Curveto.prototype = extend(segmentPrototype, Curve.prototype, curvetoPrototype);

    var Moveto = function() {

        var args = [];
        var n = arguments.length;
        for (var i = 0; i < n; i++) {
            args.push(arguments[i]);
        }

        if (!(this instanceof Moveto)) { // switching context of `this` to Moveto when called without `new`
            return applyToNew(Moveto, args);
        }

        if (n === 0) {
            throw new Error('Moveto constructor expects 1 point or 2 coordinates (none provided).');
        }

        var outputArray;

        if (typeof args[0] === 'string' || typeof args[0] === 'number') { // coordinates provided
            if (n === 2) {
                this.end = new Point(+args[0], +args[1]);
                return this;

            } else if (n < 2) {
                throw new Error('Moveto constructor expects 1 point or 2 coordinates (' + n + ' coordinates provided).');

            } else { // this is a moveto-with-subsequent-poly-line segment
                var segmentCoords;
                outputArray = [];
                for (i = 0; i < n; i += 2) { // coords come in groups of two

                    segmentCoords = args.slice(i, i + 2); // will send one coord if args.length not divisible by 2
                    if (i === 0) outputArray.push(applyToNew(Moveto, segmentCoords));
                    else outputArray.push(applyToNew(Lineto, segmentCoords));
                }
                return outputArray;
            }

        } else { // points provided
            if (n === 1) {
                this.end = new Point(args[0]);
                return this;

            } else { // this is a moveto-with-subsequent-poly-line segment
                var segmentPoint;
                outputArray = [];
                for (i = 0; i < n; i += 1) { // points come one by one

                    segmentPoint = args[i];
                    if (i === 0) outputArray.push(new Moveto(segmentPoint));
                    else outputArray.push(new Lineto(segmentPoint));
                }
                return outputArray;
            }
        }
    };

    var movetoPrototype = {

        bbox: function() {

            return null;
        },

        clone: function() {

            return new Moveto(this.end);
        },

        closestPoint: function() {

            return this.end.clone();
        },

        closestPointNormalizedLength: function() {

            return 0;
        },

        closestPointLength: function() {

            return 0;
        },

        closestPointT: function() {

            return 1;
        },

        closestPointTangent: function() {

            return null;
        },

        equals: function(m) {

            return this.end.equals(m.end);
        },

        getSubdivisions: function() {

            return [];
        },

        isDifferentiable: function() {

            return false;
        },

        isSubpathStart: true,

        isVisible: false,

        length: function() {

            return 0;
        },

        lengthAtT: function() {

            return 0;
        },

        pointAt: function() {

            return this.end.clone();
        },

        pointAtLength: function() {

            return this.end.clone();
        },

        pointAtT: function() {

            return this.end.clone();
        },

        scale: function(sx, sy, origin) {

            this.end.scale(sx, sy, origin);
            return this;
        },

        tangentAt: function() {

            return null;
        },

        tangentAtLength: function() {

            return null;
        },

        tangentAtT: function() {

            return null;
        },

        translate: function(tx, ty) {

            this.end.translate(tx, ty);
            return this;
        },

        type: 'M',

        serialize: function() {

            var end = this.end;
            return this.type + ' ' + end.x + ' ' + end.y;
        },

        toString: function() {

            return this.type + ' ' + this.end;
        }
    };

    Object.defineProperty(movetoPrototype, 'start', {

        configurable: true,

        enumerable: true,

        get: function() {

            throw new Error('Illegal access. Moveto segments should not need a start property.');
        }
    })

    Moveto.prototype = extend(segmentPrototype, movetoPrototype); // does not inherit from any other geometry object

    var Closepath = function() {

        var args = [];
        var n = arguments.length;
        for (var i = 0; i < n; i++) {
            args.push(arguments[i]);
        }

        if (!(this instanceof Closepath)) { // switching context of `this` to Closepath when called without `new`
            return applyToNew(Closepath, args);
        }

        if (n > 0) {
            throw new Error('Closepath constructor expects no arguments.');
        }

        return this;
    };

    var closepathPrototype = {

        clone: function() {

            return new Closepath();
        },

        getSubdivisions: function() {

            return [];
        },

        isDifferentiable: function() {

            if (!this.previousSegment || !this.subpathStartSegment) return false;

            return !this.start.equals(this.end);
        },

        scale: function() {

            return this;
        },

        translate: function() {

            return this;
        },

        type: 'Z',

        serialize: function() {

            return this.type;
        },

        toString: function() {

            return this.type + ' ' + this.start + ' ' + this.end;
        }
    };

    Object.defineProperty(closepathPrototype, 'start', {
        // get a reference to the end point of previous segment

        configurable: true,

        enumerable: true,

        get: function() {

            if (!this.previousSegment) throw new Error('Missing previous segment. (This segment cannot be the first segment of a path; OR segment has not yet been added to a path.)');

            return this.previousSegment.end;
        }
    });

    Object.defineProperty(closepathPrototype, 'end', {
        // get a reference to the end point of subpath start segment

        configurable: true,

        enumerable: true,

        get: function() {

            if (!this.subpathStartSegment) throw new Error('Missing subpath start segment. (This segment needs a subpath start segment (e.g. Moveto); OR segment has not yet been added to a path.)');

            return this.subpathStartSegment.end;
        }
    })

    Closepath.prototype = extend(segmentPrototype, Line.prototype, closepathPrototype);

    var segmentTypes = Path.segmentTypes = {
        L: Lineto,
        C: Curveto,
        M: Moveto,
        Z: Closepath,
        z: Closepath
    };

    Path.regexSupportedData = new RegExp('^[\\s\\d' + Object.keys(segmentTypes).join('') + ',.]*$');

    Path.isDataSupported = function(d) {
        if (typeof d !== 'string') return false;
        return this.regexSupportedData.test(d);
    }

    return g;

})();

// Vectorizer.
// -----------

// A tiny library for making your life easier when dealing with SVG.
// The only Vectorizer dependency is the Geometry library.

var V;
var Vectorizer;

V = Vectorizer = (function() {

    'use strict';

    var hasSvg = typeof window === 'object' &&
                !!(
                    window.SVGAngle ||
                    document.implementation.hasFeature('http://www.w3.org/TR/SVG11/feature#BasicStructure', '1.1')
                );

    // SVG support is required.
    if (!hasSvg) {

        // Return a function that throws an error when it is used.
        return function() {
            throw new Error('SVG is required to use Vectorizer.');
        };
    }

    // XML namespaces.
    var ns = {
        xmlns: 'http://www.w3.org/2000/svg',
        xml: 'http://www.w3.org/XML/1998/namespace',
        xlink: 'http://www.w3.org/1999/xlink',
        xhtml: 'http://www.w3.org/1999/xhtml'
    };

    var SVGversion = '1.1';

    // Declare shorthands to the most used math functions.
    var math = Math;
    var PI = math.PI;
    var atan2 = math.atan2;
    var sqrt = math.sqrt;
    var min = math.min;
    var max = math.max;
    var cos = math.cos;
    var sin = math.sin;

    var V = function(el, attrs, children) {

        // This allows using V() without the new keyword.
        if (!(this instanceof V)) {
            return V.apply(Object.create(V.prototype), arguments);
        }

        if (!el) return;

        if (V.isV(el)) {
            el = el.node;
        }

        attrs = attrs || {};

        if (V.isString(el)) {

            if (el.toLowerCase() === 'svg') {

                // Create a new SVG canvas.
                el = V.createSvgDocument();

            } else if (el[0] === '<') {

                // Create element from an SVG string.
                // Allows constructs of type: `document.appendChild(V('<rect></rect>').node)`.

                var svgDoc = V.createSvgDocument(el);

                // Note that `V()` might also return an array should the SVG string passed as
                // the first argument contain more than one root element.
                if (svgDoc.childNodes.length > 1) {

                    // Map child nodes to `V`s.
                    var arrayOfVels = [];
                    var i, len;

                    for (i = 0, len = svgDoc.childNodes.length; i < len; i++) {

                        var childNode = svgDoc.childNodes[i];
                        arrayOfVels.push(new V(document.importNode(childNode, true)));
                    }

                    return arrayOfVels;
                }

                el = document.importNode(svgDoc.firstChild, true);

            } else {

                el = document.createElementNS(ns.xmlns, el);
            }

            V.ensureId(el);
        }

        this.node = el;

        this.setAttributes(attrs);

        if (children) {
            this.append(children);
        }

        return this;
    };

    var VPrototype = V.prototype;

    Object.defineProperty(VPrototype, 'id', {
        enumerable: true,
        get: function() {
            return this.node.id;
        },
        set: function(id) {
            this.node.id = id;
        }
    });

    /**
     * @param {SVGGElement} toElem
     * @returns {SVGMatrix}
     */
    VPrototype.getTransformToElement = function(toElem) {
        toElem = V.toNode(toElem);
        return toElem.getScreenCTM().inverse().multiply(this.node.getScreenCTM());
    };

    /**
     * @param {SVGMatrix} matrix
     * @param {Object=} opt
     * @returns {Vectorizer|SVGMatrix} Setter / Getter
     */
    VPrototype.transform = function(matrix, opt) {

        var node = this.node;
        if (V.isUndefined(matrix)) {
            return V.transformStringToMatrix(this.attr('transform'));
        }

        if (opt && opt.absolute) {
            return this.attr('transform', V.matrixToTransformString(matrix));
        }

        var svgTransform = V.createSVGTransform(matrix);
        node.transform.baseVal.appendItem(svgTransform);
        return this;
    };

    VPrototype.translate = function(tx, ty, opt) {

        opt = opt || {};
        ty = ty || 0;

        var transformAttr = this.attr('transform') || '';
        var transform = V.parseTransformString(transformAttr);
        transformAttr = transform.value;
        // Is it a getter?
        if (V.isUndefined(tx)) {
            return transform.translate;
        }

        transformAttr = transformAttr.replace(/translate\([^\)]*\)/g, '').trim();

        var newTx = opt.absolute ? tx : transform.translate.tx + tx;
        var newTy = opt.absolute ? ty : transform.translate.ty + ty;
        var newTranslate = 'translate(' + newTx + ',' + newTy + ')';

        // Note that `translate()` is always the first transformation. This is
        // usually the desired case.
        this.attr('transform', (newTranslate + ' ' + transformAttr).trim());
        return this;
    };

    VPrototype.rotate = function(angle, cx, cy, opt) {

        opt = opt || {};

        var transformAttr = this.attr('transform') || '';
        var transform = V.parseTransformString(transformAttr);
        transformAttr = transform.value;

        // Is it a getter?
        if (V.isUndefined(angle)) {
            return transform.rotate;
        }

        transformAttr = transformAttr.replace(/rotate\([^\)]*\)/g, '').trim();

        angle %= 360;

        var newAngle = opt.absolute ? angle : transform.rotate.angle + angle;
        var newOrigin = (cx !== undefined && cy !== undefined) ? ',' + cx + ',' + cy : '';
        var newRotate = 'rotate(' + newAngle + newOrigin + ')';

        this.attr('transform', (transformAttr + ' ' + newRotate).trim());
        return this;
    };

    // Note that `scale` as the only transformation does not combine with previous values.
    VPrototype.scale = function(sx, sy) {

        sy = V.isUndefined(sy) ? sx : sy;

        var transformAttr = this.attr('transform') || '';
        var transform = V.parseTransformString(transformAttr);
        transformAttr = transform.value;

        // Is it a getter?
        if (V.isUndefined(sx)) {
            return transform.scale;
        }

        transformAttr = transformAttr.replace(/scale\([^\)]*\)/g, '').trim();

        var newScale = 'scale(' + sx + ',' + sy + ')';

        this.attr('transform', (transformAttr + ' ' + newScale).trim());
        return this;
    };

    // Get SVGRect that contains coordinates and dimension of the real bounding box,
    // i.e. after transformations are applied.
    // If `target` is specified, bounding box will be computed relatively to `target` element.
    VPrototype.bbox = function(withoutTransformations, target) {

        var box;
        var node = this.node;
        var ownerSVGElement = node.ownerSVGElement;

        // If the element is not in the live DOM, it does not have a bounding box defined and
        // so fall back to 'zero' dimension element.
        if (!ownerSVGElement) {
            return new g.Rect(0, 0, 0, 0);
        }

        try {

            box = node.getBBox();

        } catch (e) {

            // Fallback for IE.
            box = {
                x: node.clientLeft,
                y: node.clientTop,
                width: node.clientWidth,
                height: node.clientHeight
            };
        }

        if (withoutTransformations) {
            return new g.Rect(box);
        }

        var matrix = this.getTransformToElement(target || ownerSVGElement);

        return V.transformRect(box, matrix);
    };

    // Returns an SVGRect that contains coordinates and dimensions of the real bounding box,
    // i.e. after transformations are applied.
    // Fixes a browser implementation bug that returns incorrect bounding boxes for groups of svg elements.
    // Takes an (Object) `opt` argument (optional) with the following attributes:
    // (Object) `target` (optional): if not undefined, transform bounding boxes relative to `target`; if undefined, transform relative to this
    // (Boolean) `recursive` (optional): if true, recursively enter all groups and get a union of element bounding boxes (svg bbox fix); if false or undefined, return result of native function this.node.getBBox();
    VPrototype.getBBox = function(opt) {

        var options = {};

        var outputBBox;
        var node = this.node;
        var ownerSVGElement = node.ownerSVGElement;

        // If the element is not in the live DOM, it does not have a bounding box defined and
        // so fall back to 'zero' dimension element.
        if (!ownerSVGElement) {
            return new g.Rect(0, 0, 0, 0);
        }

        if (opt) {
            if (opt.target) { // check if target exists
                options.target = V.toNode(opt.target); // works for V objects, jquery objects, and node objects
            }
            if (opt.recursive) {
                options.recursive = opt.recursive;
            }
        }

        if (!options.recursive) {
            try {
                outputBBox = node.getBBox();
            } catch (e) {
                // Fallback for IE.
                outputBBox = {
                    x: node.clientLeft,
                    y: node.clientTop,
                    width: node.clientWidth,
                    height: node.clientHeight
                };
            }

            if (!options.target) {
                // transform like this (that is, not at all)
                return new g.Rect(outputBBox);
            } else {
                // transform like target
                var matrix = this.getTransformToElement(options.target);
                return V.transformRect(outputBBox, matrix);
            }
        } else { // if we want to calculate the bbox recursively
            // browsers report correct bbox around svg elements (one that envelops the path lines tightly)
            // but some browsers fail to report the same bbox when the elements are in a group (returning a looser bbox that also includes control points, like node.getClientRect())
            // this happens even if we wrap a single svg element into a group!
            // this option setting makes the function recursively enter all the groups from this and deeper, get bboxes of the elements inside, then return a union of those bboxes

            var children = this.children();
            var n = children.length;

            if (n === 0) {
                return this.getBBox({ target: options.target, recursive: false });
            }

            // recursion's initial pass-through setting:
            // recursive passes-through just keep the target as whatever was set up here during the initial pass-through
            if (!options.target) {
                // transform children/descendants like this (their parent/ancestor)
                options.target = this;
            } // else transform children/descendants like target

            for (var i = 0; i < n; i++) {
                var currentChild = children[i];

                var childBBox;

                // if currentChild is not a group element, get its bbox with a nonrecursive call
                if (currentChild.children().length === 0) {
                    childBBox = currentChild.getBBox({ target: options.target, recursive: false });
                }
                else {
                    // if currentChild is a group element (determined by checking the number of children), enter it with a recursive call
                    childBBox = currentChild.getBBox({ target: options.target, recursive: true });
                }

                if (!outputBBox) {
                    // if this is the first iteration
                    outputBBox = childBBox;
                } else {
                    // make a new bounding box rectangle that contains this child's bounding box and previous bounding box
                    outputBBox = outputBBox.union(childBBox);
                }
            }

            return outputBBox;
        }
    };

    // Text() helpers

    function createTextPathNode(attrs, vel) {
        attrs || (attrs = {});
        var textPathElement = V('textPath');
        var d = attrs.d;
        if (d && attrs['xlink:href'] === undefined) {
            // If `opt.attrs` is a plain string, consider it to be directly the
            // SVG path data for the text to go along (this is a shortcut).
            // Otherwise if it is an object and contains the `d` property, then this is our path.
            // Wrap the text in the SVG <textPath> element that points
            // to a path defined by `opt.attrs` inside the `<defs>` element.
            var linkedPath = V('path').attr('d', d).appendTo(vel.defs());
            textPathElement.attr('xlink:href', '#' + linkedPath.id);
        }
        if (V.isObject(attrs)) {
            // Set attributes on the `<textPath>`. The most important one
            // is the `xlink:href` that points to our newly created `<path/>` element in `<defs/>`.
            // Note that we also allow the following construct:
            // `t.text('my text', { textPath: { 'xlink:href': '#my-other-path' } })`.
            // In other words, one can completely skip the auto-creation of the path
            // and use any other arbitrary path that is in the document.
            textPathElement.attr(attrs);
        }
        return textPathElement.node;
    }

    function annotateTextLine(lineNode, lineAnnotations, opt) {
        opt || (opt = {});
        var includeAnnotationIndices = opt.includeAnnotationIndices;
        var eol = opt.eol;
        var lineHeight = opt.lineHeight;
        var baseSize = opt.baseSize;
        var maxFontSize = 0;
        var fontMetrics = {};
        var lastJ = lineAnnotations.length - 1;
        for (var j = 0; j <= lastJ; j++) {
            var annotation = lineAnnotations[j];
            var fontSize = null;
            if (V.isObject(annotation)) {
                var annotationAttrs = annotation.attrs;
                var vTSpan = V('tspan', annotationAttrs);
                var tspanNode = vTSpan.node;
                var t = annotation.t;
                if (eol && j === lastJ) t += eol;
                tspanNode.textContent = t;
                // Per annotation className
                var annotationClass = annotationAttrs['class'];
                if (annotationClass) vTSpan.addClass(annotationClass);
                // If `opt.includeAnnotationIndices` is `true`,
                // set the list of indices of all the applied annotations
                // in the `annotations` attribute. This list is a comma
                // separated list of indices.
                if (includeAnnotationIndices) vTSpan.attr('annotations', annotation.annotations);
                // Check for max font size
                fontSize = parseFloat(annotationAttrs['font-size']);
                if (fontSize === undefined) fontSize = baseSize;
                if (fontSize && fontSize > maxFontSize) maxFontSize = fontSize;
            } else {
                if (eol && j === lastJ) annotation += eol;
                tspanNode = document.createTextNode(annotation || ' ');
                if (baseSize && baseSize > maxFontSize) maxFontSize = baseSize;
            }
            lineNode.appendChild(tspanNode);
        }

        if (maxFontSize) fontMetrics.maxFontSize = maxFontSize;
        if (lineHeight) {
            fontMetrics.lineHeight = lineHeight;
        } else if (maxFontSize) {
            fontMetrics.lineHeight = (maxFontSize * 1.2);
        }
        return fontMetrics;
    }

    var emRegex = /em$/;

    function convertEmToPx(em, fontSize) {
        var numerical = parseFloat(em);
        if (emRegex.test(em)) return numerical * fontSize;
        return numerical;
    }

    function calculateDY(alignment, linesMetrics, baseSizePx, lineHeight) {
        if (!Array.isArray(linesMetrics)) return 0;
        var n = linesMetrics.length;
        if (!n) return 0;
        var lineMetrics = linesMetrics[0];
        var flMaxFont = convertEmToPx(lineMetrics.maxFontSize, baseSizePx) || baseSizePx;
        var rLineHeights = 0;
        var lineHeightPx = convertEmToPx(lineHeight, baseSizePx);
        for (var i = 1; i < n; i++) {
            lineMetrics = linesMetrics[i];
            var iLineHeight = convertEmToPx(lineMetrics.lineHeight, baseSizePx) || lineHeightPx;
            rLineHeights += iLineHeight;
        }
        var llMaxFont = convertEmToPx(lineMetrics.maxFontSize, baseSizePx) || baseSizePx;
        var dy;
        switch (alignment) {
            case 'middle':
                dy = (flMaxFont / 2) - (0.15 * llMaxFont) - (rLineHeights / 2);
                break;
            case 'bottom':
                dy = -(0.25 * llMaxFont) - rLineHeights;
                break;
            default:
            case 'top':
                dy = (0.8 * flMaxFont)
                break;
        }
        return dy;
    }

    VPrototype.text = function(content, opt) {

        if (content && typeof content !== 'string') throw new Error('Vectorizer: text() expects the first argument to be a string.');

        // Replace all spaces with the Unicode No-break space (http://www.fileformat.info/info/unicode/char/a0/index.htm).
        // IE would otherwise collapse all spaces into one.
        content = V.sanitizeText(content);
        opt || (opt = {});

        // End of Line character
        var eol = opt.eol;
        // Text along path
        var textPath = opt.textPath
        // Vertical shift
        var verticalAnchor = opt.textVerticalAnchor;
        var namedVerticalAnchor = (verticalAnchor === 'middle' || verticalAnchor === 'bottom' || verticalAnchor === 'top');
        // Horizontal shift applied to all the lines but the first.
        var x = opt.x;
        if (x === undefined) x = this.attr('x') || 0;
        // Annotations
        var iai = opt.includeAnnotationIndices;
        var annotations = opt.annotations;
        if (annotations && !V.isArray(annotations)) annotations = [annotations];
        // Shift all the <tspan> but first by one line (`1em`)
        var defaultLineHeight = opt.lineHeight;
        var autoLineHeight = (defaultLineHeight === 'auto');
        var lineHeight = (autoLineHeight) ? '1.5em' : (defaultLineHeight || '1em');
        // Clearing the element
        this.empty();
        this.attr({
            // Preserve spaces. In other words, we do not want consecutive spaces to get collapsed to one.
            'xml:space': 'preserve',
            // An empty text gets rendered into the DOM in webkit-based browsers.
            // In order to unify this behaviour across all browsers
            // we rather hide the text element when it's empty.
            'display': (content) ? null : 'none'
        });
        // Set default font-size if none
        var fontSize = parseFloat(this.attr('font-size'));
        if (!fontSize) {
            fontSize = 16;
            if (namedVerticalAnchor || annotations) this.attr('font-size', fontSize);
        }

        var doc = document;
        var containerNode;
        if (textPath) {
            // Now all the `<tspan>`s will be inside the `<textPath>`.
            if (typeof textPath === 'string') textPath = { d: textPath };
            containerNode = createTextPathNode(textPath, this);
        } else {
            containerNode = doc.createDocumentFragment();
        }
        var offset = 0;
        var lines = content.split('\n');
        var linesMetrics = [];
        var annotatedY;
        for (var i = 0, lastI = lines.length - 1; i <= lastI; i++) {
            var dy = lineHeight;
            var lineClassName = 'v-line';
            var lineNode = doc.createElementNS(V.namespace.xmlns, 'tspan');
            var line = lines[i];
            var lineMetrics;
            if (line) {
                if (annotations) {
                    // Find the *compacted* annotations for this line.
                    var lineAnnotations = V.annotateString(line, annotations, {
                        offset: -offset,
                        includeAnnotationIndices: iai
                    });
                    lineMetrics = annotateTextLine(lineNode, lineAnnotations, {
                        includeAnnotationIndices: iai,
                        eol: (i !== lastI && eol),
                        lineHeight: (autoLineHeight) ? null : lineHeight,
                        baseSize: fontSize
                    });
                    // Get the line height based on the biggest font size in the annotations for this line.
                    var iLineHeight = lineMetrics.lineHeight;
                    if (iLineHeight && autoLineHeight && i !== 0) dy = iLineHeight;
                    if (i === 0) annotatedY = lineMetrics.maxFontSize * 0.8;
                } else {
                    if (eol && i !== lastI) line += eol;
                    lineNode.textContent = line;
                }
            } else {
                // Make sure the textContent is never empty. If it is, add a dummy
                // character and make it invisible, making the following lines correctly
                // relatively positioned. `dy=1em` won't work with empty lines otherwise.
                lineNode.textContent = '-';
                lineClassName += ' v-empty-line';
                // 'opacity' needs to be specified with fill, stroke. Opacity without specification
                // is not applied in Firefox
                var lineNodeStyle = lineNode.style;
                lineNodeStyle.fillOpacity = 0;
                lineNodeStyle.strokeOpacity = 0;
                if (annotations) lineMetrics = {};
            }
            if (lineMetrics) linesMetrics.push(lineMetrics);
            if (i > 0) lineNode.setAttribute('dy', dy);
            // Firefox requires 'x' to be set on the first line when inside a text path
            if (i > 0 || textPath) lineNode.setAttribute('x', x);
            lineNode.className.baseVal = lineClassName;
            containerNode.appendChild(lineNode);
            offset += line.length + 1;      // + 1 = newline character.
        }
        // Y Alignment calculation
        if (namedVerticalAnchor) {
            if (annotations) {
                dy = calculateDY(verticalAnchor, linesMetrics, fontSize, lineHeight);
            } else if (verticalAnchor === 'top') {
                // A shortcut for top alignment. It does not depend on font-size nor line-height
                dy = '0.8em';
            } else {
                var rh; // remaining height
                if (lastI > 0) {
                    rh = parseFloat(lineHeight) || 1;
                    rh *= lastI;
                    if (!emRegex.test(lineHeight)) rh /= fontSize;
                } else {
                    // Single-line text
                    rh = 0;
                }
                switch (verticalAnchor) {
                    case 'middle':
                        dy = (0.3 - (rh / 2)) + 'em'
                        break;
                    case 'bottom':
                        dy = (-rh - 0.3) + 'em'
                        break;
                }
            }
        } else {
            if (verticalAnchor === 0) {
                dy = '0em';
            } else if (verticalAnchor) {
                dy = verticalAnchor;
            } else {
                // No vertical anchor is defined
                dy = 0;
                // Backwards compatibility - we change the `y` attribute instead of `dy`.
                if (this.attr('y') === null) this.attr('y', annotatedY || '0.8em');
            }
        }
        containerNode.firstChild.setAttribute('dy', dy);
        // Appending lines to the element.
        this.append(containerNode);
        return this;
    };

    /**
     * @public
     * @param {string} name
     * @returns {Vectorizer}
     */
    VPrototype.removeAttr = function(name) {

        var qualifiedName = V.qualifyAttr(name);
        var el = this.node;

        if (qualifiedName.ns) {
            if (el.hasAttributeNS(qualifiedName.ns, qualifiedName.local)) {
                el.removeAttributeNS(qualifiedName.ns, qualifiedName.local);
            }
        } else if (el.hasAttribute(name)) {
            el.removeAttribute(name);
        }
        return this;
    };

    VPrototype.attr = function(name, value) {

        if (V.isUndefined(name)) {

            // Return all attributes.
            var attributes = this.node.attributes;
            var attrs = {};

            for (var i = 0; i < attributes.length; i++) {
                attrs[attributes[i].name] = attributes[i].value;
            }

            return attrs;
        }

        if (V.isString(name) && V.isUndefined(value)) {
            return this.node.getAttribute(name);
        }

        if (typeof name === 'object') {

            for (var attrName in name) {
                if (name.hasOwnProperty(attrName)) {
                    this.setAttribute(attrName, name[attrName]);
                }
            }

        } else {

            this.setAttribute(name, value);
        }

        return this;
    };

    VPrototype.normalizePath = function() {

        var tagName = this.tagName();
        if (tagName === 'PATH') {
            this.attr('d', V.normalizePathData(this.attr('d')));
        }

        return this;
    }

    VPrototype.remove = function() {

        if (this.node.parentNode) {
            this.node.parentNode.removeChild(this.node);
        }

        return this;
    };

    VPrototype.empty = function() {

        while (this.node.firstChild) {
            this.node.removeChild(this.node.firstChild);
        }

        return this;
    };

    /**
     * @private
     * @param {object} attrs
     * @returns {Vectorizer}
     */
    VPrototype.setAttributes = function(attrs) {

        for (var key in attrs) {
            if (attrs.hasOwnProperty(key)) {
                this.setAttribute(key, attrs[key]);
            }
        }

        return this;
    };

    VPrototype.append = function(els) {

        if (!V.isArray(els)) {
            els = [els];
        }

        for (var i = 0, len = els.length; i < len; i++) {
            this.node.appendChild(V.toNode(els[i]));
        }

        return this;
    };

    VPrototype.prepend = function(els) {

        var child = this.node.firstChild;
        return child ? V(child).before(els) : this.append(els);
    };

    VPrototype.before = function(els) {

        var node = this.node;
        var parent = node.parentNode;

        if (parent) {

            if (!V.isArray(els)) {
                els = [els];
            }

            for (var i = 0, len = els.length; i < len; i++) {
                parent.insertBefore(V.toNode(els[i]), node);
            }
        }

        return this;
    };

    VPrototype.appendTo = function(node) {
        V.toNode(node).appendChild(this.node);
        return this;
    },

    VPrototype.svg = function() {

        return this.node instanceof window.SVGSVGElement ? this : V(this.node.ownerSVGElement);
    };

    VPrototype.tagName = function() {

        return this.node.tagName.toUpperCase();
    };

    VPrototype.defs = function() {
        var context = this.svg() || this;
        var defsNode = context.node.getElementsByTagName('defs')[0];
        if (defsNode) return V(defsNode);
        return V('defs').appendTo(context);
    };

    VPrototype.clone = function() {

        var clone = V(this.node.cloneNode(true/* deep */));
        // Note that clone inherits also ID. Therefore, we need to change it here.
        clone.node.id = V.uniqueId();
        return clone;
    };

    VPrototype.findOne = function(selector) {

        var found = this.node.querySelector(selector);
        return found ? V(found) : undefined;
    };

    VPrototype.find = function(selector) {

        var vels = [];
        var nodes = this.node.querySelectorAll(selector);

        if (nodes) {

            // Map DOM elements to `V`s.
            for (var i = 0; i < nodes.length; i++) {
                vels.push(V(nodes[i]));
            }
        }

        return vels;
    };

    // Returns an array of V elements made from children of this.node.
    VPrototype.children = function() {

        var children = this.node.childNodes;

        var outputArray = [];
        for (var i = 0; i < children.length; i++) {
            var currentChild = children[i];
            if (currentChild.nodeType === 1) {
                outputArray.push(V(children[i]));
            }
        }
        return outputArray;
    };

    // Find an index of an element inside its container.
    VPrototype.index = function() {

        var index = 0;
        var node = this.node.previousSibling;

        while (node) {
            // nodeType 1 for ELEMENT_NODE
            if (node.nodeType === 1) index++;
            node = node.previousSibling;
        }

        return index;
    };

    VPrototype.findParentByClass = function(className, terminator) {

        var ownerSVGElement = this.node.ownerSVGElement;
        var node = this.node.parentNode;

        while (node && node !== terminator && node !== ownerSVGElement) {

            var vel = V(node);
            if (vel.hasClass(className)) {
                return vel;
            }

            node = node.parentNode;
        }

        return null;
    };

    // https://jsperf.com/get-common-parent
    VPrototype.contains = function(el) {

        var a = this.node;
        var b = V.toNode(el);
        var bup = b && b.parentNode;

        return (a === bup) || !!(bup && bup.nodeType === 1 && (a.compareDocumentPosition(bup) & 16));
    };

    // Convert global point into the coordinate space of this element.
    VPrototype.toLocalPoint = function(x, y) {

        var svg = this.svg().node;

        var p = svg.createSVGPoint();
        p.x = x;
        p.y = y;

        try {

            var globalPoint = p.matrixTransform(svg.getScreenCTM().inverse());
            var globalToLocalMatrix = this.getTransformToElement(svg).inverse();

        } catch (e) {
            // IE9 throws an exception in odd cases. (`Unexpected call to method or property access`)
            // We have to make do with the original coordianates.
            return p;
        }

        return globalPoint.matrixTransform(globalToLocalMatrix);
    };

    VPrototype.translateCenterToPoint = function(p) {

        var bbox = this.getBBox({ target: this.svg() });
        var center = bbox.center();

        this.translate(p.x - center.x, p.y - center.y);
        return this;
    };

    // Efficiently auto-orient an element. This basically implements the orient=auto attribute
    // of markers. The easiest way of understanding on what this does is to imagine the element is an
    // arrowhead. Calling this method on the arrowhead makes it point to the `position` point while
    // being auto-oriented (properly rotated) towards the `reference` point.
    // `target` is the element relative to which the transformations are applied. Usually a viewport.
    VPrototype.translateAndAutoOrient = function(position, reference, target) {

        // Clean-up previously set transformations except the scale. If we didn't clean up the
        // previous transformations then they'd add up with the old ones. Scale is an exception as
        // it doesn't add up, consider: `this.scale(2).scale(2).scale(2)`. The result is that the
        // element is scaled by the factor 2, not 8.

        var s = this.scale();
        this.attr('transform', '');
        this.scale(s.sx, s.sy);

        var svg = this.svg().node;
        var bbox = this.getBBox({ target: target || svg });

        // 1. Translate to origin.
        var translateToOrigin = svg.createSVGTransform();
        translateToOrigin.setTranslate(-bbox.x - bbox.width / 2, -bbox.y - bbox.height / 2);

        // 2. Rotate around origin.
        var rotateAroundOrigin = svg.createSVGTransform();
        var angle = (new g.Point(position)).changeInAngle(position.x - reference.x, position.y - reference.y, reference);
        rotateAroundOrigin.setRotate(angle, 0, 0);

        // 3. Translate to the `position` + the offset (half my width) towards the `reference` point.
        var translateFinal = svg.createSVGTransform();
        var finalPosition = (new g.Point(position)).move(reference, bbox.width / 2);
        translateFinal.setTranslate(position.x + (position.x - finalPosition.x), position.y + (position.y - finalPosition.y));

        // 4. Apply transformations.
        var ctm = this.getTransformToElement(target || svg);
        var transform = svg.createSVGTransform();
        transform.setMatrix(
            translateFinal.matrix.multiply(
                rotateAroundOrigin.matrix.multiply(
                    translateToOrigin.matrix.multiply(
                        ctm)))
        );

        // Instead of directly setting the `matrix()` transform on the element, first, decompose
        // the matrix into separate transforms. This allows us to use normal Vectorizer methods
        // as they don't work on matrices. An example of this is to retrieve a scale of an element.
        // this.node.transform.baseVal.initialize(transform);

        var decomposition = V.decomposeMatrix(transform.matrix);

        this.translate(decomposition.translateX, decomposition.translateY);
        this.rotate(decomposition.rotation);
        // Note that scale has been already applied, hence the following line stays commented. (it's here just for reference).
        //this.scale(decomposition.scaleX, decomposition.scaleY);

        return this;
    };

    VPrototype.animateAlongPath = function(attrs, path) {

        path = V.toNode(path);

        var id = V.ensureId(path);
        var animateMotion = V('animateMotion', attrs);
        var mpath = V('mpath', { 'xlink:href': '#' + id });

        animateMotion.append(mpath);

        this.append(animateMotion);
        try {
            animateMotion.node.beginElement();
        } catch (e) {
            // Fallback for IE 9.
            // Run the animation programatically if FakeSmile (`http://leunen.me/fakesmile/`) present
            if (document.documentElement.getAttribute('smiling') === 'fake') {

                // Register the animation. (See `https://answers.launchpad.net/smil/+question/203333`)
                var animation = animateMotion.node;
                animation.animators = [];

                var animationID = animation.getAttribute('id');
                if (animationID) id2anim[animationID] = animation;

                var targets = getTargets(animation);
                for (var i = 0, len = targets.length; i < len; i++) {
                    var target = targets[i];
                    var animator = new Animator(animation, target, i);
                    animators.push(animator);
                    animation.animators[i] = animator;
                    animator.register();
                }
            }
        }
        return this;
    };

    VPrototype.hasClass = function(className) {

        return new RegExp('(\\s|^)' + className + '(\\s|$)').test(this.node.getAttribute('class'));
    };

    VPrototype.addClass = function(className) {

        if (!this.hasClass(className)) {
            var prevClasses = this.node.getAttribute('class') || '';
            this.node.setAttribute('class', (prevClasses + ' ' + className).trim());
        }

        return this;
    };

    VPrototype.removeClass = function(className) {

        if (this.hasClass(className)) {
            var newClasses = this.node.getAttribute('class').replace(new RegExp('(\\s|^)' + className + '(\\s|$)', 'g'), '$2');
            this.node.setAttribute('class', newClasses);
        }

        return this;
    };

    VPrototype.toggleClass = function(className, toAdd) {

        var toRemove = V.isUndefined(toAdd) ? this.hasClass(className) : !toAdd;

        if (toRemove) {
            this.removeClass(className);
        } else {
            this.addClass(className);
        }

        return this;
    };

    // Interpolate path by discrete points. The precision of the sampling
    // is controlled by `interval`. In other words, `sample()` will generate
    // a point on the path starting at the beginning of the path going to the end
    // every `interval` pixels.
    // The sampler can be very useful for e.g. finding intersection between two
    // paths (finding the two closest points from two samples).
    VPrototype.sample = function(interval) {

        interval = interval || 1;
        var node = this.node;
        var length = node.getTotalLength();
        var samples = [];
        var distance = 0;
        var sample;
        while (distance < length) {
            sample = node.getPointAtLength(distance);
            samples.push({ x: sample.x, y: sample.y, distance: distance });
            distance += interval;
        }
        return samples;
    };

    VPrototype.convertToPath = function() {

        var path = V('path');
        path.attr(this.attr());
        var d = this.convertToPathData();
        if (d) {
            path.attr('d', d);
        }
        return path;
    };

    VPrototype.convertToPathData = function() {

        var tagName = this.tagName();

        switch (tagName) {
            case 'PATH':
                return this.attr('d');
            case 'LINE':
                return V.convertLineToPathData(this.node);
            case 'POLYGON':
                return V.convertPolygonToPathData(this.node);
            case 'POLYLINE':
                return V.convertPolylineToPathData(this.node);
            case 'ELLIPSE':
                return V.convertEllipseToPathData(this.node);
            case 'CIRCLE':
                return V.convertCircleToPathData(this.node);
            case 'RECT':
                return V.convertRectToPathData(this.node);
        }

        throw new Error(tagName + ' cannot be converted to PATH.');
    };

    V.prototype.toGeometryShape = function() {
        var x, y, width, height, cx, cy, r, rx, ry, points, d;
        switch (this.tagName()) {

            case 'RECT':
                x = parseFloat(this.attr('x')) || 0;
                y = parseFloat(this.attr('y')) || 0;
                width = parseFloat(this.attr('width')) || 0;
                height = parseFloat(this.attr('height')) || 0;
                return new g.Rect(x, y, width, height);

            case 'CIRCLE':
                cx = parseFloat(this.attr('cx')) || 0;
                cy = parseFloat(this.attr('cy')) || 0;
                r = parseFloat(this.attr('r')) || 0;
                return new g.Ellipse({ x: cx, y: cy }, r, r);

            case 'ELLIPSE':
                cx = parseFloat(this.attr('cx')) || 0;
                cy = parseFloat(this.attr('cy')) || 0;
                rx = parseFloat(this.attr('rx')) || 0;
                ry = parseFloat(this.attr('ry')) || 0;
                return new g.Ellipse({ x: cx, y: cy }, rx, ry);

            case 'POLYLINE':
                points = V.getPointsFromSvgNode(this);
                return new g.Polyline(points);

            case 'POLYGON':
                points = V.getPointsFromSvgNode(this);
                if (points.length > 1) points.push(points[0]);
                return new g.Polyline(points);

            case 'PATH':
                d = this.attr('d');
                if (!g.Path.isDataSupported(d)) d = V.normalizePathData(d);
                return new g.Path(d);

            case 'LINE':
                x1 = parseFloat(this.attr('x1')) || 0;
                y1 = parseFloat(this.attr('y1')) || 0;
                x2 = parseFloat(this.attr('x2')) || 0;
                y2 = parseFloat(this.attr('y2')) || 0;
                return new g.Line({ x: x1, y: y1 }, { x: x2, y: y2 });
        }

        // Anything else is a rectangle
        return this.getBBox();
    },

    // Find the intersection of a line starting in the center
    // of the SVG `node` ending in the point `ref`.
    // `target` is an SVG element to which `node`s transformations are relative to.
    // In JointJS, `target` is the `paper.viewport` SVG group element.
    // Note that `ref` point must be in the coordinate system of the `target` for this function to work properly.
    // Returns a point in the `target` coordinte system (the same system as `ref` is in) if
    // an intersection is found. Returns `undefined` otherwise.
    VPrototype.findIntersection = function(ref, target) {

        var svg = this.svg().node;
        target = target || svg;
        var bbox = this.getBBox({ target: target });
        var center = bbox.center();

        if (!bbox.intersectionWithLineFromCenterToPoint(ref)) return undefined;

        var spot;
        var tagName = this.tagName();

        // Little speed up optimalization for `<rect>` element. We do not do conversion
        // to path element and sampling but directly calculate the intersection through
        // a transformed geometrical rectangle.
        if (tagName === 'RECT') {

            var gRect = new g.Rect(
                parseFloat(this.attr('x') || 0),
                parseFloat(this.attr('y') || 0),
                parseFloat(this.attr('width')),
                parseFloat(this.attr('height'))
            );
            // Get the rect transformation matrix with regards to the SVG document.
            var rectMatrix = this.getTransformToElement(target);
            // Decompose the matrix to find the rotation angle.
            var rectMatrixComponents = V.decomposeMatrix(rectMatrix);
            // Now we want to rotate the rectangle back so that we
            // can use `intersectionWithLineFromCenterToPoint()` passing the angle as the second argument.
            var resetRotation = svg.createSVGTransform();
            resetRotation.setRotate(-rectMatrixComponents.rotation, center.x, center.y);
            var rect = V.transformRect(gRect, resetRotation.matrix.multiply(rectMatrix));
            spot = (new g.Rect(rect)).intersectionWithLineFromCenterToPoint(ref, rectMatrixComponents.rotation);

        } else if (tagName === 'PATH' || tagName === 'POLYGON' || tagName === 'POLYLINE' || tagName === 'CIRCLE' || tagName === 'ELLIPSE') {

            var pathNode = (tagName === 'PATH') ? this : this.convertToPath();
            var samples = pathNode.sample();
            var minDistance = Infinity;
            var closestSamples = [];

            var i, sample, gp, centerDistance, refDistance, distance;

            for (i = 0; i < samples.length; i++) {

                sample = samples[i];
                // Convert the sample point in the local coordinate system to the global coordinate system.
                gp = V.createSVGPoint(sample.x, sample.y);
                gp = gp.matrixTransform(this.getTransformToElement(target));
                sample = new g.Point(gp);
                centerDistance = sample.distance(center);
                // Penalize a higher distance to the reference point by 10%.
                // This gives better results. This is due to
                // inaccuracies introduced by rounding errors and getPointAtLength() returns.
                refDistance = sample.distance(ref) * 1.1;
                distance = centerDistance + refDistance;

                if (distance < minDistance) {
                    minDistance = distance;
                    closestSamples = [{ sample: sample, refDistance: refDistance }];
                } else if (distance < minDistance + 1) {
                    closestSamples.push({ sample: sample, refDistance: refDistance });
                }
            }

            closestSamples.sort(function(a, b) {
                return a.refDistance - b.refDistance;
            });

            if (closestSamples[0]) {
                spot = closestSamples[0].sample;
            }
        }

        return spot;
    };

    /**
     * @private
     * @param {string} name
     * @param {string} value
     * @returns {Vectorizer}
     */
    VPrototype.setAttribute = function(name, value) {

        var el = this.node;

        if (value === null) {
            this.removeAttr(name);
            return this;
        }

        var qualifiedName = V.qualifyAttr(name);

        if (qualifiedName.ns) {
            // Attribute names can be namespaced. E.g. `image` elements
            // have a `xlink:href` attribute to set the source of the image.
            el.setAttributeNS(qualifiedName.ns, name, value);
        } else if (name === 'id') {
            el.id = value;
        } else {
            el.setAttribute(name, value);
        }

        return this;
    };

    // Create an SVG document element.
    // If `content` is passed, it will be used as the SVG content of the `<svg>` root element.
    V.createSvgDocument = function(content) {

        var svg = '<svg xmlns="' + ns.xmlns + '" xmlns:xlink="' + ns.xlink + '" version="' + SVGversion + '">' + (content || '') + '</svg>';
        var xml = V.parseXML(svg, { async: false });
        return xml.documentElement;
    };

    V.idCounter = 0;

    // A function returning a unique identifier for this client session with every call.
    V.uniqueId = function() {

        return 'v-' + (++V.idCounter);
    };

    V.toNode = function(el) {

        return V.isV(el) ? el.node : (el.nodeName && el || el[0]);
    };

    V.ensureId = function(node) {

        node = V.toNode(node);
        return node.id || (node.id = V.uniqueId());
    };

    // Replace all spaces with the Unicode No-break space (http://www.fileformat.info/info/unicode/char/a0/index.htm).
    // IE would otherwise collapse all spaces into one. This is used in the text() method but it is
    // also exposed so that the programmer can use it in case he needs to. This is useful e.g. in tests
    // when you want to compare the actual DOM text content without having to add the unicode character in
    // the place of all spaces.
    V.sanitizeText = function(text) {

        return (text || '').replace(/ /g, '\u00A0');
    };

    V.isUndefined = function(value) {

        return typeof value === 'undefined';
    };

    V.isString = function(value) {

        return typeof value === 'string';
    };

    V.isObject = function(value) {

        return value && (typeof value === 'object');
    };

    V.isArray = Array.isArray;

    V.parseXML = function(data, opt) {

        opt = opt || {};

        var xml;

        try {
            var parser = new DOMParser();

            if (!V.isUndefined(opt.async)) {
                parser.async = opt.async;
            }

            xml = parser.parseFromString(data, 'text/xml');
        } catch (error) {
            xml = undefined;
        }

        if (!xml || xml.getElementsByTagName('parsererror').length) {
            throw new Error('Invalid XML: ' + data);
        }

        return xml;
    };

    /**
     * @param {string} name
     * @returns {{ns: string|null, local: string}} namespace and attribute name
     */
    V.qualifyAttr = function(name) {

        if (name.indexOf(':') !== -1) {
            var combinedKey = name.split(':');
            return {
                ns: ns[combinedKey[0]],
                local: combinedKey[1]
            };
        }

        return {
            ns: null,
            local: name
        };
    };

    V.transformRegex = /(\w+)\(([^,)]+),?([^)]+)?\)/gi;
    V.transformSeparatorRegex = /[ ,]+/;
    V.transformationListRegex = /^(\w+)\((.*)\)/;

    V.transformStringToMatrix = function(transform) {

        var transformationMatrix = V.createSVGMatrix();
        var matches = transform && transform.match(V.transformRegex);
        if (!matches) {
            return transformationMatrix;
        }

        for (var i = 0, n = matches.length; i < n; i++) {
            var transformationString = matches[i];

            var transformationMatch = transformationString.match(V.transformationListRegex);
            if (transformationMatch) {
                var sx, sy, tx, ty, angle;
                var ctm = V.createSVGMatrix();
                var args = transformationMatch[2].split(V.transformSeparatorRegex);
                switch (transformationMatch[1].toLowerCase()) {
                    case 'scale':
                        sx = parseFloat(args[0]);
                        sy = (args[1] === undefined) ? sx : parseFloat(args[1]);
                        ctm = ctm.scaleNonUniform(sx, sy);
                        break;
                    case 'translate':
                        tx = parseFloat(args[0]);
                        ty = parseFloat(args[1]);
                        ctm = ctm.translate(tx, ty);
                        break;
                    case 'rotate':
                        angle = parseFloat(args[0]);
                        tx = parseFloat(args[1]) || 0;
                        ty = parseFloat(args[2]) || 0;
                        if (tx !== 0 || ty !== 0) {
                            ctm = ctm.translate(tx, ty).rotate(angle).translate(-tx, -ty);
                        } else {
                            ctm = ctm.rotate(angle);
                        }
                        break;
                    case 'skewx':
                        angle = parseFloat(args[0]);
                        ctm = ctm.skewX(angle);
                        break;
                    case 'skewy':
                        angle = parseFloat(args[0]);
                        ctm = ctm.skewY(angle);
                        break;
                    case 'matrix':
                        ctm.a = parseFloat(args[0]);
                        ctm.b = parseFloat(args[1]);
                        ctm.c = parseFloat(args[2]);
                        ctm.d = parseFloat(args[3]);
                        ctm.e = parseFloat(args[4]);
                        ctm.f = parseFloat(args[5]);
                        break;
                    default:
                        continue;
                }

                transformationMatrix = transformationMatrix.multiply(ctm);
            }

        }
        return transformationMatrix;
    };

    V.matrixToTransformString = function(matrix) {
        matrix || (matrix = true);

        return 'matrix(' +
            (matrix.a !== undefined ? matrix.a : 1) + ',' +
            (matrix.b !== undefined ? matrix.b : 0) + ',' +
            (matrix.c !== undefined ? matrix.c : 0) + ',' +
            (matrix.d !== undefined ? matrix.d : 1) + ',' +
            (matrix.e !== undefined ? matrix.e : 0) + ',' +
            (matrix.f !== undefined ? matrix.f : 0) +
            ')';
    };

    V.parseTransformString = function(transform) {

        var translate, rotate, scale;

        if (transform) {

            var separator = V.transformSeparatorRegex;

            // Allow reading transform string with a single matrix
            if (transform.trim().indexOf('matrix') >= 0) {

                var matrix = V.transformStringToMatrix(transform);
                var decomposedMatrix = V.decomposeMatrix(matrix);

                translate = [decomposedMatrix.translateX, decomposedMatrix.translateY];
                scale = [decomposedMatrix.scaleX, decomposedMatrix.scaleY];
                rotate = [decomposedMatrix.rotation];

                var transformations = [];
                if (translate[0] !== 0 ||  translate[0] !== 0) {
                    transformations.push('translate(' + translate + ')');
                }
                if (scale[0] !== 1 ||  scale[1] !== 1) {
                    transformations.push('scale(' + scale + ')');
                }
                if (rotate[0] !== 0) {
                    transformations.push('rotate(' + rotate + ')');
                }
                transform = transformations.join(' ');

            } else {

                var translateMatch = transform.match(/translate\((.*?)\)/);
                if (translateMatch) {
                    translate = translateMatch[1].split(separator);
                }
                var rotateMatch = transform.match(/rotate\((.*?)\)/);
                if (rotateMatch) {
                    rotate = rotateMatch[1].split(separator);
                }
                var scaleMatch = transform.match(/scale\((.*?)\)/);
                if (scaleMatch) {
                    scale = scaleMatch[1].split(separator);
                }
            }
        }

        var sx = (scale && scale[0]) ? parseFloat(scale[0]) : 1;

        return {
            value: transform,
            translate: {
                tx: (translate && translate[0]) ? parseInt(translate[0], 10) : 0,
                ty: (translate && translate[1]) ? parseInt(translate[1], 10) : 0
            },
            rotate: {
                angle: (rotate && rotate[0]) ? parseInt(rotate[0], 10) : 0,
                cx: (rotate && rotate[1]) ? parseInt(rotate[1], 10) : undefined,
                cy: (rotate && rotate[2]) ? parseInt(rotate[2], 10) : undefined
            },
            scale: {
                sx: sx,
                sy: (scale && scale[1]) ? parseFloat(scale[1]) : sx
            }
        };
    };

    V.deltaTransformPoint = function(matrix, point) {

        var dx = point.x * matrix.a + point.y * matrix.c + 0;
        var dy = point.x * matrix.b + point.y * matrix.d + 0;
        return { x: dx, y: dy };
    };

    V.decomposeMatrix = function(matrix) {

        // @see https://gist.github.com/2052247

        // calculate delta transform point
        var px = V.deltaTransformPoint(matrix, { x: 0, y: 1 });
        var py = V.deltaTransformPoint(matrix, { x: 1, y: 0 });

        // calculate skew
        var skewX = ((180 / PI) * atan2(px.y, px.x) - 90);
        var skewY = ((180 / PI) * atan2(py.y, py.x));

        return {

            translateX: matrix.e,
            translateY: matrix.f,
            scaleX: sqrt(matrix.a * matrix.a + matrix.b * matrix.b),
            scaleY: sqrt(matrix.c * matrix.c + matrix.d * matrix.d),
            skewX: skewX,
            skewY: skewY,
            rotation: skewX // rotation is the same as skew x
        };
    };

    // Return the `scale` transformation from the following equation:
    // `translate(tx, ty) . rotate(angle) . scale(sx, sy) === matrix(a,b,c,d,e,f)`
    V.matrixToScale = function(matrix) {

        var a,b,c,d;
        if (matrix) {
            a = V.isUndefined(matrix.a) ? 1 : matrix.a;
            d = V.isUndefined(matrix.d) ? 1 : matrix.d;
            b = matrix.b;
            c = matrix.c;
        } else {
            a = d = 1;
        }
        return {
            sx: b ? sqrt(a * a + b * b) : a,
            sy: c ? sqrt(c * c + d * d) : d
        };
    },

    // Return the `rotate` transformation from the following equation:
    // `translate(tx, ty) . rotate(angle) . scale(sx, sy) === matrix(a,b,c,d,e,f)`
    V.matrixToRotate = function(matrix) {

        var p = { x: 0, y: 1 };
        if (matrix) {
            p =  V.deltaTransformPoint(matrix, p);
        }

        return {
            angle: g.normalizeAngle(g.toDeg(atan2(p.y, p.x)) - 90)
        };
    },

    // Return the `translate` transformation from the following equation:
    // `translate(tx, ty) . rotate(angle) . scale(sx, sy) === matrix(a,b,c,d,e,f)`
    V.matrixToTranslate = function(matrix) {

        return {
            tx: (matrix && matrix.e) || 0,
            ty: (matrix && matrix.f) || 0
        };
    },

    V.isV = function(object) {

        return object instanceof V;
    };

    // For backwards compatibility:
    V.isVElement = V.isV;

    var svgDocument = V('svg').node;

    V.createSVGMatrix = function(matrix) {

        var svgMatrix = svgDocument.createSVGMatrix();
        for (var component in matrix) {
            svgMatrix[component] = matrix[component];
        }

        return svgMatrix;
    };

    V.createSVGTransform = function(matrix) {

        if (!V.isUndefined(matrix)) {

            if (!(matrix instanceof SVGMatrix)) {
                matrix = V.createSVGMatrix(matrix);
            }

            return svgDocument.createSVGTransformFromMatrix(matrix);
        }

        return svgDocument.createSVGTransform();
    };

    V.createSVGPoint = function(x, y) {

        var p = svgDocument.createSVGPoint();
        p.x = x;
        p.y = y;
        return p;
    };

    V.transformRect = function(r, matrix) {

        var p = svgDocument.createSVGPoint();

        p.x = r.x;
        p.y = r.y;
        var corner1 = p.matrixTransform(matrix);

        p.x = r.x + r.width;
        p.y = r.y;
        var corner2 = p.matrixTransform(matrix);

        p.x = r.x + r.width;
        p.y = r.y + r.height;
        var corner3 = p.matrixTransform(matrix);

        p.x = r.x;
        p.y = r.y + r.height;
        var corner4 = p.matrixTransform(matrix);

        var minX = min(corner1.x, corner2.x, corner3.x, corner4.x);
        var maxX = max(corner1.x, corner2.x, corner3.x, corner4.x);
        var minY = min(corner1.y, corner2.y, corner3.y, corner4.y);
        var maxY = max(corner1.y, corner2.y, corner3.y, corner4.y);

        return new g.Rect(minX, minY, maxX - minX, maxY - minY);
    };

    V.transformPoint = function(p, matrix) {

        return new g.Point(V.createSVGPoint(p.x, p.y).matrixTransform(matrix));
    };

    V.transformLine = function(l, matrix) {

        return new g.Line(
            V.transformPoint(l.start, matrix),
            V.transformPoint(l.end, matrix)
        );
    };

    V.transformPolyline = function(p, matrix) {

        var inPoints = (p instanceof g.Polyline) ? p.points : p;
        if (!V.isArray(inPoints)) inPoints = [];
        var outPoints = [];
        for (var i = 0, n = inPoints.length; i < n; i++) outPoints[i] = V.transformPoint(inPoints[i], matrix);
        return new g.Polyline(outPoints);
    },

    // Convert a style represented as string (e.g. `'fill="blue"; stroke="red"'`) to
    // an object (`{ fill: 'blue', stroke: 'red' }`).
    V.styleToObject = function(styleString) {
        var ret = {};
        var styles = styleString.split(';');
        for (var i = 0; i < styles.length; i++) {
            var style = styles[i];
            var pair = style.split('=');
            ret[pair[0].trim()] = pair[1].trim();
        }
        return ret;
    };

    // Inspired by d3.js https://github.com/mbostock/d3/blob/master/src/svg/arc.js
    V.createSlicePathData = function(innerRadius, outerRadius, startAngle, endAngle) {

        var svgArcMax = 2 * PI - 1e-6;
        var r0 = innerRadius;
        var r1 = outerRadius;
        var a0 = startAngle;
        var a1 = endAngle;
        var da = (a1 < a0 && (da = a0, a0 = a1, a1 = da), a1 - a0);
        var df = da < PI ? '0' : '1';
        var c0 = cos(a0);
        var s0 = sin(a0);
        var c1 = cos(a1);
        var s1 = sin(a1);

        return (da >= svgArcMax)
            ? (r0
               ? 'M0,' + r1
               + 'A' + r1 + ',' + r1 + ' 0 1,1 0,' + (-r1)
               + 'A' + r1 + ',' + r1 + ' 0 1,1 0,' + r1
               + 'M0,' + r0
               + 'A' + r0 + ',' + r0 + ' 0 1,0 0,' + (-r0)
               + 'A' + r0 + ',' + r0 + ' 0 1,0 0,' + r0
               + 'Z'
               : 'M0,' + r1
               + 'A' + r1 + ',' + r1 + ' 0 1,1 0,' + (-r1)
               + 'A' + r1 + ',' + r1 + ' 0 1,1 0,' + r1
               + 'Z')
            : (r0
               ? 'M' + r1 * c0 + ',' + r1 * s0
               + 'A' + r1 + ',' + r1 + ' 0 ' + df + ',1 ' + r1 * c1 + ',' + r1 * s1
               + 'L' + r0 * c1 + ',' + r0 * s1
               + 'A' + r0 + ',' + r0 + ' 0 ' + df + ',0 ' + r0 * c0 + ',' + r0 * s0
               + 'Z'
               : 'M' + r1 * c0 + ',' + r1 * s0
               + 'A' + r1 + ',' + r1 + ' 0 ' + df + ',1 ' + r1 * c1 + ',' + r1 * s1
               + 'L0,0'
               + 'Z');
    };

    // Merge attributes from object `b` with attributes in object `a`.
    // Note that this modifies the object `a`.
    // Also important to note that attributes are merged but CSS classes are concatenated.
    V.mergeAttrs = function(a, b) {

        for (var attr in b) {

            if (attr === 'class') {
                // Concatenate classes.
                a[attr] = a[attr] ? a[attr] + ' ' + b[attr] : b[attr];
            } else if (attr === 'style') {
                // `style` attribute can be an object.
                if (V.isObject(a[attr]) && V.isObject(b[attr])) {
                    // `style` stored in `a` is an object.
                    a[attr] = V.mergeAttrs(a[attr], b[attr]);
                } else if (V.isObject(a[attr])) {
                    // `style` in `a` is an object but it's a string in `b`.
                    // Convert the style represented as a string to an object in `b`.
                    a[attr] = V.mergeAttrs(a[attr], V.styleToObject(b[attr]));
                } else if (V.isObject(b[attr])) {
                    // `style` in `a` is a string, in `b` it's an object.
                    a[attr] = V.mergeAttrs(V.styleToObject(a[attr]), b[attr]);
                } else {
                    // Both styles are strings.
                    a[attr] = V.mergeAttrs(V.styleToObject(a[attr]), V.styleToObject(b[attr]));
                }
            } else {
                a[attr] = b[attr];
            }
        }

        return a;
    };

    V.annotateString = function(t, annotations, opt) {

        annotations = annotations || [];
        opt = opt || {};

        var offset = opt.offset || 0;
        var compacted = [];
        var batch;
        var ret = [];
        var item;
        var prev;

        for (var i = 0; i < t.length; i++) {

            item = ret[i] = t[i];

            for (var j = 0; j < annotations.length; j++) {

                var annotation = annotations[j];
                var start = annotation.start + offset;
                var end = annotation.end + offset;

                if (i >= start && i < end) {
                    // Annotation applies.
                    if (V.isObject(item)) {
                        // There is more than one annotation to be applied => Merge attributes.
                        item.attrs = V.mergeAttrs(V.mergeAttrs({}, item.attrs), annotation.attrs);
                    } else {
                        item = ret[i] = { t: t[i], attrs: annotation.attrs };
                    }
                    if (opt.includeAnnotationIndices) {
                        (item.annotations || (item.annotations = [])).push(j);
                    }
                }
            }

            prev = ret[i - 1];

            if (!prev) {

                batch = item;

            } else if (V.isObject(item) && V.isObject(prev)) {
                // Both previous item and the current one are annotations. If the attributes
                // didn't change, merge the text.
                if (JSON.stringify(item.attrs) === JSON.stringify(prev.attrs)) {
                    batch.t += item.t;
                } else {
                    compacted.push(batch);
                    batch = item;
                }

            } else if (V.isObject(item)) {
                // Previous item was a string, current item is an annotation.
                compacted.push(batch);
                batch = item;

            } else if (V.isObject(prev)) {
                // Previous item was an annotation, current item is a string.
                compacted.push(batch);
                batch = item;

            } else {
                // Both previous and current item are strings.
                batch = (batch || '') + item;
            }
        }

        if (batch) {
            compacted.push(batch);
        }

        return compacted;
    };

    V.findAnnotationsAtIndex = function(annotations, index) {

        var found = [];

        if (annotations) {

            annotations.forEach(function(annotation) {

                if (annotation.start < index && index <= annotation.end) {
                    found.push(annotation);
                }
            });
        }

        return found;
    };

    V.findAnnotationsBetweenIndexes = function(annotations, start, end) {

        var found = [];

        if (annotations) {

            annotations.forEach(function(annotation) {

                if ((start >= annotation.start && start < annotation.end) || (end > annotation.start && end <= annotation.end) || (annotation.start >= start && annotation.end < end)) {
                    found.push(annotation);
                }
            });
        }

        return found;
    };

    // Shift all the text annotations after character `index` by `offset` positions.
    V.shiftAnnotations = function(annotations, index, offset) {

        if (annotations) {

            annotations.forEach(function(annotation) {

                if (annotation.start < index && annotation.end >= index) {
                    annotation.end += offset;
                } else if (annotation.start >= index) {
                    annotation.start += offset;
                    annotation.end += offset;
                }
            });
        }

        return annotations;
    };

    V.convertLineToPathData = function(line) {

        line = V(line);
        var d = [
            'M', line.attr('x1'), line.attr('y1'),
            'L', line.attr('x2'), line.attr('y2')
        ].join(' ');
        return d;
    };

    V.convertPolygonToPathData = function(polygon) {

        var points = V.getPointsFromSvgNode(polygon);
        if (points.length === 0) return null;

        return V.svgPointsToPath(points) + ' Z';
    };

    V.convertPolylineToPathData = function(polyline) {

        var points = V.getPointsFromSvgNode(polyline);
        if (points.length === 0) return null;

        return V.svgPointsToPath(points);
    };

    V.svgPointsToPath = function(points) {

        for (var i = 0, n = points.length; i < n; i++) {
            points[i] = points[i].x + ' ' + points[i].y;
        }

        return 'M ' + points.join(' L');
    };

    V.getPointsFromSvgNode = function(node) {

        node = V.toNode(node);
        var points = [];
        var nodePoints = node.points;
        if (nodePoints) {
            for (var i = 0, n = nodePoints.numberOfItems; i < n; i++) {
                points.push(nodePoints.getItem(i));
            }
        }

        return points;
    };

    V.KAPPA = 0.551784;

    V.convertCircleToPathData = function(circle) {

        circle = V(circle);
        var cx = parseFloat(circle.attr('cx')) || 0;
        var cy = parseFloat(circle.attr('cy')) || 0;
        var r = parseFloat(circle.attr('r'));
        var cd = r * V.KAPPA; // Control distance.

        var d = [
            'M', cx, cy - r,    // Move to the first point.
            'C', cx + cd, cy - r, cx + r, cy - cd, cx + r, cy, // I. Quadrant.
            'C', cx + r, cy + cd, cx + cd, cy + r, cx, cy + r, // II. Quadrant.
            'C', cx - cd, cy + r, cx - r, cy + cd, cx - r, cy, // III. Quadrant.
            'C', cx - r, cy - cd, cx - cd, cy - r, cx, cy - r, // IV. Quadrant.
            'Z'
        ].join(' ');
        return d;
    };

    V.convertEllipseToPathData = function(ellipse) {

        ellipse = V(ellipse);
        var cx = parseFloat(ellipse.attr('cx')) || 0;
        var cy = parseFloat(ellipse.attr('cy')) || 0;
        var rx = parseFloat(ellipse.attr('rx'));
        var ry = parseFloat(ellipse.attr('ry')) || rx;
        var cdx = rx * V.KAPPA; // Control distance x.
        var cdy = ry * V.KAPPA; // Control distance y.

        var d = [
            'M', cx, cy - ry,    // Move to the first point.
            'C', cx + cdx, cy - ry, cx + rx, cy - cdy, cx + rx, cy, // I. Quadrant.
            'C', cx + rx, cy + cdy, cx + cdx, cy + ry, cx, cy + ry, // II. Quadrant.
            'C', cx - cdx, cy + ry, cx - rx, cy + cdy, cx - rx, cy, // III. Quadrant.
            'C', cx - rx, cy - cdy, cx - cdx, cy - ry, cx, cy - ry, // IV. Quadrant.
            'Z'
        ].join(' ');
        return d;
    };

    V.convertRectToPathData = function(rect) {

        rect = V(rect);

        return V.rectToPath({
            x: parseFloat(rect.attr('x')) || 0,
            y: parseFloat(rect.attr('y')) || 0,
            width: parseFloat(rect.attr('width')) || 0,
            height: parseFloat(rect.attr('height')) || 0,
            rx: parseFloat(rect.attr('rx')) || 0,
            ry: parseFloat(rect.attr('ry')) || 0
        });
    };

    // Convert a rectangle to SVG path commands. `r` is an object of the form:
    // `{ x: [number], y: [number], width: [number], height: [number], top-ry: [number], top-ry: [number], bottom-rx: [number], bottom-ry: [number] }`,
    // where `x, y, width, height` are the usual rectangle attributes and [top-/bottom-]rx/ry allows for
    // specifying radius of the rectangle for all its sides (as opposed to the built-in SVG rectangle
    // that has only `rx` and `ry` attributes).
    V.rectToPath = function(r) {

        var d;
        var x = r.x;
        var y = r.y;
        var width = r.width;
        var height = r.height;
        var topRx = min(r.rx || r['top-rx'] || 0, width / 2);
        var bottomRx = min(r.rx || r['bottom-rx'] || 0, width / 2);
        var topRy = min(r.ry || r['top-ry'] || 0, height / 2);
        var bottomRy = min(r.ry || r['bottom-ry'] || 0, height / 2);

        if (topRx || bottomRx || topRy || bottomRy) {
            d = [
                'M', x, y + topRy,
                'v', height - topRy - bottomRy,
                'a', bottomRx, bottomRy, 0, 0, 0, bottomRx, bottomRy,
                'h', width - 2 * bottomRx,
                'a', bottomRx, bottomRy, 0, 0, 0, bottomRx, -bottomRy,
                'v', -(height - bottomRy - topRy),
                'a', topRx, topRy, 0, 0, 0, -topRx, -topRy,
                'h', -(width - 2 * topRx),
                'a', topRx, topRy, 0, 0, 0, -topRx, topRy,
                'Z'
            ];
        } else {
            d = [
                'M', x, y,
                'H', x + width,
                'V', y + height,
                'H', x,
                'V', y,
                'Z'
            ];
        }

        return d.join(' ');
    };

    // Take a path data string
    // Return a normalized path data string
    // If data cannot be parsed, return 'M 0 0'
    // Adapted from Rappid normalizePath polyfill
    // Highly inspired by Raphael Library (www.raphael.com)
    V.normalizePathData = (function() {

        var spaces = '\x09\x0a\x0b\x0c\x0d\x20\xa0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u202f\u205f\u3000\u2028\u2029';
        var pathCommand = new RegExp('([a-z])[' + spaces + ',]*((-?\\d*\\.?\\d*(?:e[\\-+]?\\d+)?[' + spaces + ']*,?[' + spaces + ']*)+)', 'ig');
        var pathValues = new RegExp('(-?\\d*\\.?\\d*(?:e[\\-+]?\\d+)?)[' + spaces + ']*,?[' + spaces + ']*', 'ig');

        var math = Math;
        var PI = math.PI;
        var sin = math.sin;
        var cos = math.cos;
        var tan = math.tan;
        var asin = math.asin;
        var sqrt = math.sqrt;
        var abs = math.abs;

        function q2c(x1, y1, ax, ay, x2, y2) {

            var _13 = 1 / 3;
            var _23 = 2 / 3;
            return [(_13 * x1) + (_23 * ax), (_13 * y1) + (_23 * ay), (_13 * x2) + (_23 * ax), (_13 * y2) + (_23 * ay), x2, y2];
        }

        function a2c(x1, y1, rx, ry, angle, large_arc_flag, sweep_flag, x2, y2, recursive) {
            // for more information of where this math came from visit:
            // http://www.w3.org/TR/SVG11/implnote.html#ArcImplementationNotes

            var _120 = (PI * 120) / 180;
            var rad = (PI / 180) * (+angle || 0);
            var res = [];
            var xy;

            var rotate = function(x, y, rad) {

                var X = (x * cos(rad)) - (y * sin(rad));
                var Y = (x * sin(rad)) + (y * cos(rad));
                return { x: X, y: Y };
            };

            if (!recursive) {
                xy = rotate(x1, y1, -rad);
                x1 = xy.x;
                y1 = xy.y;

                xy = rotate(x2, y2, -rad);
                x2 = xy.x;
                y2 = xy.y;

                var x = (x1 - x2) / 2;
                var y = (y1 - y2) / 2;
                var h = ((x * x) / (rx * rx)) + ((y * y) / (ry * ry));

                if (h > 1) {
                    h = sqrt(h);
                    rx = h * rx;
                    ry = h * ry;
                }

                var rx2 = rx * rx;
                var ry2 = ry * ry;

                var k = ((large_arc_flag == sweep_flag) ? -1 : 1) * sqrt(abs(((rx2 * ry2) - (rx2 * y * y) - (ry2 * x * x)) / ((rx2 * y * y) + (ry2 * x * x))));

                var cx = ((k * rx * y) / ry) + ((x1 + x2) / 2);
                var cy = ((k * -ry * x) / rx) + ((y1 + y2) / 2);

                var f1 = asin(((y1 - cy) / ry).toFixed(9));
                var f2 = asin(((y2 - cy) / ry).toFixed(9));

                f1 = ((x1 < cx) ? (PI - f1) : f1);
                f2 = ((x2 < cx) ? (PI - f2) : f2);

                if (f1 < 0) f1 = (PI * 2) + f1;
                if (f2 < 0) f2 = (PI * 2) + f2;

                if ((sweep_flag && f1) > f2) f1 = f1 - (PI * 2);
                if ((!sweep_flag && f2) > f1) f2 = f2 - (PI * 2);

            } else {
                f1 = recursive[0];
                f2 = recursive[1];
                cx = recursive[2];
                cy = recursive[3];
            }

            var df = f2 - f1;

            if (abs(df) > _120) {
                var f2old = f2;
                var x2old = x2;
                var y2old = y2;

                f2 = f1 + (_120 * (((sweep_flag && f2) > f1) ? 1 : -1));
                x2 = cx + (rx * cos(f2));
                y2 = cy + (ry * sin(f2));

                res = a2c(x2, y2, rx, ry, angle, 0, sweep_flag, x2old, y2old, [f2, f2old, cx, cy]);
            }

            df = f2 - f1;

            var c1 = cos(f1);
            var s1 = sin(f1);
            var c2 = cos(f2);
            var s2 = sin(f2);

            var t = tan(df / 4);

            var hx = (4 / 3) * (rx * t);
            var hy = (4 / 3) * (ry * t);

            var m1 = [x1, y1];
            var m2 = [x1 + (hx * s1), y1 - (hy * c1)];
            var m3 = [x2 + (hx * s2), y2 - (hy * c2)];
            var m4 = [x2, y2];

            m2[0] = (2 * m1[0]) - m2[0];
            m2[1] = (2 * m1[1]) - m2[1];

            if (recursive) {
                return [m2, m3, m4].concat(res);

            } else {
                res = [m2, m3, m4].concat(res).join().split(',');

                var newres = [];
                var ii = res.length;
                for (var i = 0; i < ii; i++) {
                    newres[i] = (i % 2) ? rotate(res[i - 1], res[i], rad).y : rotate(res[i], res[i + 1], rad).x;
                }

                return newres;
            }
        }

        function parsePathString(pathString) {

            if (!pathString) return null;

            var paramCounts = { a: 7, c: 6, h: 1, l: 2, m: 2, q: 4, s: 4, t: 2, v: 1, z: 0 };
            var data = [];

            String(pathString).replace(pathCommand, function(a, b, c) {

                var params = [];
                var name = b.toLowerCase();
                c.replace(pathValues, function(a, b) {
                    if (b) params.push(+b);
                });

                if ((name === 'm') && (params.length > 2)) {
                    data.push([b].concat(params.splice(0, 2)));
                    name = 'l';
                    b = ((b === 'm') ? 'l' : 'L');
                }

                while (params.length >= paramCounts[name]) {
                    data.push([b].concat(params.splice(0, paramCounts[name])));
                    if (!paramCounts[name]) break;
                }
            });

            return data;
        }

        function pathToAbsolute(pathArray) {

            if (!Array.isArray(pathArray) || !Array.isArray(pathArray && pathArray[0])) { // rough assumption
                pathArray = parsePathString(pathArray);
            }

            // if invalid string, return 'M 0 0'
            if (!pathArray || !pathArray.length) return [['M', 0, 0]];

            var res = [];
            var x = 0;
            var y = 0;
            var mx = 0;
            var my = 0;
            var start = 0;
            var pa0;

            var ii = pathArray.length;
            for (var i = start; i < ii; i++) {

                var r = [];
                res.push(r);

                var pa = pathArray[i];
                pa0 = pa[0];

                if (pa0 != pa0.toUpperCase()) {
                    r[0] = pa0.toUpperCase();

                    var jj;
                    var j;
                    switch (r[0]) {
                        case 'A':
                            r[1] = pa[1];
                            r[2] = pa[2];
                            r[3] = pa[3];
                            r[4] = pa[4];
                            r[5] = pa[5];
                            r[6] = +pa[6] + x;
                            r[7] = +pa[7] + y;
                            break;

                        case 'V':
                            r[1] = +pa[1] + y;
                            break;

                        case 'H':
                            r[1] = +pa[1] + x;
                            break;

                        case 'M':
                            mx = +pa[1] + x;
                            my = +pa[2] + y;

                            jj = pa.length;
                            for (j = 1; j < jj; j++) {
                                r[j] = +pa[j] + ((j % 2) ? x : y);
                            }
                            break;

                        default:
                            jj = pa.length;
                            for (j = 1; j < jj; j++) {
                                r[j] = +pa[j] + ((j % 2) ? x : y);
                            }
                            break;
                    }
                } else {
                    var kk = pa.length;
                    for (var k = 0; k < kk; k++) {
                        r[k] = pa[k];
                    }
                }

                switch (r[0]) {
                    case 'Z':
                        x = +mx;
                        y = +my;
                        break;

                    case 'H':
                        x = r[1];
                        break;

                    case 'V':
                        y = r[1];
                        break;

                    case 'M':
                        mx = r[r.length - 2];
                        my = r[r.length - 1];
                        x = r[r.length - 2];
                        y = r[r.length - 1];
                        break;

                    default:
                        x = r[r.length - 2];
                        y = r[r.length - 1];
                        break;
                }
            }

            return res;
        }

        function normalize(path) {

            var p = pathToAbsolute(path);
            var attrs = { x: 0, y: 0, bx: 0, by: 0, X: 0, Y: 0, qx: null, qy: null };

            function processPath(path, d, pcom) {

                var nx, ny;

                if (!path) return ['C', d.x, d.y, d.x, d.y, d.x, d.y];

                if (!(path[0] in { T: 1, Q: 1 })) {
                    d.qx = null;
                    d.qy = null;
                }

                switch (path[0]) {
                    case 'M':
                        d.X = path[1];
                        d.Y = path[2];
                        break;

                    case 'A':
                        path = ['C'].concat(a2c.apply(0, [d.x, d.y].concat(path.slice(1))));
                        break;

                    case 'S':
                        if (pcom === 'C' || pcom === 'S') { // In 'S' case we have to take into account, if the previous command is C/S.
                            nx = (d.x * 2) - d.bx;          // And reflect the previous
                            ny = (d.y * 2) - d.by;          // command's control point relative to the current point.
                        }
                        else {                            // or some else or nothing
                            nx = d.x;
                            ny = d.y;
                        }
                        path = ['C', nx, ny].concat(path.slice(1));
                        break;

                    case 'T':
                        if (pcom === 'Q' || pcom === 'T') { // In 'T' case we have to take into account, if the previous command is Q/T.
                            d.qx = (d.x * 2) - d.qx;        // And make a reflection similar
                            d.qy = (d.y * 2) - d.qy;        // to case 'S'.
                        }
                        else {                            // or something else or nothing
                            d.qx = d.x;
                            d.qy = d.y;
                        }
                        path = ['C'].concat(q2c(d.x, d.y, d.qx, d.qy, path[1], path[2]));
                        break;

                    case 'Q':
                        d.qx = path[1];
                        d.qy = path[2];
                        path = ['C'].concat(q2c(d.x, d.y, path[1], path[2], path[3], path[4]));
                        break;

                    case 'H':
                        path = ['L'].concat(path[1], d.y);
                        break;

                    case 'V':
                        path = ['L'].concat(d.x, path[1]);
                        break;

                    // leave 'L' & 'Z' commands as they were:

                    case 'L':
                        break;

                    case 'Z':
                        break;
                }

                return path;
            }

            function fixArc(pp, i) {

                if (pp[i].length > 7) {

                    pp[i].shift();
                    var pi = pp[i];

                    while (pi.length) {
                        pcoms[i] = 'A'; // if created multiple 'C's, their original seg is saved
                        pp.splice(i++, 0, ['C'].concat(pi.splice(0, 6)));
                    }

                    pp.splice(i, 1);
                    ii = p.length;
                }
            }

            var pcoms = []; // path commands of original path p
            var pfirst = ''; // temporary holder for original path command
            var pcom = ''; // holder for previous path command of original path

            var ii = p.length;
            for (var i = 0; i < ii; i++) {
                if (p[i]) pfirst = p[i][0]; // save current path command

                if (pfirst !== 'C') { // C is not saved yet, because it may be result of conversion
                    pcoms[i] = pfirst; // Save current path command
                    if (i > 0) pcom = pcoms[i - 1]; // Get previous path command pcom
                }

                p[i] = processPath(p[i], attrs, pcom); // Previous path command is inputted to processPath

                if (pcoms[i] !== 'A' && pfirst === 'C') pcoms[i] = 'C'; // 'A' is the only command
                // which may produce multiple 'C's
                // so we have to make sure that 'C' is also 'C' in original path

                fixArc(p, i); // fixArc adds also the right amount of 'A's to pcoms

                var seg = p[i];
                var seglen = seg.length;

                attrs.x = seg[seglen - 2];
                attrs.y = seg[seglen - 1];

                attrs.bx = parseFloat(seg[seglen - 4]) || attrs.x;
                attrs.by = parseFloat(seg[seglen - 3]) || attrs.y;
            }

            // make sure normalized path data string starts with an M segment
            if (!p[0][0] || p[0][0] !== 'M') {
                p.unshift(['M', 0, 0]);
            }

            return p;
        }

        return function(pathData) {
            return normalize(pathData).join(',').split(',').join(' ');
        };
    })();

    V.namespace = ns;

    return V;

})();

// Global namespace.

var joint = {

    version: '2.1.2',

    config: {
        // The class name prefix config is for advanced use only.
        // Be aware that if you change the prefix, the JointJS CSS will no longer function properly.
        classNamePrefix: 'joint-',
        defaultTheme: 'default'
    },

    // `joint.dia` namespace.
    dia: {},

    // `joint.ui` namespace.
    ui: {},

    // `joint.layout` namespace.
    layout: {},

    // `joint.shapes` namespace.
    shapes: {},

    // `joint.format` namespace.
    format: {},

    // `joint.connectors` namespace.
    connectors: {},

    // `joint.highlighters` namespace.
    highlighters: {},

    // `joint.routers` namespace.
    routers: {},

    // `joint.anchors` namespace.
    anchors: {},

    // `joint.connectionPoints` namespace.
    connectionPoints: {},

    // `joint.connectionStrategies` namespace.
    connectionStrategies: {},

    // `joint.linkTools` namespace.
    linkTools: {},

    // `joint.mvc` namespace.
    mvc: {
        views: {}
    },

    setTheme: function(theme, opt) {

        opt = opt || {};

        joint.util.invoke(joint.mvc.views, 'setTheme', theme, opt);

        // Update the default theme on the view prototype.
        joint.mvc.View.prototype.defaultTheme = theme;
    },

    // `joint.env` namespace.
    env: {

        _results: {},

        _tests: {

            svgforeignobject: function() {
                return !!document.createElementNS &&
              /SVGForeignObject/.test(({}).toString.call(document.createElementNS('http://www.w3.org/2000/svg', 'foreignObject')));
            }
        },

        addTest: function(name, fn) {

            return joint.env._tests[name] = fn;
        },

        test: function(name) {

            var fn = joint.env._tests[name];

            if (!fn) {
                throw new Error('Test not defined ("' + name + '"). Use `joint.env.addTest(name, fn) to add a new test.`');
            }

            var result = joint.env._results[name];

            if (typeof result !== 'undefined') {
                return result;
            }

            try {
                result = fn();
            } catch (error) {
                result = false;
            }

            // Cache the test result.
            joint.env._results[name] = result;

            return result;
        }
    },

    util: {

        // Return a simple hash code from a string. See http://werxltd.com/wp/2010/05/13/javascript-implementation-of-javas-string-hashcode-method/.
        hashCode: function(str) {

            var hash = 0;
            if (str.length == 0) return hash;
            for (var i = 0; i < str.length; i++) {
                var c = str.charCodeAt(i);
                hash = ((hash << 5) - hash) + c;
                hash = hash & hash; // Convert to 32bit integer
            }
            return hash;
        },

        getByPath: function(obj, path, delim) {

            var keys = Array.isArray(path) ? path.slice() : path.split(delim || '/');
            var key;

            while (keys.length) {
                key = keys.shift();
                if (Object(obj) === obj && key in obj) {
                    obj = obj[key];
                } else {
                    return undefined;
                }
            }
            return obj;
        },

        setByPath: function(obj, path, value, delim) {

            var keys = Array.isArray(path) ? path : path.split(delim || '/');

            var diver = obj;
            var i = 0;

            for (var len = keys.length; i < len - 1; i++) {
                // diver creates an empty object if there is no nested object under such a key.
                // This means that one can populate an empty nested object with setByPath().
                diver = diver[keys[i]] || (diver[keys[i]] = {});
            }
            diver[keys[len - 1]] = value;

            return obj;
        },

        unsetByPath: function(obj, path, delim) {

            delim = delim || '/';

            var pathArray = Array.isArray(path) ? path.slice() : path.split(delim);

            var propertyToRemove = pathArray.pop();
            if (pathArray.length > 0) {

                // unsetting a nested attribute
                var parent = joint.util.getByPath(obj, pathArray, delim);

                if (parent) {
                    delete parent[propertyToRemove];
                }

            } else {

                // unsetting a primitive attribute
                delete obj[propertyToRemove];
            }

            return obj;
        },

        flattenObject: function(obj, delim, stop) {

            delim = delim || '/';
            var ret = {};

            for (var key in obj) {

                if (!obj.hasOwnProperty(key)) continue;

                var shouldGoDeeper = typeof obj[key] === 'object';
                if (shouldGoDeeper && stop && stop(obj[key])) {
                    shouldGoDeeper = false;
                }

                if (shouldGoDeeper) {

                    var flatObject = this.flattenObject(obj[key], delim, stop);

                    for (var flatKey in flatObject) {
                        if (!flatObject.hasOwnProperty(flatKey)) continue;
                        ret[key + delim + flatKey] = flatObject[flatKey];
                    }

                } else {

                    ret[key] = obj[key];
                }
            }

            return ret;
        },

        uuid: function() {

            // credit: http://stackoverflow.com/posts/2117523/revisions

            return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
                var r = Math.random() * 16|0;
                var v = c == 'x' ? r : (r&0x3|0x8);
                return v.toString(16);
            });
        },

        // Generate global unique id for obj and store it as a property of the object.
        guid: function(obj) {

            this.guid.id = this.guid.id || 1;
            obj.id = (obj.id === undefined ? 'j_' + this.guid.id++ : obj.id);
            return obj.id;
        },

        toKebabCase: function(string) {

            return string.replace(/[A-Z]/g, '-$&').toLowerCase();
        },

        // Copy all the properties to the first argument from the following arguments.
        // All the properties will be overwritten by the properties from the following
        // arguments. Inherited properties are ignored.
        mixin: _.assign,

        // Copy all properties to the first argument from the following
        // arguments only in case if they don't exists in the first argument.
        // All the function propererties in the first argument will get
        // additional property base pointing to the extenders same named
        // property function's call method.
        supplement: _.defaults,

        // Same as `mixin()` but deep version.
        deepMixin: _.mixin,

        // Same as `supplement()` but deep version.
        deepSupplement: _.defaultsDeep,

        normalizeEvent: function(evt) {

            var touchEvt = evt.originalEvent && evt.originalEvent.changedTouches && evt.originalEvent.changedTouches[0];
            if (touchEvt) {
                for (var property in evt) {
                    // copy all the properties from the input event that are not
                    // defined on the touch event (functions included).
                    if (touchEvt[property] === undefined) {
                        touchEvt[property] = evt[property];
                    }
                }
                return touchEvt;
            }

            return evt;
        },

        nextFrame: (function() {

            var raf;

            if (typeof window !== 'undefined') {

                raf = window.requestAnimationFrame ||
                        window.webkitRequestAnimationFrame ||
                        window.mozRequestAnimationFrame ||
                        window.oRequestAnimationFrame ||
                        window.msRequestAnimationFrame;
            }

            if (!raf) {

                var lastTime = 0;

                raf = function(callback) {

                    var currTime = new Date().getTime();
                    var timeToCall = Math.max(0, 16 - (currTime - lastTime));
                    var id = setTimeout(function() { callback(currTime + timeToCall); }, timeToCall);

                    lastTime = currTime + timeToCall;

                    return id;
                };
            }

            return function(callback, context) {
                return context
                    ? raf(callback.bind(context))
                    : raf(callback);
            };

        })(),

        cancelFrame: (function() {

            var caf;
            var client = typeof window != 'undefined';

            if (client) {

                caf = window.cancelAnimationFrame ||
                        window.webkitCancelAnimationFrame ||
                        window.webkitCancelRequestAnimationFrame ||
                        window.msCancelAnimationFrame ||
                        window.msCancelRequestAnimationFrame ||
                        window.oCancelAnimationFrame ||
                        window.oCancelRequestAnimationFrame ||
                        window.mozCancelAnimationFrame ||
                        window.mozCancelRequestAnimationFrame;
            }

            caf = caf || clearTimeout;

            return client ? caf.bind(window) : caf;

        })(),

        // ** Deprecated **
        shapePerimeterConnectionPoint: function(linkView, view, magnet, reference) {

            var bbox;
            var spot;

            if (!magnet) {

                // There is no magnet, try to make the best guess what is the
                // wrapping SVG element. This is because we want this "smart"
                // connection points to work out of the box without the
                // programmer to put magnet marks to any of the subelements.
                // For example, we want the functoin to work on basic.Path elements
                // without any special treatment of such elements.
                // The code below guesses the wrapping element based on
                // one simple assumption. The wrapping elemnet is the
                // first child of the scalable group if such a group exists
                // or the first child of the rotatable group if not.
                // This makese sense because usually the wrapping element
                // is below any other sub element in the shapes.
                var scalable = view.$('.scalable')[0];
                var rotatable = view.$('.rotatable')[0];

                if (scalable && scalable.firstChild) {

                    magnet = scalable.firstChild;

                } else if (rotatable && rotatable.firstChild) {

                    magnet = rotatable.firstChild;
                }
            }

            if (magnet) {

                spot = V(magnet).findIntersection(reference, linkView.paper.viewport);
                if (!spot) {
                    bbox = V(magnet).getBBox({ target: linkView.paper.viewport });
                }

            } else {

                bbox = view.model.getBBox();
                spot = bbox.intersectionWithLineFromCenterToPoint(reference);
            }
            return spot || bbox.center();
        },

        isPercentage: function(val) {

            return joint.util.isString(val) && val.slice(-1) === '%';
        },

        parseCssNumeric: function(strValue, restrictUnits) {

            restrictUnits = restrictUnits || [];
            var cssNumeric = { value: parseFloat(strValue) };

            if (Number.isNaN(cssNumeric.value)) {
                return null;
            }

            var validUnitsExp = restrictUnits.join('|');

            if (joint.util.isString(strValue)) {
                var matches = new RegExp('(\\d+)(' + validUnitsExp + ')$').exec(strValue);
                if (!matches) {
                    return null;
                }
                if (matches[2]) {
                    cssNumeric.unit = matches[2];
                }
            }
            return cssNumeric;
        },

        breakText: function(text, size, styles, opt) {

            opt = opt || {};
            styles = styles || {};

            var width = size.width;
            var height = size.height;

            var svgDocument = opt.svgDocument || V('svg').node;
            var textSpan = V('tspan').node;
            var textElement = V('text').attr(styles).append(textSpan).node;
            var textNode = document.createTextNode('');

            // Prevent flickering
            textElement.style.opacity = 0;
            // Prevent FF from throwing an uncaught exception when `getBBox()`
            // called on element that is not in the render tree (is not measurable).
            // <tspan>.getComputedTextLength() returns always 0 in this case.
            // Note that the `textElement` resp. `textSpan` can become hidden
            // when it's appended to the DOM and a `display: none` CSS stylesheet
            // rule gets applied.
            textElement.style.display = 'block';
            textSpan.style.display = 'block';

            textSpan.appendChild(textNode);
            svgDocument.appendChild(textElement);

            if (!opt.svgDocument) {

                document.body.appendChild(svgDocument);
            }

            var separator = opt.separator || ' ';
            var eol = opt.eol || '\n';

            var words = text.split(separator);
            var full = [];
            var lines = [];
            var p;
            var lineHeight;

            for (var i = 0, l = 0, len = words.length; i < len; i++) {

                var word = words[i];

                if (!word) continue;

                if (eol && word.indexOf(eol) >= 0) {
                    // word cotains end-of-line character
                    if (word.length > 1) {
                        // separate word and continue cycle
                        var eolWords = word.split(eol);
                        for (var j = 0, jl = eolWords.length - 1; j < jl; j++) {
                            eolWords.splice(2 * j + 1, 0, eol);
                        }
                        Array.prototype.splice.apply(words, [i, 1].concat(eolWords));
                        i--;
                        len += eolWords.length - 1;
                    } else {
                        // creates new line
                        l++;
                    }
                    continue;
                }


                textNode.data = lines[l] ? lines[l] + ' ' + word : word;

                if (textSpan.getComputedTextLength() <= width) {

                    // the current line fits
                    lines[l] = textNode.data;

                    if (p) {
                        // We were partitioning. Put rest of the word onto next line
                        full[l++] = true;

                        // cancel partitioning
                        p = 0;
                    }

                } else {

                    if (!lines[l] || p) {

                        var partition = !!p;

                        p = word.length - 1;

                        if (partition || !p) {

                            // word has only one character.
                            if (!p) {

                                if (!lines[l]) {

                                    // we won't fit this text within our rect
                                    lines = [];

                                    break;
                                }

                                // partitioning didn't help on the non-empty line
                                // try again, but this time start with a new line

                                // cancel partitions created
                                words.splice(i, 2, word + words[i + 1]);

                                // adjust word length
                                len--;

                                full[l++] = true;
                                i--;

                                continue;
                            }

                            // move last letter to the beginning of the next word
                            words[i] = word.substring(0, p);
                            words[i + 1] = word.substring(p) + words[i + 1];

                        } else {

                            // We initiate partitioning
                            // split the long word into two words
                            words.splice(i, 1, word.substring(0, p), word.substring(p));

                            // adjust words length
                            len++;

                            if (l && !full[l - 1]) {
                                // if the previous line is not full, try to fit max part of
                                // the current word there
                                l--;
                            }
                        }

                        i--;

                        continue;
                    }

                    l++;
                    i--;
                }

                // if size.height is defined we have to check whether the height of the entire
                // text exceeds the rect height
                if (height !== undefined) {

                    if (lineHeight === undefined) {

                        var heightValue;

                        // use the same defaults as in V.prototype.text
                        if (styles.lineHeight === 'auto') {
                            heightValue = { value: 1.5, unit: 'em' };
                        } else {
                            heightValue = joint.util.parseCssNumeric(styles.lineHeight, ['em']) || { value: 1, unit: 'em' };
                        }

                        lineHeight = heightValue.value;
                        if (heightValue.unit === 'em' ) {
                            lineHeight *= textElement.getBBox().height;
                        }
                    }

                    if (lineHeight * lines.length > height) {

                        // remove overflowing lines
                        lines.splice(Math.floor(height / lineHeight));

                        break;
                    }
                }
            }

            if (opt.svgDocument) {

                // svg document was provided, remove the text element only
                svgDocument.removeChild(textElement);

            } else {

                // clean svg document
                document.body.removeChild(svgDocument);
            }

            return lines.join(eol);
        },

        // Sanitize HTML
        // Based on https://gist.github.com/ufologist/5a0da51b2b9ef1b861c30254172ac3c9
        // Parses a string into an array of DOM nodes.
        // Then outputs it back as a string.
        sanitizeHTML: function(html) {

            // Ignores tags that are invalid inside a <div> tag (e.g. <body>, <head>)

            // If documentContext (second parameter) is not specified or given as `null` or `undefined`, a new document is used.
            // Inline events will not execute when the HTML is parsed; this includes, for example, sending GET requests for images.

            // If keepScripts (last parameter) is `false`, scripts are not executed.
            var output = $($.parseHTML('<div>' + html + '</div>', null, false));

            output.find('*').each(function() { // for all nodes
                var currentNode = this;

                $.each(currentNode.attributes, function() { // for all attributes in each node
                    var currentAttribute = this;

                    var attrName = currentAttribute.name;
                    var attrValue = currentAttribute.value;

                    // Remove attribute names that start with "on" (e.g. onload, onerror...).
                    // Remove attribute values that start with "javascript:" pseudo protocol (e.g. `href="javascript:alert(1)"`).
                    if (attrName.indexOf('on') === 0 || attrValue.indexOf('javascript:') === 0) {
                        $(currentNode).removeAttr(attrName);
                    }
                });
            });

            return output.html();
        },

        // Download `blob` as file with `fileName`.
        // Does not work in IE9.
        downloadBlob: function(blob, fileName) {

            if (window.navigator.msSaveBlob) { // requires IE 10+
                // pulls up a save dialog
                window.navigator.msSaveBlob(blob, fileName);

            } else { // other browsers
                // downloads directly in Chrome and Safari

                // presents a save/open dialog in Firefox
                // Firefox bug: `from` field in save dialog always shows `from:blob:`
                // https://bugzilla.mozilla.org/show_bug.cgi?id=1053327

                var url = window.URL.createObjectURL(blob);
                var link = document.createElement('a');

                link.href = url;
                link.download = fileName;
                document.body.appendChild(link);

                link.click();

                document.body.removeChild(link);
                window.URL.revokeObjectURL(url); // mark the url for garbage collection
            }
        },

        // Download `dataUri` as file with `fileName`.
        // Does not work in IE9.
        downloadDataUri: function(dataUri, fileName) {

            var blob = joint.util.dataUriToBlob(dataUri);
            joint.util.downloadBlob(blob, fileName);
        },

        // Convert an uri-encoded data component (possibly also base64-encoded) to a blob.
        dataUriToBlob: function(dataUri) {

            // first, make sure there are no newlines in the data uri
            dataUri = dataUri.replace(/\s/g, '');
            dataUri = decodeURIComponent(dataUri);

            var firstCommaIndex = dataUri.indexOf(','); // split dataUri as `dataTypeString`,`data`

            var dataTypeString = dataUri.slice(0, firstCommaIndex); // e.g. 'data:image/jpeg;base64'
            var mimeString = dataTypeString.split(':')[1].split(';')[0]; // e.g. 'image/jpeg'

            var data = dataUri.slice(firstCommaIndex + 1);
            var decodedString;
            if (dataTypeString.indexOf('base64') >= 0) { // data may be encoded in base64
                decodedString = atob(data); // decode data
            } else {
                // convert the decoded string to UTF-8
                decodedString = unescape(encodeURIComponent(data));
            }
            // write the bytes of the string to a typed array
            var ia = new window.Uint8Array(decodedString.length);
            for (var i = 0; i < decodedString.length; i++) {
                ia[i] = decodedString.charCodeAt(i);
            }

            return new Blob([ia], { type: mimeString }); // return the typed array as Blob
        },

        // Read an image at `url` and return it as base64-encoded data uri.
        // The mime type of the image is inferred from the `url` file extension.
        // If data uri is provided as `url`, it is returned back unchanged.
        // `callback` is a method with `err` as first argument and `dataUri` as second argument.
        // Works with IE9.
        imageToDataUri: function(url, callback) {

            if (!url || url.substr(0, 'data:'.length) === 'data:') {
                // No need to convert to data uri if it is already in data uri.

                // This not only convenient but desired. For example,
                // IE throws a security error if data:image/svg+xml is used to render
                // an image to the canvas and an attempt is made to read out data uri.
                // Now if our image is already in data uri, there is no need to render it to the canvas
                // and so we can bypass this error.

                // Keep the async nature of the function.
                return setTimeout(function() {
                    callback(null, url);
                }, 0);
            }

            // chrome, IE10+
            var modernHandler = function(xhr, callback) {

                if (xhr.status === 200) {

                    var reader = new FileReader();

                    reader.onload = function(evt) {
                        var dataUri = evt.target.result;
                        callback(null, dataUri);
                    };

                    reader.onerror = function() {
                        callback(new Error('Failed to load image ' + url));
                    };

                    reader.readAsDataURL(xhr.response);
                } else {
                    callback(new Error('Failed to load image ' + url));
                }
            };

            var legacyHandler = function(xhr, callback) {

                var Uint8ToString = function(u8a) {
                    var CHUNK_SZ = 0x8000;
                    var c = [];
                    for (var i = 0; i < u8a.length; i += CHUNK_SZ) {
                        c.push(String.fromCharCode.apply(null, u8a.subarray(i, i + CHUNK_SZ)));
                    }
                    return c.join('');
                };

                if (xhr.status === 200) {

                    var bytes = new Uint8Array(xhr.response);

                    var suffix = (url.split('.').pop()) || 'png';
                    var map = {
                        'svg': 'svg+xml'
                    };
                    var meta = 'data:image/' + (map[suffix] || suffix) + ';base64,';
                    var b64encoded = meta + btoa(Uint8ToString(bytes));
                    callback(null, b64encoded);
                } else {
                    callback(new Error('Failed to load image ' + url));
                }
            };

            var xhr = new XMLHttpRequest();

            xhr.open('GET', url, true);
            xhr.addEventListener('error', function() {
                callback(new Error('Failed to load image ' + url));
            });

            xhr.responseType = window.FileReader ? 'blob' : 'arraybuffer';

            xhr.addEventListener('load', function() {
                if (window.FileReader) {
                    modernHandler(xhr, callback);
                } else {
                    legacyHandler(xhr, callback);
                }
            });

            xhr.send();
        },

        getElementBBox: function(el) {

            var $el = $(el);
            if ($el.length === 0) {
                throw new Error('Element not found')
            }

            var element = $el[0];
            var doc = element.ownerDocument;
            var clientBBox = element.getBoundingClientRect();

            var strokeWidthX = 0;
            var strokeWidthY = 0;

            // Firefox correction
            if (element.ownerSVGElement) {

                var vel = V(element);
                var bbox = vel.getBBox({ target: vel.svg() });

                // if FF getBoundingClientRect includes stroke-width, getBBox doesn't.
                // To unify this across all browsers we need to adjust the final bBox with `stroke-width` value.
                strokeWidthX = (clientBBox.width - bbox.width);
                strokeWidthY = (clientBBox.height - bbox.height);
            }

            return  {
                x: clientBBox.left + window.pageXOffset - doc.documentElement.offsetLeft + strokeWidthX / 2,
                y: clientBBox.top + window.pageYOffset - doc.documentElement.offsetTop + strokeWidthY / 2,
                width: clientBBox.width - strokeWidthX,
                height: clientBBox.height - strokeWidthY
            };
        },


        // Highly inspired by the jquery.sortElements plugin by Padolsey.
        // See http://james.padolsey.com/javascript/sorting-elements-with-jquery/.
        sortElements: function(elements, comparator) {

            var $elements = $(elements);
            var placements = $elements.map(function() {

                var sortElement = this;
                var parentNode = sortElement.parentNode;
                // Since the element itself will change position, we have
                // to have some way of storing it's original position in
                // the DOM. The easiest way is to have a 'flag' node:
                var nextSibling = parentNode.insertBefore(document.createTextNode(''), sortElement.nextSibling);

                return function() {

                    if (parentNode === this) {
                        throw new Error('You can\'t sort elements if any one is a descendant of another.');
                    }

                    // Insert before flag:
                    parentNode.insertBefore(this, nextSibling);
                    // Remove flag:
                    parentNode.removeChild(nextSibling);
                };
            });

            return Array.prototype.sort.call($elements, comparator).each(function(i) {
                placements[i].call(this);
            });
        },

        // Sets attributes on the given element and its descendants based on the selector.
        // `attrs` object: { [SELECTOR1]: { attrs1 }, [SELECTOR2]: { attrs2}, ... } e.g. { 'input': { color : 'red' }}
        setAttributesBySelector: function(element, attrs) {

            var $element = $(element);

            joint.util.forIn(attrs, function(attrs, selector) {
                var $elements = $element.find(selector).addBack().filter(selector);
                // Make a special case for setting classes.
                // We do not want to overwrite any existing class.
                if (joint.util.has(attrs, 'class')) {
                    $elements.addClass(attrs['class']);
                    attrs = joint.util.omit(attrs, 'class');
                }
                $elements.attr(attrs);
            });
        },

        // Return a new object with all four sides (top, right, bottom, left) in it.
        // Value of each side is taken from the given argument (either number or object).
        // Default value for a side is 0.
        // Examples:
        // joint.util.normalizeSides(5) --> { top: 5, right: 5, bottom: 5, left: 5 }
        // joint.util.normalizeSides({ horizontal: 5 }) --> { top: 0, right: 5, bottom: 0, left: 5 }
        // joint.util.normalizeSides({ left: 5 }) --> { top: 0, right: 0, bottom: 0, left: 5 }
        // joint.util.normalizeSides({ horizontal: 10, left: 5 }) --> { top: 0, right: 10, bottom: 0, left: 5 }
        // joint.util.normalizeSides({ horizontal: 0, left: 5 }) --> { top: 0, right: 0, bottom: 0, left: 5 }
        normalizeSides: function(box) {

            if (Object(box) !== box) { // `box` is not an object
                var val = 0; // `val` left as 0 if `box` cannot be understood as finite number
                if (isFinite(box)) val = +box; // actually also accepts string numbers (e.g. '100')

                return { top: val, right: val, bottom: val, left: val };
            }

            // `box` is an object
            var top, right, bottom, left;
            top = right = bottom = left = 0;

            if (isFinite(box.vertical)) top = bottom = +box.vertical;
            if (isFinite(box.horizontal)) right = left = +box.horizontal;

            if (isFinite(box.top)) top = +box.top; // overwrite vertical
            if (isFinite(box.right)) right = +box.right; // overwrite horizontal
            if (isFinite(box.bottom)) bottom = +box.bottom; // overwrite vertical
            if (isFinite(box.left)) left = +box.left; // overwrite horizontal

            return { top: top, right: right, bottom: bottom, left: left };
        },

        timing: {

            linear: function(t) {
                return t;
            },

            quad: function(t) {
                return t * t;
            },

            cubic: function(t) {
                return t * t * t;
            },

            inout: function(t) {
                if (t <= 0) return 0;
                if (t >= 1) return 1;
                var t2 = t * t;
                var t3 = t2 * t;
                return 4 * (t < .5 ? t3 : 3 * (t - t2) + t3 - .75);
            },

            exponential: function(t) {
                return Math.pow(2, 10 * (t - 1));
            },

            bounce: function(t) {
                for (var a = 0, b = 1; 1; a += b, b /= 2) {
                    if (t >= (7 - 4 * a) / 11) {
                        var q = (11 - 6 * a - 11 * t) / 4;
                        return -q * q + b * b;
                    }
                }
            },

            reverse: function(f) {
                return function(t) {
                    return 1 - f(1 - t);
                };
            },

            reflect: function(f) {
                return function(t) {
                    return .5 * (t < .5 ? f(2 * t) : (2 - f(2 - 2 * t)));
                };
            },

            clamp: function(f, n, x) {
                n = n || 0;
                x = x || 1;
                return function(t) {
                    var r = f(t);
                    return r < n ? n : r > x ? x : r;
                };
            },

            back: function(s) {
                if (!s) s = 1.70158;
                return function(t) {
                    return t * t * ((s + 1) * t - s);
                };
            },

            elastic: function(x) {
                if (!x) x = 1.5;
                return function(t) {
                    return Math.pow(2, 10 * (t - 1)) * Math.cos(20 * Math.PI * x / 3 * t);
                };
            }
        },

        interpolate: {

            number: function(a, b) {
                var d = b - a;
                return function(t) { return a + d * t; };
            },

            object: function(a, b) {
                var s = Object.keys(a);
                return function(t) {
                    var i, p;
                    var r = {};
                    for (i = s.length - 1; i != -1; i--) {
                        p = s[i];
                        r[p] = a[p] + (b[p] - a[p]) * t;
                    }
                    return r;
                };
            },

            hexColor: function(a, b) {

                var ca = parseInt(a.slice(1), 16);
                var cb = parseInt(b.slice(1), 16);
                var ra = ca & 0x0000ff;
                var rd = (cb & 0x0000ff) - ra;
                var ga = ca & 0x00ff00;
                var gd = (cb & 0x00ff00) - ga;
                var ba = ca & 0xff0000;
                var bd = (cb & 0xff0000) - ba;

                return function(t) {

                    var r = (ra + rd * t) & 0x000000ff;
                    var g = (ga + gd * t) & 0x0000ff00;
                    var b = (ba + bd * t) & 0x00ff0000;

                    return '#' + (1 << 24 | r | g | b ).toString(16).slice(1);
                };
            },

            unit: function(a, b) {

                var r = /(-?[0-9]*.[0-9]*)(px|em|cm|mm|in|pt|pc|%)/;
                var ma = r.exec(a);
                var mb = r.exec(b);
                var p = mb[1].indexOf('.');
                var f = p > 0 ? mb[1].length - p - 1 : 0;
                a = +ma[1];
                var d = +mb[1] - a;
                var u = ma[2];

                return function(t) {
                    return (a + d * t).toFixed(f) + u;
                };
            }
        },

        // SVG filters.
        filter: {

            // `color` ... outline color
            // `width`... outline width
            // `opacity` ... outline opacity
            // `margin` ... gap between outline and the element
            outline: function(args) {

                var tpl = '<filter><feFlood flood-color="${color}" flood-opacity="${opacity}" result="colored"/><feMorphology in="SourceAlpha" result="morphedOuter" operator="dilate" radius="${outerRadius}" /><feMorphology in="SourceAlpha" result="morphedInner" operator="dilate" radius="${innerRadius}" /><feComposite result="morphedOuterColored" in="colored" in2="morphedOuter" operator="in"/><feComposite operator="xor" in="morphedOuterColored" in2="morphedInner" result="outline"/><feMerge><feMergeNode in="outline"/><feMergeNode in="SourceGraphic"/></feMerge></filter>';

                var margin = Number.isFinite(args.margin) ? args.margin : 2;
                var width = Number.isFinite(args.width) ? args.width : 1;

                return joint.util.template(tpl)({
                    color: args.color || 'blue',
                    opacity: Number.isFinite(args.opacity) ? args.opacity : 1,
                    outerRadius: margin + width,
                    innerRadius: margin
                });
            },

            // `color` ... color
            // `width`... width
            // `blur` ... blur
            // `opacity` ... opacity
            highlight: function(args) {

                var tpl = '<filter><feFlood flood-color="${color}" flood-opacity="${opacity}" result="colored"/><feMorphology result="morphed" in="SourceGraphic" operator="dilate" radius="${width}"/><feComposite result="composed" in="colored" in2="morphed" operator="in"/><feGaussianBlur result="blured" in="composed" stdDeviation="${blur}"/><feBlend in="SourceGraphic" in2="blured" mode="normal"/></filter>';

                return joint.util.template(tpl)({
                    color: args.color || 'red',
                    width: Number.isFinite(args.width) ? args.width : 1,
                    blur: Number.isFinite(args.blur) ? args.blur : 0,
                    opacity: Number.isFinite(args.opacity) ? args.opacity : 1
                });
            },

            // `x` ... horizontal blur
            // `y` ... vertical blur (optional)
            blur: function(args) {

                var x = Number.isFinite(args.x) ? args.x : 2;

                return joint.util.template('<filter><feGaussianBlur stdDeviation="${stdDeviation}"/></filter>')({
                    stdDeviation: Number.isFinite(args.y) ? [x, args.y] : x
                });
            },

            // `dx` ... horizontal shift
            // `dy` ... vertical shift
            // `blur` ... blur
            // `color` ... color
            // `opacity` ... opacity
            dropShadow: function(args) {

                var tpl = 'SVGFEDropShadowElement' in window
                    ? '<filter><feDropShadow stdDeviation="${blur}" dx="${dx}" dy="${dy}" flood-color="${color}" flood-opacity="${opacity}"/></filter>'
                    : '<filter><feGaussianBlur in="SourceAlpha" stdDeviation="${blur}"/><feOffset dx="${dx}" dy="${dy}" result="offsetblur"/><feFlood flood-color="${color}"/><feComposite in2="offsetblur" operator="in"/><feComponentTransfer><feFuncA type="linear" slope="${opacity}"/></feComponentTransfer><feMerge><feMergeNode/><feMergeNode in="SourceGraphic"/></feMerge></filter>';

                return joint.util.template(tpl)({
                    dx: args.dx || 0,
                    dy: args.dy || 0,
                    opacity: Number.isFinite(args.opacity) ? args.opacity : 1,
                    color: args.color || 'black',
                    blur: Number.isFinite(args.blur) ? args.blur : 4
                });
            },

            // `amount` ... the proportion of the conversion. A value of 1 is completely grayscale. A value of 0 leaves the input unchanged.
            grayscale: function(args) {

                var amount = Number.isFinite(args.amount) ? args.amount : 1;

                return joint.util.template('<filter><feColorMatrix type="matrix" values="${a} ${b} ${c} 0 0 ${d} ${e} ${f} 0 0 ${g} ${b} ${h} 0 0 0 0 0 1 0"/></filter>')({
                    a: 0.2126 + 0.7874 * (1 - amount),
                    b: 0.7152 - 0.7152 * (1 - amount),
                    c: 0.0722 - 0.0722 * (1 - amount),
                    d: 0.2126 - 0.2126 * (1 - amount),
                    e: 0.7152 + 0.2848 * (1 - amount),
                    f: 0.0722 - 0.0722 * (1 - amount),
                    g: 0.2126 - 0.2126 * (1 - amount),
                    h: 0.0722 + 0.9278 * (1 - amount)
                });
            },

            // `amount` ... the proportion of the conversion. A value of 1 is completely sepia. A value of 0 leaves the input unchanged.
            sepia: function(args) {

                var amount = Number.isFinite(args.amount) ? args.amount : 1;

                return joint.util.template('<filter><feColorMatrix type="matrix" values="${a} ${b} ${c} 0 0 ${d} ${e} ${f} 0 0 ${g} ${h} ${i} 0 0 0 0 0 1 0"/></filter>')({
                    a: 0.393 + 0.607 * (1 - amount),
                    b: 0.769 - 0.769 * (1 - amount),
                    c: 0.189 - 0.189 * (1 - amount),
                    d: 0.349 - 0.349 * (1 - amount),
                    e: 0.686 + 0.314 * (1 - amount),
                    f: 0.168 - 0.168 * (1 - amount),
                    g: 0.272 - 0.272 * (1 - amount),
                    h: 0.534 - 0.534 * (1 - amount),
                    i: 0.131 + 0.869 * (1 - amount)
                });
            },

            // `amount` ... the proportion of the conversion. A value of 0 is completely un-saturated. A value of 1 leaves the input unchanged.
            saturate: function(args) {

                var amount = Number.isFinite(args.amount) ? args.amount : 1;

                return joint.util.template('<filter><feColorMatrix type="saturate" values="${amount}"/></filter>')({
                    amount: 1 - amount
                });
            },

            // `angle` ...  the number of degrees around the color circle the input samples will be adjusted.
            hueRotate: function(args) {

                return joint.util.template('<filter><feColorMatrix type="hueRotate" values="${angle}"/></filter>')({
                    angle: args.angle || 0
                });
            },

            // `amount` ... the proportion of the conversion. A value of 1 is completely inverted. A value of 0 leaves the input unchanged.
            invert: function(args) {

                var amount = Number.isFinite(args.amount) ? args.amount : 1;

                return joint.util.template('<filter><feComponentTransfer><feFuncR type="table" tableValues="${amount} ${amount2}"/><feFuncG type="table" tableValues="${amount} ${amount2}"/><feFuncB type="table" tableValues="${amount} ${amount2}"/></feComponentTransfer></filter>')({
                    amount: amount,
                    amount2: 1 - amount
                });
            },

            // `amount` ... proportion of the conversion. A value of 0 will create an image that is completely black. A value of 1 leaves the input unchanged.
            brightness: function(args) {

                return joint.util.template('<filter><feComponentTransfer><feFuncR type="linear" slope="${amount}"/><feFuncG type="linear" slope="${amount}"/><feFuncB type="linear" slope="${amount}"/></feComponentTransfer></filter>')({
                    amount: Number.isFinite(args.amount) ? args.amount : 1
                });
            },

            // `amount` ... proportion of the conversion. A value of 0 will create an image that is completely black. A value of 1 leaves the input unchanged.
            contrast: function(args) {

                var amount = Number.isFinite(args.amount) ? args.amount : 1;

                return joint.util.template('<filter><feComponentTransfer><feFuncR type="linear" slope="${amount}" intercept="${amount2}"/><feFuncG type="linear" slope="${amount}" intercept="${amount2}"/><feFuncB type="linear" slope="${amount}" intercept="${amount2}"/></feComponentTransfer></filter>')({
                    amount: amount,
                    amount2: .5 - amount / 2
                });
            }
        },

        format: {

            // Formatting numbers via the Python Format Specification Mini-language.
            // See http://docs.python.org/release/3.1.3/library/string.html#format-specification-mini-language.
            // Heavilly inspired by the D3.js library implementation.
            number: function(specifier, value, locale) {

                locale = locale || {

                    currency: ['$', ''],
                    decimal: '.',
                    thousands: ',',
                    grouping: [3]
                };

                // See Python format specification mini-language: http://docs.python.org/release/3.1.3/library/string.html#format-specification-mini-language.
                // [[fill]align][sign][symbol][0][width][,][.precision][type]
                var re = /(?:([^{])?([<>=^]))?([+\- ])?([$#])?(0)?(\d+)?(,)?(\.-?\d+)?([a-z%])?/i;

                var match = re.exec(specifier);
                var fill = match[1] || ' ';
                var align = match[2] || '>';
                var sign = match[3] || '';
                var symbol = match[4] || '';
                var zfill = match[5];
                var width = +match[6];
                var comma = match[7];
                var precision = match[8];
                var type = match[9];
                var scale = 1;
                var prefix = '';
                var suffix = '';
                var integer = false;

                if (precision) precision = +precision.substring(1);

                if (zfill || fill === '0' && align === '=') {
                    zfill = fill = '0';
                    align = '=';
                    if (comma) width -= Math.floor((width - 1) / 4);
                }

                switch (type) {
                    case 'n':
                        comma = true; type = 'g';
                        break;
                    case '%':
                        scale = 100; suffix = '%'; type = 'f';
                        break;
                    case 'p':
                        scale = 100; suffix = '%'; type = 'r';
                        break;
                    case 'b':
                    case 'o':
                    case 'x':
                    case 'X':
                        if (symbol === '#') prefix = '0' + type.toLowerCase();
                        break;
                    case 'c':
                    case 'd':
                        integer = true; precision = 0;
                        break;
                    case 's':
                        scale = -1; type = 'r';
                        break;
                }

                if (symbol === '$') {
                    prefix = locale.currency[0];
                    suffix = locale.currency[1];
                }

                // If no precision is specified for `'r'`, fallback to general notation.
                if (type == 'r' && !precision) type = 'g';

                // Ensure that the requested precision is in the supported range.
                if (precision != null) {
                    if (type == 'g') precision = Math.max(1, Math.min(21, precision));
                    else if (type == 'e' || type == 'f') precision = Math.max(0, Math.min(20, precision));
                }

                var zcomma = zfill && comma;

                // Return the empty string for floats formatted as ints.
                if (integer && (value % 1)) return '';

                // Convert negative to positive, and record the sign prefix.
                var negative = value < 0 || value === 0 && 1 / value < 0 ? (value = -value, '-') : sign;

                var fullSuffix = suffix;

                // Apply the scale, computing it from the value's exponent for si format.
                // Preserve the existing suffix, if any, such as the currency symbol.
                if (scale < 0) {
                    var unit = this.prefix(value, precision);
                    value = unit.scale(value);
                    fullSuffix = unit.symbol + suffix;
                } else {
                    value *= scale;
                }

                // Convert to the desired precision.
                value = this.convert(type, value, precision);

                // Break the value into the integer part (before) and decimal part (after).
                var i = value.lastIndexOf('.');
                var before = i < 0 ? value : value.substring(0, i);
                var after = i < 0 ? '' : locale.decimal + value.substring(i + 1);

                function formatGroup(value) {

                    var i = value.length;
                    var t = [];
                    var j = 0;
                    var g = locale.grouping[0];
                    while (i > 0 && g > 0) {
                        t.push(value.substring(i -= g, i + g));
                        g = locale.grouping[j = (j + 1) % locale.grouping.length];
                    }
                    return t.reverse().join(locale.thousands);
                }

                // If the fill character is not `'0'`, grouping is applied before padding.
                if (!zfill && comma && locale.grouping) {

                    before = formatGroup(before);
                }

                var length = prefix.length + before.length + after.length + (zcomma ? 0 : negative.length);
                var padding = length < width ? new Array(length = width - length + 1).join(fill) : '';

                // If the fill character is `'0'`, grouping is applied after padding.
                if (zcomma) before = formatGroup(padding + before);

                // Apply prefix.
                negative += prefix;

                // Rejoin integer and decimal parts.
                value = before + after;

                return (align === '<' ? negative + value + padding
                        : align === '>' ? padding + negative + value
                        : align === '^' ? padding.substring(0, length >>= 1) + negative + value + padding.substring(length)
                        : negative + (zcomma ? value : padding + value)) + fullSuffix;
            },

            // Formatting string via the Python Format string.
            // See https://docs.python.org/2/library/string.html#format-string-syntax)
            string: function(formatString, value) {

                var fieldDelimiterIndex;
                var fieldDelimiter = '{';
                var endPlaceholder = false;
                var formattedStringArray = [];

                while ((fieldDelimiterIndex = formatString.indexOf(fieldDelimiter)) !== -1) {

                    var pieceFormatedString, formatSpec, fieldName;

                    pieceFormatedString = formatString.slice(0, fieldDelimiterIndex);

                    if (endPlaceholder) {
                        formatSpec = pieceFormatedString.split(':');
                        fieldName = formatSpec.shift().split('.');
                        pieceFormatedString = value;

                        for (var i = 0; i < fieldName.length; i++)
                            pieceFormatedString = pieceFormatedString[fieldName[i]];

                        if (formatSpec.length)
                            pieceFormatedString = this.number(formatSpec, pieceFormatedString);
                    }

                    formattedStringArray.push(pieceFormatedString);

                    formatString = formatString.slice(fieldDelimiterIndex + 1);
                    fieldDelimiter = (endPlaceholder = !endPlaceholder) ? '}' : '{';
                }
                formattedStringArray.push(formatString);

                return formattedStringArray.join('');
            },

            convert: function(type, value, precision) {

                switch (type) {
                    case 'b': return value.toString(2);
                    case 'c': return String.fromCharCode(value);
                    case 'o': return value.toString(8);
                    case 'x': return value.toString(16);
                    case 'X': return value.toString(16).toUpperCase();
                    case 'g': return value.toPrecision(precision);
                    case 'e': return value.toExponential(precision);
                    case 'f': return value.toFixed(precision);
                    case 'r': return (value = this.round(value, this.precision(value, precision))).toFixed(Math.max(0, Math.min(20, this.precision(value * (1 + 1e-15), precision))));
                    default: return value + '';
                }
            },

            round: function(value, precision) {

                return precision
                    ? Math.round(value * (precision = Math.pow(10, precision))) / precision
                    : Math.round(value);
            },

            precision: function(value, precision) {

                return precision - (value ? Math.ceil(Math.log(value) / Math.LN10) : 1);
            },

            prefix: function(value, precision) {

                var prefixes = ['y', 'z', 'a', 'f', 'p', 'n', 'µ', 'm', '', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'].map(function(d, i) {
                    var k = Math.pow(10, Math.abs(8 - i) * 3);
                    return {
                        scale: i > 8 ? function(d) { return d / k; } : function(d) { return d * k; },
                        symbol: d
                    };
                });

                var i = 0;
                if (value) {
                    if (value < 0) value *= -1;
                    if (precision) value = this.round(value, this.precision(value, precision));
                    i = 1 + Math.floor(1e-12 + Math.log(value) / Math.LN10);
                    i = Math.max(-24, Math.min(24, Math.floor((i <= 0 ? i + 1 : i - 1) / 3) * 3));
                }
                return prefixes[8 + i / 3];
            }
        },

        /*
            Pre-compile the HTML to be used as a template.
        */
        template: function(html) {

            /*
                Must support the variation in templating syntax found here:
                https://lodash.com/docs#template
            */
            var regex = /<%= ([^ ]+) %>|\$\{ ?([^\{\} ]+) ?\}|\{\{([^\{\} ]+)\}\}/g;

            return function(data) {

                data = data || {};

                return html.replace(regex, function(match) {

                    var args = Array.from(arguments);
                    var attr = args.slice(1, 4).find(function(_attr) {
                        return !!_attr;
                    });

                    var attrArray = attr.split('.');
                    var value = data[attrArray.shift()];

                    while (value !== undefined && attrArray.length) {
                        value = value[attrArray.shift()];
                    }

                    return value !== undefined ? value : '';
                });
            };
        },

        /**
         * @param {Element=} el Element, which content is intent to display in full-screen mode, 'window.top.document.body' is default.
         */
        toggleFullScreen: function(el) {

            var topDocument = window.top.document;
            el = el || topDocument.body;

            function prefixedResult(el, prop) {

                var prefixes = ['webkit', 'moz', 'ms', 'o', ''];
                for (var i = 0; i < prefixes.length; i++) {
                    var prefix = prefixes[i];
                    var propName = prefix ? (prefix + prop) : (prop.substr(0, 1).toLowerCase() + prop.substr(1));
                    if (el[propName] !== undefined) {
                        return joint.util.isFunction(el[propName]) ? el[propName]() : el[propName];
                    }
                }
            }

            if (prefixedResult(topDocument, 'FullscreenElement') || prefixedResult(topDocument, 'FullScreenElement')) {
                prefixedResult(topDocument, 'ExitFullscreen') || // Spec.
                prefixedResult(topDocument, 'CancelFullScreen'); // Firefox
            } else {
                prefixedResult(el, 'RequestFullscreen') || // Spec.
                prefixedResult(el, 'RequestFullScreen'); // Firefox
            }
        },

        addClassNamePrefix: function(className) {

            if (!className) return className;

            return className.toString().split(' ').map(function(_className) {

                if (_className.substr(0, joint.config.classNamePrefix.length) !== joint.config.classNamePrefix) {
                    _className = joint.config.classNamePrefix + _className;
                }

                return _className;

            }).join(' ');
        },

        removeClassNamePrefix: function(className) {

            if (!className) return className;

            return className.toString().split(' ').map(function(_className) {

                if (_className.substr(0, joint.config.classNamePrefix.length) === joint.config.classNamePrefix) {
                    _className = _className.substr(joint.config.classNamePrefix.length);
                }

                return _className;

            }).join(' ');
        },

        wrapWith: function(object, methods, wrapper) {

            if (joint.util.isString(wrapper)) {

                if (!joint.util.wrappers[wrapper]) {
                    throw new Error('Unknown wrapper: "' + wrapper + '"');
                }

                wrapper = joint.util.wrappers[wrapper];
            }

            if (!joint.util.isFunction(wrapper)) {
                throw new Error('Wrapper must be a function.');
            }

            this.toArray(methods).forEach(function(method) {
                object[method] = wrapper(object[method]);
            });
        },

        wrappers: {

            /*
                Prepares a function with the following usage:

                    fn([cell, cell, cell], opt);
                    fn([cell, cell, cell]);
                    fn(cell, cell, cell, opt);
                    fn(cell, cell, cell);
                    fn(cell);
            */
            cells: function(fn) {

                return function() {

                    var args = Array.from(arguments);
                    var n = args.length;
                    var cells = n > 0 && args[0] || [];
                    var opt = n > 1 && args[n - 1] || {};

                    if (!Array.isArray(cells)) {

                        if (opt instanceof joint.dia.Cell) {
                            cells = args;
                        } else if (cells instanceof joint.dia.Cell) {
                            if (args.length > 1) {
                                args.pop();
                            }
                            cells = args;
                        }
                    }

                    if (opt instanceof joint.dia.Cell) {
                        opt = {};
                    }

                    return fn.call(this, cells, opt);
                };
            }
        },

        parseDOMJSON: function(json, namespace) {

            var selectors = {};
            var svgNamespace = V.namespace.xmlns;
            var ns = namespace || svgNamespace;
            var fragment = document.createDocumentFragment();
            var queue = [json, fragment, ns];
            while (queue.length > 0) {
                ns = queue.pop();
                var parentNode = queue.pop();
                var siblingsDef = queue.pop();
                for (var i = 0, n = siblingsDef.length; i < n; i++) {
                    var nodeDef = siblingsDef[i];
                    // TagName
                    if (!nodeDef.hasOwnProperty('tagName')) throw new Error('json-dom-parser: missing tagName');
                    var tagName = nodeDef.tagName;
                    // Namespace URI
                    if (nodeDef.hasOwnProperty('namespaceURI')) ns = nodeDef.namespaceURI;
                    var node = document.createElementNS(ns, tagName);
                    var svg = (ns === svgNamespace);
                    var wrapper = (svg) ? V : $;
                    // Attributes
                    var attributes = nodeDef.attributes;
                    if (attributes) wrapper(node).attr(attributes);
                    // Style
                    var style = nodeDef.style;
                    if (style) $(node).css(style);
                    // ClassName
                    if (nodeDef.hasOwnProperty('className')) {
                        var className = nodeDef.className;
                        if (svg) {
                            node.className.baseVal = className;
                        } else {
                            node.className = className;
                        }
                    }
                    // Selector
                    if (nodeDef.hasOwnProperty('selector')) {
                        var nodeSelector = nodeDef.selector;
                        if (selectors[nodeSelector]) throw new Error('json-dom-parser: selector must be unique');
                        selectors[nodeSelector] = node;
                        wrapper(node).attr('joint-selector', nodeSelector);
                    }
                    parentNode.appendChild(node);
                    // Children
                    var childrenDef = nodeDef.children;
                    if (Array.isArray(childrenDef)) queue.push(childrenDef, node, ns);
                }
            }
            return {
                fragment: fragment,
                selectors: selectors
            }
        },

        // lodash 3 vs 4 incompatible
        sortedIndex: _.sortedIndexBy || _.sortedIndex,
        uniq: _.uniqBy || _.uniq,
        uniqueId: _.uniqueId,
        sortBy: _.sortBy,
        isFunction: _.isFunction,
        result: _.result,
        union: _.union,
        invoke: _.invokeMap || _.invoke,
        difference: _.difference,
        intersection: _.intersection,
        omit: _.omit,
        pick: _.pick,
        has: _.has,
        bindAll: _.bindAll,
        assign: _.assign,
        defaults: _.defaults,
        defaultsDeep: _.defaultsDeep,
        isPlainObject: _.isPlainObject,
        isEmpty: _.isEmpty,
        isEqual: _.isEqual,
        noop: function() {},
        cloneDeep: _.cloneDeep,
        toArray: _.toArray,
        flattenDeep: _.flattenDeep,
        camelCase: _.camelCase,
        groupBy: _.groupBy,
        forIn: _.forIn,
        without: _.without,
        debounce: _.debounce,
        clone: _.clone,

        isBoolean: function(value) {
            var toString = Object.prototype.toString;
            return value === true || value === false || (!!value && typeof value === 'object' && toString.call(value) === '[object Boolean]');
        },

        isObject: function(value) {
            return !!value && (typeof value === 'object' || typeof value === 'function');
        },

        isNumber: function(value) {
            var toString = Object.prototype.toString;
            return typeof value === 'number' || (!!value && typeof value === 'object' && toString.call(value) === '[object Number]');
        },

        isString: function(value) {
            var toString = Object.prototype.toString;
            return typeof value === 'string' || (!!value && typeof value === 'object' && toString.call(value) === '[object String]');
        },

        merge: function() {
            if (_.mergeWith) {
                var args = Array.from(arguments);
                var last = args[args.length - 1];

                var customizer =  this.isFunction(last) ? last : this.noop;
                args.push(function(a,b) {
                    var customResult = customizer(a, b);
                    if (customResult !== undefined) {
                        return customResult;
                    }

                    if (Array.isArray(a) && !Array.isArray(b)) {
                        return b;
                    }
                });

                return _.mergeWith.apply(this, args)
            }
            return _.merge.apply(this, arguments);
        }
    }
};


joint.mvc.View = Backbone.View.extend({

    options: {},
    theme: null,
    themeClassNamePrefix: joint.util.addClassNamePrefix('theme-'),
    requireSetThemeOverride: false,
    defaultTheme: joint.config.defaultTheme,
    children: null,
    childNodes: null,

    constructor: function(options) {

        this.requireSetThemeOverride = options && !!options.theme;
        this.options = joint.util.assign({}, this.options, options);

        Backbone.View.call(this, options);
    },

    initialize: function(options) {

        joint.util.bindAll(this, 'setTheme', 'onSetTheme', 'remove', 'onRemove');

        joint.mvc.views[this.cid] = this;

        this.setTheme(this.options.theme || this.defaultTheme);
        this.init();
    },

    renderChildren: function(children) {
        children || (children = this.children);
        if (children) {
            var namespace = V.namespace[this.svgElement ? 'xmlns' : 'xhtml'];
            var doc = joint.util.parseDOMJSON(children, namespace);
            this.vel.empty().append(doc.fragment);
            this.childNodes = doc.selectors;
        }
        return this;
    },

    // Override the Backbone `_ensureElement()` method in order to create an
    // svg element (e.g., `<g>`) node that wraps all the nodes of the Cell view.
    // Expose class name setter as a separate method.
    _ensureElement: function() {
        if (!this.el) {
            var tagName = joint.util.result(this, 'tagName');
            var attrs = joint.util.assign({}, joint.util.result(this, 'attributes'));
            if (this.id) attrs.id = joint.util.result(this, 'id');
            this.setElement(this._createElement(tagName));
            this._setAttributes(attrs);
        } else {
            this.setElement(joint.util.result(this, 'el'));
        }
        this._ensureElClassName();
    },

    _setAttributes: function(attrs) {
        if (this.svgElement) {
            this.vel.attr(attrs);
        } else {
            this.$el.attr(attrs);
        }
    },

    _createElement: function(tagName) {
        if (this.svgElement) {
            return document.createElementNS(V.namespace.xmlns, tagName);
        } else {
            return document.createElement(tagName);
        }
    },

    // Utilize an alternative DOM manipulation API by
    // adding an element reference wrapped in Vectorizer.
    _setElement: function(el) {
        this.$el = el instanceof Backbone.$ ? el : Backbone.$(el);
        this.el = this.$el[0];
        if (this.svgElement) this.vel = V(this.el);
    },

    _ensureElClassName: function() {
        var className = joint.util.result(this, 'className');
        var prefixedClassName = joint.util.addClassNamePrefix(className);
        // Note: className removal here kept for backwards compatibility only
        if (this.svgElement) {
            this.vel.removeClass(className).addClass(prefixedClassName);
        } else {
            this.$el.removeClass(className).addClass(prefixedClassName);
        }
    },

    init: function() {
        // Intentionally empty.
        // This method is meant to be overriden.
    },

    onRender: function() {
        // Intentionally empty.
        // This method is meant to be overriden.
    },

    setTheme: function(theme, opt) {

        opt = opt || {};

        // Theme is already set, override is required, and override has not been set.
        // Don't set the theme.
        if (this.theme && this.requireSetThemeOverride && !opt.override) {
            return this;
        }

        this.removeThemeClassName();
        this.addThemeClassName(theme);
        this.onSetTheme(this.theme/* oldTheme */, theme/* newTheme */);
        this.theme = theme;

        return this;
    },

    addThemeClassName: function(theme) {

        theme = theme || this.theme;

        var className = this.themeClassNamePrefix + theme;

        if (this.svgElement) {
            this.vel.addClass(className);
        } else {
            this.$el.addClass(className);
        }

        return this;
    },

    removeThemeClassName: function(theme) {

        theme = theme || this.theme;

        var className = this.themeClassNamePrefix + theme;

        if (this.svgElement) {
            this.vel.removeClass(className);
        } else {
            this.$el.removeClass(className);
        }

        return this;
    },

    onSetTheme: function(oldTheme, newTheme) {
        // Intentionally empty.
        // This method is meant to be overriden.
    },

    remove: function() {

        this.onRemove();
        this.undelegateDocumentEvents();

        joint.mvc.views[this.cid] = null;

        Backbone.View.prototype.remove.apply(this, arguments);

        return this;
    },

    onRemove: function() {
        // Intentionally empty.
        // This method is meant to be overriden.
    },

    getEventNamespace: function() {
        // Returns a per-session unique namespace
        return '.joint-event-ns-' + this.cid;
    },

    delegateElementEvents: function(element, events, data) {
        if (!events) return this;
        data || (data = {});
        var eventNS = this.getEventNamespace();
        for (var eventName in events) {
            var method = events[eventName];
            if (typeof method !== 'function') method = this[method];
            if (!method) continue;
            $(element).on(eventName + eventNS, data, method.bind(this));
        }
        return this;
    },

    undelegateElementEvents: function(element) {
        $(element).off(this.getEventNamespace());
        return this;
    },

    delegateDocumentEvents: function(events, data) {
        events || (events = joint.util.result(this, 'documentEvents'));
        return this.delegateElementEvents(document, events, data);
    },

    undelegateDocumentEvents: function() {
        return this.undelegateElementEvents(document);
    },

    eventData: function(evt, data) {
        if (!evt) throw new Error('eventData(): event object required.');
        var currentData = evt.data;
        var key = '__' + this.cid + '__';
        if (data === undefined) {
            if (!currentData) return {};
            return currentData[key] || {};
        }
        currentData || (currentData = evt.data = {});
        currentData[key] || (currentData[key] = {});
        joint.util.assign(currentData[key], data);
        return this;
    }

}, {

    extend: function() {

        var args = Array.from(arguments);

        // Deep clone the prototype and static properties objects.
        // This prevents unexpected behavior where some properties are overwritten outside of this function.
        var protoProps = args[0] && joint.util.assign({}, args[0]) || {};
        var staticProps = args[1] && joint.util.assign({}, args[1]) || {};

        // Need the real render method so that we can wrap it and call it later.
        var renderFn = protoProps.render || (this.prototype && this.prototype.render) || null;

        /*
            Wrap the real render method so that:
                .. `onRender` is always called.
                .. `this` is always returned.
        */
        protoProps.render = function() {

            if (renderFn) {
                // Call the original render method.
                renderFn.apply(this, arguments);
            }

            // Should always call onRender() method.
            this.onRender();

            // Should always return itself.
            return this;
        };

        return Backbone.View.extend.call(this, protoProps, staticProps);
    }
});



joint.dia.GraphCells = Backbone.Collection.extend({

    cellNamespace: joint.shapes,

    initialize: function(models, opt) {

        // Set the optional namespace where all model classes are defined.
        if (opt.cellNamespace) {
            this.cellNamespace = opt.cellNamespace;
        }

        this.graph = opt.graph;
    },

    model: function(attrs, opt) {

        var collection = opt.collection;
        var namespace = collection.cellNamespace;

        // Find the model class in the namespace or use the default one.
        var ModelClass = (attrs.type === 'link')
            ? joint.dia.Link
            : joint.util.getByPath(namespace, attrs.type, '.') || joint.dia.Element;

        var cell = new ModelClass(attrs, opt);
        // Add a reference to the graph. It is necessary to do this here because this is the earliest place
        // where a new model is created from a plain JS object. For other objects, see `joint.dia.Graph>>_prepareCell()`.
        if (!opt.dry) {
            cell.graph = collection.graph;
        }

        return cell;
    },

    // `comparator` makes it easy to sort cells based on their `z` index.
    comparator: function(model) {

        return model.get('z') || 0;
    }
});


joint.dia.Graph = Backbone.Model.extend({

    _batches: {},

    initialize: function(attrs, opt) {

        opt = opt || {};

        // Passing `cellModel` function in the options object to graph allows for
        // setting models based on attribute objects. This is especially handy
        // when processing JSON graphs that are in a different than JointJS format.
        var cells = new joint.dia.GraphCells([], {
            model: opt.cellModel,
            cellNamespace: opt.cellNamespace,
            graph: this
        });
        Backbone.Model.prototype.set.call(this, 'cells', cells);

        // Make all the events fired in the `cells` collection available.
        // to the outside world.
        cells.on('all', this.trigger, this);

        // Backbone automatically doesn't trigger re-sort if models attributes are changed later when
        // they're already in the collection. Therefore, we're triggering sort manually here.
        this.on('change:z', this._sortOnChangeZ, this);

        // `joint.dia.Graph` keeps an internal data structure (an adjacency list)
        // for fast graph queries. All changes that affect the structure of the graph
        // must be reflected in the `al` object. This object provides fast answers to
        // questions such as "what are the neighbours of this node" or "what
        // are the sibling links of this link".

        // Outgoing edges per node. Note that we use a hash-table for the list
        // of outgoing edges for a faster lookup.
        // [node ID] -> Object [edge] -> true
        this._out = {};
        // Ingoing edges per node.
        // [node ID] -> Object [edge] -> true
        this._in = {};
        // `_nodes` is useful for quick lookup of all the elements in the graph, without
        // having to go through the whole cells array.
        // [node ID] -> true
        this._nodes = {};
        // `_edges` is useful for quick lookup of all the links in the graph, without
        // having to go through the whole cells array.
        // [edge ID] -> true
        this._edges = {};

        cells.on('add', this._restructureOnAdd, this);
        cells.on('remove', this._restructureOnRemove, this);
        cells.on('reset', this._restructureOnReset, this);
        cells.on('change:source', this._restructureOnChangeSource, this);
        cells.on('change:target', this._restructureOnChangeTarget, this);
        cells.on('remove', this._removeCell, this);
    },

    _sortOnChangeZ: function() {

        this.get('cells').sort();
    },

    _restructureOnAdd: function(cell) {

        if (cell.isLink()) {
            this._edges[cell.id] = true;
            var source = cell.get('source');
            var target = cell.get('target');
            if (source.id) {
                (this._out[source.id] || (this._out[source.id] = {}))[cell.id] = true;
            }
            if (target.id) {
                (this._in[target.id] || (this._in[target.id] = {}))[cell.id] = true;
            }
        } else {
            this._nodes[cell.id] = true;
        }
    },

    _restructureOnRemove: function(cell) {

        if (cell.isLink()) {
            delete this._edges[cell.id];
            var source = cell.get('source');
            var target = cell.get('target');
            if (source.id && this._out[source.id] && this._out[source.id][cell.id]) {
                delete this._out[source.id][cell.id];
            }
            if (target.id && this._in[target.id] && this._in[target.id][cell.id]) {
                delete this._in[target.id][cell.id];
            }
        } else {
            delete this._nodes[cell.id];
        }
    },

    _restructureOnReset: function(cells) {

        // Normalize into an array of cells. The original `cells` is GraphCells Backbone collection.
        cells = cells.models;

        this._out = {};
        this._in = {};
        this._nodes = {};
        this._edges = {};

        cells.forEach(this._restructureOnAdd, this);
    },

    _restructureOnChangeSource: function(link) {

        var prevSource = link.previous('source');
        if (prevSource.id && this._out[prevSource.id]) {
            delete this._out[prevSource.id][link.id];
        }
        var source = link.get('source');
        if (source.id) {
            (this._out[source.id] || (this._out[source.id] = {}))[link.id] = true;
        }
    },

    _restructureOnChangeTarget: function(link) {

        var prevTarget = link.previous('target');
        if (prevTarget.id && this._in[prevTarget.id]) {
            delete this._in[prevTarget.id][link.id];
        }
        var target = link.get('target');
        if (target.id) {
            (this._in[target.id] || (this._in[target.id] = {}))[link.id] = true;
        }
    },

    // Return all outbound edges for the node. Return value is an object
    // of the form: [edge] -> true
    getOutboundEdges: function(node) {

        return (this._out && this._out[node]) || {};
    },

    // Return all inbound edges for the node. Return value is an object
    // of the form: [edge] -> true
    getInboundEdges: function(node) {

        return (this._in && this._in[node]) || {};
    },

    toJSON: function() {

        // Backbone does not recursively call `toJSON()` on attributes that are themselves models/collections.
        // It just clones the attributes. Therefore, we must call `toJSON()` on the cells collection explicitely.
        var json = Backbone.Model.prototype.toJSON.apply(this, arguments);
        json.cells = this.get('cells').toJSON();
        return json;
    },

    fromJSON: function(json, opt) {

        if (!json.cells) {

            throw new Error('Graph JSON must contain cells array.');
        }

        return this.set(json, opt);
    },

    set: function(key, val, opt) {

        var attrs;

        // Handle both `key`, value and {key: value} style arguments.
        if (typeof key === 'object') {
            attrs = key;
            opt = val;
        } else {
            (attrs = {})[key] = val;
        }

        // Make sure that `cells` attribute is handled separately via resetCells().
        if (attrs.hasOwnProperty('cells')) {
            this.resetCells(attrs.cells, opt);
            attrs = joint.util.omit(attrs, 'cells');
        }

        // The rest of the attributes are applied via original set method.
        return Backbone.Model.prototype.set.call(this, attrs, opt);
    },

    clear: function(opt) {

        opt = joint.util.assign({}, opt, { clear: true });

        var collection = this.get('cells');

        if (collection.length === 0) return this;

        this.startBatch('clear', opt);

        // The elements come after the links.
        var cells = collection.sortBy(function(cell) {
            return cell.isLink() ? 1 : 2;
        });

        do {

            // Remove all the cells one by one.
            // Note that all the links are removed first, so it's
            // safe to remove the elements without removing the connected
            // links first.
            cells.shift().remove(opt);

        } while (cells.length > 0);

        this.stopBatch('clear');

        return this;
    },

    _prepareCell: function(cell, opt) {

        var attrs;
        if (cell instanceof Backbone.Model) {
            attrs = cell.attributes;
            if (!cell.graph && (!opt || !opt.dry)) {
                // An element can not be member of more than one graph.
                // A cell stops being the member of the graph after it's explicitely removed.
                cell.graph = this;
            }
        } else {
            // In case we're dealing with a plain JS object, we have to set the reference
            // to the `graph` right after the actual model is created. This happens in the `model()` function
            // of `joint.dia.GraphCells`.
            attrs = cell;
        }

        if (!joint.util.isString(attrs.type)) {
            throw new TypeError('dia.Graph: cell type must be a string.');
        }

        return cell;
    },

    minZIndex: function() {

        var firstCell = this.get('cells').first();
        return firstCell ? (firstCell.get('z') || 0) : 0;
    },

    maxZIndex: function() {

        var lastCell = this.get('cells').last();
        return lastCell ? (lastCell.get('z') || 0) : 0;
    },

    addCell: function(cell, opt) {

        if (Array.isArray(cell)) {

            return this.addCells(cell, opt);
        }

        if (cell instanceof Backbone.Model) {

            if (!cell.has('z')) {
                cell.set('z', this.maxZIndex() + 1);
            }

        } else if (cell.z === undefined) {

            cell.z = this.maxZIndex() + 1;
        }

        this.get('cells').add(this._prepareCell(cell, opt), opt || {});

        return this;
    },

    addCells: function(cells, opt) {

        if (cells.length) {

            cells = joint.util.flattenDeep(cells);
            opt.position = cells.length;

            this.startBatch('add');
            cells.forEach(function(cell) {
                opt.position--;
                this.addCell(cell, opt);
            }, this);
            this.stopBatch('add');
        }

        return this;
    },

    // When adding a lot of cells, it is much more efficient to
    // reset the entire cells collection in one go.
    // Useful for bulk operations and optimizations.
    resetCells: function(cells, opt) {

        var preparedCells = joint.util.toArray(cells).map(function(cell) {
            return this._prepareCell(cell, opt);
        }, this);
        this.get('cells').reset(preparedCells, opt);

        return this;
    },

    removeCells: function(cells, opt) {

        if (cells.length) {

            this.startBatch('remove');
            joint.util.invoke(cells, 'remove', opt);
            this.stopBatch('remove');
        }

        return this;
    },

    _removeCell: function(cell, collection, options) {

        options = options || {};

        if (!options.clear) {
            // Applications might provide a `disconnectLinks` option set to `true` in order to
            // disconnect links when a cell is removed rather then removing them. The default
            // is to remove all the associated links.
            if (options.disconnectLinks) {

                this.disconnectLinks(cell, options);

            } else {

                this.removeLinks(cell, options);
            }
        }
        // Silently remove the cell from the cells collection. Silently, because
        // `joint.dia.Cell.prototype.remove` already triggers the `remove` event which is
        // then propagated to the graph model. If we didn't remove the cell silently, two `remove` events
        // would be triggered on the graph model.
        this.get('cells').remove(cell, { silent: true });

        if (cell.graph === this) {
            // Remove the element graph reference only if the cell is the member of this graph.
            cell.graph = null;
        }
    },

    // Get a cell by `id`.
    getCell: function(id) {

        return this.get('cells').get(id);
    },

    getCells: function() {

        return this.get('cells').toArray();
    },

    getElements: function() {
        return Object.keys(this._nodes).map(this.getCell, this);
    },

    getLinks: function() {
        return Object.keys(this._edges).map(this.getCell, this);
    },

    getFirstCell: function() {

        return this.get('cells').first();
    },

    getLastCell: function() {

        return this.get('cells').last();
    },

    // Get all inbound and outbound links connected to the cell `model`.
    getConnectedLinks: function(model, opt) {

        opt = opt || {};

        var inbound = opt.inbound;
        var outbound = opt.outbound;
        if (inbound === undefined && outbound === undefined) {
            inbound = outbound = true;
        }

        // The final array of connected link models.
        var links = [];
        // Connected edges. This hash table ([edge] -> true) serves only
        // for a quick lookup to check if we already added a link.
        var edges = {};

        if (outbound) {
            joint.util.forIn(this.getOutboundEdges(model.id), function(exists, edge) {
                if (!edges[edge]) {
                    links.push(this.getCell(edge));
                    edges[edge] = true;
                }
            }.bind(this));
        }
        if (inbound) {
            joint.util.forIn(this.getInboundEdges(model.id), function(exists, edge) {
                // Skip links that were already added. Those must be self-loop links
                // because they are both inbound and outbond edges of the same element.
                if (!edges[edge]) {
                    links.push(this.getCell(edge));
                    edges[edge] = true;
                }
            }.bind(this));
        }

        // If 'deep' option is 'true', return all the links that are connected to any of the descendent cells
        // and are not descendents themselves.
        if (opt.deep) {

            var embeddedCells = model.getEmbeddedCells({ deep: true });
            // In the first round, we collect all the embedded edges so that we can exclude
            // them from the final result.
            var embeddedEdges = {};
            embeddedCells.forEach(function(cell) {
                if (cell.isLink()) {
                    embeddedEdges[cell.id] = true;
                }
            });
            embeddedCells.forEach(function(cell) {
                if (cell.isLink()) return;
                if (outbound) {
                    joint.util.forIn(this.getOutboundEdges(cell.id), function(exists, edge) {
                        if (!edges[edge] && !embeddedEdges[edge]) {
                            links.push(this.getCell(edge));
                            edges[edge] = true;
                        }
                    }.bind(this));
                }
                if (inbound) {
                    joint.util.forIn(this.getInboundEdges(cell.id), function(exists, edge) {
                        if (!edges[edge] && !embeddedEdges[edge]) {
                            links.push(this.getCell(edge));
                            edges[edge] = true;
                        }
                    }.bind(this));
                }
            }, this);
        }

        return links;
    },

    getNeighbors: function(model, opt) {

        opt = opt || {};

        var inbound = opt.inbound;
        var outbound = opt.outbound;
        if (inbound === undefined && outbound === undefined) {
            inbound = outbound = true;
        }

        var neighbors = this.getConnectedLinks(model, opt).reduce(function(res, link) {

            var source = link.get('source');
            var target = link.get('target');
            var loop = link.hasLoop(opt);

            // Discard if it is a point, or if the neighbor was already added.
            if (inbound && joint.util.has(source, 'id') && !res[source.id]) {

                var sourceElement = this.getCell(source.id);

                if (loop || (sourceElement && sourceElement !== model && (!opt.deep || !sourceElement.isEmbeddedIn(model)))) {
                    res[source.id] = sourceElement;
                }
            }

            // Discard if it is a point, or if the neighbor was already added.
            if (outbound && joint.util.has(target, 'id') && !res[target.id]) {

                var targetElement = this.getCell(target.id);

                if (loop || (targetElement && targetElement !== model && (!opt.deep || !targetElement.isEmbeddedIn(model)))) {
                    res[target.id] = targetElement;
                }
            }

            return res;
        }.bind(this), {});

        return joint.util.toArray(neighbors);
    },

    getCommonAncestor: function(/* cells */) {

        var cellsAncestors = Array.from(arguments).map(function(cell) {

            var ancestors = [];
            var parentId = cell.get('parent');

            while (parentId) {

                ancestors.push(parentId);
                parentId = this.getCell(parentId).get('parent');
            }

            return ancestors;

        }, this);

        cellsAncestors = cellsAncestors.sort(function(a, b) {
            return a.length - b.length;
        });

        var commonAncestor = joint.util.toArray(cellsAncestors.shift()).find(function(ancestor) {
            return cellsAncestors.every(function(cellAncestors) {
                return cellAncestors.includes(ancestor);
            });
        });

        return this.getCell(commonAncestor);
    },

    // Find the whole branch starting at `element`.
    // If `opt.deep` is `true`, take into account embedded elements too.
    // If `opt.breadthFirst` is `true`, use the Breadth-first search algorithm, otherwise use Depth-first search.
    getSuccessors: function(element, opt) {

        opt = opt || {};
        var res = [];
        // Modify the options so that it includes the `outbound` neighbors only. In other words, search forwards.
        this.search(element, function(el) {
            if (el !== element) {
                res.push(el);
            }
        }, joint.util.assign({}, opt, { outbound: true }));
        return res;
    },

    // Clone `cells` returning an object that maps the original cell ID to the clone. The number
    // of clones is exactly the same as the `cells.length`.
    // This function simply clones all the `cells`. However, it also reconstructs
    // all the `source/target` and `parent/embed` references within the `cells`.
    // This is the main difference from the `cell.clone()` method. The
    // `cell.clone()` method works on one single cell only.
    // For example, for a graph: `A --- L ---> B`, `cloneCells([A, L, B])`
    // returns `[A2, L2, B2]` resulting to a graph: `A2 --- L2 ---> B2`, i.e.
    // the source and target of the link `L2` is changed to point to `A2` and `B2`.
    cloneCells: function(cells) {

        cells = joint.util.uniq(cells);

        // A map of the form [original cell ID] -> [clone] helping
        // us to reconstruct references for source/target and parent/embeds.
        // This is also the returned value.
        var cloneMap = joint.util.toArray(cells).reduce(function(map, cell) {
            map[cell.id] = cell.clone();
            return map;
        }, {});

        joint.util.toArray(cells).forEach(function(cell) {

            var clone = cloneMap[cell.id];
            // assert(clone exists)

            if (clone.isLink()) {
                var source = clone.get('source');
                var target = clone.get('target');
                if (source.id && cloneMap[source.id]) {
                    // Source points to an element and the element is among the clones.
                    // => Update the source of the cloned link.
                    clone.prop('source/id', cloneMap[source.id].id);
                }
                if (target.id && cloneMap[target.id]) {
                    // Target points to an element and the element is among the clones.
                    // => Update the target of the cloned link.
                    clone.prop('target/id', cloneMap[target.id].id);
                }
            }

            // Find the parent of the original cell
            var parent = cell.get('parent');
            if (parent && cloneMap[parent]) {
                clone.set('parent', cloneMap[parent].id);
            }

            // Find the embeds of the original cell
            var embeds = joint.util.toArray(cell.get('embeds')).reduce(function(newEmbeds, embed) {
                // Embedded cells that are not being cloned can not be carried
                // over with other embedded cells.
                if (cloneMap[embed]) {
                    newEmbeds.push(cloneMap[embed].id);
                }
                return newEmbeds;
            }, []);

            if (!joint.util.isEmpty(embeds)) {
                clone.set('embeds', embeds);
            }
        });

        return cloneMap;
    },

    // Clone the whole subgraph (including all the connected links whose source/target is in the subgraph).
    // If `opt.deep` is `true`, also take into account all the embedded cells of all the subgraph cells.
    // Return a map of the form: [original cell ID] -> [clone].
    cloneSubgraph: function(cells, opt) {

        var subgraph = this.getSubgraph(cells, opt);
        return this.cloneCells(subgraph);
    },

    // Return `cells` and all the connected links that connect cells in the `cells` array.
    // If `opt.deep` is `true`, return all the cells including all their embedded cells
    // and all the links that connect any of the returned cells.
    // For example, for a single shallow element, the result is that very same element.
    // For two elements connected with a link: `A --- L ---> B`, the result for
    // `getSubgraph([A, B])` is `[A, L, B]`. The same goes for `getSubgraph([L])`, the result is again `[A, L, B]`.
    getSubgraph: function(cells, opt) {

        opt = opt || {};

        var subgraph = [];
        // `cellMap` is used for a quick lookup of existance of a cell in the `cells` array.
        var cellMap = {};
        var elements = [];
        var links = [];

        joint.util.toArray(cells).forEach(function(cell) {
            if (!cellMap[cell.id]) {
                subgraph.push(cell);
                cellMap[cell.id] = cell;
                if (cell.isLink()) {
                    links.push(cell);
                } else {
                    elements.push(cell);
                }
            }

            if (opt.deep) {
                var embeds = cell.getEmbeddedCells({ deep: true });
                embeds.forEach(function(embed) {
                    if (!cellMap[embed.id]) {
                        subgraph.push(embed);
                        cellMap[embed.id] = embed;
                        if (embed.isLink()) {
                            links.push(embed);
                        } else {
                            elements.push(embed);
                        }
                    }
                });
            }
        });

        links.forEach(function(link) {
            // For links, return their source & target (if they are elements - not points).
            var source = link.get('source');
            var target = link.get('target');
            if (source.id && !cellMap[source.id]) {
                var sourceElement = this.getCell(source.id);
                subgraph.push(sourceElement);
                cellMap[sourceElement.id] = sourceElement;
                elements.push(sourceElement);
            }
            if (target.id && !cellMap[target.id]) {
                var targetElement = this.getCell(target.id);
                subgraph.push(this.getCell(target.id));
                cellMap[targetElement.id] = targetElement;
                elements.push(targetElement);
            }
        }, this);

        elements.forEach(function(element) {
            // For elements, include their connected links if their source/target is in the subgraph;
            var links = this.getConnectedLinks(element, opt);
            links.forEach(function(link) {
                var source = link.get('source');
                var target = link.get('target');
                if (!cellMap[link.id] && source.id && cellMap[source.id] && target.id && cellMap[target.id]) {
                    subgraph.push(link);
                    cellMap[link.id] = link;
                }
            });
        }, this);

        return subgraph;
    },

    // Find all the predecessors of `element`. This is a reverse operation of `getSuccessors()`.
    // If `opt.deep` is `true`, take into account embedded elements too.
    // If `opt.breadthFirst` is `true`, use the Breadth-first search algorithm, otherwise use Depth-first search.
    getPredecessors: function(element, opt) {

        opt = opt || {};
        var res = [];
        // Modify the options so that it includes the `inbound` neighbors only. In other words, search backwards.
        this.search(element, function(el) {
            if (el !== element) {
                res.push(el);
            }
        }, joint.util.assign({}, opt, { inbound: true }));
        return res;
    },

    // Perform search on the graph.
    // If `opt.breadthFirst` is `true`, use the Breadth-first Search algorithm, otherwise use Depth-first search.
    // By setting `opt.inbound` to `true`, you can reverse the direction of the search.
    // If `opt.deep` is `true`, take into account embedded elements too.
    // `iteratee` is a function of the form `function(element) {}`.
    // If `iteratee` explicitely returns `false`, the searching stops.
    search: function(element, iteratee, opt) {

        opt = opt || {};
        if (opt.breadthFirst) {
            this.bfs(element, iteratee, opt);
        } else {
            this.dfs(element, iteratee, opt);
        }
    },

    // Breadth-first search.
    // If `opt.deep` is `true`, take into account embedded elements too.
    // If `opt.inbound` is `true`, reverse the search direction (it's like reversing all the link directions).
    // `iteratee` is a function of the form `function(element, distance) {}`.
    // where `element` is the currently visited element and `distance` is the distance of that element
    // from the root `element` passed the `bfs()`, i.e. the element we started the search from.
    // Note that the `distance` is not the shortest or longest distance, it is simply the number of levels
    // crossed till we visited the `element` for the first time. It is especially useful for tree graphs.
    // If `iteratee` explicitely returns `false`, the searching stops.
    bfs: function(element, iteratee, opt) {

        opt = opt || {};
        var visited = {};
        var distance = {};
        var queue = [];

        queue.push(element);
        distance[element.id] = 0;

        while (queue.length > 0) {
            var next = queue.shift();
            if (!visited[next.id]) {
                visited[next.id] = true;
                if (iteratee(next, distance[next.id]) === false) return;
                this.getNeighbors(next, opt).forEach(function(neighbor) {
                    distance[neighbor.id] = distance[next.id] + 1;
                    queue.push(neighbor);
                });
            }
        }
    },

    // Depth-first search.
    // If `opt.deep` is `true`, take into account embedded elements too.
    // If `opt.inbound` is `true`, reverse the search direction (it's like reversing all the link directions).
    // `iteratee` is a function of the form `function(element, distance) {}`.
    // If `iteratee` explicitely returns `false`, the search stops.
    dfs: function(element, iteratee, opt, _visited, _distance) {

        opt = opt || {};
        var visited = _visited || {};
        var distance = _distance || 0;
        if (iteratee(element, distance) === false) return;
        visited[element.id] = true;

        this.getNeighbors(element, opt).forEach(function(neighbor) {
            if (!visited[neighbor.id]) {
                this.dfs(neighbor, iteratee, opt, visited, distance + 1);
            }
        }, this);
    },

    // Get all the roots of the graph. Time complexity: O(|V|).
    getSources: function() {

        var sources = [];
        joint.util.forIn(this._nodes, function(exists, node) {
            if (!this._in[node] || joint.util.isEmpty(this._in[node])) {
                sources.push(this.getCell(node));
            }
        }.bind(this));
        return sources;
    },

    // Get all the leafs of the graph. Time complexity: O(|V|).
    getSinks: function() {

        var sinks = [];
        joint.util.forIn(this._nodes, function(exists, node) {
            if (!this._out[node] || joint.util.isEmpty(this._out[node])) {
                sinks.push(this.getCell(node));
            }
        }.bind(this));
        return sinks;
    },

    // Return `true` if `element` is a root. Time complexity: O(1).
    isSource: function(element) {

        return !this._in[element.id] || joint.util.isEmpty(this._in[element.id]);
    },

    // Return `true` if `element` is a leaf. Time complexity: O(1).
    isSink: function(element) {

        return !this._out[element.id] || joint.util.isEmpty(this._out[element.id]);
    },

    // Return `true` is `elementB` is a successor of `elementA`. Return `false` otherwise.
    isSuccessor: function(elementA, elementB) {

        var isSuccessor = false;
        this.search(elementA, function(element) {
            if (element === elementB && element !== elementA) {
                isSuccessor = true;
                return false;
            }
        }, { outbound: true });
        return isSuccessor;
    },

    // Return `true` is `elementB` is a predecessor of `elementA`. Return `false` otherwise.
    isPredecessor: function(elementA, elementB) {

        var isPredecessor = false;
        this.search(elementA, function(element) {
            if (element === elementB && element !== elementA) {
                isPredecessor = true;
                return false;
            }
        }, { inbound: true });
        return isPredecessor;
    },

    // Return `true` is `elementB` is a neighbor of `elementA`. Return `false` otherwise.
    // `opt.deep` controls whether to take into account embedded elements as well. See `getNeighbors()`
    // for more details.
    // If `opt.outbound` is set to `true`, return `true` only if `elementB` is a successor neighbor.
    // Similarly, if `opt.inbound` is set to `true`, return `true` only if `elementB` is a predecessor neighbor.
    isNeighbor: function(elementA, elementB, opt) {

        opt = opt || {};

        var inbound = opt.inbound;
        var outbound = opt.outbound;
        if (inbound === undefined && outbound === undefined) {
            inbound = outbound = true;
        }

        var isNeighbor = false;

        this.getConnectedLinks(elementA, opt).forEach(function(link) {

            var source = link.get('source');
            var target = link.get('target');

            // Discard if it is a point.
            if (inbound && joint.util.has(source, 'id') && source.id === elementB.id) {
                isNeighbor = true;
                return false;
            }

            // Discard if it is a point, or if the neighbor was already added.
            if (outbound && joint.util.has(target, 'id') && target.id === elementB.id) {
                isNeighbor = true;
                return false;
            }
        });

        return isNeighbor;
    },

    // Disconnect links connected to the cell `model`.
    disconnectLinks: function(model, opt) {

        this.getConnectedLinks(model).forEach(function(link) {

            link.set(link.get('source').id === model.id ? 'source' : 'target', { x: 0, y: 0 }, opt);
        });
    },

    // Remove links connected to the cell `model` completely.
    removeLinks: function(model, opt) {

        joint.util.invoke(this.getConnectedLinks(model), 'remove', opt);
    },

    // Find all elements at given point
    findModelsFromPoint: function(p) {

        return this.getElements().filter(function(el) {
            return el.getBBox().containsPoint(p);
        });
    },

    // Find all elements in given area
    findModelsInArea: function(rect, opt) {

        rect = g.rect(rect);
        opt = joint.util.defaults(opt || {}, { strict: false });

        var method = opt.strict ? 'containsRect' : 'intersect';

        return this.getElements().filter(function(el) {
            return rect[method](el.getBBox());
        });
    },

    // Find all elements under the given element.
    findModelsUnderElement: function(element, opt) {

        opt = joint.util.defaults(opt || {}, { searchBy: 'bbox' });

        var bbox = element.getBBox();
        var elements = (opt.searchBy === 'bbox')
            ? this.findModelsInArea(bbox)
            : this.findModelsFromPoint(bbox[opt.searchBy]());

        // don't account element itself or any of its descendents
        return elements.filter(function(el) {
            return element.id !== el.id && !el.isEmbeddedIn(element);
        });
    },


    // Return bounding box of all elements.
    getBBox: function(cells, opt) {

        return this.getCellsBBox(cells || this.getElements(), opt);
    },

    // Return the bounding box of all cells in array provided.
    // Links are being ignored.
    getCellsBBox: function(cells, opt) {

        return joint.util.toArray(cells).reduce(function(memo, cell) {
            if (cell.isLink()) return memo;
            if (memo) {
                return memo.union(cell.getBBox(opt));
            } else {
                return cell.getBBox(opt);
            }
        }, null);
    },

    translate: function(dx, dy, opt) {

        // Don't translate cells that are embedded in any other cell.
        var cells = this.getCells().filter(function(cell) {
            return !cell.isEmbedded();
        });

        joint.util.invoke(cells, 'translate', dx, dy, opt);

        return this;
    },

    resize: function(width, height, opt) {

        return this.resizeCells(width, height, this.getCells(), opt);
    },

    resizeCells: function(width, height, cells, opt) {

        // `getBBox` method returns `null` if no elements provided.
        // i.e. cells can be an array of links
        var bbox = this.getCellsBBox(cells);
        if (bbox) {
            var sx = Math.max(width / bbox.width, 0);
            var sy = Math.max(height / bbox.height, 0);
            joint.util.invoke(cells, 'scale', sx, sy, bbox.origin(), opt);
        }

        return this;
    },

    startBatch: function(name, data) {

        data = data || {};
        this._batches[name] = (this._batches[name] || 0) + 1;

        return this.trigger('batch:start', joint.util.assign({}, data, { batchName: name }));
    },

    stopBatch: function(name, data) {

        data = data || {};
        this._batches[name] = (this._batches[name] || 0) - 1;

        return this.trigger('batch:stop', joint.util.assign({}, data, { batchName: name }));
    },

    hasActiveBatch: function(name) {
        if (arguments.length === 0) {
            return joint.util.toArray(this._batches).some(function(batches) {
                return batches > 0;
            });
        }
        if (Array.isArray(name)) {
            return name.some(function(name) {
                return !!this._batches[name];
            }, this);
        }
        return !!this._batches[name];
    }

}, {

    validations: {

        multiLinks: function(graph, link) {

            // Do not allow multiple links to have the same source and target.
            var source = link.get('source');
            var target = link.get('target');

            if (source.id && target.id) {

                var sourceModel = link.getSourceElement();
                if (sourceModel) {

                    var connectedLinks = graph.getConnectedLinks(sourceModel, { outbound: true });
                    var sameLinks = connectedLinks.filter(function(_link) {

                        var _source = _link.get('source');
                        var _target = _link.get('target');

                        return _source && _source.id === source.id &&
                            (!_source.port || (_source.port === source.port)) &&
                            _target && _target.id === target.id &&
                            (!_target.port || (_target.port === target.port));

                    });

                    if (sameLinks.length > 1) {
                        return false;
                    }
                }
            }

            return true;
        },

        linkPinning: function(graph, link) {
            return link.source().id && link.target().id;
        }
    }

});

joint.util.wrapWith(joint.dia.Graph.prototype, ['resetCells', 'addCells', 'removeCells'], 'cells');

(function(joint, V, g, $, util) {

    function setWrapper(attrName, dimension) {
        return function(value, refBBox) {
            var isValuePercentage = util.isPercentage(value);
            value = parseFloat(value);
            if (isValuePercentage) {
                value /= 100;
            }

            var attrs = {};
            if (isFinite(value)) {
                var attrValue = (isValuePercentage || value >= 0 && value <= 1)
                    ? value * refBBox[dimension]
                    : Math.max(value + refBBox[dimension], 0);
                attrs[attrName] = attrValue;
            }

            return attrs;
        };
    }

    function positionWrapper(axis, dimension, origin) {
        return function(value, refBBox) {
            var valuePercentage = util.isPercentage(value);
            value = parseFloat(value);
            if (valuePercentage) {
                value /= 100;
            }

            var delta;
            if (isFinite(value)) {
                var refOrigin = refBBox[origin]();
                if (valuePercentage || value > 0 && value < 1) {
                    delta = refOrigin[axis] + refBBox[dimension] * value;
                } else {
                    delta = refOrigin[axis] + value;
                }
            }

            var point = g.Point();
            point[axis] = delta || 0;
            return point;
        };
    }

    function offsetWrapper(axis, dimension, corner) {
        return function(value, nodeBBox) {
            var delta;
            if (value === 'middle') {
                delta = nodeBBox[dimension] / 2;
            } else if (value === corner) {
                delta = nodeBBox[dimension];
            } else if (isFinite(value)) {
                // TODO: or not to do a breaking change?
                delta = (value > -1 && value < 1) ? (-nodeBBox[dimension] * value) : -value;
            } else if (util.isPercentage(value)) {
                delta = nodeBBox[dimension] * parseFloat(value) / 100;
            } else {
                delta = 0;
            }

            var point = g.Point();
            point[axis] = -(nodeBBox[axis] + delta);
            return point;
        };
    }

    function shapeWrapper(shapeConstructor, opt) {
        var cacheName = 'joint-shape';
        var resetOffset = opt && opt.resetOffset;
        return function(value, refBBox, node) {
            var $node = $(node);
            var cache = $node.data(cacheName);
            if (!cache || cache.value !== value) {
                // only recalculate if value has changed
                var cachedShape = shapeConstructor(value);
                cache = {
                    value: value,
                    shape: cachedShape,
                    shapeBBox: cachedShape.bbox()
                };
                $node.data(cacheName, cache);
            }

            var shape = cache.shape.clone();
            var shapeBBox = cache.shapeBBox.clone();
            var shapeOrigin = shapeBBox.origin();
            var refOrigin = refBBox.origin();

            shapeBBox.x = refOrigin.x;
            shapeBBox.y = refOrigin.y;

            var fitScale = refBBox.maxRectScaleToFit(shapeBBox, refOrigin);
            // `maxRectScaleToFit` can give Infinity if width or height is 0
            var sx = (shapeBBox.width === 0 || refBBox.width === 0) ? 1 : fitScale.sx;
            var sy = (shapeBBox.height === 0 || refBBox.height === 0) ? 1 : fitScale.sy;

            shape.scale(sx, sy, shapeOrigin);
            if (resetOffset) {
                shape.translate(-shapeOrigin.x, -shapeOrigin.y);
            }

            return shape;
        };
    }

    // `d` attribute for SVGPaths
    function dWrapper(opt) {
        function pathConstructor(value) {
            return new g.Path(V.normalizePathData(value));
        }
        var shape = shapeWrapper(pathConstructor, opt);
        return function(value, refBBox, node) {
            var path = shape(value, refBBox, node);
            return {
                d: path.serialize()
            };
        };
    }

    // `points` attribute for SVGPolylines and SVGPolygons
    function pointsWrapper(opt) {
        var shape = shapeWrapper(g.Polyline, opt);
        return function(value, refBBox, node) {
            var polyline = shape(value, refBBox, node);
            return {
                points: polyline.serialize()
            };
        };
    }

    function atConnectionWrapper(method, opt) {
        var zeroVector = new g.Point(1, 0);
        return function(value) {
            var p, angle;
            var tangent = this[method](value);
            if (tangent) {
                angle = (opt.rotate) ? tangent.vector().vectorAngle(zeroVector) : 0;
                p = tangent.start;
            } else {
                p = this.path.start;
                angle = 0;
            }
            if (angle === 0) return { transform: 'translate(' + p.x + ',' + p.y + ')' };
            return { transform: 'translate(' + p.x + ',' + p.y + ') rotate(' + angle + ')' };
        }
    }

    function isTextInUse(lineHeight, node, attrs) {
        return (attrs.text !== undefined);
    }

    function isLinkView() {
        return this instanceof joint.dia.LinkView;
    }

    function contextMarker(context) {
        var marker = {};
        // Stroke
        // The context 'fill' is disregared here. The usual case is to use the marker with a connection
        // (for which 'fill' attribute is set to 'none').
        var stroke = context.stroke;
        if (typeof stroke === 'string') {
            marker['stroke'] = stroke;
            marker['fill'] = stroke;
        }
        // Opacity
        // Again the context 'fill-opacity' is ignored.
        var strokeOpacity = context.strokeOpacity;
        if (strokeOpacity === undefined) strokeOpacity = context['stroke-opacity'];
        if (strokeOpacity === undefined) strokeOpacity = context.opacity
        if (strokeOpacity !== undefined) {
            marker['stroke-opacity'] = strokeOpacity;
            marker['fill-opacity'] = strokeOpacity;
        }
        return marker;
    }

    var attributesNS = joint.dia.attributes = {

        xlinkHref: {
            set: 'xlink:href'
        },

        xlinkShow: {
            set: 'xlink:show'
        },

        xlinkRole: {
            set: 'xlink:role'
        },

        xlinkType: {
            set: 'xlink:type'
        },

        xlinkArcrole: {
            set: 'xlink:arcrole'
        },

        xlinkTitle: {
            set: 'xlink:title'
        },

        xlinkActuate: {
            set: 'xlink:actuate'
        },

        xmlSpace: {
            set: 'xml:space'
        },

        xmlBase: {
            set: 'xml:base'
        },

        xmlLang: {
            set: 'xml:lang'
        },

        preserveAspectRatio: {
            set: 'preserveAspectRatio'
        },

        requiredExtension: {
            set: 'requiredExtension'
        },

        requiredFeatures: {
            set: 'requiredFeatures'
        },

        systemLanguage: {
            set: 'systemLanguage'
        },

        externalResourcesRequired: {
            set: 'externalResourceRequired'
        },

        filter: {
            qualify: util.isPlainObject,
            set: function(filter) {
                return 'url(#' + this.paper.defineFilter(filter) + ')';
            }
        },

        fill: {
            qualify: util.isPlainObject,
            set: function(fill) {
                return 'url(#' + this.paper.defineGradient(fill) + ')';
            }
        },

        stroke: {
            qualify: util.isPlainObject,
            set: function(stroke) {
                return 'url(#' + this.paper.defineGradient(stroke) + ')';
            }
        },

        sourceMarker: {
            qualify: util.isPlainObject,
            set: function(marker, refBBox, node, attrs) {
                marker = util.assign(contextMarker(attrs), marker);
                return { 'marker-start': 'url(#' + this.paper.defineMarker(marker) + ')' };
            }
        },

        targetMarker: {
            qualify: util.isPlainObject,
            set: function(marker, refBBox, node, attrs) {
                marker = util.assign(contextMarker(attrs), { 'transform': 'rotate(180)' }, marker);
                return { 'marker-end': 'url(#' + this.paper.defineMarker(marker) + ')' };
            }
        },

        vertexMarker: {
            qualify: util.isPlainObject,
            set: function(marker, refBBox, node, attrs) {
                marker = util.assign(contextMarker(attrs), marker);
                return { 'marker-mid': 'url(#' + this.paper.defineMarker(marker) + ')' };
            }
        },

        text: {
            qualify: function(text, node, attrs) {
                return !attrs.textWrap || !util.isPlainObject(attrs.textWrap);
            },
            set: function(text, refBBox, node, attrs) {
                var $node = $(node);
                var cacheName = 'joint-text';
                var cache = $node.data(cacheName);
                var textAttrs = joint.util.pick(attrs, 'lineHeight', 'annotations', 'textPath', 'x', 'textVerticalAnchor', 'eol');
                var fontSize = textAttrs.fontSize = attrs['font-size'] || attrs['fontSize'];
                var textHash = JSON.stringify([text, textAttrs]);
                // Update the text only if there was a change in the string
                // or any of its attributes.
                if (cache === undefined || cache !== textHash) {
                    // Chrome bug:
                    // Tspans positions defined as `em` are not updated
                    // when container `font-size` change.
                    if (fontSize) node.setAttribute('font-size', fontSize);
                    // Text Along Path Selector
                    var textPath = textAttrs.textPath;
                    if (util.isObject(textPath)) {
                        var pathSelector = textPath.selector;
                        if (typeof pathSelector === 'string') {
                            var pathNode = this.findBySelector(pathSelector)[0];
                            if (pathNode instanceof SVGPathElement) {
                                textAttrs.textPath = util.assign({ 'xlink:href': '#' + pathNode.id }, textPath);
                            }
                        }
                    }
                    V(node).text('' + text, textAttrs);
                    $node.data(cacheName, textHash);
                }
            }
        },

        textWrap: {
            qualify: util.isPlainObject,
            set: function(value, refBBox, node, attrs) {
                // option `width`
                var width = value.width || 0;
                if (util.isPercentage(width)) {
                    refBBox.width *= parseFloat(width) / 100;
                } else if (width <= 0) {
                    refBBox.width += width;
                } else {
                    refBBox.width = width;
                }
                // option `height`
                var height = value.height || 0;
                if (util.isPercentage(height)) {
                    refBBox.height *= parseFloat(height) / 100;
                } else if (height <= 0) {
                    refBBox.height += height;
                } else {
                    refBBox.height = height;
                }
                // option `text`
                var text = value.text;
                if (text === undefined) text = attr.text;
                if (text !== undefined) {
                    var wrappedText = joint.util.breakText('' + text, refBBox, {
                        'font-weight': attrs['font-weight'] || attrs.fontWeight,
                        'font-size': attrs['font-size'] || attrs.fontSize,
                        'font-family': attrs['font-family'] || attrs.fontFamily,
                        'lineHeight': attrs.lineHeight
                    }, {
                        // Provide an existing SVG Document here
                        // instead of creating a temporary one over again.
                        svgDocument: this.paper.svg
                    });
                }
                joint.dia.attributes.text.set.call(this, wrappedText, refBBox, node, attrs);
            }
        },

        title: {
            qualify: function(title, node) {
                // HTMLElement title is specified via an attribute (i.e. not an element)
                return node instanceof SVGElement;
            },
            set: function(title, refBBox, node) {
                var $node = $(node);
                var cacheName = 'joint-title';
                var cache = $node.data(cacheName);
                if (cache === undefined || cache !== title) {
                    $node.data(cacheName, title);
                    // Generally <title> element should be the first child element of its parent.
                    var firstChild = node.firstChild;
                    if (firstChild && firstChild.tagName.toUpperCase() === 'TITLE') {
                        // Update an existing title
                        firstChild.textContent = title;
                    } else {
                        // Create a new title
                        var titleNode = document.createElementNS(node.namespaceURI, 'title');
                        titleNode.textContent = title;
                        node.insertBefore(titleNode, firstChild);
                    }
                }
            }
        },

        lineHeight: {
            qualify: isTextInUse
        },

        textVerticalAnchor: {
            qualify: isTextInUse
        },

        textPath: {
            qualify: isTextInUse
        },

        annotations: {
            qualify: isTextInUse
        },

        // `port` attribute contains the `id` of the port that the underlying magnet represents.
        port: {
            set: function(port) {
                return (port === null || port.id === undefined) ? port : port.id;
            }
        },

        // `style` attribute is special in the sense that it sets the CSS style of the subelement.
        style: {
            qualify: util.isPlainObject,
            set: function(styles, refBBox, node) {
                $(node).css(styles);
            }
        },

        html: {
            set: function(html, refBBox, node) {
                $(node).html(html + '');
            }
        },

        ref: {
            // We do not set `ref` attribute directly on an element.
            // The attribute itself does not qualify for relative positioning.
        },

        // if `refX` is in [0, 1] then `refX` is a fraction of bounding box width
        // if `refX` is < 0 then `refX`'s absolute values is the right coordinate of the bounding box
        // otherwise, `refX` is the left coordinate of the bounding box

        refX: {
            position: positionWrapper('x', 'width', 'origin')
        },

        refY: {
            position: positionWrapper('y', 'height', 'origin')
        },

        // `ref-dx` and `ref-dy` define the offset of the subelement relative to the right and/or bottom
        // coordinate of the reference element.

        refDx: {
            position: positionWrapper('x', 'width', 'corner')
        },

        refDy: {
            position: positionWrapper('y', 'height', 'corner')
        },

        // 'ref-width'/'ref-height' defines the width/height of the subelement relatively to
        // the reference element size
        // val in 0..1         ref-width = 0.75 sets the width to 75% of the ref. el. width
        // val < 0 || val > 1  ref-height = -20 sets the height to the the ref. el. height shorter by 20

        refWidth: {
            set: setWrapper('width', 'width')
        },

        refHeight: {
            set: setWrapper('height', 'height')
        },

        refRx: {
            set: setWrapper('rx', 'width')
        },

        refRy: {
            set: setWrapper('ry', 'height')
        },

        refRInscribed: {
            set: (function(attrName) {
                var widthFn = setWrapper(attrName, 'width');
                var heightFn = setWrapper(attrName, 'height');
                return function(value, refBBox) {
                    var fn = (refBBox.height > refBBox.width) ? widthFn : heightFn;
                    return fn(value, refBBox);
                }
            })('r')
        },

        refRCircumscribed: {
            set: function(value, refBBox) {
                var isValuePercentage = util.isPercentage(value);
                value = parseFloat(value);
                if (isValuePercentage) {
                    value /= 100;
                }

                var diagonalLength = Math.sqrt((refBBox.height * refBBox.height) + (refBBox.width * refBBox.width));

                var rValue;
                if (isFinite(value)) {
                    if (isValuePercentage || value >= 0 && value <= 1) rValue = value * diagonalLength;
                    else rValue = Math.max(value + diagonalLength, 0);
                }

                return { r: rValue };
            }
        },

        refCx: {
            set: setWrapper('cx', 'width')
        },

        refCy: {
            set: setWrapper('cy', 'height')
        },

        // `x-alignment` when set to `middle` causes centering of the subelement around its new x coordinate.
        // `x-alignment` when set to `right` uses the x coordinate as referenced to the right of the bbox.

        xAlignment: {
            offset: offsetWrapper('x', 'width', 'right')
        },

        // `y-alignment` when set to `middle` causes centering of the subelement around its new y coordinate.
        // `y-alignment` when set to `bottom` uses the y coordinate as referenced to the bottom of the bbox.

        yAlignment: {
            offset: offsetWrapper('y', 'height', 'bottom')
        },

        resetOffset: {
            offset: function(val, nodeBBox) {
                return (val)
                    ? { x: -nodeBBox.x, y: -nodeBBox.y }
                    : { x: 0, y: 0 };
            }

        },

        refDResetOffset: {
            set: dWrapper({ resetOffset: true })
        },

        refDKeepOffset: {
            set: dWrapper({ resetOffset: false })
        },

        refPointsResetOffset: {
            set: pointsWrapper({ resetOffset: true })
        },

        refPointsKeepOffset: {
            set: pointsWrapper({ resetOffset: false })
        },

        // LinkView Attributes

        connection: {
            qualify: isLinkView,
            set: function() {
                return { d: this.getSerializedConnection() };
            }
        },

        atConnectionLengthKeepGradient: {
            qualify: isLinkView,
            set: atConnectionWrapper('getTangentAtLength', { rotate: true })
        },

        atConnectionLengthIgnoreGradient: {
            qualify: isLinkView,
            set: atConnectionWrapper('getTangentAtLength', { rotate: false })
        },

        atConnectionRatioKeepGradient: {
            qualify: isLinkView,
            set: atConnectionWrapper('getTangentAtRatio', { rotate: true })
        },

        atConnectionRatioIgnoreGradient: {
            qualify: isLinkView,
            set: atConnectionWrapper('getTangentAtRatio', { rotate: false })
        }
    };

    // Aliases
    attributesNS.refR = attributesNS.refRInscribed;
    attributesNS.refD = attributesNS.refDResetOffset;
    attributesNS.refPoints = attributesNS.refPointsResetOffset;
    attributesNS.atConnectionLength = attributesNS.atConnectionLengthKeepGradient;
    attributesNS.atConnectionRatio = attributesNS.atConnectionRatioKeepGradient;

    // This allows to combine both absolute and relative positioning
    // refX: 50%, refX2: 20
    attributesNS.refX2 = attributesNS.refX;
    attributesNS.refY2 = attributesNS.refY;

    // Aliases for backwards compatibility
    attributesNS['ref-x'] = attributesNS.refX;
    attributesNS['ref-y'] = attributesNS.refY;
    attributesNS['ref-dy'] = attributesNS.refDy;
    attributesNS['ref-dx'] = attributesNS.refDx;
    attributesNS['ref-width'] = attributesNS.refWidth;
    attributesNS['ref-height'] = attributesNS.refHeight;
    attributesNS['x-alignment'] = attributesNS.xAlignment;
    attributesNS['y-alignment'] = attributesNS.yAlignment;

})(joint, V, g, $, joint.util);

(function(joint, util) {

    var ToolView = joint.mvc.View.extend({
        name: null,
        tagName: 'g',
        className: 'tool',
        svgElement: true,
        _visible: true,

        init: function() {
            var name = this.name;
            if (name) this.vel.attr('data-tool-name', name);
        },

        configure: function(view, toolsView) {
            this.relatedView = view;
            this.paper = view.paper;
            this.parentView = toolsView;
            this.simulateRelatedView(this.el);
            return this;
        },

        simulateRelatedView: function(el) {
            if (el) el.setAttribute('model-id', this.relatedView.model.id);
        },

        getName: function() {
            return this.name;
        },

        show: function() {
            this.el.style.display = '';
            this._visible = true;
        },

        hide: function() {
            this.el.style.display = 'none';
            this._visible = false;
        },

        isVisible: function() {
            return !!this._visible;
        },

        focus: function() {
            var opacity = this.options.focusOpacity;
            if (isFinite(opacity)) this.el.style.opacity = opacity;
            this.parentView.focusTool(this);
        },

        blur: function() {
            this.el.style.opacity = '';
            this.parentView.blurTool(this);
        },

        update: function() {
            // to be overriden
        }
    });

    var ToolsView = joint.mvc.View.extend({
        tagName: 'g',
        className: 'tools',
        svgElement: true,
        tools: null,
        options: {
            tools: null,
            relatedView: null,
            name: null,
            component: false
        },

        configure: function(options) {
            options = util.assign(this.options, options);
            var tools = options.tools;
            if (!Array.isArray(tools)) return this;
            var relatedView = options.relatedView;
            if (!(relatedView instanceof joint.dia.CellView)) return this;
            var views = this.tools = [];
            for (var i = 0, n = tools.length; i < n; i++) {
                var tool = tools[i];
                if (!(tool instanceof ToolView)) continue;
                tool.configure(relatedView, this);
                tool.render();
                this.vel.append(tool.el);
                views.push(tool);
            }
            return this;
        },

        getName: function() {
            return this.options.name;
        },

        update: function(opt) {

            opt || (opt = {});
            var tools = this.tools;
            if (!tools) return;
            for (var i = 0, n = tools.length; i < n; i++) {
                var tool = tools[i];
                if (opt.tool !== tool.cid && tool.isVisible()) {
                    tool.update();
                }
            }
            return this;
        },

        focusTool: function(focusedTool) {

            var tools = this.tools;
            if (!tools) return this;
            for (var i = 0, n = tools.length; i < n; i++) {
                var tool = tools[i];
                if (focusedTool === tool) {
                    tool.show();
                } else {
                    tool.hide();
                }
            }
            return this;
        },

        blurTool: function(blurredTool) {
            var tools = this.tools;
            if (!tools) return this;
            for (var i = 0, n = tools.length; i < n; i++) {
                var tool = tools[i];
                if (tool !== blurredTool && !tool.isVisible()) {
                    tool.show();
                    tool.update();
                }
            }
            return this;
        },

        hide: function() {
            return this.focusTool(null);
        },

        show: function() {
            return this.blurTool(null);
        },

        onRemove: function() {

            var tools = this.tools;
            if (!tools) return this;
            for (var i = 0, n = tools.length; i < n; i++) {
                tools[i].remove();
            }
            this.tools = null;
        },

        mount: function() {
            var options = this.options;
            var relatedView = options.relatedView;
            if (relatedView) {
                var container = (options.component) ? relatedView.el : relatedView.paper.tools;
                container.appendChild(this.el);
            }
            return this;
        }

    });

    joint.dia.ToolsView = ToolsView;
    joint.dia.ToolView = ToolView;

})(joint, joint.util);


// joint.dia.Cell base model.
// --------------------------

joint.dia.Cell = Backbone.Model.extend({

    // This is the same as Backbone.Model with the only difference that is uses joint.util.merge
    // instead of just _.extend. The reason is that we want to mixin attributes set in upper classes.
    constructor: function(attributes, options) {

        var defaults;
        var attrs = attributes || {};
        this.cid = joint.util.uniqueId('c');
        this.attributes = {};
        if (options && options.collection) this.collection = options.collection;
        if (options && options.parse) attrs = this.parse(attrs, options) || {};
        if ((defaults = joint.util.result(this, 'defaults'))) {
            //<custom code>
            // Replaced the call to _.defaults with joint.util.merge.
            attrs = joint.util.merge({}, defaults, attrs);
            //</custom code>
        }
        this.set(attrs, options);
        this.changed = {};
        this.initialize.apply(this, arguments);
    },

    translate: function(dx, dy, opt) {

        throw new Error('Must define a translate() method.');
    },

    toJSON: function() {

        var defaultAttrs = this.constructor.prototype.defaults.attrs || {};
        var attrs = this.attributes.attrs;
        var finalAttrs = {};

        // Loop through all the attributes and
        // omit the default attributes as they are implicitly reconstructable by the cell 'type'.
        joint.util.forIn(attrs, function(attr, selector) {

            var defaultAttr = defaultAttrs[selector];

            joint.util.forIn(attr, function(value, name) {

                // attr is mainly flat though it might have one more level (consider the `style` attribute).
                // Check if the `value` is object and if yes, go one level deep.
                if (joint.util.isObject(value) && !Array.isArray(value)) {

                    joint.util.forIn(value, function(value2, name2) {

                        if (!defaultAttr || !defaultAttr[name] || !joint.util.isEqual(defaultAttr[name][name2], value2)) {

                            finalAttrs[selector] = finalAttrs[selector] || {};
                            (finalAttrs[selector][name] || (finalAttrs[selector][name] = {}))[name2] = value2;
                        }
                    });

                } else if (!defaultAttr || !joint.util.isEqual(defaultAttr[name], value)) {
                    // `value` is not an object, default attribute for such a selector does not exist
                    // or it is different than the attribute value set on the model.

                    finalAttrs[selector] = finalAttrs[selector] || {};
                    finalAttrs[selector][name] = value;
                }
            });
        });

        var attributes = joint.util.cloneDeep(joint.util.omit(this.attributes, 'attrs'));
        //var attributes = JSON.parse(JSON.stringify(_.omit(this.attributes, 'attrs')));
        attributes.attrs = finalAttrs;

        return attributes;
    },

    initialize: function(options) {

        if (!options || !options.id) {

            this.set('id', joint.util.uuid(), { silent: true });
        }

        this._transitionIds = {};

        // Collect ports defined in `attrs` and keep collecting whenever `attrs` object changes.
        this.processPorts();
        this.on('change:attrs', this.processPorts, this);
    },

    /**
     * @deprecated
     */
    processPorts: function() {

        // Whenever `attrs` changes, we extract ports from the `attrs` object and store it
        // in a more accessible way. Also, if any port got removed and there were links that had `target`/`source`
        // set to that port, we remove those links as well (to follow the same behaviour as
        // with a removed element).

        var previousPorts = this.ports;

        // Collect ports from the `attrs` object.
        var ports = {};
        joint.util.forIn(this.get('attrs'), function(attrs, selector) {

            if (attrs && attrs.port) {

                // `port` can either be directly an `id` or an object containing an `id` (and potentially other data).
                if (attrs.port.id !== undefined) {
                    ports[attrs.port.id] = attrs.port;
                } else {
                    ports[attrs.port] = { id: attrs.port };
                }
            }
        });

        // Collect ports that have been removed (compared to the previous ports) - if any.
        // Use hash table for quick lookup.
        var removedPorts = {};
        joint.util.forIn(previousPorts, function(port, id) {

            if (!ports[id]) removedPorts[id] = true;
        });

        // Remove all the incoming/outgoing links that have source/target port set to any of the removed ports.
        if (this.graph && !joint.util.isEmpty(removedPorts)) {

            var inboundLinks = this.graph.getConnectedLinks(this, { inbound: true });
            inboundLinks.forEach(function(link) {

                if (removedPorts[link.get('target').port]) link.remove();
            });

            var outboundLinks = this.graph.getConnectedLinks(this, { outbound: true });
            outboundLinks.forEach(function(link) {

                if (removedPorts[link.get('source').port]) link.remove();
            });
        }

        // Update the `ports` object.
        this.ports = ports;
    },

    remove: function(opt) {

        opt = opt || {};

        // Store the graph in a variable because `this.graph` won't' be accessbile after `this.trigger('remove', ...)` down below.
        var graph = this.graph;
        if (graph) {
            graph.startBatch('remove');
        }

        // First, unembed this cell from its parent cell if there is one.
        var parentCell = this.getParentCell();
        if (parentCell) parentCell.unembed(this);

        joint.util.invoke(this.getEmbeddedCells(), 'remove', opt);

        this.trigger('remove', this, this.collection, opt);

        if (graph) {
            graph.stopBatch('remove');
        }

        return this;
    },

    toFront: function(opt) {

        var graph = this.graph;
        if (graph) {

            opt = opt || {};

            var z = graph.maxZIndex();

            var cells;

            if (opt.deep) {
                cells = this.getEmbeddedCells({ deep: true, breadthFirst: true });
                cells.unshift(this);
            } else {
                cells = [this];
            }

            z = z - cells.length + 1;

            var collection = graph.get('cells');
            var shouldUpdate = (collection.indexOf(this) !== (collection.length - cells.length));
            if (!shouldUpdate) {
                shouldUpdate = cells.some(function(cell, index) {
                    return cell.get('z') !== z + index;
                });
            }

            if (shouldUpdate) {
                this.startBatch('to-front');

                z = z + cells.length;

                cells.forEach(function(cell, index) {
                    cell.set('z', z + index, opt);
                });

                this.stopBatch('to-front');
            }
        }

        return this;
    },

    toBack: function(opt) {

        var graph = this.graph;
        if (graph) {

            opt = opt || {};

            var z = graph.minZIndex();

            var cells;

            if (opt.deep) {
                cells = this.getEmbeddedCells({ deep: true, breadthFirst: true });
                cells.unshift(this);
            } else {
                cells = [this];
            }

            var collection = graph.get('cells');
            var shouldUpdate = (collection.indexOf(this) !== 0);
            if (!shouldUpdate) {
                shouldUpdate = cells.some(function(cell, index) {
                    return cell.get('z') !== z + index;
                });
            }

            if (shouldUpdate) {
                this.startBatch('to-back');

                z -= cells.length;

                cells.forEach(function(cell, index) {
                    cell.set('z', z + index, opt);
                });

                this.stopBatch('to-back');
            }
        }

        return this;
    },

    parent: function(parent, opt) {

        // getter
        if (parent === undefined) return this.get('parent');
        // setter
        return this.set('parent', parent, opt);
    },

    embed: function(cell, opt) {

        if (this === cell || this.isEmbeddedIn(cell)) {

            throw new Error('Recursive embedding not allowed.');

        } else {

            this.startBatch('embed');

            var embeds = joint.util.assign([], this.get('embeds'));

            // We keep all element ids after link ids.
            embeds[cell.isLink() ? 'unshift' : 'push'](cell.id);

            cell.parent(this.id, opt);
            this.set('embeds', joint.util.uniq(embeds), opt);

            this.stopBatch('embed');
        }

        return this;
    },

    unembed: function(cell, opt) {

        this.startBatch('unembed');

        cell.unset('parent', opt);
        this.set('embeds', joint.util.without(this.get('embeds'), cell.id), opt);

        this.stopBatch('unembed');

        return this;
    },

    getParentCell: function() {

        // unlike link.source/target, cell.parent stores id directly as a string
        var parentId = this.parent();
        var graph = this.graph;

        return (parentId && graph && graph.getCell(parentId)) || null;
    },

    // Return an array of ancestor cells.
    // The array is ordered from the parent of the cell
    // to the most distant ancestor.
    getAncestors: function() {

        var ancestors = [];

        if (!this.graph) {
            return ancestors;
        }

        var parentCell = this.getParentCell();
        while (parentCell) {
            ancestors.push(parentCell);
            parentCell = parentCell.getParentCell();
        }

        return ancestors;
    },

    getEmbeddedCells: function(opt) {

        opt = opt || {};

        // Cell models can only be retrieved when this element is part of a collection.
        // There is no way this element knows about other cells otherwise.
        // This also means that calling e.g. `translate()` on an element with embeds before
        // adding it to a graph does not translate its embeds.
        if (this.graph) {

            var cells;

            if (opt.deep) {

                if (opt.breadthFirst) {

                    // breadthFirst algorithm
                    cells = [];
                    var queue = this.getEmbeddedCells();

                    while (queue.length > 0) {

                        var parent = queue.shift();
                        cells.push(parent);
                        queue.push.apply(queue, parent.getEmbeddedCells());
                    }

                } else {

                    // depthFirst algorithm
                    cells = this.getEmbeddedCells();
                    cells.forEach(function(cell) {
                        cells.push.apply(cells, cell.getEmbeddedCells(opt));
                    });
                }

            } else {

                cells = joint.util.toArray(this.get('embeds')).map(this.graph.getCell, this.graph);
            }

            return cells;
        }
        return [];
    },

    isEmbeddedIn: function(cell, opt) {

        var cellId = joint.util.isString(cell) ? cell : cell.id;
        var parentId = this.parent();

        opt = joint.util.defaults({ deep: true }, opt);

        // See getEmbeddedCells().
        if (this.graph && opt.deep) {

            while (parentId) {
                if (parentId === cellId) {
                    return true;
                }
                parentId = this.graph.getCell(parentId).parent();
            }

            return false;

        } else {

            // When this cell is not part of a collection check
            // at least whether it's a direct child of given cell.
            return parentId === cellId;
        }
    },

    // Whether or not the cell is embedded in any other cell.
    isEmbedded: function() {

        return !!this.parent();
    },

    // Isolated cloning. Isolated cloning has two versions: shallow and deep (pass `{ deep: true }` in `opt`).
    // Shallow cloning simply clones the cell and returns a new cell with different ID.
    // Deep cloning clones the cell and all its embedded cells recursively.
    clone: function(opt) {

        opt = opt || {};

        if (!opt.deep) {
            // Shallow cloning.

            var clone = Backbone.Model.prototype.clone.apply(this, arguments);
            // We don't want the clone to have the same ID as the original.
            clone.set('id', joint.util.uuid());
            // A shallow cloned element does not carry over the original embeds.
            clone.unset('embeds');
            // And can not be embedded in any cell
            // as the clone is not part of the graph.
            clone.unset('parent');

            return clone;

        } else {
            // Deep cloning.

            // For a deep clone, simply call `graph.cloneCells()` with the cell and all its embedded cells.
            return joint.util.toArray(joint.dia.Graph.prototype.cloneCells.call(null, [this].concat(this.getEmbeddedCells({ deep: true }))));
        }
    },

    // A convenient way to set nested properties.
    // This method merges the properties you'd like to set with the ones
    // stored in the cell and makes sure change events are properly triggered.
    // You can either set a nested property with one object
    // or use a property path.
    // The most simple use case is:
    // `cell.prop('name/first', 'John')` or
    // `cell.prop({ name: { first: 'John' } })`.
    // Nested arrays are supported too:
    // `cell.prop('series/0/data/0/degree', 50)` or
    // `cell.prop({ series: [ { data: [ { degree: 50 } ] } ] })`.
    prop: function(props, value, opt) {

        var delim = '/';
        var isString = joint.util.isString(props);

        if (isString || Array.isArray(props)) {
            // Get/set an attribute by a special path syntax that delimits
            // nested objects by the colon character.

            if (arguments.length > 1) {

                var path;
                var pathArray;

                if (isString) {
                    path = props;
                    pathArray = path.split('/')
                } else {
                    path = props.join(delim);
                    pathArray = props.slice();
                }

                var property = pathArray[0];
                var pathArrayLength = pathArray.length;

                opt = opt || {};
                opt.propertyPath = path;
                opt.propertyValue = value;
                opt.propertyPathArray = pathArray;

                if (pathArrayLength === 1) {
                    // Property is not nested. We can simply use `set()`.
                    return this.set(property, value, opt);
                }

                var update = {};
                // Initialize the nested object. Subobjects are either arrays or objects.
                // An empty array is created if the sub-key is an integer. Otherwise, an empty object is created.
                // Note that this imposes a limitation on object keys one can use with Inspector.
                // Pure integer keys will cause issues and are therefore not allowed.
                var initializer = update;
                var prevProperty = property;

                for (var i = 1; i < pathArrayLength; i++) {
                    var pathItem = pathArray[i];
                    var isArrayIndex = Number.isFinite(isString ? Number(pathItem) : pathItem);
                    initializer = initializer[prevProperty] = isArrayIndex ? [] : {};
                    prevProperty = pathItem;
                }

                // Fill update with the `value` on `path`.
                update = joint.util.setByPath(update, pathArray, value, '/');

                var baseAttributes = joint.util.merge({}, this.attributes);
                // if rewrite mode enabled, we replace value referenced by path with
                // the new one (we don't merge).
                opt.rewrite && joint.util.unsetByPath(baseAttributes, path, '/');

                // Merge update with the model attributes.
                var attributes = joint.util.merge(baseAttributes, update);
                // Finally, set the property to the updated attributes.
                return this.set(property, attributes[property], opt);

            } else {

                return joint.util.getByPath(this.attributes, props, delim);
            }
        }

        return this.set(joint.util.merge({}, this.attributes, props), value);
    },

    // A convient way to unset nested properties
    removeProp: function(path, opt) {

        // Once a property is removed from the `attrs` attribute
        // the cellView will recognize a `dirty` flag and rerender itself
        // in order to remove the attribute from SVG element.
        opt = opt || {};
        opt.dirty = true;

        var pathArray = Array.isArray(path) ? path : path.split('/');

        if (pathArray.length === 1) {
            // A top level property
            return this.unset(path, opt);
        }

        // A nested property
        var property = pathArray[0];
        var nestedPath = pathArray.slice(1);
        var propertyValue = joint.util.cloneDeep(this.get(property));

        joint.util.unsetByPath(propertyValue, nestedPath, '/');

        return this.set(property, propertyValue, opt);
    },

    // A convenient way to set nested attributes.
    attr: function(attrs, value, opt) {

        var args = Array.from(arguments);
        if (args.length === 0) {
            return this.get('attrs');
        }

        if (Array.isArray(attrs)) {
            args[0] = ['attrs'].concat(attrs);
        } else if (joint.util.isString(attrs)) {
            // Get/set an attribute by a special path syntax that delimits
            // nested objects by the colon character.
            args[0] = 'attrs/' + attrs;

        } else {

            args[0] = { 'attrs' : attrs };
        }

        return this.prop.apply(this, args);
    },

    // A convenient way to unset nested attributes
    removeAttr: function(path, opt) {

        if (Array.isArray(path)) {

            return this.removeProp(['attrs'].concat(path));
        }

        return this.removeProp('attrs/' + path, opt);
    },

    transition: function(path, value, opt, delim) {

        delim = delim || '/';

        var defaults = {
            duration: 100,
            delay: 10,
            timingFunction: joint.util.timing.linear,
            valueFunction: joint.util.interpolate.number
        };

        opt = joint.util.assign(defaults, opt);

        var firstFrameTime = 0;
        var interpolatingFunction;

        var setter = function(runtime) {

            var id, progress, propertyValue;

            firstFrameTime = firstFrameTime || runtime;
            runtime -= firstFrameTime;
            progress = runtime / opt.duration;

            if (progress < 1) {
                this._transitionIds[path] = id = joint.util.nextFrame(setter);
            } else {
                progress = 1;
                delete this._transitionIds[path];
            }

            propertyValue = interpolatingFunction(opt.timingFunction(progress));

            opt.transitionId = id;

            this.prop(path, propertyValue, opt);

            if (!id) this.trigger('transition:end', this, path);

        }.bind(this);

        var initiator = function(callback) {

            this.stopTransitions(path);

            interpolatingFunction = opt.valueFunction(joint.util.getByPath(this.attributes, path, delim), value);

            this._transitionIds[path] = joint.util.nextFrame(callback);

            this.trigger('transition:start', this, path);

        }.bind(this);

        return setTimeout(initiator, opt.delay, setter);
    },

    getTransitions: function() {

        return Object.keys(this._transitionIds);
    },

    stopTransitions: function(path, delim) {

        delim = delim || '/';

        var pathArray = path && path.split(delim);

        Object.keys(this._transitionIds).filter(pathArray && function(key) {

            return joint.util.isEqual(pathArray, key.split(delim).slice(0, pathArray.length));

        }).forEach(function(key) {

            joint.util.cancelFrame(this._transitionIds[key]);

            delete this._transitionIds[key];

            this.trigger('transition:end', this, key);

        }, this);

        return this;
    },

    // A shorcut making it easy to create constructs like the following:
    // `var el = (new joint.shapes.basic.Rect).addTo(graph)`.
    addTo: function(graph, opt) {

        graph.addCell(this, opt);
        return this;
    },

    // A shortcut for an equivalent call: `paper.findViewByModel(cell)`
    // making it easy to create constructs like the following:
    // `cell.findView(paper).highlight()`
    findView: function(paper) {

        return paper.findViewByModel(this);
    },

    isElement: function() {

        return false;
    },

    isLink: function() {

        return false;
    },

    startBatch: function(name, opt) {

        if (this.graph) { this.graph.startBatch(name, joint.util.assign({}, opt, { cell: this })); }
        return this;
    },

    stopBatch: function(name, opt) {

        if (this.graph) { this.graph.stopBatch(name, joint.util.assign({}, opt, { cell: this })); }
        return this;
    }

}, {

    getAttributeDefinition: function(attrName) {

        var defNS = this.attributes;
        var globalDefNS = joint.dia.attributes;
        return (defNS && defNS[attrName]) || globalDefNS[attrName];
    },

    define: function(type, defaults, protoProps, staticProps) {

        protoProps = joint.util.assign({
            defaults: joint.util.defaultsDeep({ type: type }, defaults, this.prototype.defaults)
        }, protoProps);

        var Cell = this.extend(protoProps, staticProps);
        joint.util.setByPath(joint.shapes, type, Cell, '.');
        return Cell;
    }
});

// joint.dia.CellView base view and controller.
// --------------------------------------------

// This is the base view and controller for `joint.dia.ElementView` and `joint.dia.LinkView`.

joint.dia.CellView = joint.mvc.View.extend({

    tagName: 'g',

    svgElement: true,

    selector: 'root',

    className: function() {

        var classNames = ['cell'];
        var type = this.model.get('type');

        if (type) {

            type.toLowerCase().split('.').forEach(function(value, index, list) {
                classNames.push('type-' + list.slice(0, index + 1).join('-'));
            });
        }

        return classNames.join(' ');
    },

    attributes: function() {

        return { 'model-id': this.model.id };
    },

    constructor: function(options) {

        // Make sure a global unique id is assigned to this view. Store this id also to the properties object.
        // The global unique id makes sure that the same view can be rendered on e.g. different machines and
        // still be associated to the same object among all those clients. This is necessary for real-time
        // collaboration mechanism.
        options.id = options.id || joint.util.guid(this);

        joint.mvc.View.call(this, options);
    },

    init: function() {

        joint.util.bindAll(this, 'remove', 'update');

        // Store reference to this to the <g> DOM element so that the view is accessible through the DOM tree.
        this.$el.data('view', this);

        // Add the cell's type to the view's element as a data attribute.
        this.$el.attr('data-type', this.model.get('type'));

        this.listenTo(this.model, 'change:attrs', this.onChangeAttrs);
    },

    onChangeAttrs: function(cell, attrs, opt) {

        if (opt.dirty) {

            // dirty flag could be set when a model attribute was removed and it needs to be cleared
            // also from the DOM element. See cell.removeAttr().
            return this.render();
        }

        return this.update(cell, attrs, opt);
    },

    // Return `true` if cell link is allowed to perform a certain UI `feature`.
    // Example: `can('vertexMove')`, `can('labelMove')`.
    can: function(feature) {

        var interactive = joint.util.isFunction(this.options.interactive)
                            ? this.options.interactive(this)
                            : this.options.interactive;

        return (joint.util.isObject(interactive) && interactive[feature] !== false) ||
                (joint.util.isBoolean(interactive) && interactive !== false);
    },

    findBySelector: function(selector, root, selectors) {

        root || (root = this.el);
        selectors || (selectors = this.selectors);

        // These are either descendants of `this.$el` of `this.$el` itself.
        // `.` is a special selector used to select the wrapping `<g>` element.
        if (!selector || selector === '.') return [root];
        if (selectors && selectors[selector]) return [selectors[selector]];
        // Maintaining backwards compatibility
        // e.g. `circle:first` would fail with querySelector() call
        return $(root).find(selector).toArray();
    },

    notify: function(eventName) {

        if (this.paper) {

            var args = Array.prototype.slice.call(arguments, 1);

            // Trigger the event on both the element itself and also on the paper.
            this.trigger.apply(this, [eventName].concat(args));

            // Paper event handlers receive the view object as the first argument.
            this.paper.trigger.apply(this.paper, [eventName, this].concat(args));
        }
    },

    // ** Deprecated **
    getStrokeBBox: function(el) {
        // Return a bounding box rectangle that takes into account stroke.
        // Note that this is a naive and ad-hoc implementation that does not
        // works only in certain cases and should be replaced as soon as browsers will
        // start supporting the getStrokeBBox() SVG method.
        // @TODO any better solution is very welcome!

        var isMagnet = !!el;

        el = el || this.el;
        var bbox = V(el).getBBox({ target: this.paper.viewport });
        var strokeWidth;
        if (isMagnet) {

            strokeWidth = V(el).attr('stroke-width');

        } else {

            strokeWidth = this.model.attr('rect/stroke-width') || this.model.attr('circle/stroke-width') || this.model.attr('ellipse/stroke-width') || this.model.attr('path/stroke-width');
        }

        strokeWidth = parseFloat(strokeWidth) || 0;

        return g.rect(bbox).moveAndExpand({ x: -strokeWidth / 2, y: -strokeWidth / 2, width: strokeWidth, height: strokeWidth });
    },

    getBBox: function() {

        return this.vel.getBBox({ target: this.paper.svg });
    },

    highlight: function(el, opt) {

        el = !el ? this.el : this.$(el)[0] || this.el;

        // set partial flag if the highlighted element is not the entire view.
        opt = opt || {};
        opt.partial = (el !== this.el);

        this.notify('cell:highlight', el, opt);
        return this;
    },

    unhighlight: function(el, opt) {

        el = !el ? this.el : this.$(el)[0] || this.el;

        opt = opt || {};
        opt.partial = el != this.el;

        this.notify('cell:unhighlight', el, opt);
        return this;
    },

    // Find the closest element that has the `magnet` attribute set to `true`. If there was not such
    // an element found, return the root element of the cell view.
    findMagnet: function(el) {

        var $el = this.$(el);
        var $rootEl = this.$el;

        if ($el.length === 0) {
            $el = $rootEl;
        }

        do {

            var magnet = $el.attr('magnet');
            if ((magnet || $el.is($rootEl)) && magnet !== 'false') {
                return $el[0];
            }

            $el = $el.parent();

        } while ($el.length > 0);

        // If the overall cell has set `magnet === false`, then return `undefined` to
        // announce there is no magnet found for this cell.
        // This is especially useful to set on cells that have 'ports'. In this case,
        // only the ports have set `magnet === true` and the overall element has `magnet === false`.
        return undefined;
    },

    // Construct a unique selector for the `el` element within this view.
    // `prevSelector` is being collected through the recursive call.
    // No value for `prevSelector` is expected when using this method.
    getSelector: function(el, prevSelector) {

        if (el === this.el) {
            return prevSelector;
        }

        var selector;

        if (el) {

            var nthChild = V(el).index() + 1;
            selector = el.tagName + ':nth-child(' + nthChild + ')';

            if (prevSelector) {
                selector += ' > ' + prevSelector;
            }

            selector = this.getSelector(el.parentNode, selector);
        }

        return selector;
    },

    getLinkEnd: function(magnet, x, y, link, endType) {

        var model = this.model;
        var id = model.id;
        var port = this.findAttribute('port', magnet);
        // Find a unique `selector` of the element under pointer that is a magnet.
        var selector = magnet.getAttribute('joint-selector');

        var end = { id: id };
        if (selector != null) end.magnet = selector;
        if (port != null) {
            end.port = port;
            if (!model.hasPort(port) && !selector) {
                // port created via the `port` attribute (not API)
                end.selector = this.getSelector(magnet);
            }
        } else if (selector == null && this.el !== magnet) {
            end.selector = this.getSelector(magnet);
        }

        var paper = this.paper;
        var connectionStrategy = paper.options.connectionStrategy;
        if (typeof connectionStrategy === 'function') {
            var strategy = connectionStrategy.call(paper, end, this, magnet, new g.Point(x, y), link, endType);
            if (strategy) end = strategy;
        }

        return end;
    },

    getMagnetFromLinkEnd: function(end) {

        var root = this.el;
        var port = end.port;
        var selector = end.magnet;
        var magnet;
        if (port != null && this.model.hasPort(port)) {
            magnet = this.findPortNode(port, selector) || root;
        } else {
            if (!selector) selector = end.selector;
            if (!selector && port != null) {
                // link end has only `id` and `port` property referencing
                // a port created via the `port` attribute (not API).
                selector = '[port="' + port + '"]';
            }
            magnet = this.findBySelector(selector, root, this.selectors)[0];
        }

        return magnet;
    },

    findAttribute: function(attributeName, node) {

        if (!node) return null;

        var attributeValue = node.getAttribute(attributeName);
        if (attributeValue === null) {
            if (node === this.el) return null;
            var currentNode = node.parentNode;
            while (currentNode && currentNode !== this.el && currentNode.nodeType === 1) {
                attributeValue = currentNode.getAttribute(attributeName)
                if (attributeValue !== null) break;
                currentNode = currentNode.parentNode;
            }
        }
        return attributeValue;
    },

    getAttributeDefinition: function(attrName) {

        return this.model.constructor.getAttributeDefinition(attrName);
    },

    setNodeAttributes: function(node, attrs) {

        if (!joint.util.isEmpty(attrs)) {
            if (node instanceof SVGElement) {
                V(node).attr(attrs);
            } else {
                $(node).attr(attrs);
            }
        }
    },

    processNodeAttributes: function(node, attrs) {

        var attrName, attrVal, def, i, n;
        var normalAttrs, setAttrs, positionAttrs, offsetAttrs;
        var relatives = [];
        // divide the attributes between normal and special
        for (attrName in attrs) {
            if (!attrs.hasOwnProperty(attrName)) continue;
            attrVal = attrs[attrName];
            def = this.getAttributeDefinition(attrName);
            if (def && (!joint.util.isFunction(def.qualify) || def.qualify.call(this, attrVal, node, attrs))) {
                if (joint.util.isString(def.set)) {
                    normalAttrs || (normalAttrs = {});
                    normalAttrs[def.set] = attrVal;
                }
                if (attrVal !== null) {
                    relatives.push(attrName, def);
                }
            } else {
                normalAttrs || (normalAttrs = {});
                normalAttrs[joint.util.toKebabCase(attrName)] = attrVal;
            }
        }

        // handle the rest of attributes via related method
        // from the special attributes namespace.
        for (i = 0, n = relatives.length; i < n; i+=2) {
            attrName = relatives[i];
            def = relatives[i+1];
            attrVal = attrs[attrName];
            if (joint.util.isFunction(def.set)) {
                setAttrs || (setAttrs = {});
                setAttrs[attrName] = attrVal;
            }
            if (joint.util.isFunction(def.position)) {
                positionAttrs || (positionAttrs = {});
                positionAttrs[attrName] = attrVal;
            }
            if (joint.util.isFunction(def.offset)) {
                offsetAttrs || (offsetAttrs = {});
                offsetAttrs[attrName] = attrVal;
            }
        }

        return {
            raw: attrs,
            normal: normalAttrs,
            set: setAttrs,
            position: positionAttrs,
            offset: offsetAttrs
        };
    },

    updateRelativeAttributes: function(node, attrs, refBBox, opt) {

        opt || (opt = {});

        var attrName, attrVal, def;
        var rawAttrs = attrs.raw || {};
        var nodeAttrs = attrs.normal || {};
        var setAttrs = attrs.set;
        var positionAttrs = attrs.position;
        var offsetAttrs = attrs.offset;

        for (attrName in setAttrs) {
            attrVal = setAttrs[attrName];
            def = this.getAttributeDefinition(attrName);
            // SET - set function should return attributes to be set on the node,
            // which will affect the node dimensions based on the reference bounding
            // box. e.g. `width`, `height`, `d`, `rx`, `ry`, `points
            var setResult = def.set.call(this, attrVal, refBBox.clone(), node, rawAttrs);
            if (joint.util.isObject(setResult)) {
                joint.util.assign(nodeAttrs, setResult);
            } else if (setResult !== undefined) {
                nodeAttrs[attrName] = setResult;
            }
        }

        if (node instanceof HTMLElement) {
            // TODO: setting the `transform` attribute on HTMLElements
            // via `node.style.transform = 'matrix(...)';` would introduce
            // a breaking change (e.g. basic.TextBlock).
            this.setNodeAttributes(node, nodeAttrs);
            return;
        }

        // The final translation of the subelement.
        var nodeTransform = nodeAttrs.transform;
        var nodeMatrix = V.transformStringToMatrix(nodeTransform);
        var nodePosition = g.Point(nodeMatrix.e, nodeMatrix.f);
        if (nodeTransform) {
            nodeAttrs = joint.util.omit(nodeAttrs, 'transform');
            nodeMatrix.e = nodeMatrix.f = 0;
        }

        // Calculate node scale determined by the scalable group
        // only if later needed.
        var sx, sy, translation;
        if (positionAttrs || offsetAttrs) {
            var nodeScale = this.getNodeScale(node, opt.scalableNode);
            sx = nodeScale.sx;
            sy = nodeScale.sy;
        }

        var positioned = false;
        for (attrName in positionAttrs) {
            attrVal = positionAttrs[attrName];
            def = this.getAttributeDefinition(attrName);
            // POSITION - position function should return a point from the
            // reference bounding box. The default position of the node is x:0, y:0 of
            // the reference bounding box or could be further specify by some
            // SVG attributes e.g. `x`, `y`
            translation = def.position.call(this, attrVal, refBBox.clone(), node, rawAttrs);
            if (translation) {
                nodePosition.offset(g.Point(translation).scale(sx, sy));
                positioned || (positioned = true);
            }
        }

        // The node bounding box could depend on the `size` set from the previous loop.
        // Here we know, that all the size attributes have been already set.
        this.setNodeAttributes(node, nodeAttrs);

        var offseted = false;
        if (offsetAttrs) {
            // Check if the node is visible
            var nodeClientRect = node.getBoundingClientRect();
            if (nodeClientRect.width > 0 && nodeClientRect.height > 0) {
                var nodeBBox = V.transformRect(node.getBBox(), nodeMatrix).scale(1 / sx, 1 / sy);
                for (attrName in offsetAttrs) {
                    attrVal = offsetAttrs[attrName];
                    def = this.getAttributeDefinition(attrName);
                    // OFFSET - offset function should return a point from the element
                    // bounding box. The default offset point is x:0, y:0 (origin) or could be further
                    // specify with some SVG attributes e.g. `text-anchor`, `cx`, `cy`
                    translation = def.offset.call(this, attrVal, nodeBBox, node, rawAttrs);
                    if (translation) {
                        nodePosition.offset(g.Point(translation).scale(sx, sy));
                        offseted || (offseted = true);
                    }
                }
            }
        }

        // Do not touch node's transform attribute if there is no transformation applied.
        if (nodeTransform !== undefined || positioned || offseted) {
            // Round the coordinates to 1 decimal point.
            nodePosition.round(1);
            nodeMatrix.e = nodePosition.x;
            nodeMatrix.f = nodePosition.y;
            node.setAttribute('transform', V.matrixToTransformString(nodeMatrix));
            // TODO: store nodeMatrix metrics?
        }
    },

    getNodeScale: function(node, scalableNode) {

        // Check if the node is a descendant of the scalable group.
        var sx, sy;
        if (scalableNode && scalableNode.contains(node)) {
            var scale = scalableNode.scale();
            sx = 1 / scale.sx;
            sy = 1 / scale.sy;
        } else {
            sx = 1;
            sy = 1;
        }

        return { sx: sx, sy: sy };
    },

    findNodesAttributes: function(attrs, root, selectorCache, selectors) {

        // TODO: merge attributes in order defined by `index` property

        // most browsers sort elements in attrs by order of addition
        // which is useful but not required

        // link.updateLabels() relies on that assumption for merging label attrs over default label attrs

        var nodesAttrs = {};

        for (var selector in attrs) {
            if (!attrs.hasOwnProperty(selector)) continue;
            var selected = selectorCache[selector] = this.findBySelector(selector, root, selectors);
            for (var i = 0, n = selected.length; i < n; i++) {
                var node = selected[i];
                var nodeId = V.ensureId(node);
                var nodeAttrs = attrs[selector];
                var prevNodeAttrs = nodesAttrs[nodeId];
                if (prevNodeAttrs) {
                    if (!prevNodeAttrs.merged) {
                        prevNodeAttrs.merged = true;
                        // if prevNode attrs is `null`, replace with `{}`
                        prevNodeAttrs.attributes = joint.util.cloneDeep(prevNodeAttrs.attributes) || {};
                    }
                    // if prevNode attrs not set (or `null` or`{}`), use node attrs
                    // if node attrs not set (or `null` or `{}`), use prevNode attrs
                    joint.util.merge(prevNodeAttrs.attributes, nodeAttrs);
                } else {
                    nodesAttrs[nodeId] = {
                        attributes: nodeAttrs,
                        node: node,
                        merged: false
                    };
                }
            }
        }

        return nodesAttrs;
    },

    // Default is to process the `model.attributes.attrs` object and set attributes on subelements based on the selectors,
    // unless `attrs` parameter was passed.
    updateDOMSubtreeAttributes: function(rootNode, attrs, opt) {

        opt || (opt = {});
        opt.rootBBox || (opt.rootBBox = g.Rect());
        opt.selectors || (opt.selectors = this.selectors); // selector collection to use

        // Cache table for query results and bounding box calculation.
        // Note that `selectorCache` needs to be invalidated for all
        // `updateAttributes` calls, as the selectors might pointing
        // to nodes designated by an attribute or elements dynamically
        // created.
        var selectorCache = {};
        var bboxCache = {};
        var relativeItems = [];
        var item, node, nodeAttrs, nodeData, processedAttrs;

        var roAttrs = opt.roAttributes;
        var nodesAttrs = this.findNodesAttributes(roAttrs || attrs, rootNode, selectorCache, opt.selectors);
        // `nodesAttrs` are different from all attributes, when
        // rendering only  attributes sent to this method.
        var nodesAllAttrs = (roAttrs)
            ? nodesAllAttrs = this.findNodesAttributes(attrs, rootNode, selectorCache, opt.selectors)
            : nodesAttrs;

        for (var nodeId in nodesAttrs) {
            nodeData = nodesAttrs[nodeId];
            nodeAttrs = nodeData.attributes;
            node = nodeData.node;
            processedAttrs = this.processNodeAttributes(node, nodeAttrs);

            if (!processedAttrs.set && !processedAttrs.position && !processedAttrs.offset) {
                // Set all the normal attributes right on the SVG/HTML element.
                this.setNodeAttributes(node, processedAttrs.normal);

            } else {

                var nodeAllAttrs = nodesAllAttrs[nodeId] && nodesAllAttrs[nodeId].attributes;
                var refSelector = (nodeAllAttrs && (nodeAttrs.ref === undefined))
                    ? nodeAllAttrs.ref
                    : nodeAttrs.ref;

                var refNode;
                if (refSelector) {
                    refNode = (selectorCache[refSelector] || this.findBySelector(refSelector, rootNode, opt.selectors))[0];
                    if (!refNode) {
                        throw new Error('dia.ElementView: "' + refSelector + '" reference does not exist.');
                    }
                } else {
                    refNode = null;
                }

                item = {
                    node: node,
                    refNode: refNode,
                    processedAttributes: processedAttrs,
                    allAttributes: nodeAllAttrs
                };

                // If an element in the list is positioned relative to this one, then
                // we want to insert this one before it in the list.
                var itemIndex = relativeItems.findIndex(function(item) {
                    return item.refNode === node;
                });

                if (itemIndex > -1) {
                    relativeItems.splice(itemIndex, 0, item);
                } else {
                    relativeItems.push(item);
                }
            }
        }

        for (var i = 0, n = relativeItems.length; i < n; i++) {
            item = relativeItems[i];
            node = item.node;
            refNode = item.refNode;

            // Find the reference element bounding box. If no reference was provided, we
            // use the optional bounding box.
            var refNodeId = refNode ? V.ensureId(refNode) : '';
            var refBBox = bboxCache[refNodeId];
            if (!refBBox) {
                // Get the bounding box of the reference element relative to the `rotatable` `<g>` (without rotation)
                // or to the root `<g>` element if no rotatable group present if reference node present.
                // Uses the bounding box provided.
                refBBox = bboxCache[refNodeId] = (refNode)
                    ? V(refNode).getBBox({ target: (opt.rotatableNode || rootNode) })
                    : opt.rootBBox;
            }

            if (roAttrs) {
                // if there was a special attribute affecting the position amongst passed-in attributes
                // we have to merge it with the rest of the element's attributes as they are necessary
                // to update the position relatively (i.e `ref-x` && 'ref-dx')
                processedAttrs = this.processNodeAttributes(node, item.allAttributes);
                this.mergeProcessedAttributes(processedAttrs, item.processedAttributes);

            } else {
                processedAttrs = item.processedAttributes;
            }

            this.updateRelativeAttributes(node, processedAttrs, refBBox, opt);
        }
    },

    mergeProcessedAttributes: function(processedAttrs, roProcessedAttrs) {

        processedAttrs.set || (processedAttrs.set = {});
        processedAttrs.position || (processedAttrs.position = {});
        processedAttrs.offset || (processedAttrs.offset = {});

        joint.util.assign(processedAttrs.set, roProcessedAttrs.set);
        joint.util.assign(processedAttrs.position, roProcessedAttrs.position);
        joint.util.assign(processedAttrs.offset, roProcessedAttrs.offset);

        // Handle also the special transform property.
        var transform = processedAttrs.normal && processedAttrs.normal.transform;
        if (transform !== undefined && roProcessedAttrs.normal) {
            roProcessedAttrs.normal.transform = transform;
        }
        processedAttrs.normal = roProcessedAttrs.normal;
    },

    onRemove: function() {
        this.removeTools();
    },

    _toolsView: null,

    hasTools: function(name) {
        var toolsView = this._toolsView;
        if (!toolsView) return false;
        if (!name) return true;
        return (toolsView.getName() === name);
    },

    addTools: function(toolsView) {

        this.removeTools();

        if (toolsView instanceof joint.dia.ToolsView) {
            this._toolsView = toolsView;
            toolsView.configure({ relatedView: this });
            toolsView.listenTo(this.paper, 'tools:event', this.onToolEvent.bind(this));
            toolsView.mount();
        }
        return this;
    },

    updateTools: function(opt) {

        var toolsView = this._toolsView;
        if (toolsView) toolsView.update(opt);
        return this;
    },

    removeTools: function() {

        var toolsView = this._toolsView;
        if (toolsView) {
            toolsView.remove();
            this._toolsView = null;
        }
        return this;
    },

    hideTools: function() {

        var toolsView = this._toolsView;
        if (toolsView) toolsView.hide();
        return this;
    },

    showTools: function() {

        var toolsView = this._toolsView;
        if (toolsView) toolsView.show();
        return this;
    },

    onToolEvent: function(event) {
        switch (event) {
            case 'remove':
                this.removeTools();
                break;
            case 'hide':
                this.hideTools();
                break;
            case 'show':
                this.showTools();
                break;
        }
    },

    // Interaction. The controller part.
    // ---------------------------------

    // Interaction is handled by the paper and delegated to the view in interest.
    // `x` & `y` parameters passed to these functions represent the coordinates already snapped to the paper grid.
    // If necessary, real coordinates can be obtained from the `evt` event object.

    // These functions are supposed to be overriden by the views that inherit from `joint.dia.Cell`,
    // i.e. `joint.dia.Element` and `joint.dia.Link`.

    pointerdblclick: function(evt, x, y) {

        this.notify('cell:pointerdblclick', evt, x, y);
    },

    pointerclick: function(evt, x, y) {

        this.notify('cell:pointerclick', evt, x, y);
    },

    contextmenu: function(evt, x, y) {

        this.notify('cell:contextmenu', evt, x, y);
    },

    pointerdown: function(evt, x, y) {

        if (this.model.graph) {
            this.model.startBatch('pointer');
            this._graph = this.model.graph;
        }

        this.notify('cell:pointerdown', evt, x, y);
    },

    pointermove: function(evt, x, y) {

        this.notify('cell:pointermove', evt, x, y);
    },

    pointerup: function(evt, x, y) {

        this.notify('cell:pointerup', evt, x, y);

        if (this._graph) {
            // we don't want to trigger event on model as model doesn't
            // need to be member of collection anymore (remove)
            this._graph.stopBatch('pointer', { cell: this.model });
            delete this._graph;
        }
    },

    mouseover: function(evt) {

        this.notify('cell:mouseover', evt);
    },

    mouseout: function(evt) {

        this.notify('cell:mouseout', evt);
    },

    mouseenter: function(evt) {

        this.notify('cell:mouseenter', evt);
    },

    mouseleave: function(evt) {

        this.notify('cell:mouseleave', evt);
    },

    mousewheel: function(evt, x, y, delta) {

        this.notify('cell:mousewheel', evt, x, y, delta);
    },

    onevent: function(evt, eventName, x, y) {

        this.notify(eventName, evt, x, y);
    },

    onmagnet: function() {

        // noop
    },

    setInteractivity: function(value) {

        this.options.interactive = value;
    }
}, {

    dispatchToolsEvent: function(paper, event) {
        if ((typeof event === 'string') && (paper instanceof joint.dia.Paper)) {
            paper.trigger('tools:event', event);
        }
    }
});


// joint.dia.Element base model.
// -----------------------------

joint.dia.Element = joint.dia.Cell.extend({

    defaults: {
        position: { x: 0, y: 0 },
        size: { width: 1, height: 1 },
        angle: 0
    },

    initialize: function() {

        this._initializePorts();
        joint.dia.Cell.prototype.initialize.apply(this, arguments);
    },

    /**
     * @abstract
     */
    _initializePorts: function() {
        // implemented in ports.js
    },

    isElement: function() {

        return true;
    },

    position: function(x, y, opt) {

        var isSetter = joint.util.isNumber(y);

        opt = (isSetter ? opt : x) || {};

        // option `parentRelative` for setting the position relative to the element's parent.
        if (opt.parentRelative) {

            // Getting the parent's position requires the collection.
            // Cell.parent() holds cell id only.
            if (!this.graph) throw new Error('Element must be part of a graph.');

            var parent = this.getParentCell();
            var parentPosition = parent && !parent.isLink()
                ? parent.get('position')
                : { x: 0, y: 0 };
        }

        if (isSetter) {

            if (opt.parentRelative) {
                x += parentPosition.x;
                y += parentPosition.y;
            }

            if (opt.deep) {
                var currentPosition = this.get('position');
                this.translate(x - currentPosition.x, y - currentPosition.y, opt);
            } else {
                this.set('position', { x: x, y: y }, opt);
            }

            return this;

        } else { // Getter returns a geometry point.

            var elementPosition = g.point(this.get('position'));

            return opt.parentRelative
                ? elementPosition.difference(parentPosition)
                : elementPosition;
        }
    },

    translate: function(tx, ty, opt) {

        tx = tx || 0;
        ty = ty || 0;

        if (tx === 0 && ty === 0) {
            // Like nothing has happened.
            return this;
        }

        opt = opt || {};
        // Pass the initiator of the translation.
        opt.translateBy = opt.translateBy || this.id;

        var position = this.get('position') || { x: 0, y: 0 };

        if (opt.restrictedArea && opt.translateBy === this.id) {

            // We are restricting the translation for the element itself only. We get
            // the bounding box of the element including all its embeds.
            // All embeds have to be translated the exact same way as the element.
            var bbox = this.getBBox({ deep: true });
            var ra = opt.restrictedArea;
            //- - - - - - - - - - - - -> ra.x + ra.width
            // - - - -> position.x      |
            // -> bbox.x
            //                ▓▓▓▓▓▓▓   |
            //         ░░░░░░░▓▓▓▓▓▓▓
            //         ░░░░░░░░░        |
            //   ▓▓▓▓▓▓▓▓░░░░░░░
            //   ▓▓▓▓▓▓▓▓               |
            //   <-dx->                     | restricted area right border
            //         <-width->        |   ░ translated element
            //   <- - bbox.width - ->       ▓ embedded element
            var dx = position.x - bbox.x;
            var dy = position.y - bbox.y;
            // Find the maximal/minimal coordinates that the element can be translated
            // while complies the restrictions.
            var x = Math.max(ra.x + dx, Math.min(ra.x + ra.width + dx - bbox.width, position.x + tx));
            var y = Math.max(ra.y + dy, Math.min(ra.y + ra.height + dy - bbox.height, position.y + ty));
            // recalculate the translation taking the resctrictions into account.
            tx = x - position.x;
            ty = y - position.y;
        }

        var translatedPosition = {
            x: position.x + tx,
            y: position.y + ty
        };

        // To find out by how much an element was translated in event 'change:position' handlers.
        opt.tx = tx;
        opt.ty = ty;

        if (opt.transition) {

            if (!joint.util.isObject(opt.transition)) opt.transition = {};

            this.transition('position', translatedPosition, joint.util.assign({}, opt.transition, {
                valueFunction: joint.util.interpolate.object
            }));

        } else {

            this.set('position', translatedPosition, opt);
        }

        // Recursively call `translate()` on all the embeds cells.
        joint.util.invoke(this.getEmbeddedCells(), 'translate', tx, ty, opt);

        return this;
    },

    size: function(width, height, opt) {

        var currentSize = this.get('size');
        // Getter
        // () signature
        if (width === undefined) {
            return {
                width: currentSize.width,
                height: currentSize.height
            };
        }
        // Setter
        // (size, opt) signature
        if (joint.util.isObject(width)) {
            opt = height;
            height = joint.util.isNumber(width.height) ? width.height : currentSize.height;
            width = joint.util.isNumber(width.width) ? width.width : currentSize.width;
        }

        return this.resize(width, height, opt);
    },

    resize: function(width, height, opt) {

        opt = opt || {};

        this.startBatch('resize', opt);

        if (opt.direction) {

            var currentSize = this.get('size');

            switch (opt.direction) {

                case 'left':
                case 'right':
                    // Don't change height when resizing horizontally.
                    height = currentSize.height;
                    break;

                case 'top':
                case 'bottom':
                    // Don't change width when resizing vertically.
                    width = currentSize.width;
                    break;
            }

            // Get the angle and clamp its value between 0 and 360 degrees.
            var angle = g.normalizeAngle(this.get('angle') || 0);

            var quadrant = {
                'top-right': 0,
                'right': 0,
                'top-left': 1,
                'top': 1,
                'bottom-left': 2,
                'left': 2,
                'bottom-right': 3,
                'bottom': 3
            }[opt.direction];

            if (opt.absolute) {

                // We are taking the element's rotation into account
                quadrant += Math.floor((angle + 45) / 90);
                quadrant %= 4;
            }

            // This is a rectangle in size of the unrotated element.
            var bbox = this.getBBox();

            // Pick the corner point on the element, which meant to stay on its place before and
            // after the rotation.
            var fixedPoint = bbox[['bottomLeft', 'corner', 'topRight', 'origin'][quadrant]]();

            // Find  an image of the previous indent point. This is the position, where is the
            // point actually located on the screen.
            var imageFixedPoint = g.point(fixedPoint).rotate(bbox.center(), -angle);

            // Every point on the element rotates around a circle with the centre of rotation
            // in the middle of the element while the whole element is being rotated. That means
            // that the distance from a point in the corner of the element (supposed its always rect) to
            // the center of the element doesn't change during the rotation and therefore it equals
            // to a distance on unrotated element.
            // We can find the distance as DISTANCE = (ELEMENTWIDTH/2)^2 + (ELEMENTHEIGHT/2)^2)^0.5.
            var radius = Math.sqrt((width * width) + (height * height)) / 2;

            // Now we are looking for an angle between x-axis and the line starting at image of fixed point
            // and ending at the center of the element. We call this angle `alpha`.

            // The image of a fixed point is located in n-th quadrant. For each quadrant passed
            // going anti-clockwise we have to add 90 degrees. Note that the first quadrant has index 0.
            //
            // 3 | 2
            // --c-- Quadrant positions around the element's center `c`
            // 0 | 1
            //
            var alpha = quadrant * Math.PI / 2;

            // Add an angle between the beginning of the current quadrant (line parallel with x-axis or y-axis
            // going through the center of the element) and line crossing the indent of the fixed point and the center
            // of the element. This is the angle we need but on the unrotated element.
            alpha += Math.atan(quadrant % 2 == 0 ? height / width : width / height);

            // Lastly we have to deduct the original angle the element was rotated by and that's it.
            alpha -= g.toRad(angle);

            // With this angle and distance we can easily calculate the centre of the unrotated element.
            // Note that fromPolar constructor accepts an angle in radians.
            var center = g.point.fromPolar(radius, alpha, imageFixedPoint);

            // The top left corner on the unrotated element has to be half a width on the left
            // and half a height to the top from the center. This will be the origin of rectangle
            // we were looking for.
            var origin = g.point(center).offset(width / -2, height / -2);

            // Resize the element (before re-positioning it).
            this.set('size', { width: width, height: height }, opt);

            // Finally, re-position the element.
            this.position(origin.x, origin.y, opt);

        } else {

            // Resize the element.
            this.set('size', { width: width, height: height }, opt);
        }

        this.stopBatch('resize', opt);

        return this;
    },

    scale: function(sx, sy, origin, opt) {

        var scaledBBox = this.getBBox().scale(sx, sy, origin);
        this.startBatch('scale', opt);
        this.position(scaledBBox.x, scaledBBox.y, opt);
        this.resize(scaledBBox.width, scaledBBox.height, opt);
        this.stopBatch('scale');
        return this;
    },

    fitEmbeds: function(opt) {

        opt = opt || {};

        // Getting the children's size and position requires the collection.
        // Cell.get('embdes') helds an array of cell ids only.
        if (!this.graph) throw new Error('Element must be part of a graph.');

        var embeddedCells = this.getEmbeddedCells();

        if (embeddedCells.length > 0) {

            this.startBatch('fit-embeds', opt);

            if (opt.deep) {
                // Recursively apply fitEmbeds on all embeds first.
                joint.util.invoke(embeddedCells, 'fitEmbeds', opt);
            }

            // Compute cell's size and position  based on the children bbox
            // and given padding.
            var bbox = this.graph.getCellsBBox(embeddedCells);
            var padding = joint.util.normalizeSides(opt.padding);

            // Apply padding computed above to the bbox.
            bbox.moveAndExpand({
                x: -padding.left,
                y: -padding.top,
                width: padding.right + padding.left,
                height: padding.bottom + padding.top
            });

            // Set new element dimensions finally.
            this.set({
                position: { x: bbox.x, y: bbox.y },
                size: { width: bbox.width, height: bbox.height }
            }, opt);

            this.stopBatch('fit-embeds');
        }

        return this;
    },

    // Rotate element by `angle` degrees, optionally around `origin` point.
    // If `origin` is not provided, it is considered to be the center of the element.
    // If `absolute` is `true`, the `angle` is considered is abslute, i.e. it is not
    // the difference from the previous angle.
    rotate: function(angle, absolute, origin, opt) {

        if (origin) {

            var center = this.getBBox().center();
            var size = this.get('size');
            var position = this.get('position');
            center.rotate(origin, this.get('angle') - angle);
            var dx = center.x - size.width / 2 - position.x;
            var dy = center.y - size.height / 2 - position.y;
            this.startBatch('rotate', { angle: angle, absolute: absolute, origin: origin });
            this.position(position.x + dx, position.y + dy, opt);
            this.rotate(angle, absolute, null, opt);
            this.stopBatch('rotate');

        } else {

            this.set('angle', absolute ? angle : (this.get('angle') + angle) % 360, opt);
        }

        return this;
    },

    angle: function() {
        return g.normalizeAngle(this.get('angle') || 0);
    },

    getBBox: function(opt) {

        opt = opt || {};

        if (opt.deep && this.graph) {

            // Get all the embedded elements using breadth first algorithm,
            // that doesn't use recursion.
            var elements = this.getEmbeddedCells({ deep: true, breadthFirst: true });
            // Add the model itself.
            elements.push(this);

            return this.graph.getCellsBBox(elements);
        }

        var position = this.get('position');
        var size = this.get('size');

        return new g.Rect(position.x, position.y, size.width, size.height);
    }
});

// joint.dia.Element base view and controller.
// -------------------------------------------

joint.dia.ElementView = joint.dia.CellView.extend({

    /**
     * @abstract
     */
    _removePorts: function() {
        // implemented in ports.js
    },

    /**
     *
     * @abstract
     */
    _renderPorts: function() {
        // implemented in ports.js
    },

    className: function() {

        var classNames = joint.dia.CellView.prototype.className.apply(this).split(' ');

        classNames.push('element');

        return classNames.join(' ');
    },

    metrics: null,

    initialize: function() {

        joint.dia.CellView.prototype.initialize.apply(this, arguments);

        var model = this.model;

        this.listenTo(model, 'change:position', this.translate);
        this.listenTo(model, 'change:size', this.resize);
        this.listenTo(model, 'change:angle', this.rotate);
        this.listenTo(model, 'change:markup', this.render);

        this._initializePorts();

        this.metrics = {};
    },

    /**
     * @abstract
     */
    _initializePorts: function() {

    },

    update: function(cell, renderingOnlyAttrs) {

        this.metrics = {};

        this._removePorts();

        var model = this.model;
        var modelAttrs = model.attr();
        this.updateDOMSubtreeAttributes(this.el, modelAttrs, {
            rootBBox: new g.Rect(model.size()),
            selectors: this.selectors,
            scalableNode: this.scalableNode,
            rotatableNode: this.rotatableNode,
            // Use rendering only attributes if they differs from the model attributes
            roAttributes: (renderingOnlyAttrs === modelAttrs) ? null : renderingOnlyAttrs
        });

        this._renderPorts();
    },

    rotatableSelector: 'rotatable',
    scalableSelector: 'scalable',
    scalableNode: null,
    rotatableNode: null,

    // `prototype.markup` is rendered by default. Set the `markup` attribute on the model if the
    // default markup is not desirable.
    renderMarkup: function() {

        var element = this.model;
        var markup = element.get('markup') || element.markup;
        if (!markup) throw new Error('dia.ElementView: markup required');
        if (Array.isArray(markup)) return this.renderJSONMarkup(markup);
        if (typeof markup === 'string') return this.renderStringMarkup(markup);
        throw new Error('dia.ElementView: invalid markup');
    },

    renderJSONMarkup: function(markup) {

        var doc = joint.util.parseDOMJSON(markup);
        // Selectors
        var selectors = this.selectors = doc.selectors;
        var rootSelector = this.selector;
        if (selectors[rootSelector]) throw new Error('dia.ElementView: ambiguous root selector.');
        selectors[rootSelector] = this.el;
        // Cache transformation groups
        this.rotatableNode = V(selectors[this.rotatableSelector]) || null;
        this.scalableNode = V(selectors[this.scalableSelector]) || null;
        // Fragment
        this.vel.append(doc.fragment);
    },

    renderStringMarkup: function(markup) {

        var vel = this.vel;
        vel.append(V(markup));
        // Cache transformation groups
        this.rotatableNode = vel.findOne('.rotatable');
        this.scalableNode = vel.findOne('.scalable');

        var selectors = this.selectors = {};
        selectors[this.selector] = this.el;
    },

    render: function() {

        this.vel.empty();
        this.renderMarkup();
        if (this.scalableNode) {
            // Double update is necessary for elements with the scalable group only
            // Note the resize() triggers the other `update`.
            this.update();
        }
        this.resize();
        if (this.rotatableNode) {
            // Translate transformation is applied on `this.el` while the rotation transformation
            // on `this.rotatableNode`
            this.rotate();
            this.translate();
            return this;
        }
        this.updateTransformation();
        return this;
    },

    resize: function() {

        if (this.scalableNode) return this.sgResize.apply(this, arguments);
        if (this.model.attributes.angle) this.rotate();
        this.update();
    },

    translate: function() {

        if (this.rotatableNode) return this.rgTranslate();
        this.updateTransformation();
    },

    rotate: function() {

        if (this.rotatableNode) return this.rgRotate();
        this.updateTransformation();
    },

    updateTransformation: function() {

        var transformation = this.getTranslateString();
        var rotateString = this.getRotateString();
        if (rotateString) transformation += ' ' + rotateString;
        this.vel.attr('transform', transformation);
    },

    getTranslateString: function() {

        var position = this.model.attributes.position;
        return 'translate(' + position.x + ',' + position.y + ')';
    },

    getRotateString: function() {
        var attributes = this.model.attributes;
        var angle = attributes.angle;
        if (!angle) return null;
        var size = attributes.size;
        return 'rotate(' + angle + ',' + (size.width / 2) + ',' + (size.height / 2) + ')';
    },

    getBBox: function(opt) {

        var bbox;
        if (opt && opt.useModelGeometry) {
            var model = this.model;
            bbox = model.getBBox().bbox(model.angle());
        } else {
            bbox = this.getNodeBBox(this.el);
        }

        return this.paper.localToPaperRect(bbox);
    },

    nodeCache: function(magnet) {

        var id = V.ensureId(magnet);
        var metrics = this.metrics[id];
        if (!metrics) metrics = this.metrics[id] = {};
        return metrics;
    },

    getNodeData: function(magnet) {

        var metrics = this.nodeCache(magnet);
        if (!metrics.data) metrics.data = {};
        return metrics.data;
    },

    getNodeBBox: function(magnet) {

        var rect = this.getNodeBoundingRect(magnet);
        var magnetMatrix = this.getNodeMatrix(magnet);
        var translateMatrix = this.getRootTranslateMatrix();
        var rotateMatrix = this.getRootRotateMatrix();
        return V.transformRect(rect, translateMatrix.multiply(rotateMatrix).multiply(magnetMatrix));
    },

    getNodeBoundingRect: function(magnet) {

        var metrics = this.nodeCache(magnet);
        if (metrics.boundingRect === undefined) metrics.boundingRect = V(magnet).getBBox();
        return new g.Rect(metrics.boundingRect);
    },

    getNodeUnrotatedBBox: function(magnet) {

        var rect = this.getNodeBoundingRect(magnet);
        var magnetMatrix = this.getNodeMatrix(magnet);
        var translateMatrix = this.getRootTranslateMatrix();
        return V.transformRect(rect, translateMatrix.multiply(magnetMatrix));
    },

    getNodeShape: function(magnet) {

        var metrics = this.nodeCache(magnet);
        if (metrics.geometryShape === undefined) metrics.geometryShape = V(magnet).toGeometryShape();
        return metrics.geometryShape.clone();
    },

    getNodeMatrix: function(magnet) {

        var metrics = this.nodeCache(magnet);
        if (metrics.magnetMatrix === undefined) {
            var target = this.rotatableNode || this.el;
            metrics.magnetMatrix = V(magnet).getTransformToElement(target);
        }
        return V.createSVGMatrix(metrics.magnetMatrix);
    },

    getRootTranslateMatrix: function() {

        var model = this.model;
        var position = model.position();
        var mt = V.createSVGMatrix().translate(position.x, position.y);
        return mt;
    },

    getRootRotateMatrix: function() {

        var mr = V.createSVGMatrix();
        var model = this.model;
        var angle = model.angle();
        if (angle) {
            var bbox = model.getBBox();
            var cx = bbox.width / 2;
            var cy = bbox.height / 2;
            mr = mr.translate(cx, cy).rotate(angle).translate(-cx, -cy);
        }
        return mr;
    },

    // Rotatable & Scalable Group
    // always slower, kept mainly for backwards compatibility

    rgRotate: function() {

        this.rotatableNode.attr('transform', this.getRotateString());
    },

    rgTranslate: function() {

        this.vel.attr('transform', this.getTranslateString());
    },

    sgResize: function(cell, changed, opt) {

        var model = this.model;
        var angle = model.get('angle') || 0;
        var size = model.get('size') || { width: 1, height: 1 };
        var scalable = this.scalableNode;

        // Getting scalable group's bbox.
        // Due to a bug in webkit's native SVG .getBBox implementation, the bbox of groups with path children includes the paths' control points.
        // To work around the issue, we need to check whether there are any path elements inside the scalable group.
        var recursive = false;
        if (scalable.node.getElementsByTagName('path').length > 0) {
            // If scalable has at least one descendant that is a path, we need to switch to recursive bbox calculation.
            // If there are no path descendants, group bbox calculation works and so we can use the (faster) native function directly.
            recursive = true;
        }
        var scalableBBox = scalable.getBBox({ recursive: recursive });

        // Make sure `scalableBbox.width` and `scalableBbox.height` are not zero which can happen if the element does not have any content. By making
        // the width/height 1, we prevent HTML errors of the type `scale(Infinity, Infinity)`.
        var sx = (size.width / (scalableBBox.width || 1));
        var sy = (size.height / (scalableBBox.height || 1));
        scalable.attr('transform', 'scale(' + sx + ',' + sy + ')');

        // Now the interesting part. The goal is to be able to store the object geometry via just `x`, `y`, `angle`, `width` and `height`
        // Order of transformations is significant but we want to reconstruct the object always in the order:
        // resize(), rotate(), translate() no matter of how the object was transformed. For that to work,
        // we must adjust the `x` and `y` coordinates of the object whenever we resize it (because the origin of the
        // rotation changes). The new `x` and `y` coordinates are computed by canceling the previous rotation
        // around the center of the resized object (which is a different origin then the origin of the previous rotation)
        // and getting the top-left corner of the resulting object. Then we clean up the rotation back to what it originally was.

        // Cancel the rotation but now around a different origin, which is the center of the scaled object.
        var rotatable = this.rotatableNode;
        var rotation = rotatable && rotatable.attr('transform');
        if (rotation && rotation !== null) {

            rotatable.attr('transform', rotation + ' rotate(' + (-angle) + ',' + (size.width / 2) + ',' + (size.height / 2) + ')');
            var rotatableBBox = scalable.getBBox({ target: this.paper.viewport });

            // Store new x, y and perform rotate() again against the new rotation origin.
            model.set('position', { x: rotatableBBox.x, y: rotatableBBox.y }, opt);
            this.rotate();
        }

        // Update must always be called on non-rotated element. Otherwise, relative positioning
        // would work with wrong (rotated) bounding boxes.
        this.update();
    },

    // Embedding mode methods.
    // -----------------------

    prepareEmbedding: function(data) {

        data || (data = {});

        var model = data.model || this.model;
        var paper = data.paper || this.paper;
        var graph = paper.model;

        model.startBatch('to-front');

        // Bring the model to the front with all his embeds.
        model.toFront({ deep: true, ui: true });

        // Note that at this point cells in the collection are not sorted by z index (it's running in the batch, see
        // the dia.Graph._sortOnChangeZ), so we can't assume that the last cell in the collection has the highest z.
        var maxZ = graph.get('cells').max('z').get('z');
        var connectedLinks = graph.getConnectedLinks(model, { deep: true });

        // Move to front also all the inbound and outbound links that are connected
        // to any of the element descendant. If we bring to front only embedded elements,
        // links connected to them would stay in the background.
        joint.util.invoke(connectedLinks, 'set', 'z', maxZ + 1, { ui: true });

        model.stopBatch('to-front');

        // Before we start looking for suitable parent we remove the current one.
        var parentId = model.parent();
        parentId && graph.getCell(parentId).unembed(model, { ui: true });
    },

    processEmbedding: function(data) {

        data || (data = {});

        var model = data.model || this.model;
        var paper = data.paper || this.paper;
        var paperOptions = paper.options;

        var candidates = [];
        if (joint.util.isFunction(paperOptions.findParentBy)) {
            var parents = joint.util.toArray(paperOptions.findParentBy.call(paper.model, this));
            candidates = parents.filter(function(el) {
                return el instanceof joint.dia.Cell && this.model.id !== el.id && !el.isEmbeddedIn(this.model);
            }.bind(this));
        } else {
            candidates = paper.model.findModelsUnderElement(model, { searchBy: paperOptions.findParentBy });
        }

        if (paperOptions.frontParentOnly) {
            // pick the element with the highest `z` index
            candidates = candidates.slice(-1);
        }

        var newCandidateView = null;
        var prevCandidateView = data.candidateEmbedView;

        // iterate over all candidates starting from the last one (has the highest z-index).
        for (var i = candidates.length - 1; i >= 0; i--) {

            var candidate = candidates[i];

            if (prevCandidateView && prevCandidateView.model.id == candidate.id) {

                // candidate remains the same
                newCandidateView = prevCandidateView;
                break;

            } else {

                var view = candidate.findView(paper);
                if (paperOptions.validateEmbedding.call(paper, this, view)) {

                    // flip to the new candidate
                    newCandidateView = view;
                    break;
                }
            }
        }

        if (newCandidateView && newCandidateView != prevCandidateView) {
            // A new candidate view found. Highlight the new one.
            this.clearEmbedding(data);
            data.candidateEmbedView = newCandidateView.highlight(null, { embedding: true });
        }

        if (!newCandidateView && prevCandidateView) {
            // No candidate view found. Unhighlight the previous candidate.
            this.clearEmbedding(data);
        }
    },

    clearEmbedding: function(data) {

        data || (data = {});

        var candidateView = data.candidateEmbedView;
        if (candidateView) {
            // No candidate view found. Unhighlight the previous candidate.
            candidateView.unhighlight(null, { embedding: true });
            data.candidateEmbedView = null;
        }
    },

    finalizeEmbedding: function(data) {

        data || (data = {});

        var candidateView = data.candidateEmbedView;
        var model = data.model || this.model;
        var paper = data.paper || this.paper;

        if (candidateView) {

            // We finished embedding. Candidate view is chosen to become the parent of the model.
            candidateView.model.embed(model, { ui: true });
            candidateView.unhighlight(null, { embedding: true });

            data.candidateEmbedView = null;
        }

        joint.util.invoke(paper.model.getConnectedLinks(model, { deep: true }), 'reparent', { ui: true });
    },

    // Interaction. The controller part.
    // ---------------------------------

    pointerdblclick: function(evt, x, y) {

        joint.dia.CellView.prototype.pointerdblclick.apply(this, arguments);
        this.notify('element:pointerdblclick', evt, x, y);
    },

    pointerclick: function(evt, x, y) {

        joint.dia.CellView.prototype.pointerclick.apply(this, arguments);
        this.notify('element:pointerclick', evt, x, y);
    },

    contextmenu: function(evt, x, y) {

        joint.dia.CellView.prototype.contextmenu.apply(this, arguments);
        this.notify('element:contextmenu', evt, x, y);
    },

    pointerdown: function(evt, x, y) {

        joint.dia.CellView.prototype.pointerdown.apply(this, arguments);
        this.notify('element:pointerdown', evt, x, y);

        this.dragStart(evt, x, y);
    },

    pointermove: function(evt, x, y) {

        var data = this.eventData(evt);
        switch (data.action) {
            case 'move':
                this.drag(evt, x, y);
                break;
            case 'magnet':
                this.dragMagnet(evt, x, y);
                break;
        }

        if (!data.stopPropagation) {
            joint.dia.CellView.prototype.pointermove.apply(this, arguments);
            this.notify('element:pointermove', evt, x, y);
        }

        // Make sure the element view data is passed along.
        // It could have been wiped out in the handlers above.
        this.eventData(evt, data);
    },

    pointerup: function(evt, x, y) {

        var data = this.eventData(evt);
        switch (data.action) {
            case 'move':
                this.dragEnd(evt, x, y);
                break;
            case 'magnet':
                this.dragMagnetEnd(evt, x, y);
                return;
        }

        if (!data.stopPropagation) {
            this.notify('element:pointerup', evt, x, y);
            joint.dia.CellView.prototype.pointerup.apply(this, arguments);
        }
    },

    mouseover: function(evt) {

        joint.dia.CellView.prototype.mouseover.apply(this, arguments);
        this.notify('element:mouseover', evt);
    },

    mouseout: function(evt) {

        joint.dia.CellView.prototype.mouseout.apply(this, arguments);
        this.notify('element:mouseout', evt);
    },

    mouseenter: function(evt) {

        joint.dia.CellView.prototype.mouseenter.apply(this, arguments);
        this.notify('element:mouseenter', evt);
    },

    mouseleave: function(evt) {

        joint.dia.CellView.prototype.mouseleave.apply(this, arguments);
        this.notify('element:mouseleave', evt);
    },

    mousewheel: function(evt, x, y, delta) {

        joint.dia.CellView.prototype.mousewheel.apply(this, arguments);
        this.notify('element:mousewheel', evt, x, y, delta);
    },

    onmagnet: function(evt, x, y) {

        this.dragMagnetStart(evt, x, y);

        var stopPropagation = this.eventData(evt).stopPropagation;
        if (stopPropagation) evt.stopPropagation();
    },

    // Drag Start Handlers

    dragStart: function(evt, x, y) {

        if (!this.can('elementMove')) return;

        this.eventData(evt, {
            action: 'move',
            x: x,
            y: y,
            restrictedArea: this.paper.getRestrictedArea(this)
        });
    },

    dragMagnetStart: function(evt, x, y) {

        if (!this.can('addLinkFromMagnet')) return;

        this.model.startBatch('add-link');

        var paper = this.paper;
        var graph = paper.model;
        var magnet = evt.target;
        var link = paper.getDefaultLink(this, magnet);
        var sourceEnd = this.getLinkEnd(magnet, x, y, link, 'source');
        var targetEnd = { x: x, y: y };

        link.set({ source: sourceEnd, target: targetEnd });
        link.addTo(graph, { async: false, ui: true });

        var linkView = link.findView(paper);
        joint.dia.CellView.prototype.pointerdown.apply(linkView, arguments);
        linkView.notify('link:pointerdown', evt, x, y);
        var data = linkView.startArrowheadMove('target', { whenNotAllowed: 'remove' });
        linkView.eventData(evt, data);

        this.eventData(evt, {
            action: 'magnet',
            linkView: linkView,
            stopPropagation: true
        });

        this.paper.delegateDragEvents(this, evt.data);
    },

    // Drag Handlers

    drag: function(evt, x, y) {

        var paper = this.paper;
        var grid = paper.options.gridSize;
        var element = this.model;
        var position = element.position();
        var data = this.eventData(evt);

        // Make sure the new element's position always snaps to the current grid after
        // translate as the previous one could be calculated with a different grid size.
        var tx = g.snapToGrid(position.x, grid) - position.x + g.snapToGrid(x - data.x, grid);
        var ty = g.snapToGrid(position.y, grid) - position.y + g.snapToGrid(y - data.y, grid);

        element.translate(tx, ty, { restrictedArea: data.restrictedArea, ui: true });

        var embedding = !!data.embedding;
        if (paper.options.embeddingMode) {
            if (!embedding) {
                // Prepare the element for embedding only if the pointer moves.
                // We don't want to do unnecessary action with the element
                // if an user only clicks/dblclicks on it.
                this.prepareEmbedding(data);
                embedding = true;
            }
            this.processEmbedding(data);
        }

        this.eventData(evt, {
            x: g.snapToGrid(x, grid),
            y: g.snapToGrid(y, grid),
            embedding: embedding
        });
    },

    dragMagnet: function(evt, x, y) {

        var data = this.eventData(evt);
        var linkView = data.linkView;
        if (linkView) linkView.pointermove(evt, x, y);
    },

    // Drag End Handlers

    dragEnd: function(evt, x, y) {

        var data = this.eventData(evt);
        if (data.embedding) this.finalizeEmbedding(data);
    },

    dragMagnetEnd: function(evt, x, y) {

        var data = this.eventData(evt);
        var linkView = data.linkView;
        if (linkView) linkView.pointerup(evt, x, y);

        this.model.stopBatch('add-link');
    }

});


// joint.dia.Link base model.
// --------------------------

joint.dia.Link = joint.dia.Cell.extend({

    // The default markup for links.
    markup: [
        '<path class="connection" stroke="black" d="M 0 0 0 0"/>',
        '<path class="marker-source" fill="black" stroke="black" d="M 0 0 0 0"/>',
        '<path class="marker-target" fill="black" stroke="black" d="M 0 0 0 0"/>',
        '<path class="connection-wrap" d="M 0 0 0 0"/>',
        '<g class="labels"/>',
        '<g class="marker-vertices"/>',
        '<g class="marker-arrowheads"/>',
        '<g class="link-tools"/>'
    ].join(''),

    toolMarkup: [
        '<g class="link-tool">',
        '<g class="tool-remove" event="remove">',
        '<circle r="11" />',
        '<path transform="scale(.8) translate(-16, -16)" d="M24.778,21.419 19.276,15.917 24.777,10.415 21.949,7.585 16.447,13.087 10.945,7.585 8.117,10.415 13.618,15.917 8.116,21.419 10.946,24.248 16.447,18.746 21.948,24.248z" />',
        '<title>Remove link.</title>',
        '</g>',
        '<g class="tool-options" event="link:options">',
        '<circle r="11" transform="translate(25)"/>',
        '<path fill="white" transform="scale(.55) translate(29, -16)" d="M31.229,17.736c0.064-0.571,0.104-1.148,0.104-1.736s-0.04-1.166-0.104-1.737l-4.377-1.557c-0.218-0.716-0.504-1.401-0.851-2.05l1.993-4.192c-0.725-0.91-1.549-1.734-2.458-2.459l-4.193,1.994c-0.647-0.347-1.334-0.632-2.049-0.849l-1.558-4.378C17.165,0.708,16.588,0.667,16,0.667s-1.166,0.041-1.737,0.105L12.707,5.15c-0.716,0.217-1.401,0.502-2.05,0.849L6.464,4.005C5.554,4.73,4.73,5.554,4.005,6.464l1.994,4.192c-0.347,0.648-0.632,1.334-0.849,2.05l-4.378,1.557C0.708,14.834,0.667,15.412,0.667,16s0.041,1.165,0.105,1.736l4.378,1.558c0.217,0.715,0.502,1.401,0.849,2.049l-1.994,4.193c0.725,0.909,1.549,1.733,2.459,2.458l4.192-1.993c0.648,0.347,1.334,0.633,2.05,0.851l1.557,4.377c0.571,0.064,1.148,0.104,1.737,0.104c0.588,0,1.165-0.04,1.736-0.104l1.558-4.377c0.715-0.218,1.399-0.504,2.049-0.851l4.193,1.993c0.909-0.725,1.733-1.549,2.458-2.458l-1.993-4.193c0.347-0.647,0.633-1.334,0.851-2.049L31.229,17.736zM16,20.871c-2.69,0-4.872-2.182-4.872-4.871c0-2.69,2.182-4.872,4.872-4.872c2.689,0,4.871,2.182,4.871,4.872C20.871,18.689,18.689,20.871,16,20.871z"/>',
        '<title>Link options.</title>',
        '</g>',
        '</g>'
    ].join(''),

    doubleToolMarkup: undefined,

    // The default markup for showing/removing vertices. These elements are the children of the .marker-vertices element (see `this.markup`).
    // Only .marker-vertex and .marker-vertex-remove element have special meaning. The former is used for
    // dragging vertices (changin their position). The latter is used for removing vertices.
    vertexMarkup: [
        '<g class="marker-vertex-group" transform="translate(<%= x %>, <%= y %>)">',
        '<circle class="marker-vertex" idx="<%= idx %>" r="10" />',
        '<path class="marker-vertex-remove-area" idx="<%= idx %>" d="M16,5.333c-7.732,0-14,4.701-14,10.5c0,1.982,0.741,3.833,2.016,5.414L2,25.667l5.613-1.441c2.339,1.317,5.237,2.107,8.387,2.107c7.732,0,14-4.701,14-10.5C30,10.034,23.732,5.333,16,5.333z" transform="translate(5, -33)"/>',
        '<path class="marker-vertex-remove" idx="<%= idx %>" transform="scale(.8) translate(9.5, -37)" d="M24.778,21.419 19.276,15.917 24.777,10.415 21.949,7.585 16.447,13.087 10.945,7.585 8.117,10.415 13.618,15.917 8.116,21.419 10.946,24.248 16.447,18.746 21.948,24.248z">',
        '<title>Remove vertex.</title>',
        '</path>',
        '</g>'
    ].join(''),

    arrowheadMarkup: [
        '<g class="marker-arrowhead-group marker-arrowhead-group-<%= end %>">',
        '<path class="marker-arrowhead" end="<%= end %>" d="M 26 0 L 0 13 L 26 26 z" />',
        '</g>'
    ].join(''),

    // may be overwritten by user to change default label (its markup, attrs, position)
    defaultLabel: undefined,

    // deprecated
    // may be overwritten by user to change default label markup
    // lower priority than defaultLabel.markup
    labelMarkup: undefined,

    // private
    _builtins: {
        defaultLabel: {
            // builtin default markup:
            // used if neither defaultLabel.markup
            // nor label.markup is set
            markup: [
                {
                    tagName: 'rect',
                    selector: 'rect' // faster than tagName CSS selector
                }, {
                    tagName: 'text',
                    selector: 'text' // faster than tagName CSS selector
                }
            ],
            // builtin default attributes:
            // applied only if builtin default markup is used
            attrs: {
                text: {
                    fill: '#000000',
                    fontSize: 14,
                    textAnchor: 'middle',
                    yAlignment: 'middle',
                    pointerEvents: 'none'
                },
                rect: {
                    ref: 'text',
                    fill: '#ffffff',
                    rx: 3,
                    ry: 3,
                    refWidth: 1,
                    refHeight: 1,
                    refX: 0,
                    refY: 0
                }
            },
            // builtin default position:
            // used if neither defaultLabel.position
            // nor label.position is set
            position: {
                distance: 0.5
            }
        }
    },

    defaults: {
        type: 'link',
        source: {},
        target: {}
    },

    isLink: function() {

        return true;
    },

    disconnect: function(opt) {

        return this.set({
            source: { x: 0, y: 0 },
            target: { x: 0, y: 0 }
        }, opt);
    },

    source: function(source, args, opt) {

        // getter
        if (source === undefined) {
            return joint.util.clone(this.get('source'));
        }

        // setter
        var localSource;
        var localOpt;

        // `source` is a cell
        // take only its `id` and combine with `args`
        var isCellProvided = source instanceof joint.dia.Cell;
        if (isCellProvided) { // three arguments
            localSource = joint.util.clone(args) || {};
            localSource.id = source.id;
            localOpt = opt;
            return this.set('source', localSource, localOpt);
        }

        // `source` is a g.Point
        // take only its `x` and `y` and combine with `args`
        var isPointProvided = source instanceof g.Point;
        if (isPointProvided) { // three arguments
            localSource = joint.util.clone(args) || {};
            localSource.x = source.x;
            localSource.y = source.y;
            localOpt = opt;
            return this.set('source', localSource, localOpt);
        }

        // `source` is an object
        // no checking
        // two arguments
        localSource = source;
        localOpt = args;
        return this.set('source', localSource, localOpt);
    },

    target: function(target, args, opt) {

        // getter
        if (target === undefined) {
            return joint.util.clone(this.get('target'));
        }

        // setter
        var localTarget;
        var localOpt;

        // `target` is a cell
        // take only its `id` argument and combine with `args`
        var isCellProvided = target instanceof joint.dia.Cell;
        if (isCellProvided) { // three arguments
            localTarget = joint.util.clone(args) || {};
            localTarget.id = target.id;
            localOpt = opt;
            return this.set('target', localTarget, localOpt);
        }

        // `target` is a g.Point
        // take only its `x` and `y` and combine with `args`
        var isPointProvided = target instanceof g.Point;
        if (isPointProvided) { // three arguments
            localTarget = joint.util.clone(args) || {};
            localTarget.x = target.x;
            localTarget.y = target.y;
            localOpt = opt;
            return this.set('target', localTarget, localOpt);
        }

        // `target` is an object
        // no checking
        // two arguments
        localTarget = target;
        localOpt = args;
        return this.set('target', localTarget, localOpt);
    },

    router: function(name, args, opt) {

        // getter
        if (name === undefined) {
            var router = this.get('router');
            if (!router) {
                if (this.get('manhattan')) return { name: 'orthogonal' }; // backwards compatibility
                return null;
            }
            if (typeof router === 'object') return joint.util.clone(router);
            return router; // e.g. a function
        }

        // setter
        var isRouterProvided = ((typeof name === 'object') || (typeof name === 'function'));
        var localRouter = isRouterProvided ? name : { name: name, args: args };
        var localOpt = isRouterProvided ? args : opt;

        return this.set('router', localRouter, localOpt);
    },

    connector: function(name, args, opt) {

        // getter
        if (name === undefined) {
            var connector = this.get('connector');
            if (!connector) {
                if (this.get('smooth')) return { name: 'smooth' }; // backwards compatibility
                return null;
            }
            if (typeof connector === 'object') return joint.util.clone(connector);
            return connector; // e.g. a function
        }

        // setter
        var isConnectorProvided = ((typeof name === 'object' || typeof name === 'function'));
        var localConnector = isConnectorProvided ? name : { name: name, args: args };
        var localOpt = isConnectorProvided ? args : opt;

        return this.set('connector', localConnector, localOpt);
    },

    // Labels API

    // A convenient way to set labels. Currently set values will be mixined with `value` if used as a setter.
    label: function(idx, label, opt) {

        var labels = this.labels();

        idx = (isFinite(idx) && idx !== null) ? (idx | 0) : 0;
        if (idx < 0) idx = labels.length + idx;

        // getter
        if (arguments.length <= 1) return this.prop(['labels', idx]);
        // setter
        return this.prop(['labels', idx], label, opt);
    },

    labels: function(labels, opt) {

        // getter
        if (arguments.length === 0) {
            labels = this.get('labels');
            if (!Array.isArray(labels)) return [];
            return labels.slice();
        }
        // setter
        if (!Array.isArray(labels)) labels = [];
        return this.set('labels', labels, opt);
    },

    insertLabel: function(idx, label, opt) {

        if (!label) throw new Error('dia.Link: no label provided');

        var labels = this.labels();
        var n = labels.length;
        idx = (isFinite(idx) && idx !== null) ? (idx | 0) : n;
        if (idx < 0) idx = n + idx + 1;

        labels.splice(idx, 0, label);
        return this.labels(labels, opt);
    },

    // convenience function
    // add label to end of labels array
    appendLabel: function(label, opt) {

        return this.insertLabel(-1, label, opt);
    },

    removeLabel: function(idx, opt) {

        var labels = this.labels();
        idx = (isFinite(idx) && idx !== null) ? (idx | 0) : -1;

        labels.splice(idx, 1);
        return this.labels(labels, opt);
    },

    // Vertices API

    vertex: function(idx, vertex, opt) {

        var vertices = this.vertices();

        idx = (isFinite(idx) && idx !== null) ? (idx | 0) : 0;
        if (idx < 0) idx = vertices.length + idx;

        // getter
        if (arguments.length <= 1) return this.prop(['vertices', idx]);
        // setter
        return this.prop(['vertices', idx], vertex, opt);
    },

    vertices: function(vertices, opt) {

        // getter
        if (arguments.length === 0) {
            vertices = this.get('vertices');
            if (!Array.isArray(vertices)) return [];
            return vertices.slice();
        }
        // setter
        if (!Array.isArray(vertices)) vertices = [];
        return this.set('vertices', vertices, opt);
    },

    insertVertex: function(idx, vertex, opt) {

        if (!vertex) throw new Error('dia.Link: no vertex provided');

        var vertices = this.vertices();
        var n = vertices.length;
        idx = (isFinite(idx) && idx !== null) ? (idx | 0) : n;
        if (idx < 0) idx = n + idx + 1;

        vertices.splice(idx, 0, vertex);
        return this.vertices(vertices, opt);
    },

    removeVertex: function(idx, opt) {

        var vertices = this.vertices();
        idx = (isFinite(idx) && idx !== null) ? (idx | 0) : -1;

        vertices.splice(idx, 1);
        return this.vertices(vertices, opt);
    },

    // Transformations

    translate: function(tx, ty, opt) {

        // enrich the option object
        opt = opt || {};
        opt.translateBy = opt.translateBy || this.id;
        opt.tx = tx;
        opt.ty = ty;

        return this.applyToPoints(function(p) {
            return { x: (p.x || 0) + tx, y: (p.y || 0) + ty };
        }, opt);
    },

    scale: function(sx, sy, origin, opt) {

        return this.applyToPoints(function(p) {
            return g.point(p).scale(sx, sy, origin).toJSON();
        }, opt);
    },

    applyToPoints: function(fn, opt) {

        if (!joint.util.isFunction(fn)) {
            throw new TypeError('dia.Link: applyToPoints expects its first parameter to be a function.');
        }

        var attrs = {};

        var source = this.source();
        if (!source.id) {
            attrs.source = fn(source);
        }

        var target = this.target();
        if (!target.id) {
            attrs.target = fn(target);
        }

        var vertices = this.vertices();
        if (vertices.length > 0) {
            attrs.vertices = vertices.map(fn);
        }

        return this.set(attrs, opt);
    },

    reparent: function(opt) {

        var newParent;

        if (this.graph) {

            var source = this.getSourceElement();
            var target = this.getTargetElement();
            var prevParent = this.getParentCell();

            if (source && target) {
                newParent = this.graph.getCommonAncestor(source, target);
            }

            if (prevParent && (!newParent || newParent.id !== prevParent.id)) {
                // Unembed the link if source and target has no common ancestor
                // or common ancestor changed
                prevParent.unembed(this, opt);
            }

            if (newParent) {
                newParent.embed(this, opt);
            }
        }

        return newParent;
    },

    hasLoop: function(opt) {

        opt = opt || {};

        var sourceId = this.source().id;
        var targetId = this.target().id;

        if (!sourceId || !targetId) {
            // Link "pinned" to the paper does not have a loop.
            return false;
        }

        var loop = sourceId === targetId;

        // Note that there in the deep mode a link can have a loop,
        // even if it connects only a parent and its embed.
        // A loop "target equals source" is valid in both shallow and deep mode.
        if (!loop && opt.deep && this.graph) {

            var sourceElement = this.getSourceElement();
            var targetElement = this.getTargetElement();

            loop = sourceElement.isEmbeddedIn(targetElement) || targetElement.isEmbeddedIn(sourceElement);
        }

        return loop;
    },

    // unlike source(), this method returns null if source is a point
    getSourceElement: function() {

        var source = this.source();
        var graph = this.graph;

        return (source && source.id && graph && graph.getCell(source.id)) || null;
    },

    // unlike target(), this method returns null if target is a point
    getTargetElement: function() {

        var target = this.target();
        var graph = this.graph;

        return (target && target.id && graph && graph.getCell(target.id)) || null;
    },

    // Returns the common ancestor for the source element,
    // target element and the link itself.
    getRelationshipAncestor: function() {

        var connectionAncestor;

        if (this.graph) {

            var cells = [
                this,
                this.getSourceElement(), // null if source is a point
                this.getTargetElement() // null if target is a point
            ].filter(function(item) {
                return !!item;
            });

            connectionAncestor = this.graph.getCommonAncestor.apply(this.graph, cells);
        }

        return connectionAncestor || null;
    },

    // Is source, target and the link itself embedded in a given cell?
    isRelationshipEmbeddedIn: function(cell) {

        var cellId = (joint.util.isString(cell) || joint.util.isNumber(cell)) ? cell : cell.id;
        var ancestor = this.getRelationshipAncestor();

        return !!ancestor && (ancestor.id === cellId || ancestor.isEmbeddedIn(cellId));
    },

    // Get resolved default label.
    _getDefaultLabel: function() {

        var defaultLabel = this.get('defaultLabel') || this.defaultLabel || {};

        var label = {};
        label.markup = defaultLabel.markup || this.get('labelMarkup') || this.labelMarkup;
        label.position = defaultLabel.position;
        label.attrs = defaultLabel.attrs;
        label.size = defaultLabel.size;

        return label;
    }
},
    {
        endsEqual: function(a, b) {

            var portsEqual = a.port === b.port || !a.port && !b.port;
            return a.id === b.id && portsEqual;
        }
    });


// joint.dia.Link base view and controller.
// ----------------------------------------

joint.dia.LinkView = joint.dia.CellView.extend({

    className: function() {

        var classNames = joint.dia.CellView.prototype.className.apply(this).split(' ');

        classNames.push('link');

        return classNames.join(' ');
    },

    options: {

        shortLinkLength: 105,
        doubleLinkTools: false,
        longLinkLength: 155,
        linkToolsOffset: 40,
        doubleLinkToolsOffset: 65,
        sampleInterval: 50,
    },

    _labelCache: null,
    _labelSelectors: null,
    _markerCache: null,
    _V: null,
    _dragData: null, // deprecated

    metrics: null,
    decimalsRounding: 2,

    initialize: function(options) {

        joint.dia.CellView.prototype.initialize.apply(this, arguments);

        // create methods in prototype, so they can be accessed from any instance and
        // don't need to be create over and over
        if (typeof this.constructor.prototype.watchSource !== 'function') {
            this.constructor.prototype.watchSource = this.createWatcher('source');
            this.constructor.prototype.watchTarget = this.createWatcher('target');
        }

        // `_.labelCache` is a mapping of indexes of labels in the `this.get('labels')` array to
        // `<g class="label">` nodes wrapped by Vectorizer. This allows for quick access to the
        // nodes in `updateLabelPosition()` in order to update the label positions.
        this._labelCache = {};

        // a cache of label selectors
        this._labelSelectors = {};

        // keeps markers bboxes and positions again for quicker access
        this._markerCache = {};

        // cache of default markup nodes
        this._V = {},

        // connection path metrics
        this.metrics = {},

        // bind events
        this.startListening();
    },

    startListening: function() {

        var model = this.model;

        this.listenTo(model, 'change:markup', this.render);
        this.listenTo(model, 'change:smooth change:manhattan change:router change:connector', this.update);
        this.listenTo(model, 'change:toolMarkup', this.onToolsChange);
        this.listenTo(model, 'change:labels change:labelMarkup', this.onLabelsChange);
        this.listenTo(model, 'change:vertices change:vertexMarkup', this.onVerticesChange);
        this.listenTo(model, 'change:source', this.onSourceChange);
        this.listenTo(model, 'change:target', this.onTargetChange);
    },

    onSourceChange: function(cell, source, opt) {

        // Start watching the new source model.
        this.watchSource(cell, source);
        // This handler is called when the source attribute is changed.
        // This can happen either when someone reconnects the link (or moves arrowhead),
        // or when an embedded link is translated by its ancestor.
        // 1. Always do update.
        // 2. Do update only if the opposite end ('target') is also a point.
        var model = this.model;
        if (!opt.translateBy || !model.get('target').id || !source.id) {
            this.update(model, null, opt);
        }
    },

    onTargetChange: function(cell, target, opt) {

        // Start watching the new target model.
        this.watchTarget(cell, target);
        // See `onSourceChange` method.
        var model = this.model;
        if (!opt.translateBy || (model.get('source').id && !target.id && joint.util.isEmpty(model.get('vertices')))) {
            this.update(model, null, opt);
        }
    },

    onVerticesChange: function(cell, changed, opt) {

        this.renderVertexMarkers();

        // If the vertices have been changed by a translation we do update only if the link was
        // the only link that was translated. If the link was translated via another element which the link
        // is embedded in, this element will be translated as well and that triggers an update.
        // Note that all embeds in a model are sorted - first comes links, then elements.
        if (!opt.translateBy || opt.translateBy === this.model.id) {
            // Vertices were changed (not as a reaction on translate)
            // or link.translate() was called or
            this.update(cell, null, opt);
        }
    },

    onToolsChange: function() {

        this.renderTools().updateToolsPosition();
    },

    onLabelsChange: function(link, labels, opt) {

        var requireRender = true;

        var previousLabels = this.model.previous('labels');

        if (previousLabels) {
            // Here is an optimalization for cases when we know, that change does
            // not require rerendering of all labels.
            if (('propertyPathArray' in opt) && ('propertyValue' in opt)) {
                // The label is setting by `prop()` method
                var pathArray = opt.propertyPathArray || [];
                var pathLength = pathArray.length;
                if (pathLength > 1) {
                    // We are changing a single label here e.g. 'labels/0/position'
                    var labelExists = !!previousLabels[pathArray[1]];
                    if (labelExists) {
                        if (pathLength === 2) {
                            // We are changing the entire label. Need to check if the
                            // markup is also being changed.
                            requireRender = ('markup' in Object(opt.propertyValue));
                        } else if (pathArray[2] !== 'markup') {
                            // We are changing a label property but not the markup
                            requireRender = false;
                        }
                    }
                }
            }
        }

        if (requireRender) {
            this.renderLabels();
        } else {
            this.updateLabels();
        }

        this.updateLabelPositions();
    },

    // Rendering.
    // ----------

    render: function() {

        this.vel.empty();
        this._V = {};
        this.renderMarkup();
        // rendering labels has to be run after the link is appended to DOM tree. (otherwise <Text> bbox
        // returns zero values)
        this.renderLabels();
        // start watching the ends of the link for changes
        var model = this.model;
        this.watchSource(model, model.source())
            .watchTarget(model, model.target())
            .update();

        return this;
    },

    renderMarkup: function() {

        var link = this.model;
        var markup = link.get('markup') || link.markup;
        if (!markup) throw new Error('dia.LinkView: markup required');
        if (Array.isArray(markup)) return this.renderJSONMarkup(markup);
        if (typeof markup === 'string') return this.renderStringMarkup(markup);
        throw new Error('dia.LinkView: invalid markup');
    },

    renderJSONMarkup: function(markup) {

        var doc = joint.util.parseDOMJSON(markup);
        // Selectors
        var selectors = this.selectors = doc.selectors;
        var rootSelector = this.selector;
        if (selectors[rootSelector]) throw new Error('dia.LinkView: ambiguous root selector.');
        selectors[rootSelector] = this.el;
        // Fragment
        this.vel.append(doc.fragment);
    },

    renderStringMarkup: function(markup) {

        // A special markup can be given in the `properties.markup` property. This might be handy
        // if e.g. arrowhead markers should be `<image>` elements or any other element than `<path>`s.
        // `.connection`, `.connection-wrap`, `.marker-source` and `.marker-target` selectors
        // of elements with special meaning though. Therefore, those classes should be preserved in any
        // special markup passed in `properties.markup`.
        var children = V(markup);
        // custom markup may contain only one children
        if (!Array.isArray(children)) children = [children];
        // Cache all children elements for quicker access.
        var cache = this._V; // vectorized markup;
        for (var i = 0, n = children.length; i < n; i++) {
            var child = children[i];
            var className = child.attr('class');
            if (className) {
                // Strip the joint class name prefix, if there is one.
                className = joint.util.removeClassNamePrefix(className);
                cache[$.camelCase(className)] = child;
            }
        }
        // partial rendering
        this.renderTools();
        this.renderVertexMarkers();
        this.renderArrowheadMarkers();
        this.vel.append(children);
    },

    _getLabelMarkup: function(labelMarkup) {

        if (!labelMarkup) return undefined;

        if (Array.isArray(labelMarkup)) return this._getLabelJSONMarkup(labelMarkup);
        if (typeof labelMarkup === 'string') return this._getLabelStringMarkup(labelMarkup);
        throw new Error('dia.linkView: invalid label markup');
    },

    _getLabelJSONMarkup: function(labelMarkup) {

        return joint.util.parseDOMJSON(labelMarkup); // fragment and selectors
    },

    _getLabelStringMarkup: function(labelMarkup) {

        var children = V(labelMarkup);
        var fragment = document.createDocumentFragment();

        if (!Array.isArray(children)) {
            fragment.append(children.node);

        } else {
            for (var i = 0, n = children.length; i < n; i++) {
                var currentChild = children[i].node;
                fragment.appendChild(currentChild);
            }
        }

        return { fragment: fragment, selectors: {} }; // no selectors
    },

    // Label markup fragment may come wrapped in <g class="label" />, or not.
    // If it doesn't, add the <g /> container here.
    _normalizeLabelMarkup: function(markup) {

        if (!markup) return undefined;

        var fragment = markup.fragment;
        if (!(markup.fragment instanceof DocumentFragment) || !markup.fragment.hasChildNodes()) throw new Error('dia.LinkView: invalid label markup.');

        var vNode;
        var childNodes = fragment.childNodes;

        if ((childNodes.length > 1) || childNodes[0].nodeName.toUpperCase() !== 'G') {
            // default markup fragment is not wrapped in <g />
            // add a <g /> container

            vNode = V('g');
            vNode.append(fragment);
            vNode.addClass('label');

        } else {
            vNode = V(childNodes[0]);
            vNode.addClass('label');
        }

        return { node: vNode.node, selectors: markup.selectors };
    },

    renderLabels: function() {

        var cache = this._V;
        var vLabels = cache.labels;
        var labelCache = this._labelCache = {};
        var labelSelectors = this._labelSelectors = {};

        if (vLabels) vLabels.empty();

        var model = this.model;
        var labels = model.get('labels') || [];
        var labelsCount = labels.length;
        if (labelsCount === 0) return this;

        if (!vLabels) {
            // there is no label container in the markup but some labels are defined
            // add a <g class="labels" /> container
            vLabels = cache.labels = V('g').addClass('labels').appendTo(this.el);
        }

        for (var i = 0; i < labelsCount; i++) {

            var label = labels[i];
            var labelMarkup = this._normalizeLabelMarkup(this._getLabelMarkup(label.markup));

            var node;
            var selectors;
            if (labelMarkup) {
                node = labelMarkup.node;
                selectors = labelMarkup.selectors;

            } else {
                var builtinDefaultLabel =  model._builtins.defaultLabel;
                var builtinDefaultLabelMarkup = this._normalizeLabelMarkup(this._getLabelMarkup(builtinDefaultLabel.markup));

                var defaultLabel = model._getDefaultLabel();
                var defaultLabelMarkup = this._normalizeLabelMarkup(this._getLabelMarkup(defaultLabel.markup));

                var defaultMarkup = defaultLabelMarkup || builtinDefaultLabelMarkup;

                node = defaultMarkup.node;
                selectors = defaultMarkup.selectors;
            }

            var vLabel = V(node);
            vLabel.attr('label-idx', i); // assign label-idx
            vLabel.appendTo(vLabels);
            labelCache[i] = vLabel; // cache node for `updateLabels()` so it can just update label node positions

            selectors[this.selector] = vLabel.node;
            labelSelectors[i] = selectors; // cache label selectors for `updateLabels()`
        }

        this.updateLabels();

        return this;
    },

    // merge default label attrs into label attrs
    // keep `undefined` or `null` because `{}` means something else
    _mergeLabelAttrs: function(hasCustomMarkup, labelAttrs, defaultLabelAttrs, builtinDefaultLabelAttrs) {

        if (labelAttrs === null) return null;
        if (labelAttrs === undefined) {

            if (defaultLabelAttrs === null) return null;
            if (defaultLabelAttrs === undefined) {

                if (hasCustomMarkup) return undefined;
                return builtinDefaultLabelAttrs;
            }

            if (hasCustomMarkup) return defaultLabelAttrs;
            return joint.util.merge({}, builtinDefaultLabelAttrs, defaultLabelAttrs);
        }

        if (hasCustomMarkup) return joint.util.merge({}, defaultLabelAttrs, labelAttrs);
        return joint.util.merge({}, builtinDefaultLabelAttrs, defaultLabelAttrs, labelAttrs);
    },

    updateLabels: function() {

        if (!this._V.labels) return this;

        var model = this.model;
        var labels = model.get('labels') || [];
        var canLabelMove = this.can('labelMove');

        var builtinDefaultLabel = model._builtins.defaultLabel;
        var builtinDefaultLabelAttrs = builtinDefaultLabel.attrs;

        var defaultLabel = model._getDefaultLabel();
        var defaultLabelMarkup = defaultLabel.markup;
        var defaultLabelAttrs = defaultLabel.attrs;

        for (var i = 0, n = labels.length; i < n; i++) {

            var vLabel = this._labelCache[i];
            vLabel.attr('cursor', (canLabelMove ? 'move' : 'default'));

            var selectors = this._labelSelectors[i];

            var label = labels[i];
            var labelMarkup = label.markup;
            var labelAttrs = label.attrs;

            var attrs = this._mergeLabelAttrs(
                (labelMarkup || defaultLabelMarkup),
                labelAttrs,
                defaultLabelAttrs,
                builtinDefaultLabelAttrs
            );

            this.updateDOMSubtreeAttributes(vLabel.node, attrs, {
                rootBBox: new g.Rect(label.size),
                selectors: selectors
            });
        }

        return this;
    },

    renderTools: function() {

        if (!this._V.linkTools) return this;

        // Tools are a group of clickable elements that manipulate the whole link.
        // A good example of this is the remove tool that removes the whole link.
        // Tools appear after hovering the link close to the `source` element/point of the link
        // but are offset a bit so that they don't cover the `marker-arrowhead`.

        var $tools = $(this._V.linkTools.node).empty();
        var toolTemplate = joint.util.template(this.model.get('toolMarkup') || this.model.toolMarkup);
        var tool = V(toolTemplate());

        $tools.append(tool.node);

        // Cache the tool node so that the `updateToolsPosition()` can update the tool position quickly.
        this._toolCache = tool;

        // If `doubleLinkTools` is enabled, we render copy of the tools on the other side of the
        // link as well but only if the link is longer than `longLinkLength`.
        if (this.options.doubleLinkTools) {

            var tool2;
            if (this.model.get('doubleToolMarkup') || this.model.doubleToolMarkup) {
                toolTemplate = joint.util.template(this.model.get('doubleToolMarkup') || this.model.doubleToolMarkup);
                tool2 = V(toolTemplate());
            } else {
                tool2 = tool.clone();
            }

            $tools.append(tool2.node);
            this._tool2Cache = tool2;
        }

        return this;
    },

    renderVertexMarkers: function() {

        if (!this._V.markerVertices) return this;

        var $markerVertices = $(this._V.markerVertices.node).empty();

        // A special markup can be given in the `properties.vertexMarkup` property. This might be handy
        // if default styling (elements) are not desired. This makes it possible to use any
        // SVG elements for .marker-vertex and .marker-vertex-remove tools.
        var markupTemplate = joint.util.template(this.model.get('vertexMarkup') || this.model.vertexMarkup);

        this.model.vertices().forEach(function(vertex, idx) {

            $markerVertices.append(V(markupTemplate(joint.util.assign({ idx: idx }, vertex))).node);
        });

        return this;
    },

    renderArrowheadMarkers: function() {

        // Custom markups might not have arrowhead markers. Therefore, jump of this function immediately if that's the case.
        if (!this._V.markerArrowheads) return this;

        var $markerArrowheads = $(this._V.markerArrowheads.node);

        $markerArrowheads.empty();

        // A special markup can be given in the `properties.vertexMarkup` property. This might be handy
        // if default styling (elements) are not desired. This makes it possible to use any
        // SVG elements for .marker-vertex and .marker-vertex-remove tools.
        var markupTemplate = joint.util.template(this.model.get('arrowheadMarkup') || this.model.arrowheadMarkup);

        this._V.sourceArrowhead = V(markupTemplate({ end: 'source' }));
        this._V.targetArrowhead = V(markupTemplate({ end: 'target' }));

        $markerArrowheads.append(this._V.sourceArrowhead.node, this._V.targetArrowhead.node);

        return this;
    },

    // Updating.
    // ---------

    // Default is to process the `attrs` object and set attributes on subelements based on the selectors.
    update: function(model, attributes, opt) {

        opt || (opt = {});

        // update the link path
        this.updateConnection(opt);

        // update SVG attributes defined by 'attrs/'.
        this.updateDOMSubtreeAttributes(this.el, this.model.attr(), { selectors: this.selectors });

        this.updateDefaultConnectionPath();

        // update the label position etc.
        this.updateLabelPositions();
        this.updateToolsPosition();
        this.updateArrowheadMarkers();

        this.updateTools(opt);
        // Local perpendicular flag (as opposed to one defined on paper).
        // Could be enabled inside a connector/router. It's valid only
        // during the update execution.
        this.options.perpendicular = null;
        // Mark that postponed update has been already executed.
        this.updatePostponed = false;

        return this;
    },

    removeRedundantLinearVertices: function(opt) {
        var link = this.model;
        var vertices = link.vertices();
        var conciseVertices = [];
        var n = vertices.length;
        var m = 0;
        for (var i = 0; i < n; i++) {
            var current = new g.Point(vertices[i]).round();
            var prev = new g.Point(conciseVertices[m - 1] || this.sourceAnchor).round();
            if (prev.equals(current)) continue;
            var next = new g.Point(vertices[i + 1] || this.targetAnchor).round();
            if (prev.equals(next)) continue;
            var line = new g.Line(prev, next);
            if (line.pointOffset(current) === 0) continue;
            conciseVertices.push(vertices[i]);
            m++;
        }
        if (n === m) return 0;
        link.vertices(conciseVertices, opt);
        return (n - m);
    },

    updateDefaultConnectionPath: function() {

        var cache = this._V;

        if (cache.connection) {
            cache.connection.attr('d', this.getSerializedConnection());
        }

        if (cache.connectionWrap) {
            cache.connectionWrap.attr('d', this.getSerializedConnection());
        }

        if (cache.markerSource && cache.markerTarget) {
            this._translateAndAutoOrientArrows(cache.markerSource, cache.markerTarget);
        }
    },

    getEndView: function(type) {
        switch (type) {
            case 'source':
                return this.sourceView || null;
            case 'target':
                return this.targetView || null;
            default:
                throw new Error('dia.LinkView: type parameter required.');
        }
    },

    getEndAnchor: function(type) {
        switch (type) {
            case 'source':
                return new g.Point(this.sourceAnchor);
            case 'target':
                return new g.Point(this.targetAnchor);
            default:
                throw new Error('dia.LinkView: type parameter required.');
        }
    },

    getEndMagnet: function(type) {
        switch (type) {
            case 'source':
                var sourceView = this.sourceView;
                if (!sourceView) break;
                return this.sourceMagnet || sourceView.el;
            case 'target':
                var targetView = this.targetView;
                if (!targetView) break;
                return this.targetMagnet || targetView.el;
            default:
                throw new Error('dia.LinkView: type parameter required.');
        }
        return null;
    },

    updateConnection: function(opt) {

        opt = opt || {};

        var model = this.model;
        var route, path;

        if (opt.translateBy && model.isRelationshipEmbeddedIn(opt.translateBy)) {
            // The link is being translated by an ancestor that will
            // shift source point, target point and all vertices
            // by an equal distance.
            var tx = opt.tx || 0;
            var ty = opt.ty || 0;

            route = (new g.Polyline(this.route)).translate(tx, ty).points;

            // translate source and target connection and marker points.
            this._translateConnectionPoints(tx, ty);

            // translate the path itself
            path = this.path;
            path.translate(tx, ty);

        } else {

            var vertices = model.vertices();
            // 1. Find Anchors

            var anchors = this.findAnchors(vertices);
            var sourceAnchor = this.sourceAnchor = anchors.source;
            var targetAnchor = this.targetAnchor = anchors.target;

            // 2. Find Route
            route = this.findRoute(vertices, opt);

            // 3. Find Connection Points
            var connectionPoints = this.findConnectionPoints(route, sourceAnchor, targetAnchor);
            var sourcePoint = this.sourcePoint = connectionPoints.source;
            var targetPoint = this.targetPoint = connectionPoints.target;

            // 3b. Find Marker Connection Point - Backwards Compatibility
            var markerPoints = this.findMarkerPoints(route, sourcePoint, targetPoint);

            // 4. Find Connection
            path = this.findPath(route, markerPoints.source || sourcePoint, markerPoints.target || targetPoint);
        }

        this.route = route;
        this.path = path;
        this.metrics = {};
    },

    findMarkerPoints: function(route, sourcePoint, targetPoint) {

        var firstWaypoint = route[0];
        var lastWaypoint = route[route.length - 1];

        // Move the source point by the width of the marker taking into account
        // its scale around x-axis. Note that scale is the only transform that
        // makes sense to be set in `.marker-source` attributes object
        // as all other transforms (translate/rotate) will be replaced
        // by the `translateAndAutoOrient()` function.
        var cache = this._markerCache;
        // cache source and target points
        var sourceMarkerPoint, targetMarkerPoint;

        if (this._V.markerSource) {

            cache.sourceBBox = cache.sourceBBox || this._V.markerSource.getBBox();
            sourceMarkerPoint = g.point(sourcePoint).move(
                firstWaypoint || targetPoint,
                cache.sourceBBox.width * this._V.markerSource.scale().sx * -1
            ).round();
        }

        if (this._V.markerTarget) {

            cache.targetBBox = cache.targetBBox || this._V.markerTarget.getBBox();
            targetMarkerPoint = g.point(targetPoint).move(
                lastWaypoint || sourcePoint,
                cache.targetBBox.width * this._V.markerTarget.scale().sx * -1
            ).round();
        }

        // if there was no markup for the marker, use the connection point.
        cache.sourcePoint = sourceMarkerPoint || sourcePoint.clone();
        cache.targetPoint = targetMarkerPoint || targetPoint.clone();

        return {
            source: sourceMarkerPoint,
            target: targetMarkerPoint
        }
    },

    findAnchors: function(vertices) {

        var model = this.model;
        var firstVertex = vertices[0];
        var lastVertex = vertices[vertices.length - 1];
        var sourceDef = model.get('source');
        var targetDef = model.get('target');
        var sourceView = this.sourceView;
        var targetView = this.targetView;
        var sourceMagnet, targetMagnet;

        // Anchor Source
        var sourceAnchor;
        if (sourceView) {
            sourceMagnet = (this.sourceMagnet || sourceView.el);
            var sourceAnchorRef;
            if (firstVertex) {
                sourceAnchorRef = new g.Point(firstVertex);
            } else if (targetView) {
                // TODO: the source anchor reference is not a point, how to deal with this?
                sourceAnchorRef = this.targetMagnet || targetView.el;
            } else {
                sourceAnchorRef = new g.Point(targetDef);
            }
            sourceAnchor = this.getAnchor(sourceDef.anchor, sourceView, sourceMagnet, sourceAnchorRef, 'source');
        } else {
            sourceAnchor = new g.Point(sourceDef);
        }

        // Anchor Target
        var targetAnchor;
        if (targetView) {
            targetMagnet = (this.targetMagnet || targetView.el);
            var targetAnchorRef = new g.Point(lastVertex || sourceAnchor);
            targetAnchor = this.getAnchor(targetDef.anchor, targetView, targetMagnet, targetAnchorRef, 'target');
        } else {
            targetAnchor = new g.Point(targetDef);
        }

        // Con
        return {
            source: sourceAnchor,
            target: targetAnchor
        }
    },

    findConnectionPoints: function(route, sourceAnchor, targetAnchor) {

        var firstWaypoint = route[0];
        var lastWaypoint = route[route.length - 1];
        var model = this.model;
        var sourceDef = model.get('source');
        var targetDef = model.get('target');
        var sourceView = this.sourceView;
        var targetView = this.targetView;
        var paperOptions = this.paper.options;
        var sourceMagnet, targetMagnet;

        // Connection Point Source
        var sourcePoint;
        if (sourceView) {
            sourceMagnet = (this.sourceMagnet || sourceView.el);
            var sourceConnectionPointDef = sourceDef.connectionPoint || paperOptions.defaultConnectionPoint;
            var sourcePointRef = firstWaypoint || targetAnchor;
            var sourceLine = new g.Line(sourcePointRef, sourceAnchor);
            sourcePoint = this.getConnectionPoint(sourceConnectionPointDef, sourceView, sourceMagnet, sourceLine, 'source');
        } else {
            sourcePoint = sourceAnchor;
        }
        // Connection Point Target
        var targetPoint;
        if (targetView) {
            targetMagnet = (this.targetMagnet || targetView.el);
            var targetConnectionPointDef = targetDef.connectionPoint || paperOptions.defaultConnectionPoint;
            var targetPointRef = lastWaypoint || sourceAnchor;
            var targetLine = new g.Line(targetPointRef, targetAnchor);
            targetPoint = this.getConnectionPoint(targetConnectionPointDef, targetView, targetMagnet, targetLine, 'target');
        } else {
            targetPoint = targetAnchor;
        }

        return {
            source: sourcePoint,
            target: targetPoint
        }
    },

    getAnchor: function(anchorDef, cellView, magnet, ref, endType) {

        if (!anchorDef) {
            var paperOptions = this.paper.options;
            if (paperOptions.perpendicularLinks || this.options.perpendicular) {
                // Backwards compatibility
                // If `perpendicularLinks` flag is set on the paper and there are vertices
                // on the link, then try to find a connection point that makes the link perpendicular
                // even though the link won't point to the center of the targeted object.
                anchorDef = { name: 'perpendicular' };
            } else {
                anchorDef = paperOptions.defaultAnchor;
            }
        }

        if (!anchorDef) throw new Error('Anchor required.');
        var anchorFn;
        if (typeof anchorDef === 'function') {
            anchorFn = anchorDef;
        } else {
            var anchorName = anchorDef.name;
            anchorFn = joint.anchors[anchorName];
            if (typeof anchorFn !== 'function') throw new Error('Unknown anchor: ' + anchorName);
        }
        var anchor = anchorFn.call(this, cellView, magnet, ref, anchorDef.args || {}, endType, this);
        if (anchor) return anchor.round(this.decimalsRounding);
        return new g.Point()
    },


    getConnectionPoint: function(connectionPointDef, view, magnet, line, endType) {

        var connectionPoint;
        var anchor = line.end;
        // Backwards compatibility
        var paperOptions = this.paper.options;
        if (typeof paperOptions.linkConnectionPoint === 'function') {
            connectionPoint = paperOptions.linkConnectionPoint(this, view, magnet, line.start, endType);
            if (connectionPoint) return connectionPoint;
        }

        if (!connectionPointDef) return anchor;
        var connectionPointFn;
        if (typeof connectionPointDef === 'function') {
            connectionPointFn = connectionPointDef;
        } else {
            var connectionPointName = connectionPointDef.name;
            connectionPointFn = joint.connectionPoints[connectionPointName];
            if (typeof connectionPointFn !== 'function') throw new Error('Unknown connection point: ' + connectionPointName);
        }
        connectionPoint = connectionPointFn.call(this, line, view, magnet, connectionPointDef.args || {}, endType, this);
        if (connectionPoint) return connectionPoint.round(this.decimalsRounding);
        return anchor;
    },

    _translateConnectionPoints: function(tx, ty) {

        var cache = this._markerCache;

        cache.sourcePoint.offset(tx, ty);
        cache.targetPoint.offset(tx, ty);
        this.sourcePoint.offset(tx, ty);
        this.targetPoint.offset(tx, ty);
        this.sourceAnchor.offset(tx, ty);
        this.targetAnchor.offset(tx, ty);
    },

     // if label position is a number, normalize it to a position object
     // this makes sure that label positions can be merged properly
    _normalizeLabelPosition: function(labelPosition) {

        if (typeof labelPosition === 'number') return { distance: labelPosition, offset: null, args: null };
        return labelPosition;
    },

    updateLabelPositions: function() {

        if (!this._V.labels) return this;

        var path = this.path;
        if (!path) return this;

        // This method assumes all the label nodes are stored in the `this._labelCache` hash table
        // by their indices in the `this.get('labels')` array. This is done in the `renderLabels()` method.

        var model = this.model;
        var labels = model.get('labels') || [];
        if (!labels.length) return this;

        var builtinDefaultLabel = model._builtins.defaultLabel;
        var builtinDefaultLabelPosition = builtinDefaultLabel.position;

        var defaultLabel = model._getDefaultLabel();
        var defaultLabelPosition = this._normalizeLabelPosition(defaultLabel.position);

        var defaultPosition = joint.util.merge({}, builtinDefaultLabelPosition, defaultLabelPosition);

        for (var idx = 0, n = labels.length; idx < n; idx++) {

            var label = labels[idx];
            var labelPosition = this._normalizeLabelPosition(label.position);

            var position = joint.util.merge({}, defaultPosition, labelPosition);

            var labelPoint = this.getLabelCoordinates(position);
            this._labelCache[idx].attr('transform', 'translate(' + labelPoint.x + ', ' + labelPoint.y + ')');
        }

        return this;
    },

    updateToolsPosition: function() {

        if (!this._V.linkTools) return this;

        // Move the tools a bit to the target position but don't cover the `sourceArrowhead` marker.
        // Note that the offset is hardcoded here. The offset should be always
        // more than the `this.$('.marker-arrowhead[end="source"]')[0].bbox().width` but looking
        // this up all the time would be slow.

        var scale = '';
        var offset = this.options.linkToolsOffset;
        var connectionLength = this.getConnectionLength();

        // Firefox returns connectionLength=NaN in odd cases (for bezier curves).
        // In that case we won't update tools position at all.
        if (!Number.isNaN(connectionLength)) {

            // If the link is too short, make the tools half the size and the offset twice as low.
            if (connectionLength < this.options.shortLinkLength) {
                scale = 'scale(.5)';
                offset /= 2;
            }

            var toolPosition = this.getPointAtLength(offset);

            this._toolCache.attr('transform', 'translate(' + toolPosition.x + ', ' + toolPosition.y + ') ' + scale);

            if (this.options.doubleLinkTools && connectionLength >= this.options.longLinkLength) {

                var doubleLinkToolsOffset = this.options.doubleLinkToolsOffset || offset;

                toolPosition = this.getPointAtLength(connectionLength - doubleLinkToolsOffset);
                this._tool2Cache.attr('transform', 'translate(' + toolPosition.x + ', ' + toolPosition.y + ') ' + scale);
                this._tool2Cache.attr('visibility', 'visible');

            } else if (this.options.doubleLinkTools) {

                this._tool2Cache.attr('visibility', 'hidden');
            }
        }

        return this;
    },

    updateArrowheadMarkers: function() {

        if (!this._V.markerArrowheads) return this;

        // getting bbox of an element with `display="none"` in IE9 ends up with access violation
        if ($.css(this._V.markerArrowheads.node, 'display') === 'none') return this;

        var sx = this.getConnectionLength() < this.options.shortLinkLength ? .5 : 1;
        this._V.sourceArrowhead.scale(sx);
        this._V.targetArrowhead.scale(sx);

        this._translateAndAutoOrientArrows(this._V.sourceArrowhead, this._V.targetArrowhead);

        return this;
    },

    // Returns a function observing changes on an end of the link. If a change happens and new end is a new model,
    // it stops listening on the previous one and starts listening to the new one.
    createWatcher: function(endType) {

        // create handler for specific end type (source|target).
        var onModelChange = function(endModel, opt) {
            this.onEndModelChange(endType, endModel, opt);
        };

        function watchEndModel(link, end) {

            end = end || {};

            var endModel = null;
            var previousEnd = link.previous(endType) || {};

            if (previousEnd.id) {
                this.stopListening(this.paper.getModelById(previousEnd.id), 'change', onModelChange);
            }

            if (end.id) {
                // If the observed model changes, it caches a new bbox and do the link update.
                endModel = this.paper.getModelById(end.id);
                this.listenTo(endModel, 'change', onModelChange);
            }

            onModelChange.call(this, endModel, { cacheOnly: true });

            return this;
        }

        return watchEndModel;
    },

    onEndModelChange: function(endType, endModel, opt) {

        var doUpdate = !opt.cacheOnly;
        var model = this.model;
        var end = model.get(endType) || {};

        if (endModel) {

            var selector = this.constructor.makeSelector(end);
            var oppositeEndType = endType == 'source' ? 'target' : 'source';
            var oppositeEnd = model.get(oppositeEndType) || {};
            var endId = end.id;
            var oppositeEndId = oppositeEnd.id;
            var oppositeSelector = oppositeEndId && this.constructor.makeSelector(oppositeEnd);

            // Caching end models bounding boxes.
            // If `opt.handleBy` equals the client-side ID of this link view and it is a loop link, then we already cached
            // the bounding boxes in the previous turn (e.g. for loop link, the change:source event is followed
            // by change:target and so on change:source, we already chached the bounding boxes of - the same - element).
            if (opt.handleBy === this.cid && (endId === oppositeEndId) && selector == oppositeSelector) {

                // Source and target elements are identical. We're dealing with a loop link. We are handling `change` event for the
                // second time now. There is no need to calculate bbox and find magnet element again.
                // It was calculated already for opposite link end.
                this[endType + 'View'] = this[oppositeEndType + 'View'];
                this[endType + 'Magnet'] = this[oppositeEndType + 'Magnet'];

            } else if (opt.translateBy) {
                // `opt.translateBy` optimizes the way we calculate bounding box of the source/target element.
                // If `opt.translateBy` is an ID of the element that was originally translated.

                // Noop

            } else {
                // The slowest path, source/target could have been rotated or resized or any attribute
                // that affects the bounding box of the view might have been changed.

                var connectedModel = this.paper.model.getCell(endId);
                if (!connectedModel) throw new Error('LinkView: invalid ' + endType + ' cell.');
                var connectedView = connectedModel.findView(this.paper);
                if (connectedView) {
                    var connectedMagnet = connectedView.getMagnetFromLinkEnd(end);
                    if (connectedMagnet === connectedView.el) connectedMagnet = null;
                    this[endType + 'View'] = connectedView;
                    this[endType + 'Magnet'] = connectedMagnet;
                } else {
                    // the view is not rendered yet
                    this[endType + 'View'] = this[endType + 'Magnet'] = null;
                }
            }

            if (opt.handleBy === this.cid && opt.translateBy &&
                model.isEmbeddedIn(endModel) &&
                !joint.util.isEmpty(model.get('vertices'))) {
                // Loop link whose element was translated and that has vertices (that need to be translated with
                // the parent in which my element is embedded).
                // If the link is embedded, has a loop and vertices and the end model
                // has been translated, do not update yet. There are vertices still to be updated (change:vertices
                // event will come in the next turn).
                doUpdate = false;
            }

            if (!this.updatePostponed && oppositeEndId) {
                // The update was not postponed (that can happen e.g. on the first change event) and the opposite
                // end is a model (opposite end is the opposite end of the link we're just updating, e.g. if
                // we're reacting on change:source event, the oppositeEnd is the target model).

                var oppositeEndModel = this.paper.getModelById(oppositeEndId);

                // Passing `handleBy` flag via event option.
                // Note that if we are listening to the same model for event 'change' twice.
                // The same event will be handled by this method also twice.
                if (end.id === oppositeEnd.id) {
                    // We're dealing with a loop link. Tell the handlers in the next turn that they should update
                    // the link instead of me. (We know for sure there will be a next turn because
                    // loop links react on at least two events: change on the source model followed by a change on
                    // the target model).
                    opt.handleBy = this.cid;
                }

                if (opt.handleBy === this.cid || (opt.translateBy && oppositeEndModel.isEmbeddedIn(opt.translateBy))) {

                    // Here are two options:
                    // - Source and target are connected to the same model (not necessarily the same port).
                    // - Both end models are translated by the same ancestor. We know that opposite end
                    //   model will be translated in the next turn as well.
                    // In both situations there will be more changes on the model that trigger an
                    // update. So there is no need to update the linkView yet.
                    this.updatePostponed = true;
                    doUpdate = false;
                }
            }

        } else {

            // the link end is a point ~ rect 1x1
            this[endType + 'View'] = this[endType + 'Magnet'] = null;
        }

        if (doUpdate) {
            this.update(model, null, opt);
        }
    },

    _translateAndAutoOrientArrows: function(sourceArrow, targetArrow) {

        // Make the markers "point" to their sticky points being auto-oriented towards
        // `targetPosition`/`sourcePosition`. And do so only if there is a markup for them.
        var route = joint.util.toArray(this.route);
        if (sourceArrow) {
            sourceArrow.translateAndAutoOrient(
                this.sourcePoint,
                route[0] || this.targetPoint,
                this.paper.viewport
            );
        }

        if (targetArrow) {
            targetArrow.translateAndAutoOrient(
                this.targetPoint,
                route[route.length - 1] || this.sourcePoint,
                this.paper.viewport
            );
        }
    },

    _getDefaultLabelPositionArgs: function() {

        var defaultLabel = this.model._getDefaultLabel();
        var defaultLabelPosition = defaultLabel.position || {};
        return defaultLabelPosition.args;
    },

    _getLabelPositionArgs: function(idx) {

        var labelPosition = this.model.label(idx).position || {};
        return labelPosition.args;
    },

    // merge default label position args into label position args
    // keep `undefined` or `null` because `{}` means something else
    _mergeLabelPositionArgs: function(labelPositionArgs, defaultLabelPositionArgs) {

        if (labelPositionArgs === null) return null;
        if (labelPositionArgs === undefined) {

            if (defaultLabelPositionArgs === null) return null;
            return defaultLabelPositionArgs;
        }

        return joint.util.merge({}, defaultLabelPositionArgs, labelPositionArgs);
    },

    // Add default label at given position at end of `labels` array.
    // Assigns relative coordinates by default.
    // `opt.absoluteDistance` forces absolute coordinates.
    // `opt.reverseDistance` forces reverse absolute coordinates (if absoluteDistance = true).
    // `opt.absoluteOffset` forces absolute coordinates for offset.
    addLabel: function(x, y, opt) {

        // accept input in form `{ x, y }, opt` or `x, y, opt`
        var isPointProvided = (typeof x !== 'number');
        var localX = isPointProvided ? x.x : x;
        var localY = isPointProvided ? x.y : y;
        var localOpt = isPointProvided ? y : opt;

        var defaultLabelPositionArgs = this._getDefaultLabelPositionArgs();
        var labelPositionArgs = localOpt;
        var positionArgs = this._mergeLabelPositionArgs(labelPositionArgs, defaultLabelPositionArgs);

        var label = { position: this.getLabelPosition(localX, localY, positionArgs) };
        var idx = -1;
        this.model.insertLabel(idx, label, localOpt);
        return idx;
    },

    // Add a new vertex at calculated index to the `vertices` array.
    addVertex: function(x, y, opt) {

        // accept input in form `{ x, y }, opt` or `x, y, opt`
        var isPointProvided = (typeof x !== 'number');
        var localX = isPointProvided ? x.x : x;
        var localY = isPointProvided ? x.y : y;
        var localOpt = isPointProvided ? y : opt;

        var vertex = { x: localX, y: localY };
        var idx = this.getVertexIndex(localX, localY);
        this.model.insertVertex(idx, vertex, localOpt);
        return idx;
    },

    // Send a token (an SVG element, usually a circle) along the connection path.
    // Example: `link.findView(paper).sendToken(V('circle', { r: 7, fill: 'green' }).node)`
    // `opt.duration` is optional and is a time in milliseconds that the token travels from the source to the target of the link. Default is `1000`.
    // `opt.directon` is optional and it determines whether the token goes from source to target or other way round (`reverse`)
    // `opt.connection` is an optional selector to the connection path.
    // `callback` is optional and is a function to be called once the token reaches the target.
    sendToken: function(token, opt, callback) {

        function onAnimationEnd(vToken, callback) {
            return function() {
                vToken.remove();
                if (typeof callback === 'function') {
                    callback();
                }
            };
        }

        var duration, isReversed, selector;
        if (joint.util.isObject(opt)) {
            duration = opt.duration;
            isReversed = (opt.direction === 'reverse');
            selector = opt.connection;
        } else {
            // Backwards compatibility
            duration = opt;
            isReversed = false;
            selector = null;
        }

        duration = duration || 1000;

        var animationAttributes = {
            dur: duration + 'ms',
            repeatCount: 1,
            calcMode: 'linear',
            fill: 'freeze'
        };

        if (isReversed) {
            animationAttributes.keyPoints = '1;0';
            animationAttributes.keyTimes = '0;1';
        }

        var vToken = V(token);
        var connection;
        if (typeof selector === 'string') {
            // Use custom connection path.
            connection = this.findBySelector(selector, this.el, this.selectors)[0];
        } else {
            // Select connection path automatically.
            var cache = this._V;
            connection = (cache.connection) ? cache.connection.node : this.el.querySelector('path');
        }

        if (!(connection instanceof SVGPathElement)) {
            throw new Error('dia.LinkView: token animation requires a valid connection path.');
        }

        vToken
            .appendTo(this.paper.viewport)
            .animateAlongPath(animationAttributes, connection);

        setTimeout(onAnimationEnd(vToken, callback), duration);
    },

    findRoute: function(vertices) {

        vertices || (vertices = []);

        var namespace = joint.routers;
        var router = this.model.router();
        var defaultRouter = this.paper.options.defaultRouter;

        if (!router) {
            if (defaultRouter) router = defaultRouter;
            else return vertices.map(g.Point, g); // no router specified
        }

        var routerFn = joint.util.isFunction(router) ? router : namespace[router.name];
        if (!joint.util.isFunction(routerFn)) {
            throw new Error('dia.LinkView: unknown router: "' + router.name + '".');
        }

        var args = router.args || {};

        var route = routerFn.call(
            this, // context
            vertices, // vertices
            args, // options
            this // linkView
        );

        if (!route) return vertices.map(g.Point, g);
        return route;
    },

    // Return the `d` attribute value of the `<path>` element representing the link
    // between `source` and `target`.
    findPath: function(route, sourcePoint, targetPoint) {

        var namespace = joint.connectors;
        var connector = this.model.connector();
        var defaultConnector = this.paper.options.defaultConnector;

        if (!connector) {
            connector = defaultConnector || {};
        }

        var connectorFn = joint.util.isFunction(connector) ? connector : namespace[connector.name];
        if (!joint.util.isFunction(connectorFn)) {
            throw new Error('dia.LinkView: unknown connector: "' + connector.name + '".');
        }

        var args = joint.util.clone(connector.args || {});
        args.raw = true; // Request raw g.Path as the result.

        var path = connectorFn.call(
            this, // context
            sourcePoint, // start point
            targetPoint, // end point
            route, // vertices
            args, // options
            this // linkView
        );

        if (typeof path === 'string') {
            // Backwards compatibility for connectors not supporting `raw` option.
            path = new g.Path(V.normalizePathData(path));
        }

        return path;
    },

    // Public API.
    // -----------

    getConnection: function() {

        var path = this.path;
        if (!path) return null;

        return path.clone();
    },

    getSerializedConnection: function() {

        var path = this.path;
        if (!path) return null;

        var metrics = this.metrics;
        if (metrics.hasOwnProperty('data')) return metrics.data;
        var data = path.serialize();
        metrics.data = data;
        return data;
    },

    getConnectionSubdivisions: function() {

        var path = this.path;
        if (!path) return null;

        var metrics = this.metrics;
        if (metrics.hasOwnProperty('segmentSubdivisions')) return metrics.segmentSubdivisions;
        var subdivisions = path.getSegmentSubdivisions();
        metrics.segmentSubdivisions = subdivisions;
        return subdivisions;
    },

    getConnectionLength: function() {

        var path = this.path;
        if (!path) return 0;

        var metrics = this.metrics;
        if (metrics.hasOwnProperty('length')) return metrics.length;
        var length = path.length({ segmentSubdivisions: this.getConnectionSubdivisions() });
        metrics.length = length;
        return length;
    },

    getPointAtLength: function(length) {

        var path = this.path;
        if (!path) return null;

        return path.pointAtLength(length, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    getPointAtRatio: function(ratio) {

        var path = this.path;
        if (!path) return null;

        return path.pointAt(ratio, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    getTangentAtLength: function(length) {

        var path = this.path;
        if (!path) return null;

        return path.tangentAtLength(length, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    getTangentAtRatio: function(ratio) {

        var path = this.path;
        if (!path) return null;

        return path.tangentAt(ratio, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    getClosestPoint: function(point) {

        var path = this.path;
        if (!path) return null;

        return path.closestPoint(point, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    getClosestPointLength: function(point) {

        var path = this.path;
        if (!path) return null;

        return path.closestPointLength(point, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    getClosestPointRatio: function(point) {

        var path = this.path;
        if (!path) return null;

        return path.closestPointNormalizedLength(point, { segmentSubdivisions: this.getConnectionSubdivisions() });
    },

    // accepts options `absoluteDistance: boolean`, `reverseDistance: boolean`, `absoluteOffset: boolean`
    // to move beyond connection endpoints, absoluteOffset has to be set
    getLabelPosition: function(x, y, opt) {

        var position = {};

        var localOpt = opt || {};
        if (opt) position.args = opt;

        var isDistanceRelative = !localOpt.absoluteDistance; // relative by default
        var isDistanceAbsoluteReverse = (localOpt.absoluteDistance && localOpt.reverseDistance); // non-reverse by default
        var isOffsetAbsolute = localOpt.absoluteOffset; // offset is non-absolute by default

        var path = this.path;
        var pathOpt = { segmentSubdivisions: this.getConnectionSubdivisions() };

        var labelPoint = new g.Point(x, y);
        var t = path.closestPointT(labelPoint, pathOpt);

        // GET DISTANCE:

        var labelDistance = path.lengthAtT(t, pathOpt);
        if (isDistanceRelative) labelDistance = (labelDistance / this.getConnectionLength()) || 0; // fix to prevent NaN for 0 length
        if (isDistanceAbsoluteReverse) labelDistance = (-1 * (this.getConnectionLength() - labelDistance)) || 1; // fix for end point (-0 => 1)

        position.distance = labelDistance;

        // GET OFFSET:
        // use absolute offset if:
        // - opt.absoluteOffset is true,
        // - opt.absoluteOffset is not true but there is no tangent

        var tangent;
        if (!isOffsetAbsolute) tangent = path.tangentAtT(t);

        var labelOffset;
        if (tangent) {
            labelOffset = tangent.pointOffset(labelPoint);

        } else {
            var closestPoint = path.pointAtT(t);
            var labelOffsetDiff = labelPoint.difference(closestPoint);
            labelOffset = { x: labelOffsetDiff.x, y: labelOffsetDiff.y };
        }

        position.offset = labelOffset;

        return position;
    },

    getLabelCoordinates: function(labelPosition) {

        var labelDistance;
        if (typeof labelPosition === 'number') labelDistance = labelPosition;
        else if (typeof labelPosition.distance === 'number') labelDistance = labelPosition.distance;
        else throw new Error('dia.LinkView: invalid label position distance.');

        var isDistanceRelative = ((labelDistance > 0) && (labelDistance <= 1));

        var labelOffset = 0;
        var labelOffsetCoordinates = { x: 0, y: 0 };
        if (labelPosition.offset) {
            var positionOffset = labelPosition.offset;
            if (typeof positionOffset === 'number') labelOffset = positionOffset;
            if (positionOffset.x) labelOffsetCoordinates.x = positionOffset.x;
            if (positionOffset.y) labelOffsetCoordinates.y = positionOffset.y;
        }

        var isOffsetAbsolute = ((labelOffsetCoordinates.x !== 0) || (labelOffsetCoordinates.y !== 0) || labelOffset === 0);

        var path = this.path;
        var pathOpt = { segmentSubdivisions: this.getConnectionSubdivisions() };

        var distance = isDistanceRelative ? (labelDistance * this.getConnectionLength()) : labelDistance;

        var point;

        if (isOffsetAbsolute) {
            point = path.pointAtLength(distance, pathOpt);
            point.offset(labelOffsetCoordinates);

        } else {
            var tangent = path.tangentAtLength(distance, pathOpt);

            if (tangent) {
                tangent.rotate(tangent.start, -90);
                tangent.setLength(labelOffset);
                point = tangent.end;

            } else {
                // fallback - the connection has zero length
                point = path.start;
            }
        }

        return point;
    },

    getVertexIndex: function(x, y) {

        var model = this.model;
        var vertices = model.vertices();

        var vertexLength = this.getClosestPointLength(new g.Point(x, y));

        var idx = 0;
        for (var n = vertices.length; idx < n; idx++) {
            var currentVertex = vertices[idx];
            var currentVertexLength = this.getClosestPointLength(currentVertex);
            if (vertexLength < currentVertexLength) break;
        }

        return idx;
    },

    // Interaction. The controller part.
    // ---------------------------------

    pointerdblclick: function(evt, x, y) {

        joint.dia.CellView.prototype.pointerdblclick.apply(this, arguments);
        this.notify('link:pointerdblclick', evt, x, y);
    },

    pointerclick: function(evt, x, y) {

        joint.dia.CellView.prototype.pointerclick.apply(this, arguments);
        this.notify('link:pointerclick', evt, x, y);
    },

    contextmenu: function(evt, x, y) {

        joint.dia.CellView.prototype.contextmenu.apply(this, arguments);
        this.notify('link:contextmenu', evt, x, y);
    },

    pointerdown: function(evt, x, y) {

        joint.dia.CellView.prototype.pointerdown.apply(this, arguments);
        this.notify('link:pointerdown', evt, x, y);

        // Backwards compatibility for the default markup
        var className = evt.target.getAttribute('class');
        switch (className) {

            case 'marker-vertex':
                this.dragVertexStart(evt, x, y);
                return;

            case 'marker-vertex-remove':
            case 'marker-vertex-remove-area':
                this.dragVertexRemoveStart(evt, x, y);
                return;

            case 'marker-arrowhead':
                this.dragArrowheadStart(evt, x, y);
                return;

            case 'connection':
            case 'connection-wrap':
                this.dragConnectionStart(evt, x, y);
                return;

            case 'marker-source':
            case 'marker-target':
                return;
        }

        this.dragStart(evt, x, y);
    },

    pointermove: function(evt, x, y) {

        // Backwards compatibility
        var dragData = this._dragData;
        if (dragData) this.eventData(evt, dragData);

        var data = this.eventData(evt);
        switch (data.action) {

            case 'vertex-move':
                this.dragVertex(evt, x, y);
                break;

            case 'label-move':
                this.dragLabel(evt, x, y);
                break;

            case 'arrowhead-move':
                this.dragArrowhead(evt, x, y);
                break;

            case 'move':
                this.drag(evt, x, y);
                break;
        }

        // Backwards compatibility
        if (dragData) joint.util.assign(dragData, this.eventData(evt));

        joint.dia.CellView.prototype.pointermove.apply(this, arguments);
        this.notify('link:pointermove', evt, x, y);
    },

    pointerup: function(evt, x, y) {

        // Backwards compatibility
        var dragData = this._dragData;
        if (dragData) {
            this.eventData(evt, dragData);
            this._dragData = null;
        }

        var data = this.eventData(evt);
        switch (data.action) {

            case 'vertex-move':
                this.dragVertexEnd(evt, x, y);
                break;

            case 'label-move':
                this.dragLabelEnd(evt, x, y);
                break;

            case 'arrowhead-move':
                this.dragArrowheadEnd(evt, x, y);
                break;

            case 'move':
                this.dragEnd(evt, x, y);
        }

        this.notify('link:pointerup', evt, x, y);
        joint.dia.CellView.prototype.pointerup.apply(this, arguments);
    },

    mouseover: function(evt) {

        joint.dia.CellView.prototype.mouseover.apply(this, arguments);
        this.notify('link:mouseover', evt);
    },

    mouseout: function(evt) {

        joint.dia.CellView.prototype.mouseout.apply(this, arguments);
        this.notify('link:mouseout', evt);
    },

    mouseenter: function(evt) {

        joint.dia.CellView.prototype.mouseenter.apply(this, arguments);
        this.notify('link:mouseenter', evt);
    },

    mouseleave: function(evt) {

        joint.dia.CellView.prototype.mouseleave.apply(this, arguments);
        this.notify('link:mouseleave', evt);
    },

    mousewheel: function(evt, x, y, delta) {

        joint.dia.CellView.prototype.mousewheel.apply(this, arguments);
        this.notify('link:mousewheel', evt, x, y, delta);
    },

    onevent: function(evt, eventName, x, y) {

        // Backwards compatibility
        var linkTool = V(evt.target).findParentByClass('link-tool', this.el);
        if (linkTool) {
            // No further action to be executed
            evt.stopPropagation();

            // Allow `interactive.useLinkTools=false`
            if (this.can('useLinkTools')) {
                if (eventName === 'remove') {
                    // Built-in remove event
                    this.model.remove({ ui: true });

                } else {
                    // link:options and other custom events inside the link tools
                    this.notify(eventName, evt, x, y);
                }
            }

        } else {
            joint.dia.CellView.prototype.onevent.apply(this, arguments);
        }
    },

    onlabel: function(evt, x, y) {

        this.dragLabelStart(evt, x, y);

        var stopPropagation = this.eventData(evt).stopPropagation;
        if (stopPropagation) evt.stopPropagation();
    },

    // Drag Start Handlers

    dragConnectionStart: function(evt, x, y) {

        if (!this.can('vertexAdd')) return;

        // Store the index at which the new vertex has just been placed.
        // We'll be update the very same vertex position in `pointermove()`.
        var vertexIdx = this.addVertex({ x: x, y: y }, { ui: true });
        this.eventData(evt, {
            action: 'vertex-move',
            vertexIdx: vertexIdx
        });
    },

    dragLabelStart: function(evt, x, y) {

        if (!this.can('labelMove')) {
            // Backwards compatibility:
            // If labels can't be dragged no default action is triggered.
            this.eventData(evt, { stopPropagation: true });
            return;
        }

        var labelNode = evt.currentTarget;
        var labelIdx = parseInt(labelNode.getAttribute('label-idx'), 10);

        var defaultLabelPositionArgs = this._getDefaultLabelPositionArgs();
        var labelPositionArgs = this._getLabelPositionArgs(labelIdx);
        var positionArgs = this._mergeLabelPositionArgs(labelPositionArgs, defaultLabelPositionArgs);

        this.eventData(evt, {
            action: 'label-move',
            labelIdx: labelIdx,
            positionArgs: positionArgs,
            stopPropagation: true
        });

        this.paper.delegateDragEvents(this, evt.data);
    },

    dragVertexStart: function(evt, x, y) {

        if (!this.can('vertexMove')) return;

        var vertexNode = evt.target;
        var vertexIdx = parseInt(vertexNode.getAttribute('idx'), 10);
        this.eventData(evt, {
            action: 'vertex-move',
            vertexIdx: vertexIdx
        });
    },

    dragVertexRemoveStart: function(evt, x, y) {

        if (!this.can('vertexRemove')) return;

        var removeNode = evt.target;
        var vertexIdx = parseInt(removeNode.getAttribute('idx'), 10);
        this.model.removeVertex(vertexIdx);
    },

    dragArrowheadStart: function(evt, x, y) {

        if (!this.can('arrowheadMove')) return;

        var arrowheadNode = evt.target;
        var arrowheadType = arrowheadNode.getAttribute('end');
        var data = this.startArrowheadMove(arrowheadType, { ignoreBackwardsCompatibility: true });

        this.eventData(evt, data);
    },

    dragStart: function(evt, x, y) {

        if (!this.can('linkMove')) return;

        this.eventData(evt, {
            action: 'move',
            dx: x,
            dy: y
        });
    },

    // Drag Handlers

    dragLabel: function(evt, x, y) {

        var data = this.eventData(evt);
        var label = { position: this.getLabelPosition(x, y, data.positionArgs) };
        this.model.label(data.labelIdx, label);
    },

    dragVertex: function(evt, x, y) {

        var data = this.eventData(evt);
        this.model.vertex(data.vertexIdx, { x: x, y: y }, { ui: true });
    },

    dragArrowhead: function(evt, x, y) {

        var data = this.eventData(evt);

        if (this.paper.options.snapLinks) {

            this._snapArrowhead(x, y, data);

        } else {
            // Touchmove event's target is not reflecting the element under the coordinates as mousemove does.
            // It holds the element when a touchstart triggered.
            var target = (evt.type === 'mousemove')
                ? evt.target
                : document.elementFromPoint(evt.clientX, evt.clientY);

            this._connectArrowhead(target, x, y, data);
        }
    },

    drag: function(evt, x, y) {

        var data = this.eventData(evt);
        this.model.translate(x - data.dx, y - data.dy, { ui: true });
        this.eventData(evt, {
            dx: x,
            dy: y
        });
    },

    // Drag End Handlers

    dragLabelEnd: function() {
        // noop
    },

    dragVertexEnd: function() {
        // noop
    },

    dragArrowheadEnd: function(evt, x, y) {

        var data = this.eventData(evt);
        var paper = this.paper;

        if (paper.options.snapLinks) {
            this._snapArrowheadEnd(data);
        } else {
            this._connectArrowheadEnd(data, x, y);
        }

        if (!paper.linkAllowed(this)) {
            // If the changed link is not allowed, revert to its previous state.
            this._disallow(data);
        } else {
            this._finishEmbedding(data);
            this._notifyConnectEvent(data, evt);
        }

        this._afterArrowheadMove(data);

        // mouseleave event is not triggered due to changing pointer-events to `none`.
        if (!this.vel.contains(evt.target)) {
            this.mouseleave(evt);
        }
    },

    dragEnd: function() {
        // noop
    },

    _disallow: function(data) {

        switch (data.whenNotAllowed) {

            case 'remove':
                this.model.remove({ ui: true });
                break;

            case 'revert':
            default:
                this.model.set(data.arrowhead, data.initialEnd, { ui: true });
                break;
        }
    },

    _finishEmbedding: function(data) {

        // Reparent the link if embedding is enabled
        if (this.paper.options.embeddingMode && this.model.reparent()) {
            // Make sure we don't reverse to the original 'z' index (see afterArrowheadMove()).
            data.z = null;
        }
    },

    _notifyConnectEvent: function(data, evt) {

        var arrowhead = data.arrowhead;
        var initialEnd = data.initialEnd;
        var currentEnd = this.model.prop(arrowhead);
        var endChanged = currentEnd && !joint.dia.Link.endsEqual(initialEnd, currentEnd);
        if (endChanged) {
            var paper = this.paper;
            if (initialEnd.id) {
                this.notify('link:disconnect', evt, paper.findViewByModel(initialEnd.id), data.initialMagnet, arrowhead);
            }
            if (currentEnd.id) {
                this.notify('link:connect', evt, paper.findViewByModel(currentEnd.id), data.magnetUnderPointer, arrowhead);
            }
        }
    },

    _snapArrowhead: function(x, y, data) {

        // checking view in close area of the pointer

        var r = this.paper.options.snapLinks.radius || 50;
        var viewsInArea = this.paper.findViewsInArea({ x: x - r, y: y - r, width: 2 * r, height: 2 * r });

        if (data.closestView) {
            data.closestView.unhighlight(data.closestMagnet, {
                connecting: true,
                snapping: true
            });
        }
        data.closestView = data.closestMagnet = null;

        var distance;
        var minDistance = Number.MAX_VALUE;
        var pointer = g.point(x, y);
        var paper = this.paper;

        viewsInArea.forEach(function(view) {

            // skip connecting to the element in case '.': { magnet: false } attribute present
            if (view.el.getAttribute('magnet') !== 'false') {

                // find distance from the center of the model to pointer coordinates
                distance = view.model.getBBox().center().distance(pointer);

                // the connection is looked up in a circle area by `distance < r`
                if (distance < r && distance < minDistance) {

                    if (paper.options.validateConnection.apply(
                        paper, data.validateConnectionArgs(view, null)
                    )) {
                        minDistance = distance;
                        data.closestView = view;
                        data.closestMagnet = view.el;
                    }
                }
            }

            view.$('[magnet]').each(function(index, magnet) {

                var bbox = view.getNodeBBox(magnet);

                distance = pointer.distance({
                    x: bbox.x + bbox.width / 2,
                    y: bbox.y + bbox.height / 2
                });

                if (distance < r && distance < minDistance) {

                    if (paper.options.validateConnection.apply(
                        paper, data.validateConnectionArgs(view, magnet)
                    )) {
                        minDistance = distance;
                        data.closestView = view;
                        data.closestMagnet = magnet;
                    }
                }

            }.bind(this));

        }, this);

        var end;
        var closestView = data.closestView;
        var closestMagnet = data.closestMagnet;
        var endType = data.arrowhead;
        if (closestView) {
            closestView.highlight(closestMagnet, {
                connecting: true,
                snapping: true
            });
            end = closestView.getLinkEnd(closestMagnet, x, y, this.model, endType);
        } else {
            end = { x: x, y: y };
        }

        this.model.set(endType, end || { x: x, y: y }, { ui: true });
    },

    _snapArrowheadEnd: function(data) {

        // Finish off link snapping.
        // Everything except view unhighlighting was already done on pointermove.
        var closestView = data.closestView;
        var closestMagnet = data.closestMagnet;
        if (closestView && closestMagnet) {

            closestView.unhighlight(closestMagnet, { connecting: true, snapping: true });
            data.magnetUnderPointer = closestView.findMagnet(closestMagnet);
        }

        data.closestView = data.closestMagnet = null;
    },

    _connectArrowhead: function(target, x, y, data) {

        // checking views right under the pointer

        if (data.eventTarget !== target) {
            // Unhighlight the previous view under pointer if there was one.
            if (data.magnetUnderPointer) {
                data.viewUnderPointer.unhighlight(data.magnetUnderPointer, {
                    connecting: true
                });
            }

            data.viewUnderPointer = this.paper.findView(target);
            if (data.viewUnderPointer) {
                // If we found a view that is under the pointer, we need to find the closest
                // magnet based on the real target element of the event.
                data.magnetUnderPointer = data.viewUnderPointer.findMagnet(target);

                if (data.magnetUnderPointer && this.paper.options.validateConnection.apply(
                    this.paper,
                    data.validateConnectionArgs(data.viewUnderPointer, data.magnetUnderPointer)
                )) {
                    // If there was no magnet found, do not highlight anything and assume there
                    // is no view under pointer we're interested in reconnecting to.
                    // This can only happen if the overall element has the attribute `'.': { magnet: false }`.
                    if (data.magnetUnderPointer) {
                        data.viewUnderPointer.highlight(data.magnetUnderPointer, {
                            connecting: true
                        });
                    }
                } else {
                    // This type of connection is not valid. Disregard this magnet.
                    data.magnetUnderPointer = null;
                }
            } else {
                // Make sure we'll unset previous magnet.
                data.magnetUnderPointer = null;
            }
        }

        data.eventTarget = target;

        this.model.set(data.arrowhead, { x: x, y: y }, { ui: true });
    },

    _connectArrowheadEnd: function(data, x, y) {

        var view = data.viewUnderPointer;
        var magnet = data.magnetUnderPointer;
        if (!magnet || !view) return;

        view.unhighlight(magnet, { connecting: true });

        var endType = data.arrowhead;
        var end = view.getLinkEnd(magnet, x, y, this.model, endType);
        this.model.set(endType, end, { ui: true });
    },

    _beforeArrowheadMove: function(data) {

        data.z = this.model.get('z');
        this.model.toFront();

        // Let the pointer propagate throught the link view elements so that
        // the `evt.target` is another element under the pointer, not the link itself.
        this.el.style.pointerEvents = 'none';

        if (this.paper.options.markAvailable) {
            this._markAvailableMagnets(data);
        }
    },

    _afterArrowheadMove: function(data) {

        if (data.z !== null) {
            this.model.set('z', data.z, { ui: true });
            data.z = null;
        }

        // Put `pointer-events` back to its original value. See `startArrowheadMove()` for explanation.
        // Value `auto` doesn't work in IE9. We force to use `visiblePainted` instead.
        // See `https://developer.mozilla.org/en-US/docs/Web/CSS/pointer-events`.
        this.el.style.pointerEvents = 'visiblePainted';

        if (this.paper.options.markAvailable) {
            this._unmarkAvailableMagnets(data);
        }
    },

    _createValidateConnectionArgs: function(arrowhead) {
        // It makes sure the arguments for validateConnection have the following form:
        // (source view, source magnet, target view, target magnet and link view)
        var args = [];

        args[4] = arrowhead;
        args[5] = this;

        var oppositeArrowhead;
        var i = 0;
        var j = 0;

        if (arrowhead === 'source') {
            i = 2;
            oppositeArrowhead = 'target';
        } else {
            j = 2;
            oppositeArrowhead = 'source';
        }

        var end = this.model.get(oppositeArrowhead);

        if (end.id) {
            args[i] = this.paper.findViewByModel(end.id);
            args[i + 1] = end.selector && args[i].el.querySelector(end.selector);
        }

        function validateConnectionArgs(cellView, magnet) {
            args[j] = cellView;
            args[j + 1] = cellView.el === magnet ? undefined : magnet;
            return args;
        }

        return validateConnectionArgs;
    },

    _markAvailableMagnets: function(data) {

        function isMagnetAvailable(view, magnet) {
            var paper = view.paper;
            var validate = paper.options.validateConnection;
            return validate.apply(paper, this.validateConnectionArgs(view, magnet));
        }

        var paper = this.paper;
        var elements = paper.model.getElements();
        data.marked = {};

        for (var i = 0, n = elements.length; i < n; i++) {
            var view = elements[i].findView(paper);

            if (!view) {
                continue;
            }

            var magnets = Array.prototype.slice.call(view.el.querySelectorAll('[magnet]'));
            if (view.el.getAttribute('magnet') !== 'false') {
                // Element wrapping group is also a magnet
                magnets.push(view.el);
            }

            var availableMagnets = magnets.filter(isMagnetAvailable.bind(data, view));

            if (availableMagnets.length > 0) {
                // highlight all available magnets
                for (var j = 0, m = availableMagnets.length; j < m; j++) {
                    view.highlight(availableMagnets[j], { magnetAvailability: true });
                }
                // highlight the entire view
                view.highlight(null, { elementAvailability: true });

                data.marked[view.model.id] = availableMagnets;
            }
        }
    },

    _unmarkAvailableMagnets: function(data) {

        var markedKeys = Object.keys(data.marked);
        var id;
        var markedMagnets;

        for (var i = 0, n = markedKeys.length; i < n; i++) {
            id = markedKeys[i];
            markedMagnets = data.marked[id];

            var view = this.paper.findViewByModel(id);
            if (view) {
                for (var j = 0, m = markedMagnets.length; j < m; j++) {
                    view.unhighlight(markedMagnets[j], { magnetAvailability: true });
                }
                view.unhighlight(null, { elementAvailability: true });
            }
        }

        data.marked = null;
    },

    startArrowheadMove: function(end, opt) {

        opt || (opt = {});

        // Allow to delegate events from an another view to this linkView in order to trigger arrowhead
        // move without need to click on the actual arrowhead dom element.
        var data = {
            action: 'arrowhead-move',
            arrowhead: end,
            whenNotAllowed: opt.whenNotAllowed || 'revert',
            initialMagnet: this[end + 'Magnet'] || (this[end + 'View'] ? this[end + 'View'].el : null),
            initialEnd: joint.util.clone(this.model.get(end)),
            validateConnectionArgs: this._createValidateConnectionArgs(end)
        };

        this._beforeArrowheadMove(data);

        if (opt.ignoreBackwardsCompatibility !== true) {
            this._dragData = data;
        }

        return data;
    }
}, {

    makeSelector: function(end) {

        var selector = '';
        // `port` has a higher precendence over `selector`. This is because the selector to the magnet
        // might change while the name of the port can stay the same.
        if (end.port) {
            selector += '[port="' + end.port + '"]';
        } else if (end.selector) {
            selector +=  end.selector;
        }

        return selector;
    }

});


Object.defineProperty(joint.dia.LinkView.prototype, 'sourceBBox', {

    enumerable: true,

    get: function() {
        var sourceView = this.sourceView;
        var sourceMagnet = this.sourceMagnet;
        if (sourceView) {
            if (!sourceMagnet) sourceMagnet = sourceView.el;
            return sourceView.getNodeBBox(sourceMagnet);
        }
        var sourceDef = this.model.source();
        return new g.Rect(sourceDef.x, sourceDef.y, 1, 1);
    }

});

Object.defineProperty(joint.dia.LinkView.prototype, 'targetBBox', {

    enumerable: true,

    get: function() {
        var targetView = this.targetView;
        var targetMagnet = this.targetMagnet;
        if (targetView) {
            if (!targetMagnet) targetMagnet = targetView.el;
            return targetView.getNodeBBox(targetMagnet);
        }
        var targetDef = this.model.target();
        return new g.Rect(targetDef.x, targetDef.y, 1, 1);
    }
});


joint.dia.Paper = joint.mvc.View.extend({

    className: 'paper',

    options: {

        width: 800,
        height: 600,
        origin: { x: 0, y: 0 }, // x,y coordinates in top-left corner
        gridSize: 1,

        // Whether or not to draw the grid lines on the paper's DOM element.
        // e.g drawGrid: true, drawGrid: { color: 'red', thickness: 2 }
        drawGrid: false,

        // Whether or not to draw the background on the paper's DOM element.
        // e.g. background: { color: 'lightblue', image: '/paper-background.png', repeat: 'flip-xy' }
        background: false,

        perpendicularLinks: false,
        elementView: joint.dia.ElementView,
        linkView: joint.dia.LinkView,
        snapLinks: false, // false, true, { radius: value }

        // When set to FALSE, an element may not have more than 1 link with the same source and target element.
        multiLinks: true,

        // For adding custom guard logic.
        guard: function(evt, view) {

            // FALSE means the event isn't guarded.
            return false;
        },

        highlighting: {
            'default': {
                name: 'stroke',
                options: {
                    padding: 3
                }
            },
            magnetAvailability: {
                name: 'addClass',
                options: {
                    className: 'available-magnet'
                }
            },
            elementAvailability: {
                name: 'addClass',
                options: {
                    className: 'available-cell'
                }
            }
        },

        // Prevent the default context menu from being displayed.
        preventContextMenu: true,

        // Prevent the default action for blank:pointer<action>.
        preventDefaultBlankAction: true,

        // Restrict the translation of elements by given bounding box.
        // Option accepts a boolean:
        //  true - the translation is restricted to the paper area
        //  false - no restrictions
        // A method:
        // restrictTranslate: function(elementView) {
        //     var parentId = elementView.model.get('parent');
        //     return parentId && this.model.getCell(parentId).getBBox();
        // },
        // Or a bounding box:
        // restrictTranslate: { x: 10, y: 10, width: 790, height: 590 }
        restrictTranslate: false,

        // Marks all available magnets with 'available-magnet' class name and all available cells with
        // 'available-cell' class name. Marks them when dragging a link is started and unmark
        // when the dragging is stopped.
        markAvailable: false,

        // Defines what link model is added to the graph after an user clicks on an active magnet.
        // Value could be the Backbone.model or a function returning the Backbone.model
        // defaultLink: function(elementView, magnet) { return condition ? new customLink1() : new customLink2() }
        defaultLink: new joint.dia.Link,

        // A connector that is used by links with no connector defined on the model.
        // e.g. { name: 'rounded', args: { radius: 5 }} or a function
        defaultConnector: { name: 'normal' },

        // A router that is used by links with no router defined on the model.
        // e.g. { name: 'oneSide', args: { padding: 10 }} or a function
        defaultRouter: { name: 'normal' },

        defaultAnchor: { name: 'center' },

        defaultConnectionPoint: { name: 'bbox' },

        /* CONNECTING */

        connectionStrategy: null,

        // Check whether to add a new link to the graph when user clicks on an a magnet.
        validateMagnet: function(cellView, magnet) {
            return magnet.getAttribute('magnet') !== 'passive';
        },

        // Check whether to allow or disallow the link connection while an arrowhead end (source/target)
        // being changed.
        validateConnection: function(cellViewS, magnetS, cellViewT, magnetT, end, linkView) {
            return (end === 'target' ? cellViewT : cellViewS) instanceof joint.dia.ElementView;
        },

        /* EMBEDDING */

        // Enables embedding. Reparents the dragged element with elements under it and makes sure that
        // all links and elements are visible taken the level of embedding into account.
        embeddingMode: false,

        // Check whether to allow or disallow the element embedding while an element being translated.
        validateEmbedding: function(childView, parentView) {
            // by default all elements can be in relation child-parent
            return true;
        },

        // Determines the way how a cell finds a suitable parent when it's dragged over the paper.
        // The cell with the highest z-index (visually on the top) will be chosen.
        findParentBy: 'bbox', // 'bbox'|'center'|'origin'|'corner'|'topRight'|'bottomLeft'

        // If enabled only the element on the very front is taken into account for the embedding.
        // If disabled the elements under the dragged view are tested one by one
        // (from front to back) until a valid parent found.
        frontParentOnly: true,

        // Interactive flags. See online docs for the complete list of interactive flags.
        interactive: {
            labelMove: false
        },

        // When set to true the links can be pinned to the paper.
        // i.e. link source/target can be a point e.g. link.get('source') ==> { x: 100, y: 100 };
        linkPinning: true,

        // Custom validation after an interaction with a link ends.
        // Recognizes a function. If `false` is returned, the link is disallowed (removed or reverted)
        // (linkView, paper) => boolean
        allowLink: null,

        // Allowed number of mousemove events after which the pointerclick event will be still triggered.
        clickThreshold: 0,

        // Number of required mousemove events before the first pointermove event will be triggered.
        moveThreshold: 0,

        // The namespace, where all the cell views are defined.
        cellViewNamespace: joint.shapes,

        // The namespace, where all the cell views are defined.
        highlighterNamespace: joint.highlighters
    },

    events: {
        'dblclick': 'pointerdblclick',
        'click': 'pointerclick', // triggered alongside pointerdown and pointerup if no movement
        'touchend': 'pointerclick', // triggered alongside pointerdown and pointerup if no movement
        'contextmenu': 'contextmenu',
        'mousedown': 'pointerdown',
        'touchstart': 'pointerdown',
        'mouseover': 'mouseover',
        'mouseout': 'mouseout',
        'mouseenter': 'mouseenter',
        'mouseleave': 'mouseleave',
        'mousewheel': 'mousewheel',
        'DOMMouseScroll': 'mousewheel',
        'mouseenter .joint-cell': 'mouseenter',
        'mouseleave .joint-cell': 'mouseleave',
        'mouseenter .joint-tools': 'mouseenter',
        'mouseleave .joint-tools': 'mouseleave',
        'mousedown .joint-cell [event]': 'onevent', // interaction with cell with `event` attribute set
        'touchstart .joint-cell [event]': 'onevent',
        'mousedown .joint-cell [magnet]': 'onmagnet', // interaction with cell with `magnet` attribute set
        'touchstart .joint-cell [magnet]': 'onmagnet',
        'mousedown .joint-link .label': 'onlabel', // interaction with link label
        'touchstart .joint-link .label': 'onlabel',
        'dragstart .joint-cell image': 'onImageDragStart' // firefox fix
    },

    documentEvents: {
        'mousemove': 'pointermove',
        'touchmove': 'pointermove',
        'mouseup': 'pointerup',
        'touchend': 'pointerup',
        'touchcancel': 'pointerup'
    },

    _highlights: {},

    init: function() {

        joint.util.bindAll(this, 'pointerup');

        var model = this.model = this.options.model || new joint.dia.Graph;

        this.setGrid(this.options.drawGrid);
        this.cloneOptions();
        this.render();
        this.setDimensions();

        this.listenTo(model, 'add', this.onCellAdded)
            .listenTo(model, 'remove', this.removeView)
            .listenTo(model, 'reset', this.resetViews)
            .listenTo(model, 'sort', this._onSort)
            .listenTo(model, 'batch:stop', this._onBatchStop);

        this.on('cell:highlight', this.onCellHighlight)
            .on('cell:unhighlight', this.onCellUnhighlight)
            .on('scale translate', this.update);

        // Hold the value when mouse has been moved: when mouse moved, no click event will be triggered.
        this._mousemoved = 0;
        // Hash of all cell views.
        this._views = {};
        // Reference to the paper owner document
        this.$document = $(this.el.ownerDocument);
    },

    cloneOptions: function() {

        var options = this.options;

        // This is a fix for the case where two papers share the same options.
        // Changing origin.x for one paper would change the value of origin.x for the other.
        // This prevents that behavior.
        options.origin = joint.util.assign({}, options.origin);
        options.defaultConnector = joint.util.assign({}, options.defaultConnector);
        // Return the default highlighting options into the user specified options.
        options.highlighting = joint.util.defaultsDeep(
            {},
            options.highlighting,
            this.constructor.prototype.options.highlighting
        );
    },

    render: function() {

        this.$el.empty();

        this.svg = V('svg').attr({ width: '100%', height: '100%' }).node;
        this.viewport = V('g').addClass(joint.util.addClassNamePrefix('viewport')).node;
        this.defs = V('defs').node;
        this.tools = V('g').addClass(joint.util.addClassNamePrefix('tools-container')).node;
        // Append `<defs>` element to the SVG document. This is useful for filters and gradients.
        // It's desired to have the defs defined before the viewport (e.g. to make a PDF document pick up defs properly).
        V(this.svg).append([this.defs, this.viewport, this.tools]);

        this.$background = $('<div/>').addClass(joint.util.addClassNamePrefix('paper-background'));
        if (this.options.background) {
            this.drawBackground(this.options.background);
        }

        this.$grid = $('<div/>').addClass(joint.util.addClassNamePrefix('paper-grid'));
        if (this.options.drawGrid) {
            this.drawGrid();
        }

        this.$el.append(this.$background, this.$grid, this.svg);

        return this;
    },

    update: function() {

        if (this.options.drawGrid) {
            this.drawGrid();
        }

        if (this._background) {
            this.updateBackgroundImage(this._background);
        }

        return this;
    },

    // For storing the current transformation matrix (CTM) of the paper's viewport.
    _viewportMatrix: null,

    // For verifying whether the CTM is up-to-date. The viewport transform attribute
    // could have been manipulated directly.
    _viewportTransformString: null,

    matrix: function(ctm) {

        var viewport = this.viewport;

        // Getter:
        if (ctm === undefined) {

            var transformString = viewport.getAttribute('transform');

            if ((this._viewportTransformString || null) === transformString) {
                // It's ok to return the cached matrix. The transform attribute has not changed since
                // the matrix was stored.
                ctm = this._viewportMatrix;
            } else {
                // The viewport transform attribute has changed. Measure the matrix and cache again.
                ctm = viewport.getCTM();
                this._viewportMatrix = ctm;
                this._viewportTransformString = transformString;
            }

            // Clone the cached current transformation matrix.
            // If no matrix previously stored the identity matrix is returned.
            return V.createSVGMatrix(ctm);
        }

        // Setter:
        ctm = V.createSVGMatrix(ctm);
        ctmString = V.matrixToTransformString(ctm);
        viewport.setAttribute('transform', ctmString);
        this.tools.setAttribute('transform', ctmString);

        this._viewportMatrix = ctm;
        this._viewportTransformString = viewport.getAttribute('transform');

        return this;
    },

    clientMatrix: function() {

        return V.createSVGMatrix(this.viewport.getScreenCTM());
    },

    _sortDelayingBatches: ['add', 'to-front', 'to-back'],

    _onSort: function() {
        if (!this.model.hasActiveBatch(this._sortDelayingBatches)) {
            this.sortViews();
        }
    },

    _onBatchStop: function(data) {
        var name = data && data.batchName;
        if (this._sortDelayingBatches.includes(name) &&
            !this.model.hasActiveBatch(this._sortDelayingBatches)) {
            this.sortViews();
        }
    },

    onRemove: function() {

        //clean up all DOM elements/views to prevent memory leaks
        this.removeViews();
    },

    setDimensions: function(width, height) {

        width = this.options.width = width || this.options.width;
        height = this.options.height = height || this.options.height;

        this.$el.css({
            width: Math.round(width),
            height: Math.round(height)
        });

        this.trigger('resize', width, height);
    },

    setOrigin: function(ox, oy) {

        return this.translate(ox || 0, oy || 0, { absolute: true });
    },

    // Expand/shrink the paper to fit the content. Snap the width/height to the grid
    // defined in `gridWidth`, `gridHeight`. `padding` adds to the resulting width/height of the paper.
    // When options { fitNegative: true } it also translates the viewport in order to make all
    // the content visible.
    fitToContent: function(gridWidth, gridHeight, padding, opt) { // alternatively function(opt)

        if (joint.util.isObject(gridWidth)) {
            // first parameter is an option object
            opt = gridWidth;
            gridWidth = opt.gridWidth || 1;
            gridHeight = opt.gridHeight || 1;
            padding = opt.padding || 0;

        } else {

            opt = opt || {};
            gridWidth = gridWidth || 1;
            gridHeight = gridHeight || 1;
            padding = padding || 0;
        }

        padding = joint.util.normalizeSides(padding);

        // Calculate the paper size to accomodate all the graph's elements.
        var bbox = V(this.viewport).getBBox();

        var currentScale = this.scale();
        var currentTranslate = this.translate();

        bbox.x *= currentScale.sx;
        bbox.y *= currentScale.sy;
        bbox.width *= currentScale.sx;
        bbox.height *= currentScale.sy;

        var calcWidth = Math.max(Math.ceil((bbox.width + bbox.x) / gridWidth), 1) * gridWidth;
        var calcHeight = Math.max(Math.ceil((bbox.height + bbox.y) / gridHeight), 1) * gridHeight;

        var tx = 0;
        var ty = 0;

        if ((opt.allowNewOrigin == 'negative' && bbox.x < 0) || (opt.allowNewOrigin == 'positive' && bbox.x >= 0) || opt.allowNewOrigin == 'any') {
            tx = Math.ceil(-bbox.x / gridWidth) * gridWidth;
            tx += padding.left;
            calcWidth += tx;
        }

        if ((opt.allowNewOrigin == 'negative' && bbox.y < 0) || (opt.allowNewOrigin == 'positive' && bbox.y >= 0) || opt.allowNewOrigin == 'any') {
            ty = Math.ceil(-bbox.y / gridHeight) * gridHeight;
            ty += padding.top;
            calcHeight += ty;
        }

        calcWidth += padding.right;
        calcHeight += padding.bottom;

        // Make sure the resulting width and height are greater than minimum.
        calcWidth = Math.max(calcWidth, opt.minWidth || 0);
        calcHeight = Math.max(calcHeight, opt.minHeight || 0);

        // Make sure the resulting width and height are lesser than maximum.
        calcWidth = Math.min(calcWidth, opt.maxWidth || Number.MAX_VALUE);
        calcHeight = Math.min(calcHeight, opt.maxHeight || Number.MAX_VALUE);

        var dimensionChange = calcWidth != this.options.width || calcHeight != this.options.height;
        var originChange = tx != currentTranslate.tx || ty != currentTranslate.ty;

        // Change the dimensions only if there is a size discrepency or an origin change
        if (originChange) {
            this.translate(tx, ty);
        }
        if (dimensionChange) {
            this.setDimensions(calcWidth, calcHeight);
        }
    },

    scaleContentToFit: function(opt) {

        var contentBBox = this.getContentBBox();

        if (!contentBBox.width || !contentBBox.height) return;

        opt = opt || {};

        joint.util.defaults(opt, {
            padding: 0,
            preserveAspectRatio: true,
            scaleGrid: null,
            minScale: 0,
            maxScale: Number.MAX_VALUE
            //minScaleX
            //minScaleY
            //maxScaleX
            //maxScaleY
            //fittingBBox
        });

        var padding = opt.padding;

        var minScaleX = opt.minScaleX || opt.minScale;
        var maxScaleX = opt.maxScaleX || opt.maxScale;
        var minScaleY = opt.minScaleY || opt.minScale;
        var maxScaleY = opt.maxScaleY || opt.maxScale;

        var fittingBBox;
        if (opt.fittingBBox) {
            fittingBBox = opt.fittingBBox;
        } else {
            var currentTranslate = this.translate();
            fittingBBox = {
                x: currentTranslate.tx,
                y: currentTranslate.ty,
                width: this.options.width,
                height: this.options.height
            };
        }

        fittingBBox = g.rect(fittingBBox).moveAndExpand({
            x: padding,
            y: padding,
            width: -2 * padding,
            height: -2 * padding
        });

        var currentScale = this.scale();

        var newSx = fittingBBox.width / contentBBox.width * currentScale.sx;
        var newSy = fittingBBox.height / contentBBox.height * currentScale.sy;

        if (opt.preserveAspectRatio) {
            newSx = newSy = Math.min(newSx, newSy);
        }

        // snap scale to a grid
        if (opt.scaleGrid) {

            var gridSize = opt.scaleGrid;

            newSx = gridSize * Math.floor(newSx / gridSize);
            newSy = gridSize * Math.floor(newSy / gridSize);
        }

        // scale min/max boundaries
        newSx = Math.min(maxScaleX, Math.max(minScaleX, newSx));
        newSy = Math.min(maxScaleY, Math.max(minScaleY, newSy));

        this.scale(newSx, newSy);

        var contentTranslation = this.getContentBBox();

        var newOx = fittingBBox.x - contentTranslation.x;
        var newOy = fittingBBox.y - contentTranslation.y;

        this.translate(newOx, newOy);
    },

    // Return the dimensions of the content area in local units (without transformations).
    getContentArea: function() {

        return V(this.viewport).getBBox();
    },

    // Return the dimensions of the content bbox in client units (as it appears on screen).
    getContentBBox: function() {

        var crect = this.viewport.getBoundingClientRect();

        // Using Screen CTM was the only way to get the real viewport bounding box working in both
        // Google Chrome and Firefox.
        var clientCTM = this.clientMatrix();

        // for non-default origin we need to take the viewport translation into account
        var currentTranslate = this.translate();

        return g.rect({
            x: crect.left - clientCTM.e + currentTranslate.tx,
            y: crect.top - clientCTM.f + currentTranslate.ty,
            width: crect.width,
            height: crect.height
        });
    },

    // Returns a geometry rectangle represeting the entire
    // paper area (coordinates from the left paper border to the right one
    // and the top border to the bottom one).
    getArea: function() {

        return this.paperToLocalRect({
            x: 0,
            y: 0,
            width: this.options.width,
            height: this.options.height
        });
    },

    getRestrictedArea: function() {

        var restrictedArea;

        if (joint.util.isFunction(this.options.restrictTranslate)) {
            // A method returning a bounding box
            restrictedArea = this.options.restrictTranslate.apply(this, arguments);
        } else if (this.options.restrictTranslate === true) {
            // The paper area
            restrictedArea = this.getArea();
        } else {
            // Either false or a bounding box
            restrictedArea = this.options.restrictTranslate || null;
        }

        return restrictedArea;
    },

    createViewForModel: function(cell) {

        // A class taken from the paper options.
        var optionalViewClass;

        // A default basic class (either dia.ElementView or dia.LinkView)
        var defaultViewClass;

        // A special class defined for this model in the corresponding namespace.
        // e.g. joint.shapes.basic.Rect searches for joint.shapes.basic.RectView
        var namespace = this.options.cellViewNamespace;
        var type = cell.get('type') + 'View';
        var namespaceViewClass = joint.util.getByPath(namespace, type, '.');

        if (cell.isLink()) {
            optionalViewClass = this.options.linkView;
            defaultViewClass = joint.dia.LinkView;
        } else {
            optionalViewClass = this.options.elementView;
            defaultViewClass = joint.dia.ElementView;
        }

        // a) the paper options view is a class (deprecated)
        //  1. search the namespace for a view
        //  2. if no view was found, use view from the paper options
        // b) the paper options view is a function
        //  1. call the function from the paper options
        //  2. if no view was return, search the namespace for a view
        //  3. if no view was found, use the default
        var ViewClass = (optionalViewClass.prototype instanceof Backbone.View)
            ? namespaceViewClass || optionalViewClass
            : optionalViewClass.call(this, cell) || namespaceViewClass || defaultViewClass;

        return new ViewClass({
            model: cell,
            interactive: this.options.interactive
        });
    },

    onCellAdded: function(cell, graph, opt) {

        if (this.options.async && opt.async !== false && joint.util.isNumber(opt.position)) {

            this._asyncCells = this._asyncCells || [];
            this._asyncCells.push(cell);

            if (opt.position == 0) {

                if (this._frameId) throw new Error('another asynchronous rendering in progress');

                this.asyncRenderViews(this._asyncCells, opt);
                delete this._asyncCells;
            }

        } else {

            this.renderView(cell);
        }
    },

    removeView: function(cell) {

        var view = this._views[cell.id];

        if (view) {
            view.remove();
            delete this._views[cell.id];
        }

        return view;
    },

    renderView: function(cell) {

        var view = this._views[cell.id] = this.createViewForModel(cell);

        V(this.viewport).append(view.el);
        view.paper = this;
        view.render();

        return view;
    },

    onImageDragStart: function() {
        // This is the only way to prevent image dragging in Firefox that works.
        // Setting -moz-user-select: none, draggable="false" attribute or user-drag: none didn't help.

        return false;
    },

    beforeRenderViews: function(cells) {

        // Make sure links are always added AFTER elements.
        // They wouldn't find their sources/targets in the DOM otherwise.
        cells.sort(function(a) { return (a.isLink()) ? 1 : -1; });

        return cells;
    },

    afterRenderViews: function() {

        this.sortViews();
    },

    resetViews: function(cellsCollection, opt) {

        // clearing views removes any event listeners
        this.removeViews();

        var cells = cellsCollection.models.slice();

        // `beforeRenderViews()` can return changed cells array (e.g sorted).
        cells = this.beforeRenderViews(cells, opt) || cells;

        this.cancelRenderViews();

        if (this.options.async) {

            this.asyncRenderViews(cells, opt);
            // Sort the cells once all elements rendered (see asyncRenderViews()).

        } else {

            for (var i = 0, n = cells.length; i < n; i++) {
                this.renderView(cells[i]);
            }

            // Sort the cells in the DOM manually as we might have changed the order they
            // were added to the DOM (see above).
            this.sortViews();
        }
    },

    cancelRenderViews: function() {
        if (this._frameId) {
            joint.util.cancelFrame(this._frameId);
            delete this._frameId;
        }
    },

    removeViews: function() {

        joint.util.invoke(this._views, 'remove');

        this._views = {};
    },

    asyncBatchAdded: joint.util.noop,

    asyncRenderViews: function(cells, opt) {

        if (this._frameId) {

            var batchSize = (this.options.async && this.options.async.batchSize) || 50;
            var batchCells = cells.splice(0, batchSize);

            batchCells.forEach(function(cell) {

                // The cell has to be part of the graph.
                // There is a chance in asynchronous rendering
                // that a cell was removed before it's rendered to the paper.
                if (cell.graph === this.model) this.renderView(cell);

            }, this);

            this.asyncBatchAdded();
        }

        if (!cells.length) {

            // No cells left to render.
            delete this._frameId;
            this.afterRenderViews(opt);
            this.trigger('render:done', opt);

        } else {

            // Schedule a next batch to render.
            this._frameId = joint.util.nextFrame(function() {
                this.asyncRenderViews(cells, opt);
            }, this);
        }
    },

    sortViews: function() {

        // Run insertion sort algorithm in order to efficiently sort DOM elements according to their
        // associated model `z` attribute.

        var $cells = $(this.viewport).children('[model-id]');
        var cells = this.model.get('cells');

        joint.util.sortElements($cells, function(a, b) {

            var cellA = cells.get($(a).attr('model-id'));
            var cellB = cells.get($(b).attr('model-id'));

            return (cellA.get('z') || 0) > (cellB.get('z') || 0) ? 1 : -1;
        });
    },

    scale: function(sx, sy, ox, oy) {

        // getter
        if (sx === undefined) {
            return V.matrixToScale(this.matrix());
        }

        // setter
        if (sy === undefined) {
            sy = sx;
        }
        if (ox === undefined) {
            ox = 0;
            oy = 0;
        }

        var translate = this.translate();

        if (ox || oy || translate.tx || translate.ty) {
            var newTx = translate.tx - ox * (sx - 1);
            var newTy = translate.ty - oy * (sy - 1);
            this.translate(newTx, newTy);
        }

        var ctm = this.matrix();
        ctm.a = sx || 0;
        ctm.d = sy || 0;

        this.matrix(ctm);

        this.trigger('scale', sx, sy, ox, oy);

        return this;
    },

    // Experimental - do not use in production.
    rotate: function(angle, cx, cy) {

        // getter
        if (angle === undefined) {
            return V.matrixToRotate(this.matrix());
        }

        // setter

        // If the origin is not set explicitely, rotate around the center. Note that
        // we must use the plain bounding box (`this.el.getBBox()` instead of the one that gives us
        // the real bounding box (`bbox()`) including transformations).
        if (cx === undefined) {
            var bbox = this.viewport.getBBox();
            cx = bbox.width / 2;
            cy = bbox.height / 2;
        }

        var ctm = this.matrix().translate(cx,cy).rotate(angle).translate(-cx,-cy);
        this.matrix(ctm);

        return this;
    },

    translate: function(tx, ty) {

        // getter
        if (tx === undefined) {
            return V.matrixToTranslate(this.matrix());
        }

        // setter

        var ctm = this.matrix();
        ctm.e = tx || 0;
        ctm.f = ty || 0;

        this.matrix(ctm);

        var newTranslate = this.translate();
        var origin = this.options.origin;
        origin.x = newTranslate.tx;
        origin.y = newTranslate.ty;

        this.trigger('translate', newTranslate.tx, newTranslate.ty);

        if (this.options.drawGrid) {
            this.drawGrid();
        }

        return this;
    },

    // Find the first view climbing up the DOM tree starting at element `el`. Note that `el` can also
    // be a selector or a jQuery object.
    findView: function($el) {

        var el = joint.util.isString($el)
            ? this.viewport.querySelector($el)
            : $el instanceof $ ? $el[0] : $el;

        while (el && el !== this.el && el !== document) {

            var id = el.getAttribute('model-id');
            if (id) return this._views[id];

            el = el.parentNode;
        }

        return undefined;
    },

    // Find a view for a model `cell`. `cell` can also be a string or number representing a model `id`.
    findViewByModel: function(cell) {

        var id = (joint.util.isString(cell) || joint.util.isNumber(cell)) ? cell : (cell && cell.id);

        return this._views[id];
    },

    // Find all views at given point
    findViewsFromPoint: function(p) {

        p = g.point(p);

        var views = this.model.getElements().map(this.findViewByModel, this);

        return views.filter(function(view) {
            return view && view.vel.getBBox({ target: this.viewport }).containsPoint(p);
        }, this);
    },

    // Find all views in given area
    findViewsInArea: function(rect, opt) {

        opt = joint.util.defaults(opt || {}, { strict: false });
        rect = g.rect(rect);

        var views = this.model.getElements().map(this.findViewByModel, this);
        var method = opt.strict ? 'containsRect' : 'intersect';

        return views.filter(function(view) {
            return view && rect[method](view.vel.getBBox({ target: this.viewport }));
        }, this);
    },

    removeTools: function() {
        joint.dia.CellView.dispatchToolsEvent(this, 'remove');
        return this;
    },

    hideTools: function() {
        joint.dia.CellView.dispatchToolsEvent(this, 'hide');
        return this;
    },

    showTools: function() {
        joint.dia.CellView.dispatchToolsEvent(this, 'show');
        return this;
    },

    getModelById: function(id) {

        return this.model.getCell(id);
    },

    snapToGrid: function(x, y) {

        // Convert global coordinates to the local ones of the `viewport`. Otherwise,
        // improper transformation would be applied when the viewport gets transformed (scaled/rotated).
        return this.clientToLocalPoint(x, y).snapToGrid(this.options.gridSize);
    },

    localToPaperPoint: function(x, y) {
        // allow `x` to be a point and `y` undefined
        var localPoint = g.Point(x, y);
        var paperPoint = V.transformPoint(localPoint, this.matrix());
        return g.Point(paperPoint);
    },

    localToPaperRect: function(x, y, width, height) {
        // allow `x` to be a rectangle and rest arguments undefined
        var localRect = g.Rect(x, y);
        var paperRect = V.transformRect(localRect, this.matrix());
        return g.Rect(paperRect);
    },

    paperToLocalPoint: function(x, y) {
        // allow `x` to be a point and `y` undefined
        var paperPoint = g.Point(x, y);
        var localPoint = V.transformPoint(paperPoint, this.matrix().inverse());
        return g.Point(localPoint);
    },

    paperToLocalRect: function(x, y, width, height) {
        // allow `x` to be a rectangle and rest arguments undefined
        var paperRect = g.Rect(x, y, width, height);
        var localRect = V.transformRect(paperRect, this.matrix().inverse());
        return g.Rect(localRect);
    },

    localToClientPoint: function(x, y) {
        // allow `x` to be a point and `y` undefined
        var localPoint = g.Point(x, y);
        var clientPoint = V.transformPoint(localPoint, this.clientMatrix());
        return g.Point(clientPoint);
    },

    localToClientRect: function(x, y, width, height) {
        // allow `x` to be a point and `y` undefined
        var localRect = g.Rect(x, y, width, height);
        var clientRect = V.transformRect(localRect, this.clientMatrix());
        return g.Rect(clientRect);
    },

    // Transform client coordinates to the paper local coordinates.
    // Useful when you have a mouse event object and you'd like to get coordinates
    // inside the paper that correspond to `evt.clientX` and `evt.clientY` point.
    // Example: var localPoint = paper.clientToLocalPoint({ x: evt.clientX, y: evt.clientY });
    clientToLocalPoint: function(x, y) {
        // allow `x` to be a point and `y` undefined
        var clientPoint = g.Point(x, y);
        var localPoint = V.transformPoint(clientPoint, this.clientMatrix().inverse());
        return g.Point(localPoint);
    },

    clientToLocalRect: function(x, y, width, height) {
        // allow `x` to be a point and `y` undefined
        var clientRect = g.Rect(x, y, width, height);
        var localRect = V.transformRect(clientRect, this.clientMatrix().inverse());
        return g.Rect(localRect);
    },

    localToPagePoint: function(x, y) {

        return this.localToPaperPoint(x, y).offset(this.pageOffset());
    },

    localToPageRect: function(x, y, width, height) {

        return this.localToPaperRect(x, y, width, height).moveAndExpand(this.pageOffset());
    },

    pageToLocalPoint: function(x, y) {

        var pagePoint = g.Point(x, y);
        var paperPoint = pagePoint.difference(this.pageOffset());
        return this.paperToLocalPoint(paperPoint);
    },

    pageToLocalRect: function(x, y, width, height) {

        var pageOffset = this.pageOffset();
        var paperRect = g.Rect(x, y, width, height);
        paperRect.x -= pageOffset.x;
        paperRect.y -= pageOffset.y;
        return this.paperToLocalRect(paperRect);
    },

    clientOffset: function() {

        var clientRect = this.svg.getBoundingClientRect();
        return g.Point(clientRect.left, clientRect.top);
    },

    pageOffset: function() {

        return this.clientOffset().offset(window.scrollX, window.scrollY);
    },

    linkAllowed: function(linkView) {

        if (!(linkView instanceof joint.dia.LinkView)) {
            throw new Error('Must provide a linkView.');
        }

        var link = linkView.model;
        var paperOptions = this.options;
        var graph = this.model;
        var ns = graph.constructor.validations;

        if (!paperOptions.multiLinks) {
            if (!ns.multiLinks.call(this, graph, link)) return false;
        }

        if (!paperOptions.linkPinning) {
            // Link pinning is not allowed and the link is not connected to the target.
            if (!ns.linkPinning.call(this, graph, link)) return false;
        }

        if (typeof paperOptions.allowLink === 'function') {
            if (!paperOptions.allowLink.call(this, linkView, this)) return false;
        }

        return true;
    },

    getDefaultLink: function(cellView, magnet) {

        return joint.util.isFunction(this.options.defaultLink)
        // default link is a function producing link model
            ? this.options.defaultLink.call(this, cellView, magnet)
        // default link is the Backbone model
            : this.options.defaultLink.clone();
    },

    // Cell highlighting.
    // ------------------

    resolveHighlighter: function(opt) {

        opt = opt || {};
        var highlighterDef = opt.highlighter;
        var paperOpt = this.options;

        /*
            Expecting opt.highlighter to have the following structure:
            {
                name: 'highlighter-name',
                options: {
                    some: 'value'
                }
            }
        */
        if (highlighterDef === undefined) {

            // check for built-in types
            var type = ['embedding', 'connecting', 'magnetAvailability', 'elementAvailability'].find(function(type) {
                return !!opt[type];
            });

            highlighterDef = (type && paperOpt.highlighting[type]) || paperOpt.highlighting['default'];
        }

        // Do nothing if opt.highlighter is falsey.
        // This allows the case to not highlight cell(s) in certain cases.
        // For example, if you want to NOT highlight when embedding elements.
        if (!highlighterDef) return false;

        // Allow specifying a highlighter by name.
        if (joint.util.isString(highlighterDef)) {
            highlighterDef = {
                name: highlighterDef
            };
        }

        var name = highlighterDef.name;
        var highlighter = paperOpt.highlighterNamespace[name];

        // Highlighter validation
        if (!highlighter) {
            throw new Error('Unknown highlighter ("' + name + '")');
        }
        if (typeof highlighter.highlight !== 'function') {
            throw new Error('Highlighter ("' + name + '") is missing required highlight() method');
        }
        if (typeof highlighter.unhighlight !== 'function') {
            throw new Error('Highlighter ("' + name + '") is missing required unhighlight() method');
        }

        return {
            highlighter: highlighter,
            options: highlighterDef.options || {},
            name: name
        };
    },

    onCellHighlight: function(cellView, magnetEl, opt) {

        opt = this.resolveHighlighter(opt);
        if (!opt) return;
        if (!magnetEl.id) {
            magnetEl.id = V.uniqueId();
        }

        var key = opt.name + magnetEl.id + JSON.stringify(opt.options);
        if (!this._highlights[key]) {

            var highlighter = opt.highlighter;
            highlighter.highlight(cellView, magnetEl, joint.util.assign({}, opt.options));

            this._highlights[key] = {
                cellView: cellView,
                magnetEl: magnetEl,
                opt: opt.options,
                highlighter: highlighter
            };
        }
    },

    onCellUnhighlight: function(cellView, magnetEl, opt) {

        opt = this.resolveHighlighter(opt);
        if (!opt) return;

        var key = opt.name + magnetEl.id + JSON.stringify(opt.options);
        var highlight = this._highlights[key];
        if (highlight) {

            // Use the cellView and magnetEl that were used by the highlighter.highlight() method.
            highlight.highlighter.unhighlight(highlight.cellView, highlight.magnetEl, highlight.opt);

            this._highlights[key] = null;
        }
    },

    // Interaction.
    // ------------

    pointerdblclick: function(evt) {

        evt.preventDefault();

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;

        var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });

        if (view) {
            view.pointerdblclick(evt, localPoint.x, localPoint.y);

        } else {
            this.trigger('blank:pointerdblclick', evt, localPoint.x, localPoint.y);
        }
    },

    pointerclick: function(evt) {

        // Trigger event only if mouse has not moved.
        if (this._mousemoved <= this.options.clickThreshold) {

            evt = joint.util.normalizeEvent(evt);

            var view = this.findView(evt.target);
            if (this.guard(evt, view)) return;

            var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });

            if (view) {
                view.pointerclick(evt, localPoint.x, localPoint.y);

            } else {
                this.trigger('blank:pointerclick', evt, localPoint.x, localPoint.y);
            }
        }
    },

    contextmenu: function(evt) {

        if (this.options.preventContextMenu) evt.preventDefault();

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;

        var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });

        if (view) {
            view.contextmenu(evt, localPoint.x, localPoint.y);

        } else {
            this.trigger('blank:contextmenu', evt, localPoint.x, localPoint.y);
        }
    },

    pointerdown: function(evt) {

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;

        var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });

        if (view) {

            evt.preventDefault();
            view.pointerdown(evt, localPoint.x, localPoint.y);

        } else {

            if (this.options.preventDefaultBlankAction) evt.preventDefault();

            this.trigger('blank:pointerdown', evt, localPoint.x, localPoint.y);
        }

        this.delegateDragEvents(view, evt.data);
    },

    pointermove: function(evt) {

        evt.preventDefault();

        // mouse moved counter
        var data = this.eventData(evt);
        data.mousemoved || (data.mousemoved = 0);
        var mousemoved = ++data.mousemoved;
        if (mousemoved <= this.options.moveThreshold) return;

        evt = joint.util.normalizeEvent(evt);

        var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });

        var view = data.sourceView;
        if (view) {
            view.pointermove(evt, localPoint.x, localPoint.y);
        } else {
            this.trigger('blank:pointermove', evt, localPoint.x, localPoint.y);
        }

        this.eventData(evt, data);
    },

    pointerup: function(evt) {

        this.undelegateDocumentEvents();

        evt = joint.util.normalizeEvent(evt);

        var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });

        var view = this.eventData(evt).sourceView;
        if (view) {
            view.pointerup(evt, localPoint.x, localPoint.y);
        } else {
            this.trigger('blank:pointerup', evt, localPoint.x, localPoint.y);
        }

        this.delegateEvents();
    },

    mouseover: function(evt) {

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;

        if (view) {
            view.mouseover(evt);

        } else {
            if (this.el === evt.target) return; // prevent border of paper from triggering this
            this.trigger('blank:mouseover', evt);
        }
    },

    mouseout: function(evt) {

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;

        if (view) {
            view.mouseout(evt);

        } else {
            if (this.el === evt.target) return; // prevent border of paper from triggering this
            this.trigger('blank:mouseout', evt);
        }
    },

    mouseenter: function(evt) {

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;
        var relatedView = this.findView(evt.relatedTarget);
        if (view) {
            // mouse moved from tool over view?
            if (relatedView === view) return;
            view.mouseenter(evt);
        } else {
            if (relatedView) return;
            // `paper` (more descriptive), not `blank`
            this.trigger('paper:mouseenter', evt);
        }
    },

    mouseleave: function(evt) {

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;
        var relatedView = this.findView(evt.relatedTarget);
        if (view) {
            // mouse moved from view over tool?
            if (relatedView === view) return;
            view.mouseleave(evt);
        } else {
            if (relatedView) return;
            // `paper` (more descriptive), not `blank`
            this.trigger('paper:mouseleave', evt);
        }
    },

    mousewheel: function(evt) {

        evt = joint.util.normalizeEvent(evt);

        var view = this.findView(evt.target);
        if (this.guard(evt, view)) return;

        var originalEvent = evt.originalEvent;
        var localPoint = this.snapToGrid({ x: originalEvent.clientX, y: originalEvent.clientY });
        var delta = Math.max(-1, Math.min(1, (originalEvent.wheelDelta || -originalEvent.detail)));

        if (view) {
            view.mousewheel(evt, localPoint.x, localPoint.y, delta);

        } else {
            this.trigger('blank:mousewheel', evt, localPoint.x, localPoint.y, delta);
        }
    },

    onevent: function(evt) {

        var eventNode = evt.currentTarget;
        var eventName = eventNode.getAttribute('event');
        if (eventName) {
            var view = this.findView(eventNode);
            if (view) {

                evt = joint.util.normalizeEvent(evt);
                if (this.guard(evt, view)) return;

                var localPoint = this.snapToGrid({ x: evt.clientX, y: evt.clientY });
                view.onevent(evt, eventName, localPoint.x, localPoint.y);
            }
        }
    },

    onmagnet: function(evt) {

        var magnetNode = evt.currentTarget;
        var magnetValue = magnetNode.getAttribute('magnet');
        if (magnetValue) {
            var view = this.findView(magnetNode);
            if (view) {

                evt = joint.util.normalizeEvent(evt);
                if (this.guard(evt, view)) return;
                if (!this.options.validateMagnet(view, magnetNode)) return;

                var localPoint = this.snapToGrid(evt.clientX, evt.clientY);
                view.onmagnet(evt, localPoint.x, localPoint.y);
            }
        }
    },

    onlabel: function(evt) {

        var labelNode = evt.currentTarget;
        var view = this.findView(labelNode);
        if (view) {

            evt = joint.util.normalizeEvent(evt);
            if (this.guard(evt, view)) return;

            var localPoint = this.snapToGrid(evt.clientX, evt.clientY);
            view.onlabel(evt, localPoint.x, localPoint.y);
        }
    },

    delegateDragEvents: function(view, data) {

        data || (data = {});
        this.eventData({ data: data }, { sourceView: view || null, mousemoved: 0 });
        this.delegateDocumentEvents(null, data);
        this.undelegateEvents();
    },

    // Guard the specified event. If the event is not interesting, guard returns `true`.
    // Otherwise, it returns `false`.
    guard: function(evt, view) {

        if (this.options.guard && this.options.guard(evt, view)) {
            return true;
        }

        if (evt.data && evt.data.guarded !== undefined) {
            return evt.data.guarded;
        }

        if (view && view.model && (view.model instanceof joint.dia.Cell)) {
            return false;
        }

        if (this.svg === evt.target || this.el === evt.target || $.contains(this.svg, evt.target)) {
            return false;
        }

        return true;    // Event guarded. Paper should not react on it in any way.
    },

    setGridSize: function(gridSize) {

        this.options.gridSize = gridSize;

        if (this.options.drawGrid) {
            this.drawGrid();
        }

        return this;
    },

    clearGrid: function() {

        if (this.$grid) {
            this.$grid.css('backgroundImage', 'none');
        }
        return this;
    },

    _getGriRefs: function() {

        if (!this._gridCache) {

            this._gridCache = {
                root: V('svg', { width: '100%', height: '100%' }, V('defs')),
                patterns: {},
                add: function(id, vel) {
                    V(this.root.node.childNodes[0]).append(vel);
                    this.patterns[id] = vel;
                    this.root.append(V('rect', { width: "100%", height: "100%", fill: 'url(#' + id + ')' }));
                },
                get: function(id) {
                    return  this.patterns[id]
                },
                exist: function(id) {
                    return this.patterns[id] !== undefined;
                }
            }
        }

        return this._gridCache;
    },

    setGrid: function(drawGrid) {

        this.clearGrid();

        this._gridCache = null;
        this._gridSettings = [];

        var optionsList = Array.isArray(drawGrid) ? drawGrid : [drawGrid || {}];
        optionsList.forEach(function(item) {
            this._gridSettings.push.apply(this._gridSettings, this._resolveDrawGridOption(item));
        }, this);
        return this;
    },

    _resolveDrawGridOption: function(opt) {

        var namespace = this.constructor.gridPatterns;
        if (joint.util.isString(opt) && Array.isArray(namespace[opt])) {
            return namespace[opt].map(function(item) {
                return joint.util.assign({}, item);
            });
        }

        var options = opt || { args: [{}] };
        var isArray = Array.isArray(options);
        var name = options.name;

        if (!isArray && !name && !options.markup ) {
            name = 'dot';
        }

        if (name && Array.isArray(namespace[name])) {
            var pattern = namespace[name].map(function(item) {
                return joint.util.assign({}, item);
            });

            var args = Array.isArray(options.args) ? options.args : [options.args || {}];

            joint.util.defaults(args[0], joint.util.omit(opt, 'args'));
            for (var i = 0; i < args.length; i++) {
                if (pattern[i]) {
                    joint.util.assign(pattern[i], args[i]);
                }
            }
            return pattern;
        }

        return isArray ? options : [options];
    },

    drawGrid: function(opt) {

        var gridSize = this.options.gridSize;
        if (gridSize <= 1) {
            return this.clearGrid();
        }

        var localOptions = Array.isArray(opt) ? opt : [opt];

        var ctm = this.matrix();
        var refs = this._getGriRefs();

        this._gridSettings.forEach(function(gridLayerSetting, index) {

            var id = 'pattern_'  + index;
            var options = joint.util.merge(gridLayerSetting, localOptions[index], {
                sx: ctm.a || 1,
                sy: ctm.d || 1,
                ox: ctm.e || 0,
                oy: ctm.f || 0
            });

            options.width = gridSize * (ctm.a || 1) * (options.scaleFactor || 1);
            options.height = gridSize * (ctm.d || 1) * (options.scaleFactor || 1);

            if (!refs.exist(id)) {
                refs.add(id, V('pattern', { id: id, patternUnits: 'userSpaceOnUse' }, V(options.markup)));
            }

            var patternDefVel = refs.get(id);

            if (joint.util.isFunction(options.update)) {
                options.update(patternDefVel.node.childNodes[0], options);
            }

            var x = options.ox % options.width;
            if (x < 0) x += options.width;

            var y = options.oy % options.height;
            if (y < 0) y += options.height;

            patternDefVel.attr({
                x: x,
                y: y,
                width: options.width,
                height: options.height
            });
        });

        var patternUri = new XMLSerializer().serializeToString(refs.root.node);
        patternUri = 'url(data:image/svg+xml;base64,' + btoa(patternUri) + ')';

        this.$grid.css('backgroundImage', patternUri);

        return this;
    },

    updateBackgroundImage: function(opt) {

        opt = opt || {};

        var backgroundPosition = opt.position || 'center';
        var backgroundSize = opt.size || 'auto auto';

        var currentScale = this.scale();
        var currentTranslate = this.translate();

        // backgroundPosition
        if (joint.util.isObject(backgroundPosition)) {
            var x = currentTranslate.tx + (currentScale.sx * (backgroundPosition.x || 0));
            var y = currentTranslate.ty + (currentScale.sy * (backgroundPosition.y || 0));
            backgroundPosition = x + 'px ' + y + 'px';
        }

        // backgroundSize
        if (joint.util.isObject(backgroundSize)) {
            backgroundSize = g.rect(backgroundSize).scale(currentScale.sx, currentScale.sy);
            backgroundSize = backgroundSize.width + 'px ' + backgroundSize.height + 'px';
        }

        this.$background.css({
            backgroundSize: backgroundSize,
            backgroundPosition: backgroundPosition
        });
    },

    drawBackgroundImage: function(img, opt) {

        // Clear the background image if no image provided
        if (!(img instanceof HTMLImageElement)) {
            this.$background.css('backgroundImage', '');
            return;
        }

        opt = opt || {};

        var backgroundImage;
        var backgroundSize = opt.size;
        var backgroundRepeat = opt.repeat || 'no-repeat';
        var backgroundOpacity = opt.opacity || 1;
        var backgroundQuality = Math.abs(opt.quality) || 1;
        var backgroundPattern = this.constructor.backgroundPatterns[joint.util.camelCase(backgroundRepeat)];

        if (joint.util.isFunction(backgroundPattern)) {
            // 'flip-x', 'flip-y', 'flip-xy', 'watermark' and custom
            img.width *= backgroundQuality;
            img.height *= backgroundQuality;
            var canvas = backgroundPattern(img, opt);
            if (!(canvas instanceof HTMLCanvasElement)) {
                throw new Error('dia.Paper: background pattern must return an HTML Canvas instance');
            }

            backgroundImage = canvas.toDataURL('image/png');
            backgroundRepeat = 'repeat';
            if (joint.util.isObject(backgroundSize)) {
                // recalculate the tile size if an object passed in
                backgroundSize.width *= canvas.width / img.width;
                backgroundSize.height *= canvas.height / img.height;
            } else if (backgroundSize === undefined) {
                // calcule the tile size if no provided
                opt.size = {
                    width: canvas.width / backgroundQuality,
                    height: canvas.height / backgroundQuality
                };
            }
        } else {
            // backgroundRepeat:
            // no-repeat', 'round', 'space', 'repeat', 'repeat-x', 'repeat-y'
            backgroundImage = img.src;
            if (backgroundSize === undefined) {
                // pass the image size for  the backgroundSize if no size provided
                opt.size = {
                    width: img.width,
                    height: img.height
                };
            }
        }

        this.$background.css({
            opacity: backgroundOpacity,
            backgroundRepeat: backgroundRepeat,
            backgroundImage: 'url(' + backgroundImage + ')'
        });

        this.updateBackgroundImage(opt);
    },

    updateBackgroundColor: function(color) {

        this.$el.css('backgroundColor', color || '');
    },

    drawBackground: function(opt) {

        opt = opt || {};

        this.updateBackgroundColor(opt.color);

        if (opt.image) {
            opt = this._background = joint.util.cloneDeep(opt);
            var img = document.createElement('img');
            img.onload = this.drawBackgroundImage.bind(this, img, opt);
            img.src = opt.image;
        } else {
            this.drawBackgroundImage(null);
            this._background = null;
        }

        return this;
    },

    setInteractivity: function(value) {

        this.options.interactive = value;

        joint.util.invoke(this._views, 'setInteractivity', value);
    },

    // Paper definitions.
    // ------------------

    isDefined: function(defId) {

        return !!this.svg.getElementById(defId);
    },

    defineFilter: function(filter) {

        if (!joint.util.isObject(filter)) {
            throw new TypeError('dia.Paper: defineFilter() requires 1. argument to be an object.');
        }

        var filterId = filter.id;
        var name = filter.name;
        // Generate a hash code from the stringified filter definition. This gives us
        // a unique filter ID for different definitions.
        if (!filterId) {
            filterId = name + this.svg.id + joint.util.hashCode(JSON.stringify(filter));
        }
        // If the filter already exists in the document,
        // we're done and we can just use it (reference it using `url()`).
        // If not, create one.
        if (!this.isDefined(filterId)) {

            var namespace = joint.util.filter;
            var filterSVGString = namespace[name] && namespace[name](filter.args || {});
            if (!filterSVGString) {
                throw new Error('Non-existing filter ' + name);
            }

            // Set the filter area to be 3x the bounding box of the cell
            // and center the filter around the cell.
            var filterAttrs = joint.util.assign({
                filterUnits: 'objectBoundingBox',
                x: -1,
                y: -1,
                width: 3,
                height: 3
            }, filter.attrs, {
                id: filterId
            });

            V(filterSVGString, filterAttrs).appendTo(this.defs);
        }

        return filterId;
    },

    defineGradient: function(gradient) {

        if (!joint.util.isObject(gradient)) {
            throw new TypeError('dia.Paper: defineGradient() requires 1. argument to be an object.');
        }

        var gradientId = gradient.id;
        var type = gradient.type;
        var stops = gradient.stops;
        // Generate a hash code from the stringified filter definition. This gives us
        // a unique filter ID for different definitions.
        if (!gradientId) {
            gradientId = type + this.svg.id + joint.util.hashCode(JSON.stringify(gradient));
        }
        // If the gradient already exists in the document,
        // we're done and we can just use it (reference it using `url()`).
        // If not, create one.
        if (!this.isDefined(gradientId)) {

            var stopTemplate = joint.util.template('<stop offset="${offset}" stop-color="${color}" stop-opacity="${opacity}"/>');
            var gradientStopsStrings = joint.util.toArray(stops).map(function(stop) {
                return stopTemplate({
                    offset: stop.offset,
                    color: stop.color,
                    opacity: Number.isFinite(stop.opacity) ? stop.opacity : 1
                });
            });

            var gradientSVGString = [
                '<' + type + '>',
                gradientStopsStrings.join(''),
                '</' + type + '>'
            ].join('');

            var gradientAttrs = joint.util.assign({ id: gradientId }, gradient.attrs);

            V(gradientSVGString, gradientAttrs).appendTo(this.defs);
        }

        return gradientId;
    },

    defineMarker: function(marker) {

        if (!joint.util.isObject(marker)) {
            throw new TypeError('dia.Paper: defineMarker() requires 1. argument to be an object.');
        }

        var markerId = marker.id;

        // Generate a hash code from the stringified filter definition. This gives us
        // a unique filter ID for different definitions.
        if (!markerId) {
            markerId = this.svg.id + joint.util.hashCode(JSON.stringify(marker));
        }

        if (!this.isDefined(markerId)) {

            var attrs = joint.util.omit(marker, 'type', 'userSpaceOnUse');
            var pathMarker = V('marker', {
                id: markerId,
                orient: 'auto',
                overflow: 'visible',
                markerUnits: marker.markerUnits || 'userSpaceOnUse'
            }, [
                V(marker.type || 'path', attrs)
            ]);

            pathMarker.appendTo(this.defs);
        }

        return markerId;
    }
}, {

    backgroundPatterns: {

        flipXy: function(img) {
            // d b
            // q p

            var canvas = document.createElement('canvas');
            var imgWidth = img.width;
            var imgHeight = img.height;

            canvas.width = 2 * imgWidth;
            canvas.height = 2 * imgHeight;

            var ctx = canvas.getContext('2d');
            // top-left image
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);
            // xy-flipped bottom-right image
            ctx.setTransform(-1, 0, 0, -1, canvas.width, canvas.height);
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);
            // x-flipped top-right image
            ctx.setTransform(-1, 0, 0, 1, canvas.width, 0);
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);
            // y-flipped bottom-left image
            ctx.setTransform(1, 0, 0, -1, 0, canvas.height);
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);

            return canvas;
        },

        flipX: function(img) {
            // d b
            // d b

            var canvas = document.createElement('canvas');
            var imgWidth = img.width;
            var imgHeight = img.height;

            canvas.width = imgWidth * 2;
            canvas.height = imgHeight;

            var ctx = canvas.getContext('2d');
            // left image
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);
            // flipped right image
            ctx.translate(2 * imgWidth, 0);
            ctx.scale(-1, 1);
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);

            return canvas;
        },

        flipY: function(img) {
            // d d
            // q q

            var canvas = document.createElement('canvas');
            var imgWidth = img.width;
            var imgHeight = img.height;

            canvas.width = imgWidth;
            canvas.height = imgHeight * 2;

            var ctx = canvas.getContext('2d');
            // top image
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);
            // flipped bottom image
            ctx.translate(0, 2 * imgHeight);
            ctx.scale(1, -1);
            ctx.drawImage(img, 0, 0, imgWidth, imgHeight);

            return canvas;
        },

        watermark: function(img, opt) {
            //   d
            // d

            opt = opt || {};

            var imgWidth = img.width;
            var imgHeight = img.height;

            var canvas = document.createElement('canvas');
            canvas.width = imgWidth * 3;
            canvas.height = imgHeight * 3;

            var ctx = canvas.getContext('2d');
            var angle = joint.util.isNumber(opt.watermarkAngle) ? -opt.watermarkAngle : -20;
            var radians = g.toRad(angle);
            var stepX = canvas.width / 4;
            var stepY = canvas.height / 4;

            for (var i = 0; i < 4; i ++) {
                for (var j = 0; j < 4; j++) {
                    if ((i + j) % 2 > 0) {
                        // reset the current transformations
                        ctx.setTransform(1, 0, 0, 1, (2 * i - 1) * stepX, (2 * j - 1)  * stepY);
                        ctx.rotate(radians);
                        ctx.drawImage(img, -imgWidth / 2, -imgHeight / 2, imgWidth, imgHeight);
                    }
                }
            }

            return canvas;
        }
    },

    gridPatterns: {
        dot: [{
            color: '#AAAAAA',
            thickness: 1,
            markup: 'rect',
            update: function(el, opt) {
                V(el).attr({
                    width: opt.thickness * opt.sx,
                    height: opt.thickness * opt.sy,
                    fill: opt.color
                });
            }
        }],
        fixedDot: [{
            color: '#AAAAAA',
            thickness: 1,
            markup: 'rect',
            update: function(el, opt) {
                var size = opt.sx <= 1 ? opt.thickness * opt.sx : opt.thickness;
                V(el).attr({ width: size, height: size, fill: opt.color });
            }
        }],
        mesh: [{
            color: '#AAAAAA',
            thickness: 1,
            markup: 'path',
            update: function(el, opt) {

                var d;
                var width = opt.width;
                var height = opt.height;
                var thickness = opt.thickness;

                if (width - thickness >= 0 && height - thickness >= 0) {
                    d = ['M', width, 0, 'H0 M0 0 V0', height].join(' ');
                } else {
                    d = 'M 0 0 0 0';
                }

                V(el).attr({ 'd': d, stroke: opt.color, 'stroke-width': opt.thickness });
            }
        }],
        doubleMesh: [{
            color: '#AAAAAA',
            thickness: 1,
            markup: 'path',
            update: function(el, opt) {

                var d;
                var width = opt.width;
                var height = opt.height;
                var thickness = opt.thickness;

                if (width - thickness >= 0 && height - thickness >= 0) {
                    d = ['M', width, 0, 'H0 M0 0 V0', height].join(' ');
                } else {
                    d = 'M 0 0 0 0';
                }

                V(el).attr({ 'd': d, stroke: opt.color, 'stroke-width': opt.thickness });
            }
        }, {
            color: '#000000',
            thickness: 3,
            scaleFactor: 4,
            markup: 'path',
            update: function(el, opt) {

                var d;
                var width = opt.width;
                var height = opt.height;
                var thickness = opt.thickness;

                if (width - thickness >= 0 && height - thickness >= 0) {
                    d = ['M', width, 0, 'H0 M0 0 V0', height].join(' ');
                } else {
                    d = 'M 0 0 0 0';
                }

                V(el).attr({ 'd': d, stroke: opt.color, 'stroke-width': opt.thickness });
            }
        }]
    }
});

(function(joint, _, util) {

    var PortData = function(data) {

        var clonedData = util.cloneDeep(data) || {};
        this.ports = [];
        this.groups = {};
        this.portLayoutNamespace = joint.layout.Port;
        this.portLabelLayoutNamespace = joint.layout.PortLabel;

        this._init(clonedData);
    };

    PortData.prototype = {

        getPorts: function() {
            return this.ports;
        },

        getGroup: function(name) {
            return this.groups[name] || {};
        },

        getPortsByGroup: function(groupName) {

            return this.ports.filter(function(port) {
                return port.group === groupName;
            });
        },

        getGroupPortsMetrics: function(groupName, elBBox) {

            var group = this.getGroup(groupName);
            var ports = this.getPortsByGroup(groupName);

            var groupPosition = group.position || {};
            var groupPositionName = groupPosition.name;
            var namespace = this.portLayoutNamespace;
            if (!namespace[groupPositionName]) {
                groupPositionName = 'left';
            }

            var groupArgs = groupPosition.args || {};
            var portsArgs = ports.map(function(port) {
                return port && port.position && port.position.args;
            });
            var groupPortTransformations = namespace[groupPositionName](portsArgs, elBBox, groupArgs);

            var accumulator = {
                ports: ports,
                result: []
            };

            util.toArray(groupPortTransformations).reduce(function(res, portTransformation, index) {
                var port = res.ports[index];
                res.result.push({
                    portId: port.id,
                    portTransformation: portTransformation,
                    labelTransformation: this._getPortLabelLayout(port, g.Point(portTransformation), elBBox),
                    portAttrs: port.attrs,
                    portSize: port.size,
                    labelSize: port.label.size
                });
                return res;
            }.bind(this), accumulator);

            return accumulator.result;
        },

        _getPortLabelLayout: function(port, portPosition, elBBox) {

            var namespace = this.portLabelLayoutNamespace;
            var labelPosition = port.label.position.name || 'left';

            if (namespace[labelPosition]) {
                return namespace[labelPosition](portPosition, elBBox, port.label.position.args);
            }

            return null;
        },

        _init: function(data) {

            // prepare groups
            if (util.isObject(data.groups)) {
                var groups = Object.keys(data.groups);
                for (var i = 0, n = groups.length; i < n; i++) {
                    var key = groups[i];
                    this.groups[key] = this._evaluateGroup(data.groups[key]);
                }
            }

            // prepare ports
            var ports = util.toArray(data.items);
            for (var j = 0, m = ports.length; j < m; j++) {
                this.ports.push(this._evaluatePort(ports[j]));
            }
        },

        _evaluateGroup: function(group) {

            return util.merge(group, {
                position: this._getPosition(group.position, true),
                label: this._getLabel(group, true)
            });
        },

        _evaluatePort: function(port) {

            var evaluated = util.assign({}, port);

            var group = this.getGroup(port.group);

            evaluated.markup = evaluated.markup || group.markup;
            evaluated.attrs = util.merge({}, group.attrs, evaluated.attrs);
            evaluated.position = this._createPositionNode(group, evaluated);
            evaluated.label = util.merge({}, group.label, this._getLabel(evaluated));
            evaluated.z = this._getZIndex(group, evaluated);
            evaluated.size = util.assign({}, group.size, evaluated.size);

            return evaluated;
        },

        _getZIndex: function(group, port) {

            if (util.isNumber(port.z)) {
                return port.z;
            }
            if (util.isNumber(group.z) || group.z === 'auto') {
                return group.z;
            }
            return 'auto';
        },

        _createPositionNode: function(group, port) {

            return util.merge({
                name: 'left',
                args: {}
            }, group.position, { args: port.args });
        },

        _getPosition: function(position, setDefault) {

            var args = {};
            var positionName;

            if (util.isFunction(position)) {
                positionName = 'fn';
                args.fn = position;
            } else if (util.isString(position)) {
                positionName = position;
            } else if (position === undefined) {
                positionName = setDefault ? 'left' : null;
            } else if (Array.isArray(position)) {
                positionName = 'absolute';
                args.x = position[0];
                args.y = position[1];
            } else if (util.isObject(position)) {
                positionName = position.name;
                util.assign(args, position.args);
            }

            var result = { args: args };

            if (positionName) {
                result.name = positionName;
            }
            return result;
        },

        _getLabel: function(item, setDefaults) {

            var label = item.label || {};

            var ret = label;
            ret.position = this._getPosition(label.position, setDefaults);

            return ret;
        }
    };

    util.assign(joint.dia.Element.prototype, {

        _initializePorts: function() {

            this._createPortData();
            this.on('change:ports', function() {

                this._processRemovedPort();
                this._createPortData();
            }, this);
        },

        /**
         * remove links tied wiht just removed element
         * @private
         */
        _processRemovedPort: function() {

            var current = this.get('ports') || {};
            var currentItemsMap = {};

            util.toArray(current.items).forEach(function(item) {
                currentItemsMap[item.id] = true;
            });

            var previous = this.previous('ports') || {};
            var removed = {};

            util.toArray(previous.items).forEach(function(item) {
                if (!currentItemsMap[item.id]) {
                    removed[item.id] = true;
                }
            });

            var graph = this.graph;
            if (graph && !util.isEmpty(removed)) {

                var inboundLinks = graph.getConnectedLinks(this, { inbound: true });
                inboundLinks.forEach(function(link) {

                    if (removed[link.get('target').port]) link.remove();
                });

                var outboundLinks = graph.getConnectedLinks(this, { outbound: true });
                outboundLinks.forEach(function(link) {

                    if (removed[link.get('source').port]) link.remove();
                });
            }
        },

        /**
         * @returns {boolean}
         */
        hasPorts: function() {

            return this.prop('ports/items').length > 0;
        },

        /**
         * @param {string} id
         * @returns {boolean}
         */
        hasPort: function(id) {

            return this.getPortIndex(id) !== -1;
        },

        /**
         * @returns {Array<object>}
         */
        getPorts: function() {

            return util.cloneDeep(this.prop('ports/items')) || [];
        },

        /**
         * @param {string} id
         * @returns {object}
         */
        getPort: function(id) {

            return util.cloneDeep(util.toArray(this.prop('ports/items')).find( function(port) {
                return port.id && port.id === id;
            }));
        },

        /**
         * @param {string} groupName
         * @returns {Object<portId, {x: number, y: number, angle: number}>}
         */
        getPortsPositions: function(groupName) {

            var portsMetrics = this._portSettingsData.getGroupPortsMetrics(groupName, g.Rect(this.size()));

            return portsMetrics.reduce(function(positions, metrics) {
                var transformation = metrics.portTransformation;
                positions[metrics.portId] = {
                    x: transformation.x,
                    y: transformation.y,
                    angle: transformation.angle
                };
                return positions;
            }, {});
        },

        /**
         * @param {string|Port} port port id or port
         * @returns {number} port index
         */
        getPortIndex: function(port) {

            var id = util.isObject(port) ? port.id : port;

            if (!this._isValidPortId(id)) {
                return -1;
            }

            return util.toArray(this.prop('ports/items')).findIndex(function(item) {
                return item.id === id;
            });
        },

        /**
         * @param {object} port
         * @param {object} [opt]
         * @returns {joint.dia.Element}
         */
        addPort: function(port, opt) {

            if (!util.isObject(port) || Array.isArray(port)) {
                throw new Error('Element: addPort requires an object.');
            }

            var ports = util.assign([], this.prop('ports/items'));
            ports.push(port);
            this.prop('ports/items', ports, opt);

            return this;
        },

        /**
         * @param {string} portId
         * @param {string|object=} path
         * @param {*=} value
         * @param {object=} opt
         * @returns {joint.dia.Element}
         */
        portProp: function(portId, path, value, opt) {

            var index = this.getPortIndex(portId);

            if (index === -1) {
                throw new Error('Element: unable to find port with id ' + portId);
            }

            var args = Array.prototype.slice.call(arguments, 1);
            if (Array.isArray(path)) {
                args[0] = ['ports', 'items', index].concat(path);
            } else if (util.isString(path)) {

                // Get/set an attribute by a special path syntax that delimits
                // nested objects by the colon character.
                args[0] = ['ports/items/', index, '/', path].join('');

            } else {

                args = ['ports/items/' + index];
                if (util.isPlainObject(path)) {
                    args.push(path);
                    args.push(value);
                }
            }

            return this.prop.apply(this, args);
        },

        _validatePorts: function() {

            var portsAttr = this.get('ports') || {};

            var errorMessages = [];
            portsAttr = portsAttr || {};
            var ports = util.toArray(portsAttr.items);

            ports.forEach(function(p) {

                if (typeof p !== 'object') {
                    errorMessages.push('Element: invalid port ', p);
                }

                if (!this._isValidPortId(p.id)) {
                    p.id = util.uuid();
                }
            }, this);

            if (joint.util.uniq(ports, 'id').length !== ports.length) {
                errorMessages.push('Element: found id duplicities in ports.');
            }

            return errorMessages;
        },

        /**
         * @param {string} id port id
         * @returns {boolean}
         * @private
         */
        _isValidPortId: function(id) {

            return id !== null && id !== undefined && !util.isObject(id);
        },

        addPorts: function(ports, opt) {

            if (ports.length) {
                this.prop('ports/items', util.assign([], this.prop('ports/items')).concat(ports), opt);
            }

            return this;
        },

        removePort: function(port, opt) {

            var options = opt || {};
            var ports = util.assign([], this.prop('ports/items'));

            var index = this.getPortIndex(port);

            if (index !== -1) {
                ports.splice(index, 1);
                options.rewrite = true;
                this.prop('ports/items', ports, options);
            }

            return this;
        },

        /**
         * @private
         */
        _createPortData: function() {

            var err = this._validatePorts();

            if (err.length > 0) {
                this.set('ports', this.previous('ports'));
                throw new Error(err.join(' '));
            }

            var prevPortData;

            if (this._portSettingsData) {

                prevPortData = this._portSettingsData.getPorts();
            }

            this._portSettingsData = new PortData(this.get('ports'));

            var curPortData = this._portSettingsData.getPorts();

            if (prevPortData) {

                var added = curPortData.filter(function(item) {
                    if (!prevPortData.find(function(prevPort) { return prevPort.id === item.id;})) {
                        return item;
                    }
                });

                var removed = prevPortData.filter(function(item) {
                    if (!curPortData.find(function(curPort) { return curPort.id === item.id;})) {
                        return item;
                    }
                });

                if (removed.length > 0) {
                    this.trigger('ports:remove', this, removed);
                }

                if (added.length > 0) {
                    this.trigger('ports:add', this, added);
                }
            }
        }
    });

    util.assign(joint.dia.ElementView.prototype, {

        portContainerMarkup: 'g',
        portMarkup: [{
            tagName: 'circle',
            selector: 'circle',
            attributes: {
                'r': 10,
                'fill': '#FFFFFF',
                'stroke': '#000000'
            }
        }],
        portLabelMarkup: [{
            tagName: 'text',
            selector: 'text',
            attributes: {
                'fill': '#000000'
            }
        }],
        /** @type {Object<string, {portElement: Vectorizer, portLabelElement: Vectorizer}>} */
        _portElementsCache: null,

        /**
         * @private
         */
        _initializePorts: function() {

            this._portElementsCache = {};

            this.listenTo(this.model, 'change:ports', function() {

                this._refreshPorts();
            });
        },

        /**
         * @typedef {Object} Port
         *
         * @property {string} id
         * @property {Object} position
         * @property {Object} label
         * @property {Object} attrs
         * @property {string} markup
         * @property {string} group
         */

        /**
         * @private
         */
        _refreshPorts: function() {

            this._removePorts();
            this._portElementsCache = {};

            this._renderPorts();
        },

        /**
         * @private
         */
        _renderPorts: function() {

            // references to rendered elements without z-index
            var elementReferences = [];
            var elem = this._getContainerElement();

            for (var i = 0, count = elem.node.childNodes.length; i < count; i++) {
                elementReferences.push(elem.node.childNodes[i]);
            }

            var portsGropsByZ = util.groupBy(this.model._portSettingsData.getPorts(), 'z');
            var withoutZKey = 'auto';

            // render non-z first
            util.toArray(portsGropsByZ[withoutZKey]).forEach(function(port) {
                var portElement = this._getPortElement(port);
                elem.append(portElement);
                elementReferences.push(portElement);
            }, this);

            var groupNames = Object.keys(portsGropsByZ);
            for (var k = 0; k < groupNames.length; k++) {
                var groupName = groupNames[k];
                if (groupName !== withoutZKey) {
                    var z = parseInt(groupName, 10);
                    this._appendPorts(portsGropsByZ[groupName], z, elementReferences);
                }
            }

            this._updatePorts();
        },

        /**
         * @returns {V}
         * @private
         */
        _getContainerElement: function() {

            return this.rotatableNode || this.vel;
        },

        /**
         * @param {Array<Port>}ports
         * @param {number} z
         * @param refs
         * @private
         */
        _appendPorts: function(ports, z, refs) {

            var containerElement = this._getContainerElement();
            var portElements = util.toArray(ports).map(this._getPortElement, this);

            if (refs[z] || z < 0) {
                V(refs[Math.max(z, 0)]).before(portElements);
            } else {
                containerElement.append(portElements);
            }
        },

        /**
         * Try to get element from cache,
         * @param port
         * @returns {*}
         * @private
         */
        _getPortElement: function(port) {

            if (this._portElementsCache[port.id]) {
                return this._portElementsCache[port.id].portElement;
            }
            return this._createPortElement(port);
        },

        findPortNode: function(portId, selector) {
            var portCache = this._portElementsCache[portId];
            if (!portCache) return null;
            var portRoot = portCache.portContentElement.node;
            var portSelectors = portCache.portContentSelectors;
            return this.findBySelector(selector, portRoot, portSelectors)[0];
        },

        /**
         * @private
         */
        _updatePorts: function() {

            // layout ports without group
            this._updatePortGroup(undefined);
            // layout ports with explicit group
            var groupsNames = Object.keys(this.model._portSettingsData.groups);
            groupsNames.forEach(this._updatePortGroup, this);
        },

        /**
         * @private
         */
        _removePorts: function() {
            util.invoke(this._portElementsCache, 'portElement.remove');
        },

        /**
         * @param {Port} port
         * @returns {V}
         * @private
         */
        _createPortElement: function(port) {


            var portElement;
            var labelElement;

            var portMarkup = this._getPortMarkup(port);
            var portSelectors;
            if (Array.isArray(portMarkup)) {
                var portDoc = util.parseDOMJSON(portMarkup);
                var portFragment = portDoc.fragment;
                if (portFragment.childNodes.length > 1) {
                    portElement = V('g').append(portFragment);
                } else {
                    portElement = V(portFragment.firstChild);
                }
                portSelectors = portDoc.selectors;
            } else {
                portElement = V(portMarkup);
                if (Array.isArray(portElement)) {
                    portElement = V('g').append(portElement);
                }
            }

            if (!portElement) {
                throw new Error('ElementView: Invalid port markup.');
            }

            portElement.attr({
                'port': port.id,
                'port-group': port.group
            });

            var labelMarkup = this._getPortLabelMarkup(port.label);
            var labelSelectors;
            if (Array.isArray(labelMarkup)) {
                var labelDoc = util.parseDOMJSON(labelMarkup);
                var labelFragment = labelDoc.fragment;
                if (labelFragment.childNodes.length > 1) {
                    labelElement = V('g').append(labelFragment);
                } else {
                    labelElement = V(labelFragment.firstChild);
                }
                labelSelectors = labelDoc.selectors;
            } else {
                labelElement = V(labelMarkup);
                if (Array.isArray(labelElement)) {
                    labelElement = V('g').append(labelElement);
                }
            }

            if (!labelElement) {
                throw new Error('ElementView: Invalid port label markup.');
            }

            var portContainerSelectors;
            if (portSelectors && labelSelectors) {
                for (var key in labelSelectors) {
                    if (portSelectors[key]) throw new Error('ElementView: selectors within port must be unique.');
                }
                portContainerSelectors = util.assign({}, portSelectors, labelSelectors);
            } else {
                portContainerSelectors = portSelectors || labelSelectors;
            }

            var portContainerElement = V(this.portContainerMarkup)
                .addClass('joint-port')
                .append([
                    portElement.addClass('joint-port-body'),
                    labelElement.addClass('joint-port-label')
                ]);

            this._portElementsCache[port.id] = {
                portElement: portContainerElement,
                portLabelElement: labelElement,
                portSelectors: portContainerSelectors,
                portLabelSelectors: labelSelectors,
                portContentElement: portElement,
                portContentSelectors: portSelectors
            };

            return portContainerElement;
        },

        /**
         * @param {string=} groupName
         * @private
         */
        _updatePortGroup: function(groupName) {

            var elementBBox = g.Rect(this.model.size());
            var portsMetrics = this.model._portSettingsData.getGroupPortsMetrics(groupName, elementBBox);

            for (var i = 0, n = portsMetrics.length; i < n; i++) {
                var metrics = portsMetrics[i];
                var portId = metrics.portId;
                var cached = this._portElementsCache[portId] || {};
                var portTransformation = metrics.portTransformation;
                this.applyPortTransform(cached.portElement, portTransformation);
                this.updateDOMSubtreeAttributes(cached.portElement.node, metrics.portAttrs, {
                    rootBBox: new g.Rect(metrics.portSize),
                    selectors: cached.portSelectors
                });

                var labelTransformation = metrics.labelTransformation;
                if (labelTransformation) {
                    this.applyPortTransform(cached.portLabelElement, labelTransformation, (-portTransformation.angle || 0));
                    this.updateDOMSubtreeAttributes(cached.portLabelElement.node, labelTransformation.attrs, {
                        rootBBox: new g.Rect(metrics.labelSize),
                        selectors: cached.portLabelSelectors
                    });
                }
            }
        },

        /**
         * @param {Vectorizer} element
         * @param {{dx:number, dy:number, angle: number, attrs: Object, x:number: y:number}} transformData
         * @param {number=} initialAngle
         * @constructor
         */
        applyPortTransform: function(element, transformData, initialAngle) {

            var matrix = V.createSVGMatrix()
                .rotate(initialAngle || 0)
                .translate(transformData.x || 0, transformData.y || 0)
                .rotate(transformData.angle || 0);

            element.transform(matrix, { absolute: true });
        },

        /**
         * @param {Port} port
         * @returns {string}
         * @private
         */
        _getPortMarkup: function(port) {

            return port.markup || this.model.get('portMarkup') || this.model.portMarkup || this.portMarkup;
        },

        /**
         * @param {Object} label
         * @returns {string}
         * @private
         */
        _getPortLabelMarkup: function(label) {

            return label.markup || this.model.get('portLabelMarkup') || this.model.portLabelMarkup || this.portLabelMarkup;
        }

    });
}(joint, _, joint.util));

joint.dia.Element.define('basic.Generic', {
    attrs: {
        '.': { fill: '#ffffff', stroke: 'none' }
    }
});

joint.shapes.basic.Generic.define('basic.Rect', {
    attrs: {
        'rect': {
            fill: '#ffffff',
            stroke: '#000000',
            width: 100,
            height: 60
        },
        'text': {
            fill: '#000000',
            text: '',
            'font-size': 14,
            'ref-x': .5,
            'ref-y': .5,
            'text-anchor': 'middle',
            'y-alignment': 'middle',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><rect/></g><text/></g>'
});

joint.shapes.basic.TextView = joint.dia.ElementView.extend({

    initialize: function() {
        joint.dia.ElementView.prototype.initialize.apply(this, arguments);
        // The element view is not automatically rescaled to fit the model size
        // when the attribute 'attrs' is changed.
        this.listenTo(this.model, 'change:attrs', this.resize);
    }
});

joint.shapes.basic.Generic.define('basic.Text', {
    attrs: {
        'text': {
            'font-size': 18,
            fill: '#000000'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><text/></g></g>',
});

joint.shapes.basic.Generic.define('basic.Circle', {
    size: { width: 60, height: 60 },
    attrs: {
        'circle': {
            fill: '#ffffff',
            stroke: '#000000',
            r: 30,
            cx: 30,
            cy: 30
        },
        'text': {
            'font-size': 14,
            text: '',
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-y': .5,
            'y-alignment': 'middle',
            fill: '#000000',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><circle/></g><text/></g>',
});

joint.shapes.basic.Generic.define('basic.Ellipse', {
    size: { width: 60, height: 40 },
    attrs: {
        'ellipse': {
            fill: '#ffffff',
            stroke: '#000000',
            rx: 30,
            ry: 20,
            cx: 30,
            cy: 20
        },
        'text': {
            'font-size': 14,
            text: '',
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-y': .5,
            'y-alignment': 'middle',
            fill: '#000000',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><ellipse/></g><text/></g>',
});

joint.shapes.basic.Generic.define('basic.Polygon', {
    size: { width: 60, height: 40 },
    attrs: {
        'polygon': {
            fill: '#ffffff',
            stroke: '#000000'
        },
        'text': {
            'font-size': 14,
            text: '',
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-dy': 20,
            'y-alignment': 'middle',
            fill: '#000000',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><polygon/></g><text/></g>',
});

joint.shapes.basic.Generic.define('basic.Polyline', {
    size: { width: 60, height: 40 },
    attrs: {
        'polyline': {
            fill: '#ffffff',
            stroke: '#000000'
        },
        'text': {
            'font-size': 14,
            text: '',
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-dy': 20,
            'y-alignment': 'middle',
            fill: '#000000',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><polyline/></g><text/></g>',
});

joint.shapes.basic.Generic.define('basic.Image', {
    attrs: {
        'text': {
            'font-size': 14,
            text: '',
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-dy': 20,
            'y-alignment': 'middle',
            fill: '#000000',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><image/></g><text/></g>',
});

joint.shapes.basic.Generic.define('basic.Path', {
    size: { width: 60, height: 60 },
    attrs: {
        'path': {
            fill: '#ffffff',
            stroke: '#000000'
        },
        'text': {
            'font-size': 14,
            text: '',
            'text-anchor': 'middle',
            'ref': 'path',
            'ref-x': .5,
            'ref-dy': 10,
            fill: '#000000',
            'font-family': 'Arial, helvetica, sans-serif'
        }
    }

}, {
    markup: '<g class="rotatable"><g class="scalable"><path/></g><text/></g>',
});

joint.shapes.basic.Path.define('basic.Rhombus', {
    attrs: {
        'path': {
            d: 'M 30 0 L 60 30 30 60 0 30 z'
        },
        'text': {
            'ref-y': .5,
            'ref-dy': null,
            'y-alignment': 'middle'
        }
    }
});


/**
 * @deprecated use the port api instead
 */
// PortsModelInterface is a common interface for shapes that have ports. This interface makes it easy
// to create new shapes with ports functionality. It is assumed that the new shapes have
// `inPorts` and `outPorts` array properties. Only these properties should be used to set ports.
// In other words, using this interface, it is no longer recommended to set ports directly through the
// `attrs` object.

// Usage:
// joint.shapes.custom.MyElementWithPorts = joint.shapes.basic.Path.extend(_.extend({}, joint.shapes.basic.PortsModelInterface, {
//     getPortAttrs: function(portName, index, total, selector, type) {
//         var attrs = {};
//         var portClass = 'port' + index;
//         var portSelector = selector + '>.' + portClass;
//         var portTextSelector = portSelector + '>text';
//         var portBodySelector = portSelector + '>.port-body';
//
//         attrs[portTextSelector] = { text: portName };
//         attrs[portBodySelector] = { port: { id: portName || _.uniqueId(type) , type: type } };
//         attrs[portSelector] = { ref: 'rect', 'ref-y': (index + 0.5) * (1 / total) };
//
//         if (selector === '.outPorts') { attrs[portSelector]['ref-dx'] = 0; }
//
//         return attrs;
//     }
//}));
joint.shapes.basic.PortsModelInterface = {

    initialize: function() {

        this.updatePortsAttrs();
        this.on('change:inPorts change:outPorts', this.updatePortsAttrs, this);

        // Call the `initialize()` of the parent.
        this.constructor.__super__.constructor.__super__.initialize.apply(this, arguments);
    },

    updatePortsAttrs: function(eventName) {

        if (this._portSelectors) {

            var newAttrs = joint.util.omit(this.get('attrs'), this._portSelectors);
            this.set('attrs', newAttrs, { silent: true });
        }

        // This holds keys to the `attrs` object for all the port specific attribute that
        // we set in this method. This is necessary in order to remove previously set
        // attributes for previous ports.
        this._portSelectors = [];

        var attrs = {};

        joint.util.toArray(this.get('inPorts')).forEach(function(portName, index, ports) {
            var portAttributes = this.getPortAttrs(portName, index, ports.length, '.inPorts', 'in');
            this._portSelectors = this._portSelectors.concat(Object.keys(portAttributes));
            joint.util.assign(attrs, portAttributes);
        }, this);

        joint.util.toArray(this.get('outPorts')).forEach(function(portName, index, ports) {
            var portAttributes = this.getPortAttrs(portName, index, ports.length, '.outPorts', 'out');
            this._portSelectors = this._portSelectors.concat(Object.keys(portAttributes));
            joint.util.assign(attrs, portAttributes);
        }, this);

        // Silently set `attrs` on the cell so that noone knows the attrs have changed. This makes sure
        // that, for example, command manager does not register `change:attrs` command but only
        // the important `change:inPorts`/`change:outPorts` command.
        this.attr(attrs, { silent: true });
        // Manually call the `processPorts()` method that is normally called on `change:attrs` (that we just made silent).
        this.processPorts();
        // Let the outside world (mainly the `ModelView`) know that we're done configuring the `attrs` object.
        this.trigger('process:ports');
    },

    getPortSelector: function(name) {

        var selector = '.inPorts';
        var index = this.get('inPorts').indexOf(name);

        if (index < 0) {
            selector = '.outPorts';
            index = this.get('outPorts').indexOf(name);

            if (index < 0) throw new Error("getPortSelector(): Port doesn't exist.");
        }

        return selector + '>g:nth-child(' + (index + 1) + ')>.port-body';
    }
};

joint.shapes.basic.PortsViewInterface = {

    initialize: function() {

        // `Model` emits the `process:ports` whenever it's done configuring the `attrs` object for ports.
        this.listenTo(this.model, 'process:ports', this.update);

        joint.dia.ElementView.prototype.initialize.apply(this, arguments);
    },

    update: function() {

        // First render ports so that `attrs` can be applied to those newly created DOM elements
        // in `ElementView.prototype.update()`.
        this.renderPorts();
        joint.dia.ElementView.prototype.update.apply(this, arguments);
    },

    renderPorts: function() {

        var $inPorts = this.$('.inPorts').empty();
        var $outPorts = this.$('.outPorts').empty();

        var portTemplate = joint.util.template(this.model.portMarkup);

        var ports = this.model.ports || [];
        ports.filter(function(p) {
            return p.type === 'in';
        }).forEach(function(port, index) {

            $inPorts.append(V(portTemplate({ id: index, port: port })).node);
        });

        ports.filter(function(p) {
            return p.type === 'out';
        }).forEach(function(port, index) {

            $outPorts.append(V(portTemplate({ id: index, port: port })).node);
        });
    }
};

joint.shapes.basic.Generic.define('basic.TextBlock', {
    // see joint.css for more element styles
    attrs: {
        rect: {
            fill: '#ffffff',
            stroke: '#000000',
            width: 80,
            height: 100
        },
        text: {
            fill: '#000000',
            'font-size': 14,
            'font-family': 'Arial, helvetica, sans-serif'
        },
        '.content': {
            text: '',
            'ref-x': .5,
            'ref-y': .5,
            'y-alignment': 'middle',
            'x-alignment': 'middle'
        }
    },

    content: ''
}, {
    markup: [
        '<g class="rotatable">',
        '<g class="scalable"><rect/></g>',
        joint.env.test('svgforeignobject') ? '<foreignObject class="fobj"><body xmlns="http://www.w3.org/1999/xhtml"><div class="content"/></body></foreignObject>' : '<text class="content"/>',
        '</g>'
    ].join(''),

    initialize: function() {

        this.listenTo(this, 'change:size', this.updateSize);
        this.listenTo(this, 'change:content', this.updateContent);
        this.updateSize(this, this.get('size'));
        this.updateContent(this, this.get('content'));
        joint.shapes.basic.Generic.prototype.initialize.apply(this, arguments);
    },

    updateSize: function(cell, size) {

        // Selector `foreignObject' doesn't work across all browsers, we're using class selector instead.
        // We have to clone size as we don't want attributes.div.style to be same object as attributes.size.
        this.attr({
            '.fobj': joint.util.assign({}, size),
            div: {
                style: joint.util.assign({}, size)
            }
        });
    },

    updateContent: function(cell, content) {

        if (joint.env.test('svgforeignobject')) {

            // Content element is a <div> element.
            this.attr({
                '.content': {
                    html: joint.util.sanitizeHTML(content)
                }
            });

        } else {

            // Content element is a <text> element.
            // SVG elements don't have innerHTML attribute.
            this.attr({
                '.content': {
                    text: content
                }
            });
        }
    },

    // Here for backwards compatibility:
    setForeignObjectSize: function() {

        this.updateSize.apply(this, arguments);
    },

    // Here for backwards compatibility:
    setDivContent: function() {

        this.updateContent.apply(this, arguments);
    }
});

// TextBlockView implements the fallback for IE when no foreignObject exists and
// the text needs to be manually broken.
joint.shapes.basic.TextBlockView = joint.dia.ElementView.extend({

    initialize: function() {

        joint.dia.ElementView.prototype.initialize.apply(this, arguments);

        // Keep this for backwards compatibility:
        this.noSVGForeignObjectElement = !joint.env.test('svgforeignobject');

        if (!joint.env.test('svgforeignobject')) {

            this.listenTo(this.model, 'change:content change:size', function(cell) {
                // avoiding pass of extra paramters
                this.updateContent(cell);
            });
        }
    },

    update: function(cell, renderingOnlyAttrs) {

        var model = this.model;

        if (!joint.env.test('svgforeignobject')) {

            // Update everything but the content first.
            var noTextAttrs = joint.util.omit(renderingOnlyAttrs || model.get('attrs'), '.content');
            joint.dia.ElementView.prototype.update.call(this, model, noTextAttrs);

            if (!renderingOnlyAttrs || joint.util.has(renderingOnlyAttrs, '.content')) {
                // Update the content itself.
                this.updateContent(model, renderingOnlyAttrs);
            }

        } else {

            joint.dia.ElementView.prototype.update.call(this, model, renderingOnlyAttrs);
        }
    },

    updateContent: function(cell, renderingOnlyAttrs) {

        // Create copy of the text attributes
        var textAttrs = joint.util.merge({}, (renderingOnlyAttrs || cell.get('attrs'))['.content']);

        textAttrs = joint.util.omit(textAttrs, 'text');

        // Break the content to fit the element size taking into account the attributes
        // set on the model.
        var text = joint.util.breakText(cell.get('content'), cell.get('size'), textAttrs, {
            // measuring sandbox svg document
            svgDocument: this.paper.svg
        });

        // Create a new attrs with same structure as the model attrs { text: { *textAttributes* }}
        var attrs = joint.util.setByPath({}, '.content', textAttrs, '/');

        // Replace text attribute with the one we just processed.
        attrs['.content'].text = text;

        // Update the view using renderingOnlyAttributes parameter.
        joint.dia.ElementView.prototype.update.call(this, cell, attrs);
    }
});

(function(dia, util, env, V) {

    'use strict';

    // ELEMENTS

    var Element = dia.Element;

    Element.define('standard.Rectangle', {
        attrs: {
            body: {
                refWidth: '100%',
                refHeight: '100%',
                strokeWidth: 2,
                stroke: '#000000',
                fill: '#FFFFFF'
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'rect',
            selector: 'body',
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.Circle', {
        attrs: {
            body: {
                refCx: '50%',
                refCy: '50%',
                refR: '50%',
                strokeWidth: 2,
                stroke: '#333333',
                fill: '#FFFFFF'
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'circle',
            selector: 'body'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.Ellipse', {
        attrs: {
            body: {
                refCx: '50%',
                refCy: '50%',
                refRx: '50%',
                refRy: '50%',
                strokeWidth: 2,
                stroke: '#333333',
                fill: '#FFFFFF'
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'ellipse',
            selector: 'body'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.Path', {
        attrs: {
            body: {
                refD: 'M 0 0 L 10 0 10 10 0 10 Z',
                strokeWidth: 2,
                stroke: '#333333',
                fill: '#FFFFFF'
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'path',
            selector: 'body'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.Polygon', {
        attrs: {
            body: {
                refPoints: '0 0 10 0 10 10 0 10',
                strokeWidth: 2,
                stroke: '#333333',
                fill: '#FFFFFF'
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'polygon',
            selector: 'body'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.Polyline', {
        attrs: {
            body: {
                refPoints: '0 0 10 0 10 10 0 10 0 0',
                strokeWidth: 2,
                stroke: '#333333',
                fill: '#FFFFFF'
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'polyline',
            selector: 'body'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.Image', {
        attrs: {
            image: {
                refWidth: '100%',
                refHeight: '100%',
                // xlinkHref: '[URL]'
            },
            label: {
                textVerticalAnchor: 'top',
                textAnchor: 'middle',
                refX: '50%',
                refY: '100%',
                refY2: 10,
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'image',
            selector: 'image'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.BorderedImage', {
        attrs: {
            border: {
                refWidth: '100%',
                refHeight: '100%',
                stroke: '#333333',
                strokeWidth: 2
            },
            image: {
                // xlinkHref: '[URL]'
                refWidth: -1,
                refHeight: -1,
                x: 0.5,
                y: 0.5
            },
            label: {
                textVerticalAnchor: 'top',
                textAnchor: 'middle',
                refX: '50%',
                refY: '100%',
                refY2: 10,
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'image',
            selector: 'image'
        }, {
            tagName: 'rect',
            selector: 'border',
            attributes: {
                'fill': 'none'
            }
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.EmbeddedImage', {
        attrs: {
            body: {
                refWidth: '100%',
                refHeight: '100%',
                stroke: '#333333',
                fill: '#FFFFFF',
                strokeWidth: 2
            },
            image: {
                // xlinkHref: '[URL]'
                refWidth: '30%',
                refHeight: -20,
                x: 10,
                y: 10,
                preserveAspectRatio: 'xMidYMin'
            },
            label: {
                textVerticalAnchor: 'top',
                textAnchor: 'left',
                refX: '30%',
                refX2: 20, // 10 + 10
                refY: 10,
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'rect',
            selector: 'body'
        }, {
            tagName: 'image',
            selector: 'image'
        }, {
            tagName: 'text',
            selector: 'label'
        }]
    });

    Element.define('standard.HeaderedRectangle', {
        attrs: {
            body: {
                refWidth: '100%',
                refHeight: '100%',
                strokeWidth: 2,
                stroke: '#000000',
                fill: '#FFFFFF'
            },
            header: {
                refWidth: '100%',
                height: 30,
                strokeWidth: 2,
                stroke: '#000000',
                fill: '#FFFFFF'
            },
            headerText: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: 15,
                fontSize: 16,
                fill: '#333333'
            },
            bodyText: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '50%',
                refY2: 15,
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'rect',
            selector: 'body'
        }, {
            tagName: 'rect',
            selector: 'header'
        }, {
            tagName: 'text',
            selector: 'headerText'
        }, {
            tagName: 'text',
            selector: 'bodyText'
        }]
    });

    var CYLINDER_TILT = 10;

    joint.dia.Element.define('standard.Cylinder', {
        attrs: {
            body: {
                lateralArea: CYLINDER_TILT,
                fill: '#FFFFFF',
                stroke: '#333333',
                strokeWidth: 2
            },
            top: {
                refCx: '50%',
                cy: CYLINDER_TILT,
                refRx: '50%',
                ry: CYLINDER_TILT,
                fill: '#FFFFFF',
                stroke: '#333333',
                strokeWidth: 2
            },
            label: {
                textVerticalAnchor: 'middle',
                textAnchor: 'middle',
                refX: '50%',
                refY: '100%',
                refY2: 15,
                fontSize: 14,
                fill: '#333333'
            }
        }
    }, {
        markup: [{
            tagName: 'path',
            selector: 'body'
        }, {
            tagName: 'ellipse',
            selector: 'top'
        }, {
            tagName: 'text',
            selector: 'label'
        }],

        topRy: function(t, opt) {
            // getter
            if (t === undefined) return this.attr('body/lateralArea');

            // setter
            var isPercentage = util.isPercentage(t);

            var bodyAttrs = { lateralArea: t };
            var topAttrs = isPercentage
                ? { refCy: t, refRy: t, cy: null, ry: null }
                : { refCy: null, refRy: null, cy: t, ry: t };

            return this.attr({ body: bodyAttrs, top: topAttrs }, opt);
        }

    }, {
        attributes: {
            lateralArea: {
                set: function(t, refBBox) {
                    var isPercentage = util.isPercentage(t);
                    if (isPercentage) t = parseFloat(t) / 100;

                    var x = refBBox.x;
                    var y = refBBox.y;
                    var w = refBBox.width;
                    var h = refBBox.height;

                    // curve control point variables
                    var rx = w / 2;
                    var ry = isPercentage ? (h * t) : t;

                    var kappa = V.KAPPA;
                    var cx = kappa * rx;
                    var cy = kappa * (isPercentage ? (h * t) : t);

                    // shape variables
                    var xLeft = x;
                    var xCenter = x + (w / 2);
                    var xRight = x + w;

                    var ySideTop = y + ry;
                    var yCurveTop = ySideTop - ry;
                    var ySideBottom = y + h - ry;
                    var yCurveBottom = y + h;

                    // return calculated shape
                    var data = [
                        'M', xLeft, ySideTop,
                        'L', xLeft, ySideBottom,
                        'C', x, (ySideBottom + cy), (xCenter - cx), yCurveBottom, xCenter, yCurveBottom,
                        'C', (xCenter + cx), yCurveBottom, xRight, (ySideBottom + cy), xRight, ySideBottom,
                        'L', xRight, ySideTop,
                        'C', xRight, (ySideTop - cy), (xCenter + cx), yCurveTop, xCenter, yCurveTop,
                        'C', (xCenter - cx), yCurveTop, xLeft, (ySideTop - cy), xLeft, ySideTop,
                        'Z'
                    ];
                    return { d: data.join(' ') };
                }
            }
        }
    });

    var foLabelMarkup = {
        tagName: 'foreignObject',
        selector: 'foreignObject',
        attributes: {
            'overflow': 'hidden'
        },
        children: [{
            tagName: 'div',
            namespaceURI: 'http://www.w3.org/1999/xhtml',
            selector: 'label',
            style: {
                width: '100%',
                height: '100%',
                position: 'static',
                backgroundColor: 'transparent',
                textAlign: 'center',
                margin: 0,
                padding: '0px 5px',
                boxSizing: 'border-box',
                display: 'flex',
                alignItems: 'center',
                justifyContent: 'center'
            }
        }]
    };

    var svgLabelMarkup = {
        tagName: 'text',
        selector: 'label',
        attributes: {
            'text-anchor': 'middle'
        }
    };

    Element.define('standard.TextBlock', {
        attrs: {
            body: {
                refWidth: '100%',
                refHeight: '100%',
                stroke: '#333333',
                fill: '#ffffff',
                strokeWidth: 2
            },
            foreignObject: {
                refWidth: '100%',
                refHeight: '100%'
            },
            label: {
                style: {
                    fontSize: 14
                }
            }
        }
    }, {
        markup: [{
            tagName: 'rect',
            selector: 'body'
        },
            (env.test('svgforeignobject')) ? foLabelMarkup : svgLabelMarkup
        ]
    }, {
        attributes: {
            text: {
                set: function(text, refBBox, node, attrs) {
                    if (node instanceof HTMLElement) {
                        node.textContent = text;
                    } else {
                        // No foreign object
                        var style = attrs.style || {};
                        var wrapValue = { text: text, width: -5, height: '100%' };
                        var wrapAttrs = util.assign({ textVerticalAnchor: 'middle' }, style);
                        dia.attributes.textWrap.set.call(this, wrapValue, refBBox, node, wrapAttrs);
                        return { fill: style.color || null };
                    }
                },
                position: function(text, refBBox, node) {
                    // No foreign object
                    if (node instanceof SVGElement) return refBBox.center();
                }
            }
        }
    });

    // LINKS

    var Link = dia.Link;

    Link.define('standard.Link', {
        attrs: {
            line: {
                connection: true,
                stroke: '#333333',
                strokeWidth: 2,
                strokeLinejoin: 'round',
                targetMarker: {
                    type: 'path',
                    d: 'M 10 -5 0 0 10 5 z'
                }
            },
            wrapper: {
                connection: true,
                strokeWidth: 10,
                strokeLinejoin: 'round'
            }
        }
    }, {
        markup: [{
            tagName: 'path',
            selector: 'wrapper',
            attributes: {
                'fill': 'none',
                'cursor': 'pointer',
                'stroke': 'transparent'
            }
        }, {
            tagName: 'path',
            selector: 'line',
            attributes: {
                'fill': 'none',
                'pointer-events': 'none'
            }
        }]
    });

    Link.define('standard.DoubleLink', {
        attrs: {
            line: {
                connection: true,
                stroke: '#DDDDDD',
                strokeWidth: 4,
                strokeLinejoin: 'round',
                targetMarker: {
                    type: 'path',
                    stroke: '#000000',
                    d: 'M 10 -3 10 -10 -2 0 10 10 10 3'
                }
            },
            outline: {
                connection: true,
                stroke: '#000000',
                strokeWidth: 6,
                strokeLinejoin: 'round'
            }
        }
    }, {
        markup: [{
            tagName: 'path',
            selector: 'outline',
            attributes: {
                'fill': 'none'
            }
        }, {
            tagName: 'path',
            selector: 'line',
            attributes: {
                'fill': 'none'
            }
        }]
    });

    Link.define('standard.ShadowLink', {
        attrs: {
            line: {
                connection: true,
                stroke: '#FF0000',
                strokeWidth: 20,
                strokeLinejoin: 'round',
                targetMarker: {
                    'type': 'path',
                    'stroke': 'none',
                    'd': 'M 0 -10 -10 0 0 10 z'
                },
                sourceMarker: {
                    'type': 'path',
                    'stroke': 'none',
                    'd': 'M -10 -10 0 0 -10 10 0 10 0 -10 z'
                }
            },
            shadow: {
                connection: true,
                refX: 3,
                refY: 6,
                stroke: '#000000',
                strokeOpacity: 0.2,
                strokeWidth: 20,
                strokeLinejoin: 'round',
                targetMarker: {
                    'type': 'path',
                    'd': 'M 0 -10 -10 0 0 10 z',
                    'stroke': 'none'
                },
                sourceMarker: {
                    'type': 'path',
                    'stroke': 'none',
                    'd': 'M -10 -10 0 0 -10 10 0 10 0 -10 z'
                }
            }
        }
    }, {
        markup: [{
            tagName: 'path',
            selector: 'shadow',
            attributes: {
                'fill': 'none'
            }
        }, {
            tagName: 'path',
            selector: 'line',
            attributes: {
                'fill': 'none'
            }
        }]
    });


})(joint.dia, joint.util, joint.env, V);

joint.routers.manhattan = (function(g, _, joint, util) {

    'use strict';

    var config = {

        // size of the step to find a route (the grid of the manhattan pathfinder)
        step: 10,

        // the number of route finding loops that cause the router to abort
        // returns fallback route instead
        maximumLoops: 2000,

        // the number of decimal places to round floating point coordinates
        precision: 10,

        // maximum change of direction
        maxAllowedDirectionChange: 90,

        // should the router use perpendicular linkView option?
        // does not connect anchor of element but rather a point close-by that is orthogonal
        // this looks much better
        perpendicular: true,

        // should the source and/or target not be considered as obstacles?
        excludeEnds: [], // 'source', 'target'

        // should certain types of elements not be considered as obstacles?
        excludeTypes: ['basic.Text'],

        // possible starting directions from an element
        startDirections: ['top', 'right', 'bottom', 'left'],

        // possible ending directions to an element
        endDirections: ['top', 'right', 'bottom', 'left'],

        // specify the directions used above and what they mean
        directionMap: {
            top: { x: 0, y: -1 },
            right: { x: 1, y: 0 },
            bottom: { x: 0, y: 1 },
            left: { x: -1, y: 0 }
        },

        // cost of an orthogonal step
        cost: function() {

            return this.step;
        },

        // an array of directions to find next points on the route
        // different from start/end directions
        directions: function() {

            var step = this.step;
            var cost = this.cost();

            return [
                { offsetX: step  , offsetY: 0     , cost: cost },
                { offsetX: 0     , offsetY: step  , cost: cost },
                { offsetX: -step , offsetY: 0     , cost: cost },
                { offsetX: 0     , offsetY: -step , cost: cost }
            ];
        },

        // a penalty received for direction change
        penalties: function() {

            return {
                0: 0,
                45: this.step / 2,
                90: this.step / 2
            };
        },

        // padding applied on the element bounding boxes
        paddingBox: function() {

            var step = this.step;

            return {
                x: -step,
                y: -step,
                width: 2 * step,
                height: 2 * step
            };
        },

        // a router to use when the manhattan router fails
        // (one of the partial routes returns null)
        fallbackRouter: function(vertices, opt, linkView) {

            if (!util.isFunction(joint.routers.orthogonal)) {
                throw new Error('Manhattan requires the orthogonal router as default fallback.');
            }

            return joint.routers.orthogonal(vertices, util.assign({}, config, opt), linkView);
        },

        /* Deprecated */
        // a simple route used in situations when main routing method fails
        // (exceed max number of loop iterations, inaccessible)
        fallbackRoute: function(from, to, opt) {

            return null; // null result will trigger the fallbackRouter

            // left for reference:
            /*// Find an orthogonal route ignoring obstacles.

            var point = ((opt.previousDirAngle || 0) % 180 === 0)
                    ? new g.Point(from.x, to.y)
                    : new g.Point(to.x, from.y);

            return [point];*/
        },

        // if a function is provided, it's used to route the link while dragging an end
        // i.e. function(from, to, opt) { return []; }
        draggingRoute: null
    };

    // HELPER CLASSES //

    // Map of obstacles
    // Helper structure to identify whether a point lies inside an obstacle.
    function ObstacleMap(opt) {

        this.map = {};
        this.options = opt;
        // tells how to divide the paper when creating the elements map
        this.mapGridSize = 100;
    }

    ObstacleMap.prototype.build = function(graph, link) {

        var opt = this.options;

        // source or target element could be excluded from set of obstacles
        var excludedEnds = util.toArray(opt.excludeEnds).reduce(function(res, item) {

            var end = link.get(item);
            if (end) {
                var cell = graph.getCell(end.id);
                if (cell) {
                    res.push(cell);
                }
            }

            return res;
        }, []);

        // Exclude any embedded elements from the source and the target element.
        var excludedAncestors = [];

        var source = graph.getCell(link.get('source').id);
        if (source) {
            excludedAncestors = util.union(excludedAncestors, source.getAncestors().map(function(cell) { return cell.id }));
        }

        var target = graph.getCell(link.get('target').id);
        if (target) {
            excludedAncestors = util.union(excludedAncestors, target.getAncestors().map(function(cell) { return cell.id }));
        }

        // Builds a map of all elements for quicker obstacle queries (i.e. is a point contained
        // in any obstacle?) (a simplified grid search).
        // The paper is divided into smaller cells, where each holds information about which
        // elements belong to it. When we query whether a point lies inside an obstacle we
        // don't need to go through all obstacles, we check only those in a particular cell.
        var mapGridSize = this.mapGridSize;

        graph.getElements().reduce(function(map, element) {

            var isExcludedType = util.toArray(opt.excludeTypes).includes(element.get('type'));
            var isExcludedEnd = excludedEnds.find(function(excluded) { return excluded.id === element.id });
            var isExcludedAncestor = excludedAncestors.includes(element.id);

            var isExcluded = isExcludedType || isExcludedEnd || isExcludedAncestor;
            if (!isExcluded) {
                var bbox = element.getBBox().moveAndExpand(opt.paddingBox);

                var origin = bbox.origin().snapToGrid(mapGridSize);
                var corner = bbox.corner().snapToGrid(mapGridSize);

                for (var x = origin.x; x <= corner.x; x += mapGridSize) {
                    for (var y = origin.y; y <= corner.y; y += mapGridSize) {
                        var gridKey = x + '@' + y;
                        map[gridKey] = map[gridKey] || [];
                        map[gridKey].push(bbox);
                    }
                }
            }

            return map;
        }, this.map);

        return this;
    };

    ObstacleMap.prototype.isPointAccessible = function(point) {

        var mapKey = point.clone().snapToGrid(this.mapGridSize).toString();

        return util.toArray(this.map[mapKey]).every( function(obstacle) {
            return !obstacle.containsPoint(point);
        });
    };

    // Sorted Set
    // Set of items sorted by given value.
    function SortedSet() {
        this.items = [];
        this.hash = {};
        this.values = {};
        this.OPEN = 1;
        this.CLOSE = 2;
    }

    SortedSet.prototype.add = function(item, value) {

        if (this.hash[item]) {
            // item removal
            this.items.splice(this.items.indexOf(item), 1);
        } else {
            this.hash[item] = this.OPEN;
        }

        this.values[item] = value;

        var index = joint.util.sortedIndex(this.items, item, function(i) {
            return this.values[i];
        }.bind(this));

        this.items.splice(index, 0, item);
    };

    SortedSet.prototype.remove = function(item) {

        this.hash[item] = this.CLOSE;
    };

    SortedSet.prototype.isOpen = function(item) {

        return this.hash[item] === this.OPEN;
    };

    SortedSet.prototype.isClose = function(item) {

        return this.hash[item] === this.CLOSE;
    };

    SortedSet.prototype.isEmpty = function() {

        return this.items.length === 0;
    };

    SortedSet.prototype.pop = function() {

        var item =  this.items.shift();
        this.remove(item);
        return item;
    };

    // HELPERS //

    // return source bbox
    function getSourceBBox(linkView, opt) {

        // expand by padding box
        if (opt && opt.paddingBox) return linkView.sourceBBox.clone().moveAndExpand(opt.paddingBox);

        return linkView.sourceBBox.clone();
    }

    // return target bbox
    function getTargetBBox(linkView, opt) {

        // expand by padding box
        if (opt && opt.paddingBox) return linkView.targetBBox.clone().moveAndExpand(opt.paddingBox);

        return linkView.targetBBox.clone();
    }

    // return source anchor
    function getSourceAnchor(linkView, opt) {

        if (linkView.sourceAnchor) return linkView.sourceAnchor;

        // fallback: center of bbox
        var sourceBBox = getSourceBBox(linkView, opt);
        return sourceBBox.center();
    }

    // return target anchor
    function getTargetAnchor(linkView, opt) {

        if (linkView.targetAnchor) return linkView.targetAnchor;

        // fallback: center of bbox
        var targetBBox = getTargetBBox(linkView, opt);
        return targetBBox.center(); // default
    }

    // returns a direction index from start point to end point
    // corrects for grid deformation between start and end
    function getDirectionAngle(start, end, numDirections, grid, opt) {

        var quadrant = 360 / numDirections;
        var angleTheta = start.theta(fixAngleEnd(start, end, grid, opt));
        var normalizedAngle = g.normalizeAngle(angleTheta + (quadrant / 2));
        return quadrant * Math.floor(normalizedAngle / quadrant);
    }

    // helper function for getDirectionAngle()
    // corrects for grid deformation
    // (if a point is one grid steps away from another in both dimensions,
    // it is considered to be 45 degrees away, even if the real angle is different)
    // this causes visible angle discrepancies if `opt.step` is much larger than `paper.gridSize`
    function fixAngleEnd(start, end, grid, opt) {

        var step = opt.step;

        var diffX = end.x - start.x;
        var diffY = end.y - start.y;

        var gridStepsX = diffX / grid.x;
        var gridStepsY = diffY / grid.y

        var distanceX = gridStepsX * step;
        var distanceY = gridStepsY * step;

        return new g.Point(start.x + distanceX, start.y + distanceY);
    }

    // return the change in direction between two direction angles
    function getDirectionChange(angle1, angle2) {

        var directionChange = Math.abs(angle1 - angle2);
        return (directionChange > 180) ? (360 - directionChange) : directionChange;
    }

    // fix direction offsets according to current grid
    function getGridOffsets(directions, grid, opt) {

        var step = opt.step;

        util.toArray(opt.directions).forEach(function(direction) {

            direction.gridOffsetX = (direction.offsetX / step) * grid.x;
            direction.gridOffsetY = (direction.offsetY / step) * grid.y;
        });
    }

    // get grid size in x and y dimensions, adapted to source and target positions
    function getGrid(step, source, target) {

        return {
            source: source.clone(),
            x: getGridDimension(target.x - source.x, step),
            y: getGridDimension(target.y - source.y, step)
        }
    }

    // helper function for getGrid()
    function getGridDimension(diff, step) {

        // return step if diff = 0
        if (!diff) return step;

        var absDiff = Math.abs(diff);
        var numSteps = Math.round(absDiff / step);

        // return absDiff if less than one step apart
        if (!numSteps) return absDiff;

        // otherwise, return corrected step
        var roundedDiff = numSteps * step;
        var remainder = absDiff - roundedDiff;
        var stepCorrection = remainder / numSteps;

        return step + stepCorrection;
    }

    // return a clone of point snapped to grid
    function snapToGrid(point, grid) {

        var source = grid.source;

        var snappedX = g.snapToGrid(point.x - source.x, grid.x) + source.x;
        var snappedY = g.snapToGrid(point.y - source.y, grid.y) + source.y;

        return new g.Point(snappedX, snappedY);
    }

    // round the point to opt.precision
    function round(point, opt) {

        if (!point) return point;

        return point.round(opt.precision);
    }

    // return a string representing the point
    // string is rounded to nearest int in both dimensions
    function getKey(point) {

        return point.clone().round().toString();
    }

    // return a normalized vector from given point
    // used to determine the direction of a difference of two points
    function normalizePoint(point) {

        return new g.Point(
            point.x === 0 ? 0 : Math.abs(point.x) / point.x,
            point.y === 0 ? 0 : Math.abs(point.y) / point.y
        );
    }

    // PATHFINDING //

    // reconstructs a route by concatenating points with their parents
    function reconstructRoute(parents, points, tailPoint, from, to, opt) {

        var route = [];

        var prevDiff = normalizePoint(to.difference(tailPoint));

        var currentKey = getKey(tailPoint);
        var parent = parents[currentKey];

        var point;
        while (parent) {

            point = round(points[currentKey], opt);

            var diff = normalizePoint(point.difference(round(parent.clone(), opt)));
            if (!diff.equals(prevDiff)) {
                route.unshift(point);
                prevDiff = diff;
            }

            currentKey = getKey(parent);
            parent = parents[currentKey];
        }

        var leadPoint = round(points[currentKey], opt);

        var fromDiff = normalizePoint(leadPoint.difference(from));
        if (!fromDiff.equals(prevDiff)) {
            route.unshift(leadPoint);
        }

        return route;
    }

    // heuristic method to determine the distance between two points
    function estimateCost(from, endPoints) {

        var min = Infinity;

        for (var i = 0, len = endPoints.length; i < len; i++) {
            var cost = from.manhattanDistance(endPoints[i]);
            if (cost < min) min = cost;
        }

        return min;
    }

    // find points around the bbox taking given directions into account
    // lines are drawn from anchor in given directions, intersections recorded
    // if anchor is outside bbox, only those directions that intersect get a rect point
    // the anchor itself is returned as rect point (representing some directions)
    // (since those directions are unobstructed by the bbox)
    function getRectPoints(anchor, bbox, directionList, grid, opt) {

        var directionMap = opt.directionMap;

        var snappedAnchor = round(snapToGrid(anchor, grid), opt);
        var snappedCenter = round(snapToGrid(bbox.center(), grid), opt);
        var anchorCenterVector = snappedAnchor.difference(snappedCenter);

        var keys = util.isObject(directionMap) ? Object.keys(directionMap) : [];
        var dirList = util.toArray(directionList);
        var rectPoints = keys.reduce(function(res, key) {

            if (dirList.includes(key)) {
                var direction = directionMap[key];

                // create a line that is guaranteed to intersect the bbox if bbox is in the direction
                // even if anchor lies outside of bbox
                var endpoint = new g.Point(
                    snappedAnchor.x + direction.x * (Math.abs(anchorCenterVector.x) + bbox.width),
                    snappedAnchor.y + direction.y * (Math.abs(anchorCenterVector.y) + bbox.height)
                );
                var intersectionLine = new g.Line(anchor, endpoint);

                // get the farther intersection, in case there are two
                // (that happens if anchor lies next to bbox)
                var intersections = intersectionLine.intersect(bbox) || [];
                var numIntersections = intersections.length;
                var farthestIntersectionDistance;
                var farthestIntersection = null;
                for (var i = 0; i < numIntersections; i++) {
                    var currentIntersection = intersections[i];
                    var distance = snappedAnchor.squaredDistance(currentIntersection);
                    if (farthestIntersectionDistance === undefined || (distance > farthestIntersectionDistance)) {
                        farthestIntersectionDistance = distance;
                        farthestIntersection = snapToGrid(currentIntersection, grid);
                    }
                }
                var point = round(farthestIntersection, opt);

                // if an intersection was found in this direction, it is our rectPoint
                if (point) {
                    // if the rectPoint lies inside the bbox, offset it by one more step
                    if (bbox.containsPoint(point)) {
                        round(point.offset(direction.x * grid.x, direction.y * grid.y), opt);
                    }

                    // then add the point to the result array
                    res.push(point);
                }
            }

            return res;
        }, []);

        // if anchor lies outside of bbox, add it to the array of points
        if (!bbox.containsPoint(snappedAnchor)) rectPoints.push(snappedAnchor);

        return rectPoints;
    }

    // finds the route between two points/rectangles (`from`, `to`) implementing A* algorithm
    // rectangles get rect points assigned by getRectPoints()
    function findRoute(from, to, map, opt) {

        // Get grid for this route.

        var sourceAnchor, targetAnchor;

        if (from instanceof g.Rect) { // `from` is sourceBBox
            sourceAnchor = getSourceAnchor(this, opt).clone();
        } else {
            sourceAnchor = from.clone();
        }

        if (to instanceof g.Rect) { // `to` is targetBBox
            targetAnchor = getTargetAnchor(this, opt).clone();
        } else {
            targetAnchor = to.clone();
        }

        var grid = getGrid(opt.step, sourceAnchor, targetAnchor);

        // Get pathfinding points.

        var start, end;
        var startPoints, endPoints;

        // set of points we start pathfinding from
        if (from instanceof g.Rect) { // `from` is sourceBBox
            start = round(snapToGrid(sourceAnchor, grid), opt);
            startPoints = getRectPoints(start, from, opt.startDirections, grid, opt);

        } else {
            start = round(snapToGrid(sourceAnchor, grid), opt);
            startPoints = [start];
        }

        // set of points we want the pathfinding to finish at
        if (to instanceof g.Rect) { // `to` is targetBBox
            end = round(snapToGrid(targetAnchor, grid), opt);
            endPoints = getRectPoints(targetAnchor, to, opt.endDirections, grid, opt);

        } else {
            end = round(snapToGrid(targetAnchor, grid), opt);
            endPoints = [end];
        }

        // take into account only accessible rect points (those not under obstacles)
        startPoints = startPoints.filter(map.isPointAccessible, map);
        endPoints = endPoints.filter(map.isPointAccessible, map);

        // Check that there is an accessible route point on both sides.
        // Otherwise, use fallbackRoute().
        if (startPoints.length > 0 && endPoints.length > 0) {

            // The set of tentative points to be evaluated, initially containing the start points.
            // Rounded to nearest integer for simplicity.
            var openSet = new SortedSet();
            // Keeps reference to actual points for given elements of the open set.
            var points = {};
            // Keeps reference to a point that is immediate predecessor of given element.
            var parents = {};
            // Cost from start to a point along best known path.
            var costs = {};

            for (var i = 0, n = startPoints.length; i < n; i++) {
                var point = startPoints[i];

                var key = getKey(point);
                openSet.add(key, estimateCost(point, endPoints));
                points[key] = point;
                costs[key] = 0;
            }

            var previousRouteDirectionAngle = opt.previousDirectionAngle; // undefined for first route
            var isPathBeginning = (previousRouteDirectionAngle === undefined);

            // directions
            var direction, directionChange;
            var directions = opt.directions;
            getGridOffsets(directions, grid, opt);

            var numDirections = directions.length;

            var endPointsKeys = util.toArray(endPoints).reduce(function(res, endPoint) {

                var key = getKey(endPoint);
                res.push(key);
                return res;
            }, []);

            // main route finding loop
            var loopsRemaining = opt.maximumLoops;
            while (!openSet.isEmpty() && loopsRemaining > 0) {

                // remove current from the open list
                var currentKey = openSet.pop();
                var currentPoint = points[currentKey];
                var currentParent = parents[currentKey];
                var currentCost = costs[currentKey];

                var isRouteBeginning = (currentParent === undefined); // undefined for route starts
                var isStart = currentPoint.equals(start); // (is source anchor or `from` point) = can leave in any direction

                var previousDirectionAngle;
                if (!isRouteBeginning) previousDirectionAngle = getDirectionAngle(currentParent, currentPoint, numDirections, grid, opt); // a vertex on the route
                else if (!isPathBeginning) previousDirectionAngle = previousRouteDirectionAngle; // beginning of route on the path
                else if (!isStart) previousDirectionAngle = getDirectionAngle(start, currentPoint, numDirections, grid, opt); // beginning of path, start rect point
                else previousDirectionAngle = null; // beginning of path, source anchor or `from` point

                // check if we reached any endpoint
                if (endPointsKeys.indexOf(currentKey) >= 0) {
                    opt.previousDirectionAngle = previousDirectionAngle;
                    return reconstructRoute(parents, points, currentPoint, start, end, opt);
                }

                // go over all possible directions and find neighbors
                for (i = 0; i < numDirections; i++) {
                    direction = directions[i];

                    var directionAngle = direction.angle;
                    directionChange = getDirectionChange(previousDirectionAngle, directionAngle);

                    // if the direction changed rapidly, don't use this point
                    // any direction is allowed for starting points
                    if (!(isPathBeginning && isStart) && directionChange > opt.maxAllowedDirectionChange) continue;

                    var neighborPoint = currentPoint.clone().offset(direction.gridOffsetX, direction.gridOffsetY);
                    var neighborKey = getKey(neighborPoint);

                    // Closed points from the openSet were already evaluated.
                    if (openSet.isClose(neighborKey) || !map.isPointAccessible(neighborPoint)) continue;

                    // We can only enter end points at an acceptable angle.
                    if (endPointsKeys.indexOf(neighborKey) >= 0) { // neighbor is an end point
                        round(neighborPoint, opt); // remove rounding errors

                        var isNeighborEnd = neighborPoint.equals(end); // (is target anchor or `to` point) = can be entered in any direction

                        if (!isNeighborEnd) {
                            var endDirectionAngle = getDirectionAngle(neighborPoint, end, numDirections, grid, opt);
                            var endDirectionChange = getDirectionChange(directionAngle, endDirectionAngle);

                            if (endDirectionChange > opt.maxAllowedDirectionChange) continue;
                        }
                    }

                    // The current direction is ok.

                    var neighborCost = direction.cost;
                    var neighborPenalty = isStart ? 0 : opt.penalties[directionChange]; // no penalties for start point
                    var costFromStart = currentCost + neighborCost + neighborPenalty;

                    if (!openSet.isOpen(neighborKey) || (costFromStart < costs[neighborKey])) {
                        // neighbor point has not been processed yet
                        // or the cost of the path from start is lower than previously calculated

                        points[neighborKey] = neighborPoint;
                        parents[neighborKey] = currentPoint;
                        costs[neighborKey] = costFromStart;
                        openSet.add(neighborKey, costFromStart + estimateCost(neighborPoint, endPoints));
                    }
                }

                loopsRemaining--;
            }
        }

        // no route found (`to` point either wasn't accessible or finding route took
        // way too much calculation)
        return opt.fallbackRoute.call(this, start, end, opt);
    }

    // resolve some of the options
    function resolveOptions(opt) {

        opt.directions = util.result(opt, 'directions');
        opt.penalties = util.result(opt, 'penalties');
        opt.paddingBox = util.result(opt, 'paddingBox');

        util.toArray(opt.directions).forEach(function(direction) {

            var point1 = new g.Point(0, 0);
            var point2 = new g.Point(direction.offsetX, direction.offsetY);

            direction.angle = g.normalizeAngle(point1.theta(point2));
        });
    }

    // initialization of the route finding
    function router(vertices, opt, linkView) {

        resolveOptions(opt);

        // enable/disable linkView perpendicular option
        linkView.options.perpendicular = !!opt.perpendicular;

        var sourceBBox = getSourceBBox(linkView, opt);
        var targetBBox = getTargetBBox(linkView, opt);

        var sourceAnchor = getSourceAnchor(linkView, opt);
        //var targetAnchor = getTargetAnchor(linkView, opt);

        // pathfinding
        var map = (new ObstacleMap(opt)).build(linkView.paper.model, linkView.model);
        var oldVertices = util.toArray(vertices).map(g.Point);
        var newVertices = [];
        var tailPoint = sourceAnchor; // the origin of first route's grid, does not need snapping

        // find a route by concatenating all partial routes (routes need to pass through vertices)
        // source -> vertex[1] -> ... -> vertex[n] -> target
        for (var i = 0, len = oldVertices.length; i <= len; i++) {

            var partialRoute = null;

            var from = to || sourceBBox;
            var to = oldVertices[i];

            if (!to) {
                // this is the last iteration
                // we ran through all vertices in oldVertices
                // 'to' is not a vertex.

                to = targetBBox;

                // If the target is a point (i.e. it's not an element), we
                // should use dragging route instead of main routing method if it has been provided.
                var isEndingAtPoint = !linkView.model.get('source').id || !linkView.model.get('target').id;

                if (isEndingAtPoint && util.isFunction(opt.draggingRoute)) {
                    // Make sure we are passing points only (not rects).
                    var dragFrom = (from === sourceBBox) ? sourceAnchor : from;
                    var dragTo = to.origin();

                    partialRoute = opt.draggingRoute.call(linkView, dragFrom, dragTo, opt);
                }
            }

            // if partial route has not been calculated yet use the main routing method to find one
            partialRoute = partialRoute || findRoute.call(linkView, from, to, map, opt);

            if (partialRoute === null) { // the partial route cannot be found
                return opt.fallbackRouter(vertices, opt, linkView);
            }

            var leadPoint = partialRoute[0];

            // remove the first point if the previous partial route had the same point as last
            if (leadPoint && leadPoint.equals(tailPoint)) partialRoute.shift();

            // save tailPoint for next iteration
            tailPoint = partialRoute[partialRoute.length - 1] || tailPoint;

            Array.prototype.push.apply(newVertices, partialRoute);
        }

        return newVertices;
    }

    // public function
    return function(vertices, opt, linkView) {

        return router(vertices, util.assign({}, config, opt), linkView);
    };

})(g, _, joint, joint.util);

joint.routers.metro = (function(util) {

    var config = {

        maxAllowedDirectionChange: 45,

        // cost of a diagonal step
        diagonalCost: function() {

            var step = this.step;
            return Math.ceil(Math.sqrt(step * step << 1));
        },

        // an array of directions to find next points on the route
        // different from start/end directions
        directions: function() {

            var step = this.step;
            var cost = this.cost();
            var diagonalCost = this.diagonalCost();

            return [
                { offsetX: step  , offsetY: 0     , cost: cost },
                { offsetX: step  , offsetY: step  , cost: diagonalCost },
                { offsetX: 0     , offsetY: step  , cost: cost },
                { offsetX: -step , offsetY: step  , cost: diagonalCost },
                { offsetX: -step , offsetY: 0     , cost: cost },
                { offsetX: -step , offsetY: -step , cost: diagonalCost },
                { offsetX: 0     , offsetY: -step , cost: cost },
                { offsetX: step  , offsetY: -step , cost: diagonalCost }
            ];
        },

        // a simple route used in situations when main routing method fails
        // (exceed max number of loop iterations, inaccessible)
        fallbackRoute: function(from, to, opt) {

            // Find a route which breaks by 45 degrees ignoring all obstacles.

            var theta = from.theta(to);

            var route = [];

            var a = { x: to.x, y: from.y };
            var b = { x: from.x, y: to.y };

            if (theta % 180 > 90) {
                var t = a;
                a = b;
                b = t;
            }

            var p1 = (theta % 90) < 45 ? a : b;
            var l1 = new g.Line(from, p1);

            var alpha = 90 * Math.ceil(theta / 90);

            var p2 = g.Point.fromPolar(l1.squaredLength(), g.toRad(alpha + 135), p1);
            var l2 = new g.Line(to, p2);

            var intersectionPoint = l1.intersection(l2);
            var point = intersectionPoint ? intersectionPoint : to;

            var directionFrom = intersectionPoint ? point : from;

            var quadrant = 360 / opt.directions.length;
            var angleTheta = directionFrom.theta(to);
            var normalizedAngle = g.normalizeAngle(angleTheta + (quadrant / 2));
            var directionAngle = quadrant * Math.floor(normalizedAngle / quadrant);

            opt.previousDirectionAngle = directionAngle;

            if (point) route.push(point.round());
            route.push(to);

            return route;
        }
    };

    // public function
    return function(vertices, opt, linkView) {

        if (!util.isFunction(joint.routers.manhattan)) {
            throw new Error('Metro requires the manhattan router.');
        }

        return joint.routers.manhattan(vertices, util.assign({}, config, opt), linkView);
    };

})(joint.util);

// Does not make any changes to vertices.
// Returns the arguments that are passed to it, unchanged.
joint.routers.normal = function(vertices, opt, linkView) {

    return vertices;
};

// Routes the link always to/from a certain side
//
// Arguments:
//   padding ... gap between the element and the first vertex. :: Default 40.
//   side ... 'left' | 'right' | 'top' | 'bottom' :: Default 'bottom'.
//
joint.routers.oneSide = function(vertices, opt, linkView) {

    var side = opt.side || 'bottom';
    var padding = opt.padding || 40;

    // LinkView contains cached source an target bboxes.
    // Note that those are Geometry rectangle objects.
    var sourceBBox = linkView.sourceBBox;
    var targetBBox = linkView.targetBBox;
    var sourcePoint = sourceBBox.center();
    var targetPoint = targetBBox.center();

    var coordinate, dimension, direction;

    switch (side) {
        case 'bottom':
            direction = 1;
            coordinate = 'y';
            dimension = 'height';
            break;
        case 'top':
            direction = -1;
            coordinate = 'y';
            dimension = 'height';
            break;
        case 'left':
            direction = -1;
            coordinate = 'x';
            dimension = 'width';
            break;
        case 'right':
            direction = 1;
            coordinate = 'x';
            dimension = 'width';
            break;
        default:
            throw new Error('Router: invalid side');
    }

    // move the points from the center of the element to outside of it.
    sourcePoint[coordinate] += direction * (sourceBBox[dimension] / 2 + padding);
    targetPoint[coordinate] += direction * (targetBBox[dimension] / 2 + padding);

    // make link orthogonal (at least the first and last vertex).
    if (direction * (sourcePoint[coordinate] - targetPoint[coordinate]) > 0) {
        targetPoint[coordinate] = sourcePoint[coordinate];
    } else {
        sourcePoint[coordinate] = targetPoint[coordinate];
    }

    return [sourcePoint].concat(vertices, targetPoint);
};

joint.routers.orthogonal = (function(util) {

    // bearing -> opposite bearing
    var opposites = {
        N: 'S',
        S: 'N',
        E: 'W',
        W: 'E'
    };

    // bearing -> radians
    var radians = {
        N: -Math.PI / 2 * 3,
        S: -Math.PI / 2,
        E: 0,
        W: Math.PI
    };

    // HELPERS //

    // returns a point `p` where lines p,p1 and p,p2 are perpendicular and p is not contained
    // in the given box
    function freeJoin(p1, p2, bbox) {

        var p = new g.Point(p1.x, p2.y);
        if (bbox.containsPoint(p)) p = new g.Point(p2.x, p1.y);
        // kept for reference
        // if (bbox.containsPoint(p)) p = null;

        return p;
    }

    // returns either width or height of a bbox based on the given bearing
    function getBBoxSize(bbox, bearing) {

        return bbox[(bearing === 'W' || bearing === 'E') ? 'width' : 'height'];
    }

    // simple bearing method (calculates only orthogonal cardinals)
    function getBearing(from, to) {

        if (from.x === to.x) return (from.y > to.y) ? 'N' : 'S';
        if (from.y === to.y) return (from.x > to.x) ? 'W' : 'E';
        return null;
    }

    // transform point to a rect
    function getPointBox(p) {

        return new g.Rect(p.x, p.y, 0, 0);
    }

    // return source bbox
    function getSourceBBox(linkView, opt) {

        var padding = (opt && opt.elementPadding) || 20;
        return linkView.sourceBBox.clone().inflate(padding);
    }

    // return target bbox
    function getTargetBBox(linkView, opt) {

        var padding = (opt && opt.elementPadding) || 20;
        return linkView.targetBBox.clone().inflate(padding);
    }

    // return source anchor
    function getSourceAnchor(linkView, opt) {

        if (linkView.sourceAnchor) return linkView.sourceAnchor;

        // fallback: center of bbox
        var sourceBBox = getSourceBBox(linkView, opt);
        return sourceBBox.center();
    }

    // return target anchor
    function getTargetAnchor(linkView, opt) {

        if (linkView.targetAnchor) return linkView.targetAnchor;

        // fallback: center of bbox
        var targetBBox = getTargetBBox(linkView, opt);
        return targetBBox.center(); // default
    }

    // PARTIAL ROUTERS //

    function vertexVertex(from, to, bearing) {

        var p1 = new g.Point(from.x, to.y);
        var p2 = new g.Point(to.x, from.y);
        var d1 = getBearing(from, p1);
        var d2 = getBearing(from, p2);
        var opposite = opposites[bearing];

        var p = (d1 === bearing || (d1 !== opposite && (d2 === opposite || d2 !== bearing))) ? p1 : p2;

        return { points: [p], direction: getBearing(p, to) };
    }

    function elementVertex(from, to, fromBBox) {

        var p = freeJoin(from, to, fromBBox);

        return { points: [p], direction: getBearing(p, to) };
    }

    function vertexElement(from, to, toBBox, bearing) {

        var route = {};

        var points = [new g.Point(from.x, to.y), new g.Point(to.x, from.y)];
        var freePoints = points.filter(function(pt) { return !toBBox.containsPoint(pt); });
        var freeBearingPoints = freePoints.filter(function(pt) { return getBearing(pt, from) !== bearing; });

        var p;

        if (freeBearingPoints.length > 0) {
            // Try to pick a point which bears the same direction as the previous segment.

            p = freeBearingPoints.filter(function(pt) { return getBearing(from, pt) === bearing; }).pop();
            p = p || freeBearingPoints[0];

            route.points = [p];
            route.direction = getBearing(p, to);

        } else {
            // Here we found only points which are either contained in the element or they would create
            // a link segment going in opposite direction from the previous one.
            // We take the point inside element and move it outside the element in the direction the
            // route is going. Now we can join this point with the current end (using freeJoin).

            p = util.difference(points, freePoints)[0];

            var p2 = (new g.Point(to)).move(p, -getBBoxSize(toBBox, bearing) / 2);
            var p1 = freeJoin(p2, from, toBBox);

            route.points = [p1, p2];
            route.direction = getBearing(p2, to);
        }

        return route;
    }

    function elementElement(from, to, fromBBox, toBBox) {

        var route = elementVertex(to, from, toBBox);
        var p1 = route.points[0];

        if (fromBBox.containsPoint(p1)) {

            route = elementVertex(from, to, fromBBox);
            var p2 = route.points[0];

            if (toBBox.containsPoint(p2)) {

                var fromBorder = (new g.Point(from)).move(p2, -getBBoxSize(fromBBox, getBearing(from, p2)) / 2);
                var toBorder = (new g.Point(to)).move(p1, -getBBoxSize(toBBox, getBearing(to, p1)) / 2);
                var mid = (new g.Line(fromBorder, toBorder)).midpoint();

                var startRoute = elementVertex(from, mid, fromBBox);
                var endRoute = vertexVertex(mid, to, startRoute.direction);

                route.points = [startRoute.points[0], endRoute.points[0]];
                route.direction = endRoute.direction;
            }
        }

        return route;
    }

    // Finds route for situations where one element is inside the other.
    // Typically the route is directed outside the outer element first and
    // then back towards the inner element.
    function insideElement(from, to, fromBBox, toBBox, bearing) {

        var route = {};
        var boundary = fromBBox.union(toBBox).inflate(1);

        // start from the point which is closer to the boundary
        var reversed = boundary.center().distance(to) > boundary.center().distance(from);
        var start = reversed ? to : from;
        var end = reversed ? from : to;

        var p1, p2, p3;

        if (bearing) {
            // Points on circle with radius equals 'W + H` are always outside the rectangle
            // with width W and height H if the center of that circle is the center of that rectangle.
            p1 = g.Point.fromPolar(boundary.width + boundary.height, radians[bearing], start);
            p1 = boundary.pointNearestToPoint(p1).move(p1, -1);

        } else {
            p1 = boundary.pointNearestToPoint(start).move(start, 1);
        }

        p2 = freeJoin(p1, end, boundary);

        if (p1.round().equals(p2.round())) {
            p2 = g.Point.fromPolar(boundary.width + boundary.height, g.toRad(p1.theta(start)) + Math.PI / 2, end);
            p2 = boundary.pointNearestToPoint(p2).move(end, 1).round();
            p3 = freeJoin(p1, p2, boundary);
            route.points = reversed ? [p2, p3, p1] : [p1, p3, p2];

        } else {
            route.points = reversed ? [p2, p1] : [p1, p2];
        }

        route.direction = reversed ? getBearing(p1, to) : getBearing(p2, to);

        return route;
    }

    // MAIN ROUTER //

    // Return points through which a connection needs to be drawn in order to obtain an orthogonal link
    // routing from source to target going through `vertices`.
    function router(vertices, opt, linkView) {

        var padding = opt.elementPadding || 20;

        var sourceBBox = getSourceBBox(linkView, opt);
        var targetBBox = getTargetBBox(linkView, opt);

        var sourceAnchor = getSourceAnchor(linkView, opt);
        var targetAnchor = getTargetAnchor(linkView, opt);

        // if anchor lies outside of bbox, the bbox expands to include it
        sourceBBox = sourceBBox.union(getPointBox(sourceAnchor));
        targetBBox = targetBBox.union(getPointBox(targetAnchor));

        vertices = util.toArray(vertices).map(g.Point);
        vertices.unshift(sourceAnchor);
        vertices.push(targetAnchor);

        var bearing; // bearing of previous route segment

        var orthogonalVertices = []; // the array of found orthogonal vertices to be returned
        for (var i = 0, max = vertices.length - 1; i < max; i++) {

            var route = null;

            var from = vertices[i];
            var to = vertices[i + 1];

            var isOrthogonal = !!getBearing(from, to);

            if (i === 0) { // source

                if (i + 1 === max) { // route source -> target

                    // Expand one of the elements by 1px to detect situations when the two
                    // elements are positioned next to each other with no gap in between.
                    if (sourceBBox.intersect(targetBBox.clone().inflate(1))) {
                        route = insideElement(from, to, sourceBBox, targetBBox);

                    } else if (!isOrthogonal) {
                        route = elementElement(from, to, sourceBBox, targetBBox);
                    }

                } else { // route source -> vertex

                    if (sourceBBox.containsPoint(to)) {
                        route = insideElement(from, to, sourceBBox, getPointBox(to).inflate(padding));

                    } else if (!isOrthogonal) {
                        route = elementVertex(from, to, sourceBBox);
                    }
                }

            } else if (i + 1 === max) { // route vertex -> target

                // prevent overlaps with previous line segment
                var isOrthogonalLoop = isOrthogonal && getBearing(to, from) === bearing;

                if (targetBBox.containsPoint(from) || isOrthogonalLoop) {
                    route = insideElement(from, to, getPointBox(from).inflate(padding), targetBBox, bearing);

                } else if (!isOrthogonal) {
                    route = vertexElement(from, to, targetBBox, bearing);
                }

            } else if (!isOrthogonal) { // route vertex -> vertex
                route = vertexVertex(from, to, bearing);
            }

            // applicable to all routes:

            // set bearing for next iteration
            if (route) {
                Array.prototype.push.apply(orthogonalVertices, route.points);
                bearing = route.direction;

            } else {
                // orthogonal route and not looped
                bearing = getBearing(from, to);
            }

            // push `to` point to identified orthogonal vertices array
            if (i + 1 < max) {
                orthogonalVertices.push(to);
            }
        }

        return orthogonalVertices;
    }

    return router;

})(joint.util);

joint.connectors.normal = function(sourcePoint, targetPoint, route, opt) {

    var raw = opt && opt.raw;
    var points = [sourcePoint].concat(route).concat([targetPoint]);

    var polyline = new g.Polyline(points);
    var path = new g.Path(polyline);

    return (raw) ? path : path.serialize();
};

joint.connectors.rounded = function(sourcePoint, targetPoint, route, opt) {

    opt || (opt = {});

    var offset = opt.radius || 10;
    var raw = opt.raw;
    var path = new g.Path();
    var segment;

    segment = g.Path.createSegment('M', sourcePoint);
    path.appendSegment(segment);

    var _13 = 1 / 3;
    var _23 = 2 / 3;

    var curr;
    var prev, next;
    var prevDistance, nextDistance;
    var startMove, endMove;
    var roundedStart, roundedEnd;
    var control1, control2;

    for (var index = 0, n = route.length; index < n; index++) {

        curr = new g.Point(route[index]);

        prev = route[index - 1] || sourcePoint;
        next = route[index + 1] || targetPoint;

        prevDistance = nextDistance || (curr.distance(prev) / 2);
        nextDistance = curr.distance(next) / 2;

        startMove = -Math.min(offset, prevDistance);
        endMove = -Math.min(offset, nextDistance);

        roundedStart = curr.clone().move(prev, startMove).round();
        roundedEnd = curr.clone().move(next, endMove).round();

        control1 = new g.Point((_13 * roundedStart.x) + (_23 * curr.x), (_23 * curr.y) + (_13 * roundedStart.y));
        control2 = new g.Point((_13 * roundedEnd.x) + (_23 * curr.x), (_23 * curr.y) + (_13 * roundedEnd.y));

        segment = g.Path.createSegment('L', roundedStart);
        path.appendSegment(segment);

        segment = g.Path.createSegment('C', control1, control2, roundedEnd);
        path.appendSegment(segment);
    }

    segment = g.Path.createSegment('L', targetPoint);
    path.appendSegment(segment);

    return (raw) ? path : path.serialize();
};

joint.connectors.smooth = function(sourcePoint, targetPoint, route, opt) {

    var raw = opt && opt.raw;
    var path;

    if (route && route.length !== 0) {

        var points = [sourcePoint].concat(route).concat([targetPoint]);
        var curves = g.Curve.throughPoints(points);

        path = new g.Path(curves);

    } else {
        // if we have no route, use a default cubic bezier curve
        // cubic bezier requires two control points
        // the control points have `x` midway between source and target
        // this produces an S-like curve

        path = new g.Path();

        var segment;

        segment = g.Path.createSegment('M', sourcePoint);
        path.appendSegment(segment);

        if ((Math.abs(sourcePoint.x - targetPoint.x)) >= (Math.abs(sourcePoint.y - targetPoint.y))) {
            var controlPointX = (sourcePoint.x + targetPoint.x) / 2;

            segment = g.Path.createSegment('C', controlPointX, sourcePoint.y, controlPointX, targetPoint.y, targetPoint.x, targetPoint.y);
            path.appendSegment(segment);

        } else {
            var controlPointY = (sourcePoint.y + targetPoint.y) / 2;

            segment = g.Path.createSegment('C', sourcePoint.x, controlPointY, targetPoint.x, controlPointY, targetPoint.x, targetPoint.y);
            path.appendSegment(segment);

        }
    }

    return (raw) ? path : path.serialize();
};

joint.connectors.jumpover = (function(_, g, util) {

    // default size of jump if not specified in options
    var JUMP_SIZE = 5;

    // available jump types
    // first one taken as default
    var JUMP_TYPES = ['arc', 'gap', 'cubic'];

    // takes care of math. error for case when jump is too close to end of line
    var CLOSE_PROXIMITY_PADDING = 1;

    // list of connector types not to jump over.
    var IGNORED_CONNECTORS = ['smooth'];

    /**
     * Transform start/end and route into series of lines
     * @param {g.point} sourcePoint start point
     * @param {g.point} targetPoint end point
     * @param {g.point[]} route optional list of route
     * @return {g.line[]} [description]
     */
    function createLines(sourcePoint, targetPoint, route) {
        // make a flattened array of all points
        var points = [].concat(sourcePoint, route, targetPoint);
        return points.reduce(function(resultLines, point, idx) {
            // if there is a next point, make a line with it
            var nextPoint = points[idx + 1];
            if (nextPoint != null) {
                resultLines[idx] = g.line(point, nextPoint);
            }
            return resultLines;
        }, []);
    }

    function setupUpdating(jumpOverLinkView) {
        var updateList = jumpOverLinkView.paper._jumpOverUpdateList;

        // first time setup for this paper
        if (updateList == null) {
            updateList = jumpOverLinkView.paper._jumpOverUpdateList = [];
            jumpOverLinkView.paper.on('cell:pointerup', updateJumpOver);
            jumpOverLinkView.paper.model.on('reset', function() {
                updateList = jumpOverLinkView.paper._jumpOverUpdateList = [];
            });
        }

        // add this link to a list so it can be updated when some other link is updated
        if (updateList.indexOf(jumpOverLinkView) < 0) {
            updateList.push(jumpOverLinkView);

            // watch for change of connector type or removal of link itself
            // to remove the link from a list of jump over connectors
            jumpOverLinkView.listenToOnce(jumpOverLinkView.model, 'change:connector remove', function() {
                updateList.splice(updateList.indexOf(jumpOverLinkView), 1);
            });
        }
    }

    /**
     * Handler for a batch:stop event to force
     * update of all registered links with jump over connector
     * @param {object} batchEvent optional object with info about batch
     */
    function updateJumpOver() {
        var updateList = this._jumpOverUpdateList;
        for (var i = 0; i < updateList.length; i++) {
            updateList[i].update();
        }
    }

    /**
     * Utility function to collect all intersection poinst of a single
     * line against group of other lines.
     * @param {g.line} line where to find points
     * @param {g.line[]} crossCheckLines lines to cross
     * @return {g.point[]} list of intersection points
     */
    function findLineIntersections(line, crossCheckLines) {
        return util.toArray(crossCheckLines).reduce(function(res, crossCheckLine) {
            var intersection = line.intersection(crossCheckLine);
            if (intersection) {
                res.push(intersection);
            }
            return res;
        }, []);
    }

    /**
     * Sorting function for list of points by their distance.
     * @param {g.point} p1 first point
     * @param {g.point} p2 second point
     * @return {number} squared distance between points
     */
    function sortPoints(p1, p2) {
        return g.line(p1, p2).squaredLength();
    }

    /**
     * Split input line into multiple based on intersection points.
     * @param {g.line} line input line to split
     * @param {g.point[]} intersections poinst where to split the line
     * @param {number} jumpSize the size of jump arc (length empty spot on a line)
     * @return {g.line[]} list of lines being split
     */
    function createJumps(line, intersections, jumpSize) {
        return intersections.reduce(function(resultLines, point, idx) {
            // skipping points that were merged with the previous line
            // to make bigger arc over multiple lines that are close to each other
            if (point.skip === true) {
                return resultLines;
            }

            // always grab the last line from buffer and modify it
            var lastLine = resultLines.pop() || line;

            // calculate start and end of jump by moving by a given size of jump
            var jumpStart = g.point(point).move(lastLine.start, -(jumpSize));
            var jumpEnd = g.point(point).move(lastLine.start, +(jumpSize));

            // now try to look at the next intersection point
            var nextPoint = intersections[idx + 1];
            if (nextPoint != null) {
                var distance = jumpEnd.distance(nextPoint);
                if (distance <= jumpSize) {
                    // next point is close enough, move the jump end by this
                    // difference and mark the next point to be skipped
                    jumpEnd = nextPoint.move(lastLine.start, distance);
                    nextPoint.skip = true;
                }
            } else {
                // this block is inside of `else` as an optimization so the distance is
                // not calculated when we know there are no other intersection points
                var endDistance = jumpStart.distance(lastLine.end);
                // if the end is too close to possible jump, draw remaining line instead of a jump
                if (endDistance < jumpSize * 2 + CLOSE_PROXIMITY_PADDING) {
                    resultLines.push(lastLine);
                    return resultLines;
                }
            }

            var startDistance = jumpEnd.distance(lastLine.start);
            if (startDistance < jumpSize * 2 + CLOSE_PROXIMITY_PADDING) {
                // if the start of line is too close to jump, draw that line instead of a jump
                resultLines.push(lastLine);
                return resultLines;
            }

            // finally create a jump line
            var jumpLine = g.line(jumpStart, jumpEnd);
            // it's just simple line but with a `isJump` property
            jumpLine.isJump = true;

            resultLines.push(
                g.line(lastLine.start, jumpStart),
                jumpLine,
                g.line(jumpEnd, lastLine.end)
            );
            return resultLines;
        }, []);
    }

    /**
     * Assemble `D` attribute of a SVG path by iterating given lines.
     * @param {g.line[]} lines source lines to use
     * @param {number} jumpSize the size of jump arc (length empty spot on a line)
     * @return {string}
     */
    function buildPath(lines, jumpSize, jumpType) {

        var path = new g.Path();
        var segment;

        // first move to the start of a first line
        segment = g.Path.createSegment('M', lines[0].start);
        path.appendSegment(segment);

        // make a paths from lines
        joint.util.toArray(lines).forEach(function(line, index) {

            if (line.isJump) {
                var angle, diff;

                var control1, control2;

                if (jumpType === 'arc') { // approximates semicircle with 2 curves
                    angle = -90;
                    // determine rotation of arc based on difference between points
                    diff = line.start.difference(line.end);
                    // make sure the arc always points up (or right)
                    var xAxisRotate = Number((diff.x < 0) || (diff.x === 0 && diff.y < 0));
                    if (xAxisRotate) angle += 180;

                    var midpoint = line.midpoint();
                    var centerLine = new g.Line(midpoint, line.end).rotate(midpoint, angle);

                    var halfLine;

                    // first half
                    halfLine = new g.Line(line.start, midpoint);

                    control1 = halfLine.pointAt(2 / 3).rotate(line.start, angle);
                    control2 = centerLine.pointAt(1 / 3).rotate(centerLine.end, -angle);

                    segment = g.Path.createSegment('C', control1, control2, centerLine.end);
                    path.appendSegment(segment);

                    // second half
                    halfLine = new g.Line(midpoint, line.end);

                    control1 = centerLine.pointAt(1 / 3).rotate(centerLine.end, angle);
                    control2 = halfLine.pointAt(1 / 3).rotate(line.end, -angle);

                    segment = g.Path.createSegment('C', control1, control2, line.end);
                    path.appendSegment(segment);

                } else if (jumpType === 'gap') {
                    segment = g.Path.createSegment('M', line.end);
                    path.appendSegment(segment);

                } else if (jumpType === 'cubic') { // approximates semicircle with 1 curve
                    angle = line.start.theta(line.end);

                    var xOffset = jumpSize * 0.6;
                    var yOffset = jumpSize * 1.35;

                    // determine rotation of arc based on difference between points
                    diff = line.start.difference(line.end);
                    // make sure the arc always points up (or right)
                    xAxisRotate = Number((diff.x < 0) || (diff.x === 0 && diff.y < 0));
                    if (xAxisRotate) yOffset *= -1;

                    control1 = g.Point(line.start.x + xOffset, line.start.y + yOffset).rotate(line.start, angle);
                    control2 = g.Point(line.end.x - xOffset, line.end.y + yOffset).rotate(line.end, angle);

                    segment = g.Path.createSegment('C', control1, control2, line.end);
                    path.appendSegment(segment);
                }

            } else {
                segment = g.Path.createSegment('L', line.end);
                path.appendSegment(segment);
            }
        });

        return path;
    }

    /**
     * Actual connector function that will be run on every update.
     * @param {g.point} sourcePoint start point of this link
     * @param {g.point} targetPoint end point of this link
     * @param {g.point[]} route of this link
     * @param {object} opt options
     * @property {number} size optional size of a jump arc
     * @return {string} created `D` attribute of SVG path
     */
    return function(sourcePoint, targetPoint, route, opt) { // eslint-disable-line max-params

        setupUpdating(this);

        var raw = opt.raw;
        var jumpSize = opt.size || JUMP_SIZE;
        var jumpType = opt.jump && ('' + opt.jump).toLowerCase();
        var ignoreConnectors = opt.ignoreConnectors || IGNORED_CONNECTORS;

        // grab the first jump type as a default if specified one is invalid
        if (JUMP_TYPES.indexOf(jumpType) === -1) {
            jumpType = JUMP_TYPES[0];
        }

        var paper = this.paper;
        var graph = paper.model;
        var allLinks = graph.getLinks();

        // there is just one link, draw it directly
        if (allLinks.length === 1) {
            return buildPath(
                createLines(sourcePoint, targetPoint, route),
                jumpSize, jumpType
            );
        }

        var thisModel = this.model;
        var thisIndex = allLinks.indexOf(thisModel);
        var defaultConnector = paper.options.defaultConnector || {};

        // not all links are meant to be jumped over.
        var links = allLinks.filter(function(link, idx) {

            var connector = link.get('connector') || defaultConnector;

            // avoid jumping over links with connector type listed in `ignored connectors`.
            if (util.toArray(ignoreConnectors).includes(connector.name)) {
                return false;
            }
            // filter out links that are above this one and  have the same connector type
            // otherwise there would double hoops for each intersection
            if (idx > thisIndex) {
                return connector.name !== 'jumpover';
            }
            return true;
        });

        // find views for all links
        var linkViews = links.map(function(link) {
            return paper.findViewByModel(link);
        });

        // create lines for this link
        var thisLines = createLines(
            sourcePoint,
            targetPoint,
            route
        );

        // create lines for all other links
        var linkLines = linkViews.map(function(linkView) {
            if (linkView == null) {
                return [];
            }
            if (linkView === this) {
                return thisLines;
            }
            return createLines(
                linkView.sourcePoint,
                linkView.targetPoint,
                linkView.route
            );
        }, this);

        // transform lines for this link by splitting with jump lines at
        // points of intersection with other links
        var jumpingLines = thisLines.reduce(function(resultLines, thisLine) {
            // iterate all links and grab the intersections with this line
            // these are then sorted by distance so the line can be split more easily

            var intersections = links.reduce(function(res, link, i) {
                // don't intersection with itself
                if (link !== thisModel) {

                    var lineIntersections = findLineIntersections(thisLine, linkLines[i]);
                    res.push.apply(res, lineIntersections);
                }
                return res;
            }, []).sort(function(a, b) {
                return sortPoints(thisLine.start, a) - sortPoints(thisLine.start, b);
            });

            if (intersections.length > 0) {
                // split the line based on found intersection points
                resultLines.push.apply(resultLines, createJumps(thisLine, intersections, jumpSize));
            } else {
                // without any intersection the line goes uninterrupted
                resultLines.push(thisLine);
            }
            return resultLines;
        }, []);

        var path = buildPath(jumpingLines, jumpSize, jumpType);
        return (raw) ? path : path.serialize();
    };
}(_, g, joint.util));

(function(_, g, joint, util) {

    function portTransformAttrs(point, angle, opt) {

        var trans = point.toJSON();

        trans.angle = angle || 0;

        return joint.util.defaults({}, opt, trans);
    }

    function lineLayout(ports, p1, p2) {
        return ports.map(function(port, index, ports) {
            var p = this.pointAt(((index + 0.5) / ports.length));
            // `dx`,`dy` per port offset option
            if (port.dx || port.dy) {
                p.offset(port.dx || 0, port.dy || 0);
            }

            return portTransformAttrs(p.round(), 0, port);
        }, g.line(p1, p2));
    }

    function ellipseLayout(ports, elBBox, startAngle, stepFn) {

        var center = elBBox.center();
        var ratio = elBBox.width / elBBox.height;
        var p1 = elBBox.topMiddle();

        var ellipse = g.Ellipse.fromRect(elBBox);

        return ports.map(function(port, index, ports) {

            var angle = startAngle + stepFn(index, ports.length);
            var p2 = p1.clone()
                .rotate(center, -angle)
                .scale(ratio, 1, center);

            var theta = port.compensateRotation ? -ellipse.tangentTheta(p2) : 0;

            // `dx`,`dy` per port offset option
            if (port.dx || port.dy) {
                p2.offset(port.dx || 0, port.dy || 0);
            }

            // `dr` delta radius option
            if (port.dr) {
                p2.move(center, port.dr);
            }

            return portTransformAttrs(p2.round(), theta, port);
        });
    }

    // Creates a point stored in arguments
    function argPoint(bbox, args) {

        var x = args.x;
        if (util.isString(x)) {
            x = parseFloat(x) / 100 * bbox.width;
        }

        var y = args.y;
        if (util.isString(y)) {
            y = parseFloat(y) / 100 * bbox.height;
        }

        return g.point(x || 0, y || 0);
    }

    joint.layout.Port = {

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        absolute: function(ports, elBBox, opt) {
            //TODO v.talas angle
            return ports.map(argPoint.bind(null, elBBox));
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        fn: function(ports, elBBox, opt) {
            return opt.fn(ports, elBBox, opt);
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        line: function(ports, elBBox, opt) {

            var start = argPoint(elBBox, opt.start || elBBox.origin());
            var end = argPoint(elBBox, opt.end || elBBox.corner());

            return lineLayout(ports, start, end);
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        left: function(ports, elBBox, opt) {
            return lineLayout(ports, elBBox.origin(), elBBox.bottomLeft());
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        right: function(ports, elBBox, opt) {
            return lineLayout(ports, elBBox.topRight(), elBBox.corner());
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        top: function(ports, elBBox, opt) {
            return lineLayout(ports, elBBox.origin(), elBBox.topRight());
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt opt Group options
         * @returns {Array<g.Point>}
         */
        bottom: function(ports, elBBox, opt) {
            return lineLayout(ports, elBBox.bottomLeft(), elBBox.corner());
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt Group options
         * @returns {Array<g.Point>}
         */
        ellipseSpread: function(ports, elBBox, opt) {

            var startAngle = opt.startAngle || 0;
            var stepAngle = opt.step || 360 / ports.length;

            return ellipseLayout(ports, elBBox, startAngle, function(index) {
                return index * stepAngle;
            });
        },

        /**
         * @param {Array<Object>} ports
         * @param {g.Rect} elBBox
         * @param {Object=} opt Group options
         * @returns {Array<g.Point>}
         */
        ellipse: function(ports, elBBox, opt) {

            var startAngle = opt.startAngle || 0;
            var stepAngle = opt.step || 20;

            return ellipseLayout(ports, elBBox, startAngle, function(index, count) {
                return (index + 0.5 - count / 2) * stepAngle;
            });
        }
    };

})(_, g, joint, joint.util);

(function(_, g, joint, util) {

    function labelAttributes(opt1, opt2) {

        return util.defaultsDeep({}, opt1, opt2, {
            x: 0,
            y: 0,
            angle: 0,
            attrs: {
                '.': {
                    y: '0',
                    'text-anchor': 'start'
                }
            }
        });

    }

    function outsideLayout(portPosition, elBBox, autoOrient, opt) {

        opt = util.defaults({}, opt, { offset: 15 });
        var angle = elBBox.center().theta(portPosition);
        var x = getBBoxAngles(elBBox);

        var tx, ty, y, textAnchor;
        var offset = opt.offset;
        var orientAngle = 0;

        if (angle < x[1] || angle > x[2]) {
            y = '.3em';
            tx = offset;
            ty = 0;
            textAnchor = 'start';
        } else if (angle < x[0]) {
            y = '0';
            tx = 0;
            ty = -offset;
            if (autoOrient) {
                orientAngle = -90;
                textAnchor = 'start';
            } else {
                textAnchor = 'middle';
            }
        } else if (angle < x[3]) {
            y = '.3em';
            tx = -offset;
            ty = 0;
            textAnchor = 'end';
        } else {
            y = '.6em';
            tx = 0;
            ty = offset;
            if (autoOrient) {
                orientAngle = 90;
                textAnchor = 'start';
            } else {
                textAnchor = 'middle';
            }
        }

        var round = Math.round;
        return labelAttributes({
            x: round(tx),
            y: round(ty),
            angle: orientAngle,
            attrs: {
                '.': {
                    y: y,
                    'text-anchor': textAnchor
                }
            }
        });
    }

    function getBBoxAngles(elBBox) {

        var center = elBBox.center();

        var tl = center.theta(elBBox.origin());
        var bl = center.theta(elBBox.bottomLeft());
        var br = center.theta(elBBox.corner());
        var tr = center.theta(elBBox.topRight());

        return [tl, tr, br, bl];
    }

    function insideLayout(portPosition, elBBox, autoOrient, opt) {

        var angle = elBBox.center().theta(portPosition);
        opt = util.defaults({}, opt, { offset: 15 });

        var tx, ty, y, textAnchor;
        var offset = opt.offset;
        var orientAngle = 0;

        var bBoxAngles = getBBoxAngles(elBBox);

        if (angle < bBoxAngles[1] || angle > bBoxAngles[2]) {
            y = '.3em';
            tx = -offset;
            ty = 0;
            textAnchor = 'end';
        } else if (angle < bBoxAngles[0]) {
            y = '.6em';
            tx = 0;
            ty = offset;
            if (autoOrient) {
                orientAngle = 90;
                textAnchor = 'start';
            } else {
                textAnchor = 'middle';
            }
        } else if (angle < bBoxAngles[3]) {
            y = '.3em';
            tx = offset;
            ty = 0;
            textAnchor = 'start';
        } else {
            y = '0em';
            tx = 0;
            ty = -offset;
            if (autoOrient) {
                orientAngle = -90;
                textAnchor = 'start';
            } else {
                textAnchor = 'middle';
            }
        }

        var round = Math.round;
        return labelAttributes({
            x: round(tx),
            y: round(ty),
            angle: orientAngle,
            attrs: {
                '.': {
                    y: y,
                    'text-anchor': textAnchor
                }
            }
        });
    }

    function radialLayout(portCenterOffset, autoOrient, opt) {

        opt = util.defaults({}, opt, { offset: 20 });

        var origin = g.point(0, 0);
        var angle = -portCenterOffset.theta(origin);
        var orientAngle = angle;
        var offset = portCenterOffset.clone()
            .move(origin, opt.offset)
            .difference(portCenterOffset)
            .round();

        var y = '.3em';
        var textAnchor;

        if ((angle + 90) % 180 === 0) {
            textAnchor = autoOrient ? 'end' : 'middle';
            if (!autoOrient && angle === -270) {
                y = '0em';
            }
        } else if (angle > -270 && angle < -90) {
            textAnchor = 'start';
            orientAngle = angle - 180;
        } else {
            textAnchor = 'end';
        }

        var round = Math.round;
        return labelAttributes({
            x: round(offset.x),
            y: round(offset.y),
            angle: autoOrient ? orientAngle : 0,
            attrs: {
                '.': {
                    y: y,
                    'text-anchor': textAnchor
                }
            }
        });
    }

    joint.layout.PortLabel = {

        manual: function(portPosition, elBBox, opt) {
            return labelAttributes(opt, elBBox);
        },

        left: function(portPosition, elBBox, opt) {
            return labelAttributes(opt, { x: -15, attrs: { '.': { y: '.3em', 'text-anchor': 'end' } } });
        },

        right: function(portPosition, elBBox, opt) {
            return labelAttributes(opt, { x: 15, attrs: { '.': { y: '.3em', 'text-anchor': 'start' } } });
        },

        top: function(portPosition, elBBox, opt) {
            return labelAttributes(opt, { y: -15, attrs: { '.': { 'text-anchor': 'middle' } } });
        },

        bottom: function(portPosition, elBBox, opt) {
            return labelAttributes(opt, { y: 15, attrs: { '.': { y: '.6em', 'text-anchor': 'middle' } } });
        },

        outsideOriented: function(portPosition, elBBox, opt) {
            return outsideLayout(portPosition, elBBox, true, opt);
        },

        outside: function(portPosition, elBBox, opt) {
            return outsideLayout(portPosition, elBBox, false, opt);
        },

        insideOriented: function(portPosition, elBBox, opt) {
            return insideLayout(portPosition, elBBox, true, opt);
        },

        inside: function(portPosition, elBBox, opt) {
            return insideLayout(portPosition, elBBox, false, opt);
        },

        radial: function(portPosition, elBBox, opt) {
            return radialLayout(portPosition.difference(elBBox.center()), false, opt);
        },

        radialOriented: function(portPosition, elBBox, opt) {
            return radialLayout(portPosition.difference(elBBox.center()), true, opt);
        }
    };

})(_, g, joint, joint.util);

joint.highlighters.addClass = {

    className: joint.util.addClassNamePrefix('highlighted'),

    /**
     * @param {joint.dia.CellView} cellView
     * @param {Element} magnetEl
     * @param {object=} opt
     */
    highlight: function(cellView, magnetEl, opt) {

        var options = opt || {};
        var className = options.className || this.className;
        V(magnetEl).addClass(className);
    },

    /**
     * @param {joint.dia.CellView} cellView
     * @param {Element} magnetEl
     * @param {object=} opt
     */
    unhighlight: function(cellView, magnetEl, opt) {

        var options = opt || {};
        var className = options.className || this.className;
        V(magnetEl).removeClass(className);
    }
};

joint.highlighters.opacity = {

    /**
     * @param {joint.dia.CellView} cellView
     * @param {Element} magnetEl
     */
    highlight: function(cellView, magnetEl) {

        V(magnetEl).addClass(joint.util.addClassNamePrefix('highlight-opacity'));
    },

    /**
     * @param {joint.dia.CellView} cellView
     * @param {Element} magnetEl
     */
    unhighlight: function(cellView, magnetEl) {

        V(magnetEl).removeClass(joint.util.addClassNamePrefix('highlight-opacity'));
    }
};

joint.highlighters.stroke = {

    defaultOptions: {
        padding: 3,
        rx: 0,
        ry: 0,
        attrs: {
            'stroke-width': 3,
            stroke: '#FEB663'
        }
    },

    _views: {},

    getHighlighterId: function(magnetEl, opt) {

        return magnetEl.id + JSON.stringify(opt);
    },

    removeHighlighter: function(id) {
        if (this._views[id]) {
            this._views[id].remove();
            this._views[id] = null;
        }
    },

    /**
     * @param {joint.dia.CellView} cellView
     * @param {Element} magnetEl
     * @param {object=} opt
     */
    highlight: function(cellView, magnetEl, opt) {

        var id = this.getHighlighterId(magnetEl, opt);

        // Only highlight once.
        if (this._views[id]) return;

        var options = joint.util.defaults(opt || {}, this.defaultOptions);

        var magnetVel = V(magnetEl);
        var magnetBBox;

        try {

            var pathData = magnetVel.convertToPathData();

        } catch (error) {

            // Failed to get path data from magnet element.
            // Draw a rectangle around the entire cell view instead.
            magnetBBox = magnetVel.bbox(true/* without transforms */);
            pathData = V.rectToPath(joint.util.assign({}, options, magnetBBox));
        }

        var highlightVel = V('path').attr({
            d: pathData,
            'pointer-events': 'none',
            'vector-effect': 'non-scaling-stroke',
            'fill': 'none'
        }).attr(options.attrs);

        var highlightMatrix = magnetVel.getTransformToElement(cellView.el);

        // Add padding to the highlight element.
        var padding = options.padding;
        if (padding) {

            magnetBBox || (magnetBBox = magnetVel.bbox(true));

            var cx = magnetBBox.x + (magnetBBox.width / 2);
            var cy = magnetBBox.y + (magnetBBox.height / 2);

            magnetBBox = V.transformRect(magnetBBox, highlightMatrix);

            var width = Math.max(magnetBBox.width, 1);
            var height = Math.max(magnetBBox.height, 1);
            var sx = (width + padding) / width;
            var sy = (height + padding) / height;

            var paddingMatrix = V.createSVGMatrix({
                a: sx,
                b: 0,
                c: 0,
                d: sy,
                e: cx - sx * cx,
                f: cy - sy * cy
            });

            highlightMatrix = highlightMatrix.multiply(paddingMatrix);
        }

        highlightVel.transform(highlightMatrix);

        // joint.mvc.View will handle the theme class name and joint class name prefix.
        var highlightView = this._views[id] = new joint.mvc.View({
            svgElement: true,
            className: 'highlight-stroke',
            el: highlightVel.node
        });

        // Remove the highlight view when the cell is removed from the graph.
        var removeHandler = this.removeHighlighter.bind(this, id);
        var cell = cellView.model;
        highlightView.listenTo(cell, 'remove', removeHandler);
        highlightView.listenTo(cell.graph, 'reset', removeHandler);

        cellView.vel.append(highlightVel);
    },

    /**
     * @param {joint.dia.CellView} cellView
     * @param {Element} magnetEl
     * @param {object=} opt
     */
    unhighlight: function(cellView, magnetEl, opt) {

        this.removeHighlighter(this.getHighlighterId(magnetEl, opt));
    }
};

(function(joint, util) {

    function bboxWrapper(method) {

        return function(view, magnet, ref, opt) {

            var rotate = !!opt.rotate;
            var bbox = (rotate) ? view.getNodeUnrotatedBBox(magnet) : view.getNodeBBox(magnet);
            var anchor = bbox[method]();

            var dx = opt.dx;
            if (dx) {
                var dxPercentage = util.isPercentage(dx);
                dx = parseFloat(dx);
                if (isFinite(dx)) {
                    if (dxPercentage) {
                        dx /= 100;
                        dx *= bbox.width;
                    }
                    anchor.x += dx;
                }
            }

            var dy = opt.dy;
            if (dy) {
                var dyPercentage = util.isPercentage(dy);
                dy = parseFloat(dy);
                if (isFinite(dy)) {
                    if (dyPercentage) {
                        dy /= 100;
                        dy *= bbox.height;
                    }
                    anchor.y += dy;
                }
            }

            return (rotate) ? anchor.rotate(view.model.getBBox().center(), -view.model.angle()) : anchor;
        }
    }

    function resolveRefAsBBoxCenter(fn) {

        return function(view, magnet, ref, opt) {

            if (ref instanceof Element) {
                var refView = this.paper.findView(ref);
                var refPoint = (refView)
                    ? refView.getNodeBBox(ref).center()
                    : new g.Point()

                return fn.call(this, view, magnet, refPoint, opt)
            }

            return fn.apply(this, arguments);
        }
    }

    function perpendicular(view, magnet, refPoint, opt) {

        var angle = view.model.angle();
        var bbox = view.getNodeBBox(magnet);
        var anchor = bbox.center();
        var topLeft = bbox.origin();
        var bottomRight = bbox.corner();

        var padding = opt.padding
        if (!isFinite(padding)) padding = 0;

        if ((topLeft.y + padding) <= refPoint.y && refPoint.y <= (bottomRight.y - padding)) {
            var dy = (refPoint.y - anchor.y);
            anchor.x += (angle === 0 || angle === 180) ? 0 : dy * 1 / Math.tan(g.toRad(angle));
            anchor.y += dy;
        } else if ((topLeft.x + padding) <= refPoint.x && refPoint.x <= (bottomRight.x - padding)) {
            var dx = (refPoint.x - anchor.x);
            anchor.y += (angle === 90 || angle === 270) ? 0 : dx * Math.tan(g.toRad(angle));
            anchor.x += dx;
        }

        return anchor;
    }

    function midSide(view, magnet, refPoint, opt) {

        var rotate = !!opt.rotate;
        var bbox, angle, center;
        if (rotate) {
            bbox = view.getNodeUnrotatedBBox(magnet);
            center = view.model.getBBox().center();
            angle = view.model.angle();
        } else {
            bbox = view.getNodeBBox(magnet);
        }

        var padding = opt.padding;
        if (isFinite(padding)) bbox.inflate(padding);

        if (rotate) refPoint.rotate(center, angle);

        var side = bbox.sideNearestToPoint(refPoint);
        var anchor;
        switch (side) {
            case 'left': anchor = bbox.leftMiddle(); break;
            case 'right': anchor = bbox.rightMiddle(); break;
            case 'top': anchor = bbox.topMiddle(); break;
            case 'bottom': anchor = bbox.bottomMiddle(); break;
        }

        return (rotate) ? anchor.rotate(center, -angle) : anchor;
    }

    // Can find anchor from model, when there is no selector or the link end
    // is connected to a port
    function modelCenter(view, magnet) {

        var model = view.model;
        var bbox = model.getBBox();
        var center = bbox.center();
        var angle = model.angle();

        var portId = view.findAttribute('port', magnet);
        if (portId) {
            portGroup = model.portProp(portId, 'group');
            var portsPositions = model.getPortsPositions(portGroup);
            var anchor = new g.Point(portsPositions[portId]).offset(bbox.origin());
            anchor.rotate(center, -angle);
            return anchor;
        }

        return center;
    }

    joint.anchors = {
        center: bboxWrapper('center'),
        top: bboxWrapper('topMiddle'),
        bottom: bboxWrapper('bottomMiddle'),
        left: bboxWrapper('leftMiddle'),
        right: bboxWrapper('rightMiddle'),
        topLeft: bboxWrapper('origin'),
        topRight: bboxWrapper('topRight'),
        bottomLeft: bboxWrapper('bottomLeft'),
        bottomRight: bboxWrapper('corner'),
        perpendicular: resolveRefAsBBoxCenter(perpendicular),
        midSide: resolveRefAsBBoxCenter(midSide),
        modelCenter: modelCenter
    }

})(joint, joint.util);

(function(joint, util, g, V) {

    function closestIntersection(intersections, refPoint) {

        if (intersections.length === 1) return intersections[0];
        return util.sortBy(intersections, function(i) { return i.squaredDistance(refPoint) })[0];
    }

    function offset(p1, p2, offset) {

        if (!isFinite(offset)) return p1;
        var length = p1.distance(p2);
        if (offset === 0 && length > 0) return p1;
        return p1.move(p2, -Math.min(offset, length - 1));
    }

    function stroke(magnet) {

        var stroke = magnet.getAttribute('stroke-width');
        if (stroke === null) return 0;
        return parseFloat(stroke) || 0;
    }

    // Connection Points

    function anchor(line, view, magnet, opt) {

        return offset(line.end, line.start, opt.offset);
    }

    function bboxIntersection(line, view, magnet, opt) {

        var bbox = view.getNodeBBox(magnet);
        if (opt.stroke) bbox.inflate(stroke(magnet) / 2);
        var intersections = line.intersect(bbox);
        var cp = (intersections)
            ? closestIntersection(intersections, line.start)
            : line.end;
        return offset(cp, line.start, opt.offset);
    }

    function rectangleIntersection(line, view, magnet, opt) {

        var angle = view.model.angle();
        if (angle === 0) {
            return bboxIntersection(line, view, magnet, opt);
        }

        var bboxWORotation = view.getNodeUnrotatedBBox(magnet);
        if (opt.stroke) bboxWORotation.inflate(stroke(magnet) / 2);
        var center = bboxWORotation.center();
        var lineWORotation = line.clone().rotate(center, angle);
        var intersections = lineWORotation.setLength(1e6).intersect(bboxWORotation);
        var cp = (intersections)
            ? closestIntersection(intersections, lineWORotation.start).rotate(center, -angle)
            : line.end;
        return offset(cp, line.start, opt.offset);
    }

    var BNDR_SUBDIVISIONS = 'segmentSubdivisons';
    var BNDR_SHAPE_BBOX = 'shapeBBox';

    function boundaryIntersection(line, view, magnet, opt) {

        var node, intersection;
        var selector = opt.selector;
        var anchor = line.end;

        if (typeof selector === 'string') {
            node = view.findBySelector(selector)[0];
        } else if (Array.isArray(selector)) {
            node = util.getByPath(magnet, selector);
        } else {
            // Find the closest non-group descendant
            node = magnet;
            do {
                var tagName = node.tagName.toUpperCase();
                if (tagName === 'G') {
                    node = node.firstChild;
                } else if (tagName === 'TITLE') {
                    node = node.nextSibling;
                } else break;
            } while (node)
        }

        if (!(node instanceof Element)) return anchor;

        var localShape = view.getNodeShape(node);
        var magnetMatrix = view.getNodeMatrix(node);
        var translateMatrix = view.getRootTranslateMatrix();
        var rotateMatrix = view.getRootRotateMatrix();
        var targetMatrix = translateMatrix.multiply(rotateMatrix).multiply(magnetMatrix);
        var localMatrix = targetMatrix.inverse();
        var localLine = V.transformLine(line, localMatrix);
        var localRef = localLine.start.clone();
        var data = view.getNodeData(node);

        if (opt.insideout === false) {
            if (!data[BNDR_SHAPE_BBOX]) data[BNDR_SHAPE_BBOX] = localShape.bbox();
            var localBBox = data[BNDR_SHAPE_BBOX];
            if (localBBox.containsPoint(localRef)) return anchor;
        }

        // Caching segment subdivisions for paths
        var pathOpt
        if (localShape instanceof g.Path) {
            var precision = opt.precision || 2;
            if (!data[BNDR_SUBDIVISIONS]) data[BNDR_SUBDIVISIONS] = localShape.getSegmentSubdivisions({ precision: precision });
            segmentSubdivisions = data[BNDR_SUBDIVISIONS];
            pathOpt = {
                precision: precision,
                segmentSubdivisions: data[BNDR_SUBDIVISIONS]
            }
        }

        if (opt.extrapolate === true) localLine.setLength(1e6);

        intersection = localLine.intersect(localShape, pathOpt);
        if (intersection) {
            // More than one intersection
            if (V.isArray(intersection)) intersection = closestIntersection(intersection, localRef);
        } else if (opt.sticky === true) {
            // No intersection, find the closest point instead
            if (localShape instanceof g.Rect) {
                intersection = localShape.pointNearestToPoint(localRef);
            } else if (localShape instanceof g.Ellipse) {
                intersection = localShape.intersectionWithLineFromCenterToPoint(localRef);
            } else {
                intersection = localShape.closestPoint(localRef, pathOpt);
            }
        }

        var cp = (intersection) ? V.transformPoint(intersection, targetMatrix) : anchor;
        var cpOffset = opt.offset || 0;
        if (opt.stroke) cpOffset += stroke(node) / 2;

        return offset(cp, line.start, cpOffset);
    }

    joint.connectionPoints = {
        anchor: anchor,
        bbox: bboxIntersection,
        rectangle: rectangleIntersection,
        boundary: boundaryIntersection
    }

})(joint, joint.util, g, V);

(function(joint, util) {

    function abs2rel(value, max) {

        if (max === 0) return '0%';
        return Math.round(value / max * 100) + '%';
    }

    function pin(relative) {

        return function(end, view, magnet, coords) {

            var angle = view.model.angle();
            var bbox = view.getNodeUnrotatedBBox(magnet);
            var origin = view.model.getBBox().center();
            coords.rotate(origin, angle);
            var dx = coords.x - bbox.x;
            var dy = coords.y - bbox.y;

            if (relative) {
                dx = abs2rel(dx, bbox.width);
                dy = abs2rel(dy, bbox.height);
            }

            end.anchor = {
                name: 'topLeft',
                args: {
                    dx: dx,
                    dy: dy,
                    rotate: true
                }
            };

            return end;
        }
    }

    joint.connectionStrategies = {
        useDefaults: util.noop,
        pinAbsolute: pin(false),
        pinRelative: pin(true)
    }

})(joint, joint.util);

(function(joint, util, V, g) {

    function getAnchor(coords, view, magnet) {
        // take advantage of an existing logic inside of the
        // pin relative connection strategy
        var end = joint.connectionStrategies.pinRelative.call(
            this.paper,
            {},
            view,
            magnet,
            coords,
            this.model
        );
        return end.anchor;
    }

    function snapAnchor(coords, view, magnet, type, relatedView, toolView) {
        var snapRadius = toolView.options.snapRadius;
        var isSource = (type === 'source');
        var refIndex = (isSource ? 0 : -1);
        var ref = this.model.vertex(refIndex) || this.getEndAnchor(isSource ? 'target' : 'source');
        if (ref) {
            if (Math.abs(ref.x - coords.x) < snapRadius) coords.x = ref.x;
            if (Math.abs(ref.y - coords.y) < snapRadius) coords.y = ref.y;
        }
        return coords;
    }

    var ToolView = joint.dia.ToolView;

    // Vertex Handles
    var VertexHandle = joint.mvc.View.extend({
        tagName: 'circle',
        svgElement: true,
        className: 'marker-vertex',
        events: {
            mousedown: 'onPointerDown',
            touchstart: 'onPointerDown',
            dblclick: 'onDoubleClick'
        },
        documentEvents: {
            mousemove: 'onPointerMove',
            touchmove: 'onPointerMove',
            mouseup: 'onPointerUp',
            touchend: 'onPointerUp'
        },
        attributes: {
            'r': 6,
            'fill': '#33334F',
            'stroke': '#FFFFFF',
            'stroke-width': 2,
            'cursor': 'move'
        },
        position: function(x, y) {
            this.vel.attr({ cx: x, cy: y });
        },
        onPointerDown: function(evt) {
            evt.stopPropagation();
            this.options.paper.undelegateEvents();
            this.delegateDocumentEvents(null, evt.data);
            this.trigger('will-change');
        },
        onPointerMove: function(evt) {
            this.trigger('changing', this, evt);
        },
        onDoubleClick: function(evt) {
            this.trigger('remove', this, evt);
        },
        onPointerUp: function(evt) {
            this.trigger('changed', this, evt);
            this.undelegateDocumentEvents();
            this.options.paper.delegateEvents();
        }
    });

    var Vertices = ToolView.extend({
        name: 'vertices',
        options: {
            handleClass: VertexHandle,
            snapRadius: 20,
            redundancyRemoval: true,
            vertexAdding: true,
        },
        children: [{
            tagName: 'path',
            selector: 'connection',
            className: 'joint-vertices-path',
            attributes: {
                'fill': 'none',
                'stroke': 'transparent',
                'stroke-width': 10,
                'cursor': 'cell'
            }
        }],
        handles: null,
        events: {
            'mousedown .joint-vertices-path': 'onPathPointerDown'
        },
        onRender: function() {
            this.resetHandles();
            if (this.options.vertexAdding) {
                this.renderChildren();
                this.updatePath();
            }
            var relatedView = this.relatedView;
            var vertices = relatedView.model.vertices();
            for (var i = 0, n = vertices.length; i < n; i++) {
                var vertex = vertices[i];
                var handle = new (this.options.handleClass)({ index: i, paper: this.paper });
                handle.render();
                handle.position(vertex.x, vertex.y);
                this.simulateRelatedView(handle.el);
                handle.vel.appendTo(this.el);
                this.handles.push(handle);
                this.startHandleListening(handle);
            }
            return this;
        },
        update: function() {
            this.render();
            return this;
        },
        updatePath: function() {
            var connection = this.childNodes.connection;
            if (connection) connection.setAttribute('d', this.relatedView.getConnection().serialize());
        },
        startHandleListening: function(handle) {
            var relatedView = this.relatedView;
            if (relatedView.can('vertexMove')) {
                this.listenTo(handle, 'will-change', this.onHandleWillChange);
                this.listenTo(handle, 'changing', this.onHandleChanging);
                this.listenTo(handle, 'changed', this.onHandleChanged);
            }
            if (relatedView.can('vertexRemove')) {
                this.listenTo(handle, 'remove', this.onHandleRemove);
            }
        },
        resetHandles: function() {
            var handles = this.handles;
            this.handles = [];
            this.stopListening();
            if (!Array.isArray(handles)) return;
            for (var i = 0, n = handles.length; i < n; i++) {
                handles[i].remove();
            }
        },
        getNeighborPoints: function(index) {
            var linkView = this.relatedView;
            var vertices = linkView.model.vertices();
            var prev = (index > 0) ? vertices[index - 1] : linkView.sourceAnchor;
            var next = (index < vertices.length - 1) ? vertices[index + 1] : linkView.targetAnchor;
            return {
                prev: new g.Point(prev),
                next: new g.Point(next)
            }
        },
        onHandleWillChange: function(handle, evt) {
            this.focus();
            this.relatedView.model.startBatch('vertex-move', { ui: true, tool: this.cid });
        },
        onHandleChanging: function(handle, evt) {
            var relatedView = this.relatedView;
            var paper = relatedView.paper;
            var index = handle.options.index;
            var vertex = paper.snapToGrid(evt.clientX, evt.clientY).toJSON();
            this.snapVertex(vertex, index);
            relatedView.model.vertex(index, vertex, { ui: true, tool: this.cid });
            handle.position(vertex.x, vertex.y);
        },
        snapVertex: function(vertex, index) {
            var snapRadius = this.options.snapRadius;
            if (snapRadius > 0) {
                var neighbors = this.getNeighborPoints(index);
                var prev = neighbors.prev;
                var next = neighbors.next;
                if (Math.abs(vertex.x - prev.x) < snapRadius) {
                    vertex.x = prev.x;
                } else if (Math.abs(vertex.x - next.x) < snapRadius) {
                    vertex.x = next.x;
                }
                if (Math.abs(vertex.y - prev.y) < snapRadius) {
                    vertex.y = neighbors.prev.y;
                } else if (Math.abs(vertex.y - next.y) < snapRadius) {
                    vertex.y = next.y;
                }
            }
        },
        onHandleChanged: function(handle, evt) {
            if (this.options.vertexAdding) this.updatePath();
            if (!this.options.redundancyRemoval) return;
            var linkView = this.relatedView;
            var verticesRemoved = linkView.removeRedundantLinearVertices({ ui: true, tool: this.cid });
            if (verticesRemoved) this.render();
            this.blur();
            linkView.model.stopBatch('vertex-move', { ui: true, tool: this.cid });
            if (this.eventData(evt).vertexAdded) {
                linkView.model.stopBatch('vertex-add', { ui: true, tool: this.cid });
            }
        },
        onHandleRemove: function(handle) {
            var index = handle.options.index;
            this.relatedView.model.removeVertex(index, { ui: true });
        },
        onPathPointerDown: function(evt) {
            evt.stopPropagation();
            var vertex = this.paper.snapToGrid(evt.clientX, evt.clientY).toJSON();
            var relatedView = this.relatedView;
            relatedView.model.startBatch('vertex-add', { ui: true, tool: this.cid });
            var index = relatedView.getVertexIndex(vertex.x, vertex.y);
            this.snapVertex(vertex, index);
            relatedView.model.insertVertex(index, vertex, { ui: true, tool: this.cid });
            this.render();
            var handle = this.handles[index];
            this.eventData(evt, { vertexAdded: true });
            handle.onPointerDown(evt);
        },
        onRemove: function() {
            this.resetHandles();
        }
    }, {
        VertexHandle: VertexHandle // keep as class property
    });

    var SegmentHandle = joint.mvc.View.extend({
        tagName: 'g',
        svgElement: true,
        className: 'marker-segment',
        events: {
            mousedown: 'onPointerDown',
            touchstart: 'onPointerDown'
        },
        documentEvents: {
            mousemove: 'onPointerMove',
            touchmove: 'onPointerMove',
            mouseup: 'onPointerUp',
            touchend: 'onPointerUp'
        },
        children: [{
            tagName: 'line',
            selector: 'line',
            attributes: {
                'stroke': '#33334F',
                'stroke-width': 2,
                'fill': 'none',
                'pointer-events': 'none'
            }
        }, {
            tagName: 'rect',
            selector: 'handle',
            attributes: {
                'width': 20,
                'height': 8,
                'x': -10,
                'y': -4,
                'rx': 4,
                'ry': 4,
                'fill': '#33334F',
                'stroke': '#FFFFFF',
                'stroke-width': 2
            }
        }],
        onRender: function() {
            this.renderChildren();
        },
        position: function(x, y, angle, view) {

            var matrix = V.createSVGMatrix().translate(x, y).rotate(angle);
            var handle = this.childNodes.handle;
            handle.setAttribute('transform', V.matrixToTransformString(matrix));
            handle.setAttribute('cursor', (angle % 180 === 0) ? 'row-resize' : 'col-resize');

            var viewPoint = view.getClosestPoint(new g.Point(x, y));
            var line = this.childNodes.line;
            line.setAttribute('x1', x);
            line.setAttribute('y1', y);
            line.setAttribute('x2', viewPoint.x);
            line.setAttribute('y2', viewPoint.y);
        },
        onPointerDown: function(evt) {
            this.trigger('change:start', this, evt);
            evt.stopPropagation();
            this.options.paper.undelegateEvents();
            this.delegateDocumentEvents(null, evt.data);
        },
        onPointerMove: function(evt) {
            this.trigger('changing', this, evt);
        },
        onPointerUp: function(evt) {
            this.undelegateDocumentEvents();
            this.options.paper.delegateEvents();
            this.trigger('change:end', this, evt);
        },
        show: function() {
            this.el.style.display = '';
        },
        hide: function() {
            this.el.style.display = 'none';
        }
    });

    var Segments = ToolView.extend({
        name: 'segments',
        precision: .5,
        options: {
            handleClass: SegmentHandle,
            segmentLengthThreshold: 40,
            redundancyRemoval: true,
            anchor: getAnchor,
            snapRadius: 10,
            snapHandle: true
        },
        handles: null,
        onRender: function() {
            this.resetHandles();
            var relatedView = this.relatedView;
            var vertices = relatedView.model.vertices();
            vertices.unshift(relatedView.sourcePoint);
            vertices.push(relatedView.targetPoint);
            for (var i = 0, n = vertices.length; i < n - 1; i++) {
                var vertex = vertices[i];
                var nextVertex = vertices[i + 1];
                var handle = this.renderHandle(vertex, nextVertex);
                this.simulateRelatedView(handle.el);
                this.handles.push(handle);
                handle.options.index = i;
            }
            return this;
        },
        renderHandle: function(vertex, nextVertex) {
            var handle = new (this.options.handleClass)({ paper: this.paper });
            handle.render();
            this.updateHandle(handle, vertex, nextVertex);
            handle.vel.appendTo(this.el);
            this.startHandleListening(handle);
            return handle;
        },
        update: function() {
            this.render();
            return this;
        },
        startHandleListening: function(handle) {
            this.listenTo(handle, 'change:start', this.onHandleChangeStart);
            this.listenTo(handle, 'changing', this.onHandleChanging);
            this.listenTo(handle, 'change:end', this.onHandleChangeEnd);
        },
        resetHandles: function() {
            var handles = this.handles;
            this.handles = [];
            this.stopListening();
            if (!Array.isArray(handles)) return;
            for (var i = 0, n = handles.length; i < n; i++) {
                handles[i].remove();
            }
        },
        shiftHandleIndexes: function(value) {
            var handles = this.handles;
            for (var i = 0, n = handles.length; i < n; i++) handles[i].options.index += value;
        },
        resetAnchor: function(type, anchor) {
            var relatedModel = this.relatedView.model;
            if (anchor) {
                relatedModel.prop([type, 'anchor'], anchor, {
                    rewrite: true,
                    ui: true,
                    tool: this.cid
                });
            } else {
                relatedModel.removeProp([type, 'anchor'], {
                    ui: true,
                    tool: this.cid
                });
            }
        },
        snapHandle: function(handle, position, data) {

            var index = handle.options.index;
            var linkView = this.relatedView;
            var link = linkView.model;
            var vertices = link.vertices();
            var axis = handle.options.axis;
            var prev = vertices[index - 2] || data.sourceAnchor;
            var next = vertices[index + 1] || data.targetAnchor;
            var snapRadius = this.options.snapRadius;
            if (Math.abs(position[axis] - prev[axis]) < snapRadius) {
                position[axis] = prev[axis];
            } else if (Math.abs(position[axis] - next[axis]) < snapRadius) {
                position[axis] = next[axis];
            }
            return position;
        },

        onHandleChanging: function(handle, evt) {

            var data = this.eventData(evt);
            var relatedView = this.relatedView;
            var paper = relatedView.paper;
            var index = handle.options.index - 1;
            var coords = paper.snapToGrid(evt.clientX, evt.clientY);
            var position = this.snapHandle(handle, coords.clone(), data);
            var axis = handle.options.axis;
            var offset = (this.options.snapHandle) ? 0 : (coords[axis] - position[axis]);
            var link = relatedView.model;
            var vertices = util.cloneDeep(link.vertices());
            var vertex = vertices[index];
            var nextVertex = vertices[index + 1];
            var anchorFn = this.options.anchor;
            if (typeof anchorFn !== 'function') anchorFn = null;

            // First Segment
            var sourceView = relatedView.sourceView;
            var sourceBBox = relatedView.sourceBBox;
            var changeSourceAnchor = false;
            var deleteSourceAnchor = false;
            if (!vertex) {
                vertex = relatedView.sourceAnchor.toJSON();
                vertex[axis] = position[axis];
                if (sourceBBox.containsPoint(vertex)) {
                    vertex[axis] = position[axis];
                    changeSourceAnchor = true;
                } else {
                    // we left the area of the source magnet for the first time
                    vertices.unshift(vertex);
                    this.shiftHandleIndexes(1);
                    delateSourceAnchor = true;
                }
            } else if (index === 0) {
                if (sourceBBox.containsPoint(vertex)) {
                    vertices.shift();
                    this.shiftHandleIndexes(-1);
                    changeSourceAnchor = true;
                } else {
                    vertex[axis] = position[axis];
                    deleteSourceAnchor = true;
                }
            } else {
                vertex[axis] = position[axis];
            }

            if (anchorFn && sourceView) {
                if (changeSourceAnchor) {
                    var sourceAnchorPosition = data.sourceAnchor.clone();
                    sourceAnchorPosition[axis] = position[axis];
                    var sourceAnchor = anchorFn.call(relatedView, sourceAnchorPosition, sourceView, relatedView.sourceMagnet || sourceView.el, 'source', relatedView);
                    this.resetAnchor('source', sourceAnchor);
                }
                if (deleteSourceAnchor) {
                    this.resetAnchor('source', data.sourceAnchorDef);
                }
            }

            // Last segment
            var targetView = relatedView.targetView;
            var targetBBox = relatedView.targetBBox;
            var changeTargetAnchor = false;
            var deleteTargetAnchor = false;
            if (!nextVertex) {
                nextVertex = relatedView.targetAnchor.toJSON();
                nextVertex[axis] = position[axis];
                if (targetBBox.containsPoint(nextVertex)) {
                    changeTargetAnchor = true;
                } else {
                    // we left the area of the target magnet for the first time
                    vertices.push(nextVertex);
                    deleteTargetAnchor = true;
                }
            } else if (index === vertices.length - 2) {
                if (targetBBox.containsPoint(nextVertex)) {
                    vertices.pop();
                    changeTargetAnchor = true;
                } else {
                    nextVertex[axis] = position[axis];
                    deleteTargetAnchor = true;
                }
            } else {
                nextVertex[axis] = position[axis];
            }

            if (anchorFn && targetView) {
                if (changeTargetAnchor) {
                    var targetAnchorPosition = data.targetAnchor.clone();
                    targetAnchorPosition[axis] = position[axis];
                    var targetAnchor = anchorFn.call(relatedView, targetAnchorPosition, targetView, relatedView.targetMagnet || targetView.el, 'target', relatedView);
                    this.resetAnchor('target', targetAnchor);
                }
                if (deleteTargetAnchor) {
                    this.resetAnchor('target', data.targetAnchorDef);
                }
            }

            link.vertices(vertices, { ui: true, tool: this.cid });
            this.updateHandle(handle, vertex, nextVertex, offset);
        },
        onHandleChangeStart: function(handle, evt) {
            var index = handle.options.index;
            var handles = this.handles;
            if (!Array.isArray(handles)) return;
            for (var i = 0, n = handles.length; i < n; i++) {
                if (i !== index) handles[i].hide()
            }
            this.focus();
            var relatedView = this.relatedView;
            var relatedModel = relatedView.model;
            this.eventData(evt, {
                sourceAnchor: relatedView.sourceAnchor.clone(),
                targetAnchor: relatedView.targetAnchor.clone(),
                sourceAnchorDef: util.clone(relatedModel.prop(['source', 'anchor'])),
                targetAnchorDef: util.clone(relatedModel.prop(['target', 'anchor']))
            });
            relatedView.model.startBatch('segment-move', { ui: true, tool: this.cid });
        },
        onHandleChangeEnd: function(handle) {
            var linkView = this.relatedView;
            if (this.options.redundancyRemoval) {
                linkView.removeRedundantLinearVertices({ ui: true, tool: this.cid });
            }
            this.render();
            this.blur();
            linkView.model.stopBatch('segment-move', { ui: true, tool: this.cid });
        },
        updateHandle: function(handle, vertex, nextVertex, offset) {
            var vertical = Math.abs(vertex.x - nextVertex.x) < this.precision;
            var horizontal = Math.abs(vertex.y - nextVertex.y) < this.precision;
            if (vertical || horizontal) {
                var segmentLine = new g.Line(vertex, nextVertex);
                var length = segmentLine.length();
                if (length < this.options.segmentLengthThreshold) {
                    handle.hide();
                } else {
                    var position = segmentLine.midpoint()
                    var axis = (vertical) ? 'x' : 'y';
                    position[axis] += offset || 0;
                    var angle = segmentLine.vector().vectorAngle(new g.Point(1, 0));
                    handle.position(position.x, position.y, angle, this.relatedView);
                    handle.show();
                    handle.options.axis = axis;
                }
            } else {
                handle.hide();
            }
        },
        onRemove: function() {
            this.resetHandles();
        }
    }, {
        SegmentHandle: SegmentHandle // keep as class property
    });

    // End Markers
    var Arrowhead = ToolView.extend({
        tagName: 'path',
        xAxisVector: new g.Point(1, 0),
        events: {
            mousedown: 'onPointerDown',
            touchstart: 'onPointerDown'
        },
        documentEvents: {
            mousemove: 'onPointerMove',
            touchmove: 'onPointerMove',
            mouseup: 'onPointerUp',
            touchend: 'onPointerUp'
        },
        onRender: function() {
            this.update()
        },
        update: function() {
            var ratio = this.ratio;
            var view = this.relatedView;
            var tangent = view.getTangentAtRatio(ratio);
            var position, angle;
            if (tangent) {
                position = tangent.start;
                angle = tangent.vector().vectorAngle(this.xAxisVector) || 0;
            } else {
                position = view.getPointAtRatio(ratio);
                angle = 0;
            }
            var matrix = V.createSVGMatrix().translate(position.x, position.y).rotate(angle);
            this.vel.transform(matrix, { absolute: true });
            return this;
        },
        onPointerDown: function(evt) {
            evt.stopPropagation();
            var relatedView = this.relatedView;
            relatedView.model.startBatch('arrowhead-move', { ui: true, tool: this.cid });
            if (relatedView.can('arrowheadMove')) {
                relatedView.startArrowheadMove(this.arrowheadType);
                this.delegateDocumentEvents();
                relatedView.paper.undelegateEvents();
            }
            this.focus();
            this.el.style.pointerEvents = 'none';
        },
        onPointerMove: function(evt) {
            var coords = this.paper.snapToGrid(evt.clientX, evt.clientY);
            this.relatedView.pointermove(evt, coords.x, coords.y);
        },
        onPointerUp: function(evt) {
            this.undelegateDocumentEvents();
            var relatedView = this.relatedView;
            var paper = relatedView.paper;
            var coords = paper.snapToGrid(evt.clientX, evt.clientY);
            relatedView.pointerup(evt, coords.x, coords.y);
            paper.delegateEvents();
            this.blur();
            this.el.style.pointerEvents = '';
            relatedView.model.stopBatch('arrowhead-move', { ui: true, tool: this.cid });
        }
    });

    var TargetArrowhead = Arrowhead.extend({
        name: 'target-arrowhead',
        ratio: 1,
        arrowheadType: 'target',
        attributes: {
            'd': 'M -10 -8 10 0 -10 8 Z',
            'fill': '#33334F',
            'stroke': '#FFFFFF',
            'stroke-width': 2,
            'cursor': 'move',
            'class': 'target-arrowhead'
        }
    });

    var SourceArrowhead = Arrowhead.extend({
        name: 'source-arrowhead',
        ratio: 0,
        arrowheadType: 'source',
        attributes: {
            'd': 'M 10 -8 -10 0 10 8 Z',
            'fill': '#33334F',
            'stroke': '#FFFFFF',
            'stroke-width': 2,
            'cursor': 'move',
            'class': 'source-arrowhead'
        }
    });

    var Button = ToolView.extend({
        name: 'button',
        events: {
            'mousedown': 'onPointerDown',
            'touchstart': 'onPointerDown'
        },
        options: {
            distance: 0,
            offset: 0,
            rotate: false
        },
        onRender: function() {
            this.renderChildren(this.options.markup);
            this.update()
        },
        update: function() {
            var tangent, position, angle;
            var distance = this.options.distance || 0;
            if (util.isPercentage(distance)) {
                tangent = this.relatedView.getTangentAtRatio(parseFloat(distance) / 100);
            } else {
                tangent = this.relatedView.getTangentAtLength(distance)
            }
            if (tangent) {
                position = tangent.start;
                angle = tangent.vector().vectorAngle(new g.Point(1,0)) || 0;
            } else {
                position = this.relatedView.getConnection().start;
                angle = 0;
            }
            var matrix = V.createSVGMatrix()
                .translate(position.x, position.y)
                .rotate(angle)
                .translate(0, this.options.offset || 0);
            if (!this.options.rotate) matrix = matrix.rotate(-angle);
            this.vel.transform(matrix, { absolute: true });
            return this;
        },
        onPointerDown: function(evt) {
            evt.stopPropagation();
            var actionFn = this.options.action;
            if (typeof actionFn === 'function') {
                actionFn.call(this.relatedView, evt, this.relatedView);
            }
        }
    });


    var Remove = Button.extend({
        children: [{
            tagName: 'circle',
            selector: 'button',
            attributes: {
                'r': 7,
                'fill': '#FF1D00',
                'cursor': 'pointer'
            }
        }, {
            tagName: 'path',
            selector: 'icon',
            attributes: {
                'd': 'M -3 -3 3 3 M -3 3 3 -3',
                'fill': 'none',
                'stroke': '#FFFFFF',
                'stroke-width': 2,
                'pointer-events': 'none'
            }
        }],
        options: {
            distance: 60,
            offset: 0,
            action: function(evt) {
                this.model.remove({ ui: true, tool: this.cid });
            }
        }
    });

    var Boundary = ToolView.extend({
        name: 'boundary',
        tagName: 'rect',
        options: {
            padding: 10
        },
        attributes: {
            'fill': 'none',
            'stroke': '#33334F',
            'stroke-width': .5,
            'stroke-dasharray': '5, 5',
            'pointer-events': 'none'
        },
        onRender: function() {
            this.update();
        },
        update: function() {
            var padding = this.options.padding;
            if (!isFinite(padding)) padding = 0;
            var bbox = this.relatedView.getConnection().bbox().inflate(padding);
            this.vel.attr(bbox.toJSON());
            return this;
        }
    });

    var Anchor = ToolView.extend({
        tagName: 'g',
        type: null,
        children: [{
            tagName: 'circle',
            selector: 'anchor',
            attributes: {
                'cursor': 'pointer'
            }
        }, {
            tagName: 'rect',
            selector: 'area',
            attributes: {
                'pointer-events': 'none',
                'fill': 'none',
                'stroke': '#33334F',
                'stroke-dasharray': '2,4',
                'rx': 5,
                'ry': 5
            }
        }],
        events: {
            mousedown: 'onPointerDown',
            touchstart: 'onPointerDown',
            dblclick: 'onPointerDblClick'
        },
        documentEvents: {
            mousemove: 'onPointerMove',
            touchmove: 'onPointerMove',
            mouseup: 'onPointerUp',
            touchend: 'onPointerUp'
        },
        options: {
            snap: snapAnchor,
            anchor: getAnchor,
            customAnchorAttributes: {
                'stroke-width': 4,
                'stroke': '#33334F',
                'fill': '#FFFFFF',
                'r': 5
            },
            defaultAnchorAttributes: {
                'stroke-width': 2,
                'stroke': '#FFFFFF',
                'fill': '#33334F',
                'r': 6
            },
            areaPadding: 6,
            snapRadius: 10,
            restrictArea: true,
            redundancyRemoval: true
        },
        onRender: function() {
            this.renderChildren();
            this.toggleArea(false);
            this.update();
        },
        update: function() {
            var type = this.type;
            var relatedView = this.relatedView;
            var view = relatedView.getEndView(type);
            if (view) {
                this.updateAnchor();
                this.updateArea();
                this.el.style.display = '';
            } else {
                this.el.style.display = 'none';
            }
            return this;
        },
        updateAnchor: function() {
            var childNodes = this.childNodes;
            if (!childNodes) return;
            var anchorNode = childNodes.anchor;
            if (!anchorNode) return;
            var relatedView = this.relatedView;
            var type = this.type;
            var position = relatedView.getEndAnchor(type);
            var options = this.options;
            var customAnchor = relatedView.model.prop([type, 'anchor']);
            anchorNode.setAttribute('transform', 'translate(' + position.x + ',' + position.y + ')');
            var anchorAttributes = (customAnchor) ? options.customAnchorAttributes : options.defaultAnchorAttributes;
            for (var attrName in anchorAttributes) {
                anchorNode.setAttribute(attrName, anchorAttributes[attrName]);
            }
        },
        updateArea: function() {
            var childNodes = this.childNodes;
            if (!childNodes) return;
            var areaNode = childNodes.area;
            if (!areaNode) return;
            var relatedView = this.relatedView;
            var type = this.type;
            var view = relatedView.getEndView(type);
            var magnet = relatedView.getEndMagnet(type);
            var padding = this.options.areaPadding;
            if (!isFinite(padding)) padding = 0;
            var bbox = view.getNodeUnrotatedBBox(magnet).inflate(padding);
            var angle = view.model.angle();
            areaNode.setAttribute('x', -bbox.width / 2);
            areaNode.setAttribute('y', -bbox.height / 2);
            areaNode.setAttribute('width', bbox.width);
            areaNode.setAttribute('height', bbox.height);
            var origin = view.model.getBBox().center();
            var center = bbox.center().rotate(origin, -angle)
            areaNode.setAttribute('transform', 'translate(' + center.x + ',' + center.y + ') rotate(' + angle +')');
        },
        toggleArea: function(visible) {
            this.childNodes.area.style.display = (visible) ? '' : 'none';
        },
        onPointerDown: function(evt) {
            evt.stopPropagation();
            this.paper.undelegateEvents();
            this.delegateDocumentEvents();
            this.focus();
            this.toggleArea(this.options.restrictArea);
            this.relatedView.model.startBatch('anchor-move', { ui: true, tool: this.cid });
        },
        resetAnchor: function(anchor) {
            var type = this.type;
            var relatedModel = this.relatedView.model;
            if (anchor) {
                relatedModel.prop([type, 'anchor'], anchor, {
                    rewrite: true,
                    ui: true,
                    tool: this.cid
                });
            } else {
                relatedModel.removeProp([type, 'anchor'], {
                    ui: true,
                    tool: this.cid
                });
            }
        },
        onPointerMove: function(evt) {

            var relatedView = this.relatedView;
            var type = this.type;
            var view = relatedView.getEndView(type);
            var magnet = relatedView.getEndMagnet(type);

            var coords = this.paper.clientToLocalPoint(evt.clientX, evt.clientY);
            var snapFn = this.options.snap;
            if (typeof snapFn === 'function') {
                coords = snapFn.call(relatedView, coords, view, magnet, type, relatedView, this);
                coords = new g.Point(coords);
            }

            if (this.options.restrictArea) {
                // snap coords within node bbox
                var bbox = view.getNodeUnrotatedBBox(magnet);
                var angle = view.model.angle();
                var origin = view.model.getBBox().center();
                var rotatedCoords = coords.clone().rotate(origin, angle);
                if (!bbox.containsPoint(rotatedCoords)) {
                    coords = bbox.pointNearestToPoint(rotatedCoords).rotate(origin, -angle);
                }
            }

            var anchor;
            var anchorFn = this.options.anchor;
            if (typeof anchorFn === 'function') {
                anchor = anchorFn.call(relatedView, coords, view, magnet, type, relatedView);
            }

            this.resetAnchor(anchor);
            this.update();
        },

        onPointerUp: function(evt) {
            this.paper.delegateEvents();
            this.undelegateDocumentEvents();
            this.blur();
            this.toggleArea(false);
            var linkView = this.relatedView;
            if (this.options.redundancyRemoval) linkView.removeRedundantLinearVertices({ ui: true, tool: this.cid });
            linkView.model.stopBatch('anchor-move', { ui: true, tool: this.cid });
        },

        onPointerDblClick: function() {
            this.resetAnchor();
            this.update();
        }
    });

    var SourceAnchor = Anchor.extend({
        name: 'source-anchor',
        type: 'source'
    });

    var TargetAnchor = Anchor.extend({
        name: 'target-anchor',
        type: 'target'
    });

    // Export
    joint.linkTools = {
        Vertices: Vertices,
        Segments: Segments,
        SourceArrowhead: SourceArrowhead,
        TargetArrowhead: TargetArrowhead,
        SourceAnchor: SourceAnchor,
        TargetAnchor: TargetAnchor,
        Button: Button,
        Remove: Remove,
        Boundary: Boundary
    };

})(joint, joint.util, V, g);

joint.dia.Element.define('erd.Entity', {
    size: { width: 150, height: 60 },
    attrs: {
        '.outer': {
            fill: '#2ECC71', stroke: '#27AE60', 'stroke-width': 2,
            points: '100,0 100,60 0,60 0,0'
        },
        '.inner': {
            fill: '#2ECC71', stroke: '#27AE60', 'stroke-width': 2,
            points: '95,5 95,55 5,55 5,5',
            display: 'none'
        },
        text: {
            text: 'Entity',
            'font-family': 'Arial', 'font-size': 14,
            'ref-x': .5, 'ref-y': .5,
            'y-alignment': 'middle', 'text-anchor': 'middle'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><polygon class="outer"/><polygon class="inner"/></g><text/></g>',
});


joint.shapes.erd.Entity.define('erd.WeakEntity', {
    attrs: {
        '.inner': { display: 'auto' },
        text: { text: 'Weak Entity' }
    }
});

joint.dia.Element.define('erd.Relationship', {
    size: { width: 80, height: 80 },
    attrs: {
        '.outer': {
            fill: '#3498DB', stroke: '#2980B9', 'stroke-width': 2,
            points: '40,0 80,40 40,80 0,40'
        },
        '.inner': {
            fill: '#3498DB', stroke: '#2980B9', 'stroke-width': 2,
            points: '40,5 75,40 40,75 5,40',
            display: 'none'
        },
        text: {
            text: 'Relationship',
            'font-family': 'Arial', 'font-size': 12,
            'ref-x': .5, 'ref-y': .5,
            'y-alignment': 'middle', 'text-anchor': 'middle'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><polygon class="outer"/><polygon class="inner"/></g><text/></g>',
});

joint.shapes.erd.Relationship.define('erd.IdentifyingRelationship', {
    attrs: {
        '.inner': { display: 'auto' },
        text: { text: 'Identifying' }
    }
});

joint.dia.Element.define('erd.Attribute', {
    size: { width: 100, height: 50 },
    attrs: {
        'ellipse': {
            transform: 'translate(50, 25)'
        },
        '.outer': {
            stroke: '#D35400', 'stroke-width': 2,
            cx: 0, cy: 0, rx: 50, ry: 25,
            fill: '#E67E22'
        },
        '.inner': {
            stroke: '#D35400', 'stroke-width': 2,
            cx: 0, cy: 0, rx: 45, ry: 20,
            fill: '#E67E22', display: 'none'
        },
        text: {
            'font-family': 'Arial', 'font-size': 14,
            'ref-x': .5, 'ref-y': .5,
            'y-alignment': 'middle', 'text-anchor': 'middle'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><ellipse class="outer"/><ellipse class="inner"/></g><text/></g>',
});

joint.shapes.erd.Attribute.define('erd.Multivalued', {
    attrs: {
        '.inner': { display: 'block' },
        text: { text: 'multivalued' }
    }
});

joint.shapes.erd.Attribute.define('erd.Derived', {
    attrs: {
        '.outer': { 'stroke-dasharray': '3,5' },
        text: { text: 'derived' }
    }
});

joint.shapes.erd.Attribute.define('erd.Key', {
    attrs: {
        ellipse: { 'stroke-width': 4 },
        text: { text: 'key', 'font-weight': '800', 'text-decoration': 'underline' }
    }
});

joint.shapes.erd.Attribute.define('erd.Normal', {
    attrs: { text: { text: 'Normal' } }
});

joint.dia.Element.define('erd.ISA', {
    type: 'erd.ISA',
    size: { width: 100, height: 50 },
    attrs: {
        polygon: {
            points: '0,0 50,50 100,0',
            fill: '#F1C40F', stroke: '#F39C12', 'stroke-width': 2
        },
        text: {
            text: 'ISA', 'font-size': 18,
            'ref-x': .5, 'ref-y': .3,
            'y-alignment': 'middle', 'text-anchor': 'middle'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><polygon/></g><text/></g>',
});

joint.dia.Link.define('erd.Line', {}, {
    cardinality: function(value) {
        this.set('labels', [{ position: -20, attrs: { text: { dy: -8, text: value } } }]);
    }
});

joint.shapes.basic.Circle.define('fsa.State', {
    attrs: {
        circle: { 'stroke-width': 3 },
        text: { 'font-weight': '800' }
    }
});

joint.dia.Element.define('fsa.StartState', {
    size: { width: 20, height: 20 },
    attrs: {
        circle: {
            transform: 'translate(10, 10)',
            r: 10,
            fill: '#000000'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><circle/></g></g>',
});

joint.dia.Element.define('fsa.EndState', {
    size: { width: 20, height: 20 },
    attrs: {
        '.outer': {
            transform: 'translate(10, 10)',
            r: 10,
            fill: '#ffffff',
            stroke: '#000000'
        },

        '.inner': {
            transform: 'translate(10, 10)',
            r: 6,
            fill: '#000000'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><circle class="outer"/><circle class="inner"/></g></g>',
});

joint.dia.Link.define('fsa.Arrow', {
    attrs: { '.marker-target': { d: 'M 10 0 L 0 5 L 10 10 z' } },
    smooth: true
});

joint.dia.Element.define('org.Member', {
    size: { width: 180, height: 70 },
    attrs: {
        rect: { width: 170, height: 60 },

        '.card': {
            fill: '#FFFFFF', stroke: '#000000', 'stroke-width': 2,
            'pointer-events': 'visiblePainted', rx: 10, ry: 10
        },

        image: {
            width: 48, height: 48,
            ref: '.card', 'ref-x': 10, 'ref-y': 5
        },

        '.rank': {
            'text-decoration': 'underline',
            ref: '.card', 'ref-x': 0.9, 'ref-y': 0.2,
            'font-family': 'Courier New', 'font-size': 14,
            'text-anchor': 'end'
        },

        '.name': {
            'font-weight': '800',
            ref: '.card', 'ref-x': 0.9, 'ref-y': 0.6,
            'font-family': 'Courier New', 'font-size': 14,
            'text-anchor': 'end'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><rect class="card"/><image/></g><text class="rank"/><text class="name"/></g>',
});

joint.dia.Link.define('org.Arrow', {
    source: { selector: '.card' }, target: { selector: '.card' },
    attrs: { '.connection': { stroke: '#585858', 'stroke-width': 3 } },
    z: -1
});

joint.shapes.basic.Generic.define('chess.KingWhite', {
    size: { width: 42, height: 38 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="fill:none; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;"><path      d="M 22.5,11.63 L 22.5,6"      style="fill:none; stroke:#000000; stroke-linejoin:miter;" />    <path      d="M 20,8 L 25,8"      style="fill:none; stroke:#000000; stroke-linejoin:miter;" />    <path      d="M 22.5,25 C 22.5,25 27,17.5 25.5,14.5 C 25.5,14.5 24.5,12 22.5,12 C 20.5,12 19.5,14.5 19.5,14.5 C 18,17.5 22.5,25 22.5,25"      style="fill:#ffffff; stroke:#000000; stroke-linecap:butt; stroke-linejoin:miter;" />    <path      d="M 11.5,37 C 17,40.5 27,40.5 32.5,37 L 32.5,30 C 32.5,30 41.5,25.5 38.5,19.5 C 34.5,13 25,16 22.5,23.5 L 22.5,27 L 22.5,23.5 C 19,16 9.5,13 6.5,19.5 C 3.5,25.5 11.5,29.5 11.5,29.5 L 11.5,37 z "      style="fill:#ffffff; stroke:#000000;" />    <path      d="M 11.5,30 C 17,27 27,27 32.5,30"      style="fill:none; stroke:#000000;" />    <path      d="M 11.5,33.5 C 17,30.5 27,30.5 32.5,33.5"      style="fill:none; stroke:#000000;" />    <path      d="M 11.5,37 C 17,34 27,34 32.5,37"      style="fill:none; stroke:#000000;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.KingBlack', {
    size: { width: 42, height: 38 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="fill:none; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <path       d="M 22.5,11.63 L 22.5,6"       style="fill:none; stroke:#000000; stroke-linejoin:miter;"       id="path6570" />    <path       d="M 22.5,25 C 22.5,25 27,17.5 25.5,14.5 C 25.5,14.5 24.5,12 22.5,12 C 20.5,12 19.5,14.5 19.5,14.5 C 18,17.5 22.5,25 22.5,25"       style="fill:#000000;fill-opacity:1; stroke-linecap:butt; stroke-linejoin:miter;" />    <path       d="M 11.5,37 C 17,40.5 27,40.5 32.5,37 L 32.5,30 C 32.5,30 41.5,25.5 38.5,19.5 C 34.5,13 25,16 22.5,23.5 L 22.5,27 L 22.5,23.5 C 19,16 9.5,13 6.5,19.5 C 3.5,25.5 11.5,29.5 11.5,29.5 L 11.5,37 z "       style="fill:#000000; stroke:#000000;" />    <path       d="M 20,8 L 25,8"       style="fill:none; stroke:#000000; stroke-linejoin:miter;" />    <path       d="M 32,29.5 C 32,29.5 40.5,25.5 38.03,19.85 C 34.15,14 25,18 22.5,24.5 L 22.51,26.6 L 22.5,24.5 C 20,18 9.906,14 6.997,19.85 C 4.5,25.5 11.85,28.85 11.85,28.85"       style="fill:none; stroke:#ffffff;" />    <path       d="M 11.5,30 C 17,27 27,27 32.5,30 M 11.5,33.5 C 17,30.5 27,30.5 32.5,33.5 M 11.5,37 C 17,34 27,34 32.5,37"       style="fill:none; stroke:#ffffff;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.QueenWhite', {
    size: { width: 42, height: 38 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:#ffffff; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <path      d="M 9 13 A 2 2 0 1 1  5,13 A 2 2 0 1 1  9 13 z"      transform="translate(-1,-1)" />    <path      d="M 9 13 A 2 2 0 1 1  5,13 A 2 2 0 1 1  9 13 z"      transform="translate(15.5,-5.5)" />    <path      d="M 9 13 A 2 2 0 1 1  5,13 A 2 2 0 1 1  9 13 z"      transform="translate(32,-1)" />    <path      d="M 9 13 A 2 2 0 1 1  5,13 A 2 2 0 1 1  9 13 z"      transform="translate(7,-4.5)" />    <path      d="M 9 13 A 2 2 0 1 1  5,13 A 2 2 0 1 1  9 13 z"      transform="translate(24,-4)" />    <path      d="M 9,26 C 17.5,24.5 30,24.5 36,26 L 38,14 L 31,25 L 31,11 L 25.5,24.5 L 22.5,9.5 L 19.5,24.5 L 14,10.5 L 14,25 L 7,14 L 9,26 z "      style="stroke-linecap:butt;" />    <path      d="M 9,26 C 9,28 10.5,28 11.5,30 C 12.5,31.5 12.5,31 12,33.5 C 10.5,34.5 10.5,36 10.5,36 C 9,37.5 11,38.5 11,38.5 C 17.5,39.5 27.5,39.5 34,38.5 C 34,38.5 35.5,37.5 34,36 C 34,36 34.5,34.5 33,33.5 C 32.5,31 32.5,31.5 33.5,30 C 34.5,28 36,28 36,26 C 27.5,24.5 17.5,24.5 9,26 z "      style="stroke-linecap:butt;" />    <path      d="M 11.5,30 C 15,29 30,29 33.5,30"      style="fill:none;" />    <path      d="M 12,33.5 C 18,32.5 27,32.5 33,33.5"      style="fill:none;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.QueenBlack', {
    size: { width: 42, height: 38 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:#000000; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <g style="fill:#000000; stroke:none;">      <circle cx="6"    cy="12" r="2.75" />      <circle cx="14"   cy="9"  r="2.75" />      <circle cx="22.5" cy="8"  r="2.75" />      <circle cx="31"   cy="9"  r="2.75" />      <circle cx="39"   cy="12" r="2.75" />    </g>    <path       d="M 9,26 C 17.5,24.5 30,24.5 36,26 L 38.5,13.5 L 31,25 L 30.7,10.9 L 25.5,24.5 L 22.5,10 L 19.5,24.5 L 14.3,10.9 L 14,25 L 6.5,13.5 L 9,26 z"       style="stroke-linecap:butt; stroke:#000000;" />    <path       d="M 9,26 C 9,28 10.5,28 11.5,30 C 12.5,31.5 12.5,31 12,33.5 C 10.5,34.5 10.5,36 10.5,36 C 9,37.5 11,38.5 11,38.5 C 17.5,39.5 27.5,39.5 34,38.5 C 34,38.5 35.5,37.5 34,36 C 34,36 34.5,34.5 33,33.5 C 32.5,31 32.5,31.5 33.5,30 C 34.5,28 36,28 36,26 C 27.5,24.5 17.5,24.5 9,26 z"       style="stroke-linecap:butt;" />    <path       d="M 11,38.5 A 35,35 1 0 0 34,38.5"       style="fill:none; stroke:#000000; stroke-linecap:butt;" />    <path       d="M 11,29 A 35,35 1 0 1 34,29"       style="fill:none; stroke:#ffffff;" />    <path       d="M 12.5,31.5 L 32.5,31.5"       style="fill:none; stroke:#ffffff;" />    <path       d="M 11.5,34.5 A 35,35 1 0 0 33.5,34.5"       style="fill:none; stroke:#ffffff;" />    <path       d="M 10.5,37.5 A 35,35 1 0 0 34.5,37.5"       style="fill:none; stroke:#ffffff;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.RookWhite', {
    size: { width: 32, height: 34 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:#ffffff; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <path      d="M 9,39 L 36,39 L 36,36 L 9,36 L 9,39 z "      style="stroke-linecap:butt;" />    <path      d="M 12,36 L 12,32 L 33,32 L 33,36 L 12,36 z "      style="stroke-linecap:butt;" />    <path      d="M 11,14 L 11,9 L 15,9 L 15,11 L 20,11 L 20,9 L 25,9 L 25,11 L 30,11 L 30,9 L 34,9 L 34,14"      style="stroke-linecap:butt;" />    <path      d="M 34,14 L 31,17 L 14,17 L 11,14" />    <path      d="M 31,17 L 31,29.5 L 14,29.5 L 14,17"      style="stroke-linecap:butt; stroke-linejoin:miter;" />    <path      d="M 31,29.5 L 32.5,32 L 12.5,32 L 14,29.5" />    <path      d="M 11,14 L 34,14"      style="fill:none; stroke:#000000; stroke-linejoin:miter;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.RookBlack', {
    size: { width: 32, height: 34 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:#000000; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <path      d="M 9,39 L 36,39 L 36,36 L 9,36 L 9,39 z "      style="stroke-linecap:butt;" />    <path      d="M 12.5,32 L 14,29.5 L 31,29.5 L 32.5,32 L 12.5,32 z "      style="stroke-linecap:butt;" />    <path      d="M 12,36 L 12,32 L 33,32 L 33,36 L 12,36 z "      style="stroke-linecap:butt;" />    <path      d="M 14,29.5 L 14,16.5 L 31,16.5 L 31,29.5 L 14,29.5 z "      style="stroke-linecap:butt;stroke-linejoin:miter;" />    <path      d="M 14,16.5 L 11,14 L 34,14 L 31,16.5 L 14,16.5 z "      style="stroke-linecap:butt;" />    <path      d="M 11,14 L 11,9 L 15,9 L 15,11 L 20,11 L 20,9 L 25,9 L 25,11 L 30,11 L 30,9 L 34,9 L 34,14 L 11,14 z "      style="stroke-linecap:butt;" />    <path      d="M 12,35.5 L 33,35.5 L 33,35.5"      style="fill:none; stroke:#ffffff; stroke-width:1; stroke-linejoin:miter;" />    <path      d="M 13,31.5 L 32,31.5"      style="fill:none; stroke:#ffffff; stroke-width:1; stroke-linejoin:miter;" />    <path      d="M 14,29.5 L 31,29.5"      style="fill:none; stroke:#ffffff; stroke-width:1; stroke-linejoin:miter;" />    <path      d="M 14,16.5 L 31,16.5"      style="fill:none; stroke:#ffffff; stroke-width:1; stroke-linejoin:miter;" />    <path      d="M 11,14 L 34,14"      style="fill:none; stroke:#ffffff; stroke-width:1; stroke-linejoin:miter;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.BishopWhite', {
    size: { width: 38, height: 38 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:none; fill-rule:evenodd; fill-opacity:1; stroke:#000000; stroke-width:1.5; stroke-linecap:round; stroke-linejoin:round; stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <g style="fill:#ffffff; stroke:#000000; stroke-linecap:butt;">       <path        d="M 9,36 C 12.39,35.03 19.11,36.43 22.5,34 C 25.89,36.43 32.61,35.03 36,36 C 36,36 37.65,36.54 39,38 C 38.32,38.97 37.35,38.99 36,38.5 C 32.61,37.53 25.89,38.96 22.5,37.5 C 19.11,38.96 12.39,37.53 9,38.5 C 7.646,38.99 6.677,38.97 6,38 C 7.354,36.06 9,36 9,36 z" />      <path        d="M 15,32 C 17.5,34.5 27.5,34.5 30,32 C 30.5,30.5 30,30 30,30 C 30,27.5 27.5,26 27.5,26 C 33,24.5 33.5,14.5 22.5,10.5 C 11.5,14.5 12,24.5 17.5,26 C 17.5,26 15,27.5 15,30 C 15,30 14.5,30.5 15,32 z" />      <path        d="M 25 8 A 2.5 2.5 0 1 1  20,8 A 2.5 2.5 0 1 1  25 8 z" />    </g>    <path      d="M 17.5,26 L 27.5,26 M 15,30 L 30,30 M 22.5,15.5 L 22.5,20.5 M 20,18 L 25,18"      style="fill:none; stroke:#000000; stroke-linejoin:miter;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.BishopBlack', {
    size: { width: 38, height: 38 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:none; fill-rule:evenodd; fill-opacity:1; stroke:#000000; stroke-width:1.5; stroke-linecap:round; stroke-linejoin:round; stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <g style="fill:#000000; stroke:#000000; stroke-linecap:butt;">       <path        d="M 9,36 C 12.39,35.03 19.11,36.43 22.5,34 C 25.89,36.43 32.61,35.03 36,36 C 36,36 37.65,36.54 39,38 C 38.32,38.97 37.35,38.99 36,38.5 C 32.61,37.53 25.89,38.96 22.5,37.5 C 19.11,38.96 12.39,37.53 9,38.5 C 7.646,38.99 6.677,38.97 6,38 C 7.354,36.06 9,36 9,36 z" />      <path        d="M 15,32 C 17.5,34.5 27.5,34.5 30,32 C 30.5,30.5 30,30 30,30 C 30,27.5 27.5,26 27.5,26 C 33,24.5 33.5,14.5 22.5,10.5 C 11.5,14.5 12,24.5 17.5,26 C 17.5,26 15,27.5 15,30 C 15,30 14.5,30.5 15,32 z" />      <path        d="M 25 8 A 2.5 2.5 0 1 1  20,8 A 2.5 2.5 0 1 1  25 8 z" />    </g>    <path       d="M 17.5,26 L 27.5,26 M 15,30 L 30,30 M 22.5,15.5 L 22.5,20.5 M 20,18 L 25,18"       style="fill:none; stroke:#ffffff; stroke-linejoin:miter;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.KnightWhite', {
    size: { width: 38, height: 37 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:none; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <path      d="M 22,10 C 32.5,11 38.5,18 38,39 L 15,39 C 15,30 25,32.5 23,18"      style="fill:#ffffff; stroke:#000000;" />    <path      d="M 24,18 C 24.38,20.91 18.45,25.37 16,27 C 13,29 13.18,31.34 11,31 C 9.958,30.06 12.41,27.96 11,28 C 10,28 11.19,29.23 10,30 C 9,30 5.997,31 6,26 C 6,24 12,14 12,14 C 12,14 13.89,12.1 14,10.5 C 13.27,9.506 13.5,8.5 13.5,7.5 C 14.5,6.5 16.5,10 16.5,10 L 18.5,10 C 18.5,10 19.28,8.008 21,7 C 22,7 22,10 22,10"      style="fill:#ffffff; stroke:#000000;" />    <path      d="M 9.5 25.5 A 0.5 0.5 0 1 1 8.5,25.5 A 0.5 0.5 0 1 1 9.5 25.5 z"      style="fill:#000000; stroke:#000000;" />    <path      d="M 15 15.5 A 0.5 1.5 0 1 1  14,15.5 A 0.5 1.5 0 1 1  15 15.5 z"      transform="matrix(0.866,0.5,-0.5,0.866,9.693,-5.173)"      style="fill:#000000; stroke:#000000;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.KnightBlack', {
    size: { width: 38, height: 37 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><g style="opacity:1; fill:none; fill-opacity:1; fill-rule:evenodd; stroke:#000000; stroke-width:1.5; stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;">    <path      d="M 22,10 C 32.5,11 38.5,18 38,39 L 15,39 C 15,30 25,32.5 23,18"      style="fill:#000000; stroke:#000000;" />    <path      d="M 24,18 C 24.38,20.91 18.45,25.37 16,27 C 13,29 13.18,31.34 11,31 C 9.958,30.06 12.41,27.96 11,28 C 10,28 11.19,29.23 10,30 C 9,30 5.997,31 6,26 C 6,24 12,14 12,14 C 12,14 13.89,12.1 14,10.5 C 13.27,9.506 13.5,8.5 13.5,7.5 C 14.5,6.5 16.5,10 16.5,10 L 18.5,10 C 18.5,10 19.28,8.008 21,7 C 22,7 22,10 22,10"      style="fill:#000000; stroke:#000000;" />    <path      d="M 9.5 25.5 A 0.5 0.5 0 1 1 8.5,25.5 A 0.5 0.5 0 1 1 9.5 25.5 z"      style="fill:#ffffff; stroke:#ffffff;" />    <path      d="M 15 15.5 A 0.5 1.5 0 1 1  14,15.5 A 0.5 1.5 0 1 1  15 15.5 z"      transform="matrix(0.866,0.5,-0.5,0.866,9.693,-5.173)"      style="fill:#ffffff; stroke:#ffffff;" />    <path      d="M 24.55,10.4 L 24.1,11.85 L 24.6,12 C 27.75,13 30.25,14.49 32.5,18.75 C 34.75,23.01 35.75,29.06 35.25,39 L 35.2,39.5 L 37.45,39.5 L 37.5,39 C 38,28.94 36.62,22.15 34.25,17.66 C 31.88,13.17 28.46,11.02 25.06,10.5 L 24.55,10.4 z "      style="fill:#ffffff; stroke:none;" />  </g></g></g>'
});

joint.shapes.basic.Generic.define('chess.PawnWhite', {
    size: { width: 28, height: 33 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><path d="M 22,9 C 19.79,9 18,10.79 18,13 C 18,13.89 18.29,14.71 18.78,15.38 C 16.83,16.5 15.5,18.59 15.5,21 C 15.5,23.03 16.44,24.84 17.91,26.03 C 14.91,27.09 10.5,31.58 10.5,39.5 L 33.5,39.5 C 33.5,31.58 29.09,27.09 26.09,26.03 C 27.56,24.84 28.5,23.03 28.5,21 C 28.5,18.59 27.17,16.5 25.22,15.38 C 25.71,14.71 26,13.89 26,13 C 26,10.79 24.21,9 22,9 z "  style="opacity:1; fill:#ffffff; fill-opacity:1; fill-rule:nonzero; stroke:#000000; stroke-width:1.5; stroke-linecap:round; stroke-linejoin:miter; stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;" /></g></g>'
});

joint.shapes.basic.Generic.define('chess.PawnBlack', {
    size: { width: 28, height: 33 }
}, {
    markup: '<g class="rotatable"><g class="scalable"><path d="M 22,9 C 19.79,9 18,10.79 18,13 C 18,13.89 18.29,14.71 18.78,15.38 C 16.83,16.5 15.5,18.59 15.5,21 C 15.5,23.03 16.44,24.84 17.91,26.03 C 14.91,27.09 10.5,31.58 10.5,39.5 L 33.5,39.5 C 33.5,31.58 29.09,27.09 26.09,26.03 C 27.56,24.84 28.5,23.03 28.5,21 C 28.5,18.59 27.17,16.5 25.22,15.38 C 25.71,14.71 26,13.89 26,13 C 26,10.79 24.21,9 22,9 z "  style="opacity:1; fill:#000000; fill-opacity:1; fill-rule:nonzero; stroke:#000000; stroke-width:1.5; stroke-linecap:round; stroke-linejoin:miter; stroke-miterlimit:4; stroke-dasharray:none; stroke-opacity:1;" /></g></g>'
});

joint.shapes.basic.Generic.define('pn.Place', {
    size: { width: 50, height: 50 },
    attrs: {
        '.root': {
            r: 25,
            fill: '#ffffff',
            stroke: '#000000',
            transform: 'translate(25, 25)'
        },
        '.label': {
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-y': -20,
            ref: '.root',
            fill: '#000000',
            'font-size': 12
        },
        '.tokens > circle': {
            fill: '#000000',
            r: 5
        },
        '.tokens.one > circle': { transform: 'translate(25, 25)' },

        '.tokens.two > circle:nth-child(1)': { transform: 'translate(19, 25)' },
        '.tokens.two > circle:nth-child(2)': { transform: 'translate(31, 25)' },

        '.tokens.three > circle:nth-child(1)': { transform: 'translate(18, 29)' },
        '.tokens.three > circle:nth-child(2)': { transform: 'translate(25, 19)' },
        '.tokens.three > circle:nth-child(3)': { transform: 'translate(32, 29)' },

        '.tokens.alot > text': {
            transform: 'translate(25, 18)',
            'text-anchor': 'middle',
            fill: '#000000'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><circle class="root"/><g class="tokens" /></g><text class="label"/></g>',
});

joint.shapes.pn.PlaceView = joint.dia.ElementView.extend({}, {

    initialize: function() {

        joint.dia.ElementView.prototype.initialize.apply(this, arguments);

        this.model.on('change:tokens', function() {

            this.renderTokens();
            this.update();

        }, this);
    },

    render: function() {

        joint.dia.ElementView.prototype.render.apply(this, arguments);

        this.renderTokens();
        this.update();
    },

    renderTokens: function() {

        var $tokens = this.$('.tokens').empty();
        $tokens[0].className.baseVal = 'tokens';

        var tokens = this.model.get('tokens');

        if (!tokens) return;

        switch (tokens) {

            case 1:
                $tokens[0].className.baseVal += ' one';
                $tokens.append(V('<circle/>').node);
                break;

            case 2:
                $tokens[0].className.baseVal += ' two';
                $tokens.append(V('<circle/>').node, V('<circle/>').node);
                break;

            case 3:
                $tokens[0].className.baseVal += ' three';
                $tokens.append(V('<circle/>').node, V('<circle/>').node, V('<circle/>').node);
                break;

            default:
                $tokens[0].className.baseVal += ' alot';
                $tokens.append(V('<text/>').text(tokens + '').node);
                break;
        }
    }
});

joint.shapes.basic.Generic.define('pn.Transition', {
    size: { width: 12, height: 50 },
    attrs: {
        'rect': {
            width: 12,
            height: 50,
            fill: '#000000',
            stroke: '#000000'
        },
        '.label': {
            'text-anchor': 'middle',
            'ref-x': .5,
            'ref-y': -20,
            ref: 'rect',
            fill: '#000000',
            'font-size': 12
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><rect class="root"/></g></g><text class="label"/>',
});

joint.dia.Link.define('pn.Link', {
    attrs: { '.marker-target': { d: 'M 10 0 L 0 5 L 10 10 z' } }
});

/**
 * @deprecated use the port api insteac
 */
joint.shapes.basic.Generic.define('devs.Model', {
    inPorts: [],
    outPorts: [],
    size: {
        width: 80,
        height: 80
    },
    attrs: {
        '.': {
            magnet: false
        },
        '.label': {
            text: 'Model',
            'ref-x': .5,
            'ref-y': 10,
            'font-size': 18,
            'text-anchor': 'middle',
            fill: '#000'
        },
        '.body': {
            'ref-width': '100%',
            'ref-height': '100%',
            stroke: '#000'
        }
    },
    ports: {
        groups: {
            'in': {
                position: {
                    name: 'left'
                },
                attrs: {
                    '.port-label': {
                        fill: '#000'
                    },
                    '.port-body': {
                        fill: '#fff',
                        stroke: '#000',
                        r: 10,
                        magnet: true
                    }
                },
                label: {
                    position: {
                        name: 'left',
                        args: {
                            y: 10
                        }
                    }
                }
            },
            'out': {
                position: {
                    name: 'right'
                },
                attrs: {
                    '.port-label': {
                        fill: '#000'
                    },
                    '.port-body': {
                        fill: '#fff',
                        stroke: '#000',
                        r: 10,
                        magnet: true
                    }
                },
                label: {
                    position: {
                        name: 'right',
                        args: {
                            y: 10
                        }
                    }
                }
            }
        }
    }
}, {
    markup: '<g class="rotatable"><rect class="body"/><text class="label"/></g>',
    portMarkup: '<circle class="port-body"/>',
    portLabelMarkup: '<text class="port-label"/>',

    initialize: function() {

        joint.shapes.basic.Generic.prototype.initialize.apply(this, arguments);

        this.on('change:inPorts change:outPorts', this.updatePortItems, this);
        this.updatePortItems();
    },

    updatePortItems: function(model, changed, opt) {

        // Make sure all ports are unique.
        var inPorts = joint.util.uniq(this.get('inPorts'));
        var outPorts = joint.util.difference(joint.util.uniq(this.get('outPorts')), inPorts);

        var inPortItems = this.createPortItems('in', inPorts);
        var outPortItems = this.createPortItems('out', outPorts);

        this.prop('ports/items', inPortItems.concat(outPortItems), joint.util.assign({ rewrite: true }, opt));
    },

    createPortItem: function(group, port) {

        return {
            id: port,
            group: group,
            attrs: {
                '.port-label': {
                    text: port
                }
            }
        };
    },

    createPortItems: function(group, ports) {

        return joint.util.toArray(ports).map(this.createPortItem.bind(this, group));
    },

    _addGroupPort: function(port, group, opt) {

        var ports = this.get(group);
        return this.set(group, Array.isArray(ports) ? ports.concat(port) : [port], opt);
    },

    addOutPort: function(port, opt) {

        return this._addGroupPort(port, 'outPorts', opt);
    },

    addInPort: function(port, opt) {

        return this._addGroupPort(port, 'inPorts', opt);
    },

    _removeGroupPort: function(port, group, opt) {

        return this.set(group, joint.util.without(this.get(group), port), opt);
    },

    removeOutPort: function(port, opt) {

        return this._removeGroupPort(port, 'outPorts', opt);
    },

    removeInPort: function(port, opt) {

        return this._removeGroupPort(port, 'inPorts', opt);
    },

    _changeGroup: function(group, properties, opt) {

        return this.prop('ports/groups/' + group, joint.util.isObject(properties) ? properties : {}, opt);
    },

    changeInGroup: function(properties, opt) {

        return this._changeGroup('in', properties, opt);
    },

    changeOutGroup: function(properties, opt) {

        return this._changeGroup('out', properties, opt);
    }
});

joint.shapes.devs.Model.define('devs.Atomic', {
    size: {
        width: 80,
        height: 80
    },
    attrs: {
        '.label': {
            text: 'Atomic'
        }
    }
});

joint.shapes.devs.Model.define('devs.Coupled', {
    size: {
        width: 200,
        height: 300
    },
    attrs: {
        '.label': {
            text: 'Coupled'
        }
    }
});

joint.dia.Link.define('devs.Link', {
    attrs: {
        '.connection': {
            'stroke-width': 2
        }
    }
});

joint.shapes.basic.Generic.define('uml.Class', {
    attrs: {
        rect: { 'width': 200 },

        '.uml-class-name-rect': { 'stroke': 'black', 'stroke-width': 2, 'fill': '#3498db' },
        '.uml-class-attrs-rect': { 'stroke': 'black', 'stroke-width': 2, 'fill': '#2980b9' },
        '.uml-class-methods-rect': { 'stroke': 'black', 'stroke-width': 2, 'fill': '#2980b9' },

        '.uml-class-name-text': {
            'ref': '.uml-class-name-rect',
            'ref-y': .5,
            'ref-x': .5,
            'text-anchor': 'middle',
            'y-alignment': 'middle',
            'font-weight': 'bold',
            'fill': 'black',
            'font-size': 12,
            'font-family': 'Times New Roman'
        },
        '.uml-class-attrs-text': {
            'ref': '.uml-class-attrs-rect', 'ref-y': 5, 'ref-x': 5,
            'fill': 'black', 'font-size': 12, 'font-family': 'Times New Roman'
        },
        '.uml-class-methods-text': {
            'ref': '.uml-class-methods-rect', 'ref-y': 5, 'ref-x': 5,
            'fill': 'black', 'font-size': 12, 'font-family': 'Times New Roman'
        }
    },

    name: [],
    attributes: [],
    methods: []
}, {
    markup: [
        '<g class="rotatable">',
        '<g class="scalable">',
        '<rect class="uml-class-name-rect"/><rect class="uml-class-attrs-rect"/><rect class="uml-class-methods-rect"/>',
        '</g>',
        '<text class="uml-class-name-text"/><text class="uml-class-attrs-text"/><text class="uml-class-methods-text"/>',
        '</g>'
    ].join(''),

    initialize: function() {

        this.on('change:name change:attributes change:methods', function() {
            this.updateRectangles();
            this.trigger('uml-update');
        }, this);

        this.updateRectangles();

        joint.shapes.basic.Generic.prototype.initialize.apply(this, arguments);
    },

    getClassName: function() {
        return this.get('name');
    },

    updateRectangles: function() {

        var attrs = this.get('attrs');

        var rects = [
            { type: 'name', text: this.getClassName() },
            { type: 'attrs', text: this.get('attributes') },
            { type: 'methods', text: this.get('methods') }
        ];

        var offsetY = 0;

        rects.forEach(function(rect) {

            var lines = Array.isArray(rect.text) ? rect.text : [rect.text];
            var rectHeight = lines.length * 20 + 20;

            attrs['.uml-class-' + rect.type + '-text'].text = lines.join('\n');
            attrs['.uml-class-' + rect.type + '-rect'].height = rectHeight;
            attrs['.uml-class-' + rect.type + '-rect'].transform = 'translate(0,' + offsetY + ')';

            offsetY += rectHeight;
        });
    }

});

joint.shapes.uml.ClassView = joint.dia.ElementView.extend({

    initialize: function() {

        joint.dia.ElementView.prototype.initialize.apply(this, arguments);

        this.listenTo(this.model, 'uml-update', function() {
            this.update();
            this.resize();
        });
    }
});

joint.shapes.uml.Class.define('uml.Abstract', {
    attrs: {
        '.uml-class-name-rect': { fill: '#e74c3c' },
        '.uml-class-attrs-rect': { fill: '#c0392b' },
        '.uml-class-methods-rect': { fill: '#c0392b' }
    }
}, {

    getClassName: function() {
        return ['<<Abstract>>', this.get('name')];
    }

});
joint.shapes.uml.AbstractView = joint.shapes.uml.ClassView;

joint.shapes.uml.Class.define('uml.Interface', {
    attrs: {
        '.uml-class-name-rect': { fill: '#f1c40f' },
        '.uml-class-attrs-rect': { fill: '#f39c12' },
        '.uml-class-methods-rect': { fill: '#f39c12' }
    }
}, {
    getClassName: function() {
        return ['<<Interface>>', this.get('name')];
    }
});
joint.shapes.uml.InterfaceView = joint.shapes.uml.ClassView;

joint.dia.Link.define('uml.Generalization', {
    attrs: { '.marker-target': { d: 'M 20 0 L 0 10 L 20 20 z', fill: 'white' } }
});

joint.dia.Link.define('uml.Implementation', {
    attrs: {
        '.marker-target': { d: 'M 20 0 L 0 10 L 20 20 z', fill: 'white' },
        '.connection': { 'stroke-dasharray': '3,3' }
    }
});

joint.dia.Link.define('uml.Aggregation', {
    attrs: { '.marker-target': { d: 'M 40 10 L 20 20 L 0 10 L 20 0 z', fill: 'white' } }
});

joint.dia.Link.define('uml.Composition', {
    attrs: { '.marker-target': { d: 'M 40 10 L 20 20 L 0 10 L 20 0 z', fill: 'black' } }
});

joint.dia.Link.define('uml.Association');

// Statechart

joint.shapes.basic.Generic.define('uml.State', {
    attrs: {
        '.uml-state-body': {
            'width': 200, 'height': 200, 'rx': 10, 'ry': 10,
            'fill': '#ecf0f1', 'stroke': '#bdc3c7', 'stroke-width': 3
        },
        '.uml-state-separator': {
            'stroke': '#bdc3c7', 'stroke-width': 2
        },
        '.uml-state-name': {
            'ref': '.uml-state-body', 'ref-x': .5, 'ref-y': 5, 'text-anchor': 'middle',
            'fill': '#000000', 'font-family': 'Courier New', 'font-size': 14
        },
        '.uml-state-events': {
            'ref': '.uml-state-separator', 'ref-x': 5, 'ref-y': 5,
            'fill': '#000000', 'font-family': 'Courier New', 'font-size': 14
        }
    },

    name: 'State',
    events: []

}, {
    markup: [
        '<g class="rotatable">',
        '<g class="scalable">',
        '<rect class="uml-state-body"/>',
        '</g>',
        '<path class="uml-state-separator"/>',
        '<text class="uml-state-name"/>',
        '<text class="uml-state-events"/>',
        '</g>'
    ].join(''),

    initialize: function() {

        this.on({
            'change:name': this.updateName,
            'change:events': this.updateEvents,
            'change:size': this.updatePath
        }, this);

        this.updateName();
        this.updateEvents();
        this.updatePath();

        joint.shapes.basic.Generic.prototype.initialize.apply(this, arguments);
    },

    updateName: function() {

        this.attr('.uml-state-name/text', this.get('name'));
    },

    updateEvents: function() {

        this.attr('.uml-state-events/text', this.get('events').join('\n'));
    },

    updatePath: function() {

        var d = 'M 0 20 L ' + this.get('size').width + ' 20';

        // We are using `silent: true` here because updatePath() is meant to be called
        // on resize and there's no need to to update the element twice (`change:size`
        // triggers also an update).
        this.attr('.uml-state-separator/d', d, { silent: true });
    }
});

joint.shapes.basic.Circle.define('uml.StartState', {
    type: 'uml.StartState',
    attrs: { circle: { 'fill': '#34495e', 'stroke': '#2c3e50', 'stroke-width': 2, 'rx': 1 } }
});

joint.shapes.basic.Generic.define('uml.EndState', {
    size: { width: 20, height: 20 },
    attrs: {
        'circle.outer': {
            transform: 'translate(10, 10)',
            r: 10,
            fill: '#ffffff',
            stroke: '#2c3e50'
        },

        'circle.inner': {
            transform: 'translate(10, 10)',
            r: 6,
            fill: '#34495e'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><circle class="outer"/><circle class="inner"/></g></g>',
});

joint.dia.Link.define('uml.Transition', {
    attrs: {
        '.marker-target': { d: 'M 10 0 L 0 5 L 10 10 z', fill: '#34495e', stroke: '#2c3e50' },
        '.connection': { stroke: '#2c3e50' }
    }
});

joint.shapes.basic.Generic.define('logic.Gate', {
    size: { width: 80, height: 40 },
    attrs: {
        '.': { magnet: false },
        '.body': { width: 100, height: 50 },
        circle: { r: 7, stroke: 'black', fill: 'transparent', 'stroke-width': 2 }
    }
}, {
    operation: function() {
        return true;
    }
});

joint.shapes.logic.Gate.define('logic.IO', {
    size: { width: 60, height: 30 },
    attrs: {
        '.body': { fill: 'white', stroke: 'black', 'stroke-width': 2 },
        '.wire': { ref: '.body', 'ref-y': .5, stroke: 'black' },
        text: {
            fill: 'black',
            ref: '.body', 'ref-x': .5, 'ref-y': .5, 'y-alignment': 'middle',
            'text-anchor': 'middle',
            'font-weight': 'bold',
            'font-variant': 'small-caps',
            'text-transform': 'capitalize',
            'font-size': '14px'
        }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><rect class="body"/></g><path class="wire"/><circle/><text/></g>',
});

joint.shapes.logic.IO.define('logic.Input', {
    attrs: {
        '.wire': { 'ref-dx': 0, d: 'M 0 0 L 23 0' },
        circle: { ref: '.body', 'ref-dx': 30, 'ref-y': 0.5, magnet: true, 'class': 'output', port: 'out' },
        text: { text: 'input' }
    }
});

joint.shapes.logic.IO.define('logic.Output', {
    attrs: {
        '.wire': { 'ref-x': 0, d: 'M 0 0 L -23 0' },
        circle: { ref: '.body', 'ref-x': -30, 'ref-y': 0.5, magnet: 'passive', 'class': 'input', port: 'in' },
        text: { text: 'output' }
    }
});

joint.shapes.logic.Gate.define('logic.Gate11', {
    attrs: {
        '.input': { ref: '.body', 'ref-x': -2, 'ref-y': 0.5, magnet: 'passive', port: 'in' },
        '.output': { ref: '.body', 'ref-dx': 2, 'ref-y': 0.5, magnet: true, port: 'out' }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><image class="body"/></g><circle class="input"/><circle class="output"/></g>',
});

joint.shapes.logic.Gate.define('logic.Gate21', {
    attrs: {
        '.input1': { ref: '.body', 'ref-x': -2, 'ref-y': 0.3, magnet: 'passive', port: 'in1' },
        '.input2': { ref: '.body', 'ref-x': -2, 'ref-y': 0.7, magnet: 'passive', port: 'in2' },
        '.output': { ref: '.body', 'ref-dx': 2, 'ref-y': 0.5, magnet: true, port: 'out' }
    }
}, {
    markup: '<g class="rotatable"><g class="scalable"><image class="body"/></g><circle class="input input1"/><circle  class="input input2"/><circle class="output"/></g>',
});

joint.shapes.logic.Gate11.define('logic.Repeater', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input) {
        return input;
    }
});

joint.shapes.logic.Gate11.define('logic.Not', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input) {
        return !input;
    }
});

joint.shapes.logic.Gate21.define('logic.Or', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input1, input2) {
        return input1 || input2;
    }
});

joint.shapes.logic.Gate21.define('logic.And', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }

}, {
    operation: function(input1, input2) {
        return input1 && input2;
    }
});

joint.shapes.logic.Gate21.define('logic.Nor', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input1, input2) {
        return !(input1 || input2);
    }
});

joint.shapes.logic.Gate21.define('logic.Nand', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input1, input2) {
        return !(input1 && input2);
    }
});

joint.shapes.logic.Gate21.define('logic.Xor', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input1, input2) {
        return (!input1 || input2) && (input1 || !input2);
    }
});

joint.shapes.logic.Gate21.define('logic.Xnor', {
    attrs: { image: { 'xlink:href': 'data:image/svg+xml;base64, ' } }
}, {
    operation: function(input1, input2) {
        return (!input1 || !input2) && (input1 || input2);
    }
});

joint.dia.Link.define('logic.Wire', {
    attrs: {
        '.connection': { 'stroke-width': 2 },
        '.marker-vertex': { r: 7 }
    },

    router: { name: 'orthogonal' },
    connector: { name: 'rounded', args: { radius: 10 } }
}, {
    arrowheadMarkup: [
        '<g class="marker-arrowhead-group marker-arrowhead-group-<%= end %>">',
        '<circle class="marker-arrowhead" end="<%= end %>" r="7"/>',
        '</g>'
    ].join(''),

    vertexMarkup: [
        '<g class="marker-vertex-group" transform="translate(<%= x %>, <%= y %>)">',
        '<circle class="marker-vertex" idx="<%= idx %>" r="10" />',
        '<g class="marker-vertex-remove-group">',
        '<path class="marker-vertex-remove-area" idx="<%= idx %>" d="M16,5.333c-7.732,0-14,4.701-14,10.5c0,1.982,0.741,3.833,2.016,5.414L2,25.667l5.613-1.441c2.339,1.317,5.237,2.107,8.387,2.107c7.732,0,14-4.701,14-10.5C30,10.034,23.732,5.333,16,5.333z" transform="translate(5, -33)"/>',
        '<path class="marker-vertex-remove" idx="<%= idx %>" transform="scale(.8) translate(9.5, -37)" d="M24.778,21.419 19.276,15.917 24.777,10.415 21.949,7.585 16.447,13.087 10.945,7.585 8.117,10.415 13.618,15.917 8.116,21.419 10.946,24.248 16.447,18.746 21.948,24.248z">',
        '<title>Remove vertex.</title>',
        '</path>',
        '</g>',
        '</g>'
    ].join('')
});

if (typeof exports === 'object') {

    var graphlib = require('graphlib');
    var dagre = require('dagre');
}

// In the browser, these variables are set to undefined because of JavaScript hoisting.
// In that case, should grab them from the window object.
graphlib = graphlib || (typeof window !== 'undefined' && window.graphlib);
dagre = dagre || (typeof window !== 'undefined' && window.dagre);

joint.layout.DirectedGraph = {

    exportElement: function(element) {

        // The width and height of the element.
        return element.size();
    },

    exportLink: function(link) {

        var labelSize = link.get('labelSize') || {};
        var edge = {
            // The number of ranks to keep between the source and target of the edge.
            minLen: link.get('minLen') || 1,
            // The weight to assign edges. Higher weight edges are generally
            // made shorter and straighter than lower weight edges.
            weight: link.get('weight') || 1,
            // Where to place the label relative to the edge.
            // l = left, c = center r = right.
            labelpos: link.get('labelPosition') || 'c',
            // How many pixels to move the label away from the edge.
            // Applies only when labelpos is l or r.
            labeloffset: link.get('labelOffset') || 0,
            // The width of the edge label in pixels.
            width: labelSize.width || 0,
            // The height of the edge label in pixels.
            height: labelSize.height || 0
        };

        return edge;
    },

    importElement: function(opt, v, gl) {

        var element = this.getCell(v);
        var glNode = gl.node(v);

        if (opt.setPosition) {
            opt.setPosition(element, glNode);
        } else {
            element.set('position', {
                x: glNode.x - glNode.width / 2,
                y: glNode.y - glNode.height / 2
            });
        }
    },

    importLink: function(opt, edgeObj, gl) {

        var link = this.getCell(edgeObj.name);
        var glEdge = gl.edge(edgeObj);
        var points = glEdge.points || [];

        // check the `setLinkVertices` here for backwards compatibility
        if (opt.setVertices || opt.setLinkVertices) {
            if (joint.util.isFunction(opt.setVertices)) {
                opt.setVertices(link, points);
            } else {
                // Remove the first and last point from points array.
                // Those are source/target element connection points
                // ie. they lies on the edge of connected elements.
                link.set('vertices', points.slice(1, points.length - 1));
            }
        }

        if (opt.setLabels && ('x' in glEdge) && ('y' in glEdge)) {
            var labelPosition = { x: glEdge.x, y: glEdge.y};
            if (joint.util.isFunction(opt.setLabels)) {
                opt.setLabels(link, labelPosition, points);
            } else {
                // Convert the absolute label position to a relative position
                // towards the closest point on the edge
                var polyline = g.Polyline(points);
                var length = polyline.closestPointLength(labelPosition);
                var closestPoint = polyline.pointAtLength(length);
                var distance = length / polyline.length();
                link.label(0, {
                    position: {
                        distance: distance,
                        offset: g.Point(labelPosition).difference(closestPoint).toJSON()
                    }
                });
            }
        }
    },

    layout: function(graphOrCells, opt) {

        var graph;

        if (graphOrCells instanceof joint.dia.Graph) {
            graph = graphOrCells;
        } else {
            // Reset cells in dry mode so the graph reference is not stored on the cells.
            // `sort: false` to prevent elements to change their order based on the z-index
            graph = (new joint.dia.Graph()).resetCells(graphOrCells, { dry: true, sort: false });
        }

        // This is not needed anymore.
        graphOrCells = null;

        opt = joint.util.defaults(opt || {}, {
            resizeClusters: true,
            clusterPadding: 10,
            exportElement: this.exportElement,
            exportLink: this.exportLink
        });

        // create a graphlib.Graph that represents the joint.dia.Graph
        var glGraph = graph.toGraphLib({
            directed: true,
            // We are about to use edge naming feature.
            multigraph: true,
            // We are able to layout graphs with embeds.
            compound: true,
            setNodeLabel: opt.exportElement,
            setEdgeLabel: opt.exportLink,
            setEdgeName: function(link) {
                // Graphlib edges have no ids. We use edge name property
                // to store and retrieve ids instead.
                return link.id;
            }
        });

        var glLabel = {};
        var marginX = opt.marginX || 0;
        var marginY = opt.marginY || 0;

        // Dagre layout accepts options as lower case.
        // Direction for rank nodes. Can be TB, BT, LR, or RL
        if (opt.rankDir) glLabel.rankdir = opt.rankDir;
        // Alignment for rank nodes. Can be UL, UR, DL, or DR
        if (opt.align) glLabel.align = opt.align;
        // Number of pixels that separate nodes horizontally in the layout.
        if (opt.nodeSep) glLabel.nodesep = opt.nodeSep;
        // Number of pixels that separate edges horizontally in the layout.
        if (opt.edgeSep) glLabel.edgesep = opt.edgeSep;
        // Number of pixels between each rank in the layout.
        if (opt.rankSep) glLabel.ranksep = opt.rankSep;
        // Type of algorithm to assign a rank to each node in the input graph.
        // Possible values: network-simplex, tight-tree or longest-path
        if (opt.ranker) glLabel.ranker = opt.ranker;
        // Number of pixels to use as a margin around the left and right of the graph.
        if (marginX) glLabel.marginx = marginX;
        // Number of pixels to use as a margin around the top and bottom of the graph.
        if (marginY) glLabel.marginy = marginY;

        // Set the option object for the graph label.
        glGraph.setGraph(glLabel);

        // Executes the layout.
        dagre.layout(glGraph, { debugTiming: !!opt.debugTiming });

        // Wrap all graph changes into a batch.
        graph.startBatch('layout');

        // Update the graph.
        graph.fromGraphLib(glGraph, {
            importNode: this.importElement.bind(graph, opt),
            importEdge: this.importLink.bind(graph, opt)
        });

        if (opt.resizeClusters) {
            // Resize and reposition cluster elements (parents of other elements)
            // to fit their children.
            // 1. filter clusters only
            // 2. map id on cells
            // 3. sort cells by their depth (the deepest first)
            // 4. resize cell to fit their direct children only.
            var clusters = glGraph.nodes()
                .filter(function(v) { return glGraph.children(v).length > 0; })
                .map(graph.getCell.bind(graph))
                .sort(function(aCluster, bCluster) {
                    return bCluster.getAncestors().length - aCluster.getAncestors().length;
                });

            joint.util.invoke(clusters, 'fitEmbeds', { padding: opt.clusterPadding });
        }

        graph.stopBatch('layout');

        // Width and height of the graph extended by margins.
        var glSize = glGraph.graph();
        // Return the bounding box of the graph after the layout.
        return g.Rect(
            marginX,
            marginY,
            Math.abs(glSize.width - 2 * marginX),
            Math.abs(glSize.height - 2 * marginY)
        );
    },

    fromGraphLib: function(glGraph, opt) {

        opt = opt || {};

        var importNode = opt.importNode || joint.util.noop;
        var importEdge = opt.importEdge || joint.util.noop;
        var graph = (this instanceof joint.dia.Graph) ? this : new joint.dia.Graph;

        // Import all nodes.
        glGraph.nodes().forEach(function(node) {
            importNode.call(graph, node, glGraph, graph, opt);
        });

        // Import all edges.
        glGraph.edges().forEach(function(edge) {
            importEdge.call(graph, edge, glGraph, graph, opt);
        });

        return graph;
    },

    // Create new graphlib graph from existing JointJS graph.
    toGraphLib: function(graph, opt) {

        opt = opt || {};

        var glGraphType = joint.util.pick(opt, 'directed', 'compound', 'multigraph');
        var glGraph = new graphlib.Graph(glGraphType);
        var setNodeLabel = opt.setNodeLabel || joint.util.noop;
        var setEdgeLabel = opt.setEdgeLabel || joint.util.noop;
        var setEdgeName = opt.setEdgeName || joint.util.noop;
        var collection = graph.get('cells');

        for (var i = 0, n = collection.length; i < n; i++) {

            var cell = collection.at(i);
            if (cell.isLink()) {

                var source = cell.get('source');
                var target = cell.get('target');

                // Links that end at a point are ignored.
                if (!source.id || !target.id) break;

                // Note that if we are creating a multigraph we can name the edges. If
                // we try to name edges on a non-multigraph an exception is thrown.
                glGraph.setEdge(source.id, target.id, setEdgeLabel(cell), setEdgeName(cell));

            } else {

                glGraph.setNode(cell.id, setNodeLabel(cell));

                // For the compound graphs we have to take embeds into account.
                if (glGraph.isCompound() && cell.has('parent')) {
                    var parentId = cell.get('parent');
                    if (collection.has(parentId)) {
                        // Make sure the parent cell is included in the graph (this can
                        // happen when the layout is run on part of the graph only).
                        glGraph.setParent(cell.id, parentId);
                    }
                }
            }
        }

        return glGraph;
    }
};

joint.dia.Graph.prototype.toGraphLib = function(opt) {

    return joint.layout.DirectedGraph.toGraphLib(this, opt);
};

joint.dia.Graph.prototype.fromGraphLib = function(glGraph, opt) {

    return joint.layout.DirectedGraph.fromGraphLib.call(this, glGraph, opt);
};


    joint.g = g;
    joint.V = joint.Vectorizer = V;

    return joint;

}));
