www/plugins-dist/statistiques/javascript/excanvas.js

   1 // Copyright 2006 Google Inc.
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 //   http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14
  15
  16 // Known Issues:
  17 //
  18 // * Patterns only support repeat.
  19 // * Radial gradient are not implemented. The VML version of these look very
  20 //   different from the canvas one.
  21 // * Clipping paths are not implemented.
  22 // * Coordsize. The width and height attribute have higher priority than the
  23 //   width and height style values which isn't correct.
  24 // * Painting mode isn't implemented.
  25 // * Canvas width/height should is using content-box by default. IE in
  26 //   Quirks mode will draw the canvas using border-box. Either change your
  27 //   doctype to HTML5
  28 //   (http://www.whatwg.org/specs/web-apps/current-work/#the-doctype)
  29 //   or use Box Sizing Behavior from WebFX
  30 //   (http://webfx.eae.net/dhtml/boxsizing/boxsizing.html)
  31 // * Non uniform scaling does not correctly scale strokes.
  32 // * Filling very large shapes (above 5000 points) is buggy.
  33 // * Optimize. There is always room for speed improvements.
  34
  35 // Only add this code if we do not already have a canvas implementation
  36 if (!document.createElement('canvas').getContext) {
  37
  38 (function() {
  39
  40   // alias some functions to make (compiled) code shorter
  41   var m = Math;
  42   var mr = m.round;
  43   var ms = m.sin;
  44   var mc = m.cos;
  45   var abs = m.abs;
  46   var sqrt = m.sqrt;
  47
  48   // this is used for sub pixel precision
  49   var Z = 10;
  50   var Z2 = Z / 2;
  51
  52   /**
  53    * This funtion is assigned to the <canvas> elements as element.getContext().
  54    * @this {HTMLElement}
  55    * @return {CanvasRenderingContext2D_}
  56    */
  57   function getContext() {
  58     return this.context_ ||
  59         (this.context_ = new CanvasRenderingContext2D_(this));
  60   }
  61
  62   var slice = Array.prototype.slice;
  63
  64   /**
  65    * Binds a function to an object. The returned function will always use the
  66    * passed in {@code obj} as {@code this}.
  67    *
  68    * Example:
  69    *
  70    *   g = bind(f, obj, a, b)
  71    *   g(c, d) // will do f.call(obj, a, b, c, d)
  72    *
  73    * @param {Function} f The function to bind the object to
  74    * @param {Object} obj The object that should act as this when the function
  75    *     is called
  76    * @param {*} var_args Rest arguments that will be used as the initial
  77    *     arguments when the function is called
  78    * @return {Function} A new function that has bound this
  79    */
  80   function bind(f, obj, var_args) {
  81     var a = slice.call(arguments, 2);
  82     return function() {
  83       return f.apply(obj, a.concat(slice.call(arguments)));
  84     };
  85   }
  86
  87   function encodeHtmlAttribute(s) {
  88     return String(s).replace(/&/g, '&amp;').replace(/"/g, '&quot;');
  89   }
  90
  91   function addNamespacesAndStylesheet(doc) {
  92     // create xmlns
  93     if (!doc.namespaces['g_vml_']) {
  94       doc.namespaces.add('g_vml_', 'urn:schemas-microsoft-com:vml',
  95                          '#default#VML');
  96
  97     }
  98     if (!doc.namespaces['g_o_']) {
  99       doc.namespaces.add('g_o_', 'urn:schemas-microsoft-com:office:office',
 100                          '#default#VML');
 101     }
 102
 103     // Setup default CSS.  Only add one style sheet per document
 104     if (!doc.styleSheets['ex_canvas_']) {
 105       var ss = doc.createStyleSheet();
 106       ss.owningElement.id = 'ex_canvas_';
 107       ss.cssText = 'canvas{display:inline-block;overflow:hidden;' +
 108           // default size is 300x150 in Gecko and Opera
 109           'text-align:left;width:300px;height:150px}';
 110     }
 111   }
 112
 113   // Add namespaces and stylesheet at startup.
 114   addNamespacesAndStylesheet(document);
 115
 116   var G_vmlCanvasManager_ = {
 117     init: function(opt_doc) {
 118       if (/MSIE/.test(navigator.userAgent) && !window.opera) {
 119         var doc = opt_doc || document;
 120         // Create a dummy element so that IE will allow canvas elements to be
 121         // recognized.
 122         doc.createElement('canvas');
 123         doc.attachEvent('onreadystatechange', bind(this.init_, this, doc));
 124       }
 125     },
 126
 127     init_: function(doc) {
 128       // find all canvas elements
 129       var els = doc.getElementsByTagName('canvas');
 130       for (var i = 0; i < els.length; i++) {
 131         this.initElement(els[i]);
 132       }
 133     },
 134
 135     /**
 136      * Public initializes a canvas element so that it can be used as canvas
 137      * element from now on. This is called automatically before the page is
 138      * loaded but if you are creating elements using createElement you need to
 139      * make sure this is called on the element.
 140      * @param {HTMLElement} el The canvas element to initialize.
 141      * @return {HTMLElement} the element that was created.
 142      */
 143     initElement: function(el) {
 144       if (!el.getContext) {
 145         el.getContext = getContext;
 146
 147         // Add namespaces and stylesheet to document of the element.
 148         addNamespacesAndStylesheet(el.ownerDocument);
 149
 150         // Remove fallback content. There is no way to hide text nodes so we
 151         // just remove all childNodes. We could hide all elements and remove
 152         // text nodes but who really cares about the fallback content.
 153         el.innerHTML = '';
 154
 155         // do not use inline function because that will leak memory
 156         el.attachEvent('onpropertychange', onPropertyChange);
 157         el.attachEvent('onresize', onResize);
 158
 159         var attrs = el.attributes;
 160         if (attrs.width && attrs.width.specified) {
 161           // TODO: use runtimeStyle and coordsize
 162           // el.getContext().setWidth_(attrs.width.nodeValue);
 163           el.style.width = attrs.width.nodeValue + 'px';
 164         } else {
 165           el.width = el.clientWidth;
 166         }
 167         if (attrs.height && attrs.height.specified) {
 168           // TODO: use runtimeStyle and coordsize
 169           // el.getContext().setHeight_(attrs.height.nodeValue);
 170           el.style.height = attrs.height.nodeValue + 'px';
 171         } else {
 172           el.height = el.clientHeight;
 173         }
 174         //el.getContext().setCoordsize_()
 175       }
 176       return el;
 177     }
 178   };
 179
 180   function onPropertyChange(e) {
 181     var el = e.srcElement;
 182
 183     switch (e.propertyName) {
 184       case 'width':
 185         el.getContext().clearRect();
 186         el.style.width = el.attributes.width.nodeValue + 'px';
 187         // In IE8 this does not trigger onresize.
 188         el.firstChild.style.width =  el.clientWidth + 'px';
 189         break;
 190       case 'height':
 191         el.getContext().clearRect();
 192         el.style.height = el.attributes.height.nodeValue + 'px';
 193         el.firstChild.style.height = el.clientHeight + 'px';
 194         break;
 195     }
 196   }
 197
 198   function onResize(e) {
 199     var el = e.srcElement;
 200     if (el.firstChild) {
 201       el.firstChild.style.width =  el.clientWidth + 'px';
 202       el.firstChild.style.height = el.clientHeight + 'px';
 203     }
 204   }
 205
 206   G_vmlCanvasManager_.init();
 207
 208   // precompute "00" to "FF"
 209   var decToHex = [];
 210   for (var i = 0; i < 16; i++) {
 211     for (var j = 0; j < 16; j++) {
 212       decToHex[i * 16 + j] = i.toString(16) + j.toString(16);
 213     }
 214   }
 215
 216   function createMatrixIdentity() {
 217     return [
 218       [1, 0, 0],
 219       [0, 1, 0],
 220       [0, 0, 1]
 221     ];
 222   }
 223
 224   function matrixMultiply(m1, m2) {
 225     var result = createMatrixIdentity();
 226
 227     for (var x = 0; x < 3; x++) {
 228       for (var y = 0; y < 3; y++) {
 229         var sum = 0;
 230
 231         for (var z = 0; z < 3; z++) {
 232           sum += m1[x][z] * m2[z][y];
 233         }
 234
 235         result[x][y] = sum;
 236       }
 237     }
 238     return result;
 239   }
 240
 241   function copyState(o1, o2) {
 242     o2.fillStyle     = o1.fillStyle;
 243     o2.lineCap       = o1.lineCap;
 244     o2.lineJoin      = o1.lineJoin;
 245     o2.lineWidth     = o1.lineWidth;
 246     o2.miterLimit    = o1.miterLimit;
 247     o2.shadowBlur    = o1.shadowBlur;
 248     o2.shadowColor   = o1.shadowColor;
 249     o2.shadowOffsetX = o1.shadowOffsetX;
 250     o2.shadowOffsetY = o1.shadowOffsetY;
 251     o2.strokeStyle   = o1.strokeStyle;
 252     o2.globalAlpha   = o1.globalAlpha;
 253     o2.font          = o1.font;
 254     o2.textAlign     = o1.textAlign;
 255     o2.textBaseline  = o1.textBaseline;
 256     o2.arcScaleX_    = o1.arcScaleX_;
 257     o2.arcScaleY_    = o1.arcScaleY_;
 258     o2.lineScale_    = o1.lineScale_;
 259   }
 260
 261   var colorData = {
 262     aliceblue: '#F0F8FF',
 263     antiquewhite: '#FAEBD7',
 264     aquamarine: '#7FFFD4',
 265     azure: '#F0FFFF',
 266     beige: '#F5F5DC',
 267     bisque: '#FFE4C4',
 268     black: '#000000',
 269     blanchedalmond: '#FFEBCD',
 270     blueviolet: '#8A2BE2',
 271     brown: '#A52A2A',
 272     burlywood: '#DEB887',
 273     cadetblue: '#5F9EA0',
 274     chartreuse: '#7FFF00',
 275     chocolate: '#D2691E',
 276     coral: '#FF7F50',
 277     cornflowerblue: '#6495ED',
 278     cornsilk: '#FFF8DC',
 279     crimson: '#DC143C',
 280     cyan: '#00FFFF',
 281     darkblue: '#00008B',
 282     darkcyan: '#008B8B',
 283     darkgoldenrod: '#B8860B',
 284     darkgray: '#A9A9A9',
 285     darkgreen: '#006400',
 286     darkgrey: '#A9A9A9',
 287     darkkhaki: '#BDB76B',
 288     darkmagenta: '#8B008B',
 289     darkolivegreen: '#556B2F',
 290     darkorange: '#FF8C00',
 291     darkorchid: '#9932CC',
 292     darkred: '#8B0000',
 293     darksalmon: '#E9967A',
 294     darkseagreen: '#8FBC8F',
 295     darkslateblue: '#483D8B',
 296     darkslategray: '#2F4F4F',
 297     darkslategrey: '#2F4F4F',
 298     darkturquoise: '#00CED1',
 299     darkviolet: '#9400D3',
 300     deeppink: '#FF1493',
 301     deepskyblue: '#00BFFF',
 302     dimgray: '#696969',
 303     dimgrey: '#696969',
 304     dodgerblue: '#1E90FF',
 305     firebrick: '#B22222',
 306     floralwhite: '#FFFAF0',
 307     forestgreen: '#228B22',
 308     gainsboro: '#DCDCDC',
 309     ghostwhite: '#F8F8FF',
 310     gold: '#FFD700',
 311     goldenrod: '#DAA520',
 312     grey: '#808080',
 313     greenyellow: '#ADFF2F',
 314     honeydew: '#F0FFF0',
 315     hotpink: '#FF69B4',
 316     indianred: '#CD5C5C',
 317     indigo: '#4B0082',
 318     ivory: '#FFFFF0',
 319     khaki: '#F0E68C',
 320     lavender: '#E6E6FA',
 321     lavenderblush: '#FFF0F5',
 322     lawngreen: '#7CFC00',
 323     lemonchiffon: '#FFFACD',
 324     lightblue: '#ADD8E6',
 325     lightcoral: '#F08080',
 326     lightcyan: '#E0FFFF',
 327     lightgoldenrodyellow: '#FAFAD2',
 328     lightgreen: '#90EE90',
 329     lightgrey: '#D3D3D3',
 330     lightpink: '#FFB6C1',
 331     lightsalmon: '#FFA07A',
 332     lightseagreen: '#20B2AA',
 333     lightskyblue: '#87CEFA',
 334     lightslategray: '#778899',
 335     lightslategrey: '#778899',
 336     lightsteelblue: '#B0C4DE',
 337     lightyellow: '#FFFFE0',
 338     limegreen: '#32CD32',
 339     linen: '#FAF0E6',
 340     magenta: '#FF00FF',
 341     mediumaquamarine: '#66CDAA',
 342     mediumblue: '#0000CD',
 343     mediumorchid: '#BA55D3',
 344     mediumpurple: '#9370DB',
 345     mediumseagreen: '#3CB371',
 346     mediumslateblue: '#7B68EE',
 347     mediumspringgreen: '#00FA9A',
 348     mediumturquoise: '#48D1CC',
 349     mediumvioletred: '#C71585',
 350     midnightblue: '#191970',
 351     mintcream: '#F5FFFA',
 352     mistyrose: '#FFE4E1',
 353     moccasin: '#FFE4B5',
 354     navajowhite: '#FFDEAD',
 355     oldlace: '#FDF5E6',
 356     olivedrab: '#6B8E23',
 357     orange: '#FFA500',
 358     orangered: '#FF4500',
 359     orchid: '#DA70D6',
 360     palegoldenrod: '#EEE8AA',
 361     palegreen: '#98FB98',
 362     paleturquoise: '#AFEEEE',
 363     palevioletred: '#DB7093',
 364     papayawhip: '#FFEFD5',
 365     peachpuff: '#FFDAB9',
 366     peru: '#CD853F',
 367     pink: '#FFC0CB',
 368     plum: '#DDA0DD',
 369     powderblue: '#B0E0E6',
 370     rosybrown: '#BC8F8F',
 371     royalblue: '#4169E1',
 372     saddlebrown: '#8B4513',
 373     salmon: '#FA8072',
 374     sandybrown: '#F4A460',
 375     seagreen: '#2E8B57',
 376     seashell: '#FFF5EE',
 377     sienna: '#A0522D',
 378     skyblue: '#87CEEB',
 379     slateblue: '#6A5ACD',
 380     slategray: '#708090',
 381     slategrey: '#708090',
 382     snow: '#FFFAFA',
 383     springgreen: '#00FF7F',
 384     steelblue: '#4682B4',
 385     tan: '#D2B48C',
 386     thistle: '#D8BFD8',
 387     tomato: '#FF6347',
 388     turquoise: '#40E0D0',
 389     violet: '#EE82EE',
 390     wheat: '#F5DEB3',
 391     whitesmoke: '#F5F5F5',
 392     yellowgreen: '#9ACD32'
 393   };
 394
 395
 396   function getRgbHslContent(styleString) {
 397     var start = styleString.indexOf('(', 3);
 398     var end = styleString.indexOf(')', start + 1);
 399     var parts = styleString.substring(start + 1, end).split(',');
 400     // add alpha if needed
 401     if (parts.length == 4 && styleString.substr(3, 1) == 'a') {
 402       alpha = Number(parts[3]);
 403     } else {
 404       parts[3] = 1;
 405     }
 406     return parts;
 407   }
 408
 409   function percent(s) {
 410     return parseFloat(s) / 100;
 411   }
 412
 413   function clamp(v, min, max) {
 414     return Math.min(max, Math.max(min, v));
 415   }
 416
 417   function hslToRgb(parts){
 418     var r, g, b;
 419     h = parseFloat(parts[0]) / 360 % 360;
 420     if (h < 0)
 421       h++;
 422     s = clamp(percent(parts[1]), 0, 1);
 423     l = clamp(percent(parts[2]), 0, 1);
 424     if (s == 0) {
 425       r = g = b = l; // achromatic
 426     } else {
 427       var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
 428       var p = 2 * l - q;
 429       r = hueToRgb(p, q, h + 1 / 3);
 430       g = hueToRgb(p, q, h);
 431       b = hueToRgb(p, q, h - 1 / 3);
 432     }
 433
 434     return '#' + decToHex[Math.floor(r * 255)] +
 435         decToHex[Math.floor(g * 255)] +
 436         decToHex[Math.floor(b * 255)];
 437   }
 438
 439   function hueToRgb(m1, m2, h) {
 440     if (h < 0)
 441       h++;
 442     if (h > 1)
 443       h--;
 444
 445     if (6 * h < 1)
 446       return m1 + (m2 - m1) * 6 * h;
 447     else if (2 * h < 1)
 448       return m2;
 449     else if (3 * h < 2)
 450       return m1 + (m2 - m1) * (2 / 3 - h) * 6;
 451     else
 452       return m1;
 453   }
 454
 455   function processStyle(styleString) {
 456     var str, alpha = 1;
 457
 458     styleString = String(styleString);
 459     if (styleString.charAt(0) == '#') {
 460       str = styleString;
 461     } else if (/^rgb/.test(styleString)) {
 462       var parts = getRgbHslContent(styleString);
 463       var str = '#', n;
 464       for (var i = 0; i < 3; i++) {
 465         if (parts[i].indexOf('%') != -1) {
 466           n = Math.floor(percent(parts[i]) * 255);
 467         } else {
 468           n = Number(parts[i]);
 469         }
 470         str += decToHex[clamp(n, 0, 255)];
 471       }
 472       alpha = parts[3];
 473     } else if (/^hsl/.test(styleString)) {
 474       var parts = getRgbHslContent(styleString);
 475       str = hslToRgb(parts);
 476       alpha = parts[3];
 477     } else {
 478       str = colorData[styleString] || styleString;
 479     }
 480     return {color: str, alpha: alpha};
 481   }
 482
 483   var DEFAULT_STYLE = {
 484     style: 'normal',
 485     variant: 'normal',
 486     weight: 'normal',
 487     size: 10,
 488     family: 'sans-serif'
 489   };
 490
 491   // Internal text style cache
 492   var fontStyleCache = {};
 493
 494   function processFontStyle(styleString) {
 495     if (fontStyleCache[styleString]) {
 496       return fontStyleCache[styleString];
 497     }
 498
 499     var el = document.createElement('div');
 500     var style = el.style;
 501     try {
 502       style.font = styleString;
 503     } catch (ex) {
 504       // Ignore failures to set to invalid font.
 505     }
 506
 507     return fontStyleCache[styleString] = {
 508       style: style.fontStyle || DEFAULT_STYLE.style,
 509       variant: style.fontVariant || DEFAULT_STYLE.variant,
 510       weight: style.fontWeight || DEFAULT_STYLE.weight,
 511       size: style.fontSize || DEFAULT_STYLE.size,
 512       family: style.fontFamily || DEFAULT_STYLE.family
 513     };
 514   }
 515
 516   function getComputedStyle(style, element) {
 517     var computedStyle = {};
 518
 519     for (var p in style) {
 520       computedStyle[p] = style[p];
 521     }
 522
 523     // Compute the size
 524     var canvasFontSize = parseFloat(element.currentStyle.fontSize),
 525         fontSize = parseFloat(style.size);
 526
 527     if (typeof style.size == 'number') {
 528       computedStyle.size = style.size;
 529     } else if (style.size.indexOf('px') != -1) {
 530       computedStyle.size = fontSize;
 531     } else if (style.size.indexOf('em') != -1) {
 532       computedStyle.size = canvasFontSize * fontSize;
 533     } else if(style.size.indexOf('%') != -1) {
 534       computedStyle.size = (canvasFontSize / 100) * fontSize;
 535     } else if (style.size.indexOf('pt') != -1) {
 536       computedStyle.size = fontSize / .75;
 537     } else {
 538       computedStyle.size = canvasFontSize;
 539     }
 540
 541     // Different scaling between normal text and VML text. This was found using
 542     // trial and error to get the same size as non VML text.
 543     computedStyle.size *= 0.981;
 544
 545     return computedStyle;
 546   }
 547
 548   function buildStyle(style) {
 549     return style.style + ' ' + style.variant + ' ' + style.weight + ' ' +
 550         style.size + 'px ' + style.family;
 551   }
 552
 553   function processLineCap(lineCap) {
 554     switch (lineCap) {
 555       case 'butt':
 556         return 'flat';
 557       case 'round':
 558         return 'round';
 559       case 'square':
 560       default:
 561         return 'square';
 562     }
 563   }
 564
 565   /**
 566    * This class implements CanvasRenderingContext2D interface as described by
 567    * the WHATWG.
 568    * @param {HTMLElement} surfaceElement The element that the 2D context should
 569    * be associated with
 570    */
 571   function CanvasRenderingContext2D_(surfaceElement) {
 572     this.m_ = createMatrixIdentity();
 573
 574     this.mStack_ = [];
 575     this.aStack_ = [];
 576     this.currentPath_ = [];
 577
 578     // Canvas context properties
 579     this.strokeStyle = '#000';
 580     this.fillStyle = '#000';
 581
 582     this.lineWidth = 1;
 583     this.lineJoin = 'miter';
 584     this.lineCap = 'butt';
 585     this.miterLimit = Z * 1;
 586     this.globalAlpha = 1;
 587     this.font = '10px sans-serif';
 588     this.textAlign = 'left';
 589     this.textBaseline = 'alphabetic';
 590     this.canvas = surfaceElement;
 591
 592     var el = surfaceElement.ownerDocument.createElement('div');
 593     el.style.width =  surfaceElement.clientWidth + 'px';
 594     el.style.height = surfaceElement.clientHeight + 'px';
 595     el.style.overflow = 'hidden';
 596     el.style.position = 'absolute';
 597     surfaceElement.appendChild(el);
 598
 599     this.element_ = el;
 600     this.arcScaleX_ = 1;
 601     this.arcScaleY_ = 1;
 602     this.lineScale_ = 1;
 603   }
 604
 605   var contextPrototype = CanvasRenderingContext2D_.prototype;
 606   contextPrototype.clearRect = function() {
 607     if (this.textMeasureEl_) {
 608       this.textMeasureEl_.removeNode(true);
 609       this.textMeasureEl_ = null;
 610     }
 611     this.element_.innerHTML = '';
 612   };
 613
 614   contextPrototype.beginPath = function() {
 615     // TODO: Branch current matrix so that save/restore has no effect
 616     //       as per safari docs.
 617     this.currentPath_ = [];
 618   };
 619
 620   contextPrototype.moveTo = function(aX, aY) {
 621     var p = this.getCoords_(aX, aY);
 622     this.currentPath_.push({type: 'moveTo', x: p.x, y: p.y});
 623     this.currentX_ = p.x;
 624     this.currentY_ = p.y;
 625   };
 626
 627   contextPrototype.lineTo = function(aX, aY) {
 628     var p = this.getCoords_(aX, aY);
 629     this.currentPath_.push({type: 'lineTo', x: p.x, y: p.y});
 630
 631     this.currentX_ = p.x;
 632     this.currentY_ = p.y;
 633   };
 634
 635   contextPrototype.bezierCurveTo = function(aCP1x, aCP1y,
 636                                             aCP2x, aCP2y,
 637                                             aX, aY) {
 638     var p = this.getCoords_(aX, aY);
 639     var cp1 = this.getCoords_(aCP1x, aCP1y);
 640     var cp2 = this.getCoords_(aCP2x, aCP2y);
 641     bezierCurveTo(this, cp1, cp2, p);
 642   };
 643
 644   // Helper function that takes the already fixed cordinates.
 645   function bezierCurveTo(self, cp1, cp2, p) {
 646     self.currentPath_.push({
 647       type: 'bezierCurveTo',
 648       cp1x: cp1.x,
 649       cp1y: cp1.y,
 650       cp2x: cp2.x,
 651       cp2y: cp2.y,
 652       x: p.x,
 653       y: p.y
 654     });
 655     self.currentX_ = p.x;
 656     self.currentY_ = p.y;
 657   }
 658
 659   contextPrototype.quadraticCurveTo = function(aCPx, aCPy, aX, aY) {
 660     // the following is lifted almost directly from
 661     // http://developer.mozilla.org/en/docs/Canvas_tutorial:Drawing_shapes
 662
 663     var cp = this.getCoords_(aCPx, aCPy);
 664     var p = this.getCoords_(aX, aY);
 665
 666     var cp1 = {
 667       x: this.currentX_ + 2.0 / 3.0 * (cp.x - this.currentX_),
 668       y: this.currentY_ + 2.0 / 3.0 * (cp.y - this.currentY_)
 669     };
 670     var cp2 = {
 671       x: cp1.x + (p.x - this.currentX_) / 3.0,
 672       y: cp1.y + (p.y - this.currentY_) / 3.0
 673     };
 674
 675     bezierCurveTo(this, cp1, cp2, p);
 676   };
 677
 678   contextPrototype.arc = function(aX, aY, aRadius,
 679                                   aStartAngle, aEndAngle, aClockwise) {
 680     aRadius *= Z;
 681     var arcType = aClockwise ? 'at' : 'wa';
 682
 683     var xStart = aX + mc(aStartAngle) * aRadius - Z2;
 684     var yStart = aY + ms(aStartAngle) * aRadius - Z2;
 685
 686     var xEnd = aX + mc(aEndAngle) * aRadius - Z2;
 687     var yEnd = aY + ms(aEndAngle) * aRadius - Z2;
 688
 689     // IE won't render arches drawn counter clockwise if xStart == xEnd.
 690     if (xStart == xEnd && !aClockwise) {
 691       xStart += 0.125; // Offset xStart by 1/80 of a pixel. Use something
 692                        // that can be represented in binary
 693     }
 694
 695     var p = this.getCoords_(aX, aY);
 696     var pStart = this.getCoords_(xStart, yStart);
 697     var pEnd = this.getCoords_(xEnd, yEnd);
 698
 699     this.currentPath_.push({type: arcType,
 700                            x: p.x,
 701                            y: p.y,
 702                            radius: aRadius,
 703                            xStart: pStart.x,
 704                            yStart: pStart.y,
 705                            xEnd: pEnd.x,
 706                            yEnd: pEnd.y});
 707
 708   };
 709
 710   contextPrototype.rect = function(aX, aY, aWidth, aHeight) {
 711     this.moveTo(aX, aY);
 712     this.lineTo(aX + aWidth, aY);
 713     this.lineTo(aX + aWidth, aY + aHeight);
 714     this.lineTo(aX, aY + aHeight);
 715     this.closePath();
 716   };
 717
 718   contextPrototype.strokeRect = function(aX, aY, aWidth, aHeight) {
 719     var oldPath = this.currentPath_;
 720     this.beginPath();
 721
 722     this.moveTo(aX, aY);
 723     this.lineTo(aX + aWidth, aY);
 724     this.lineTo(aX + aWidth, aY + aHeight);
 725     this.lineTo(aX, aY + aHeight);
 726     this.closePath();
 727     this.stroke();
 728
 729     this.currentPath_ = oldPath;
 730   };
 731
 732   contextPrototype.fillRect = function(aX, aY, aWidth, aHeight) {
 733     var oldPath = this.currentPath_;
 734     this.beginPath();
 735
 736     this.moveTo(aX, aY);
 737     this.lineTo(aX + aWidth, aY);
 738     this.lineTo(aX + aWidth, aY + aHeight);
 739     this.lineTo(aX, aY + aHeight);
 740     this.closePath();
 741     this.fill();
 742
 743     this.currentPath_ = oldPath;
 744   };
 745
 746   contextPrototype.createLinearGradient = function(aX0, aY0, aX1, aY1) {
 747     var gradient = new CanvasGradient_('gradient');
 748     gradient.x0_ = aX0;
 749     gradient.y0_ = aY0;
 750     gradient.x1_ = aX1;
 751     gradient.y1_ = aY1;
 752     return gradient;
 753   };
 754
 755   contextPrototype.createRadialGradient = function(aX0, aY0, aR0,
 756                                                    aX1, aY1, aR1) {
 757     var gradient = new CanvasGradient_('gradientradial');
 758     gradient.x0_ = aX0;
 759     gradient.y0_ = aY0;
 760     gradient.r0_ = aR0;
 761     gradient.x1_ = aX1;
 762     gradient.y1_ = aY1;
 763     gradient.r1_ = aR1;
 764     return gradient;
 765   };
 766
 767   contextPrototype.drawImage = function(image, var_args) {
 768     var dx, dy, dw, dh, sx, sy, sw, sh;
 769
 770     // to find the original width we overide the width and height
 771     var oldRuntimeWidth = image.runtimeStyle.width;
 772     var oldRuntimeHeight = image.runtimeStyle.height;
 773     image.runtimeStyle.width = 'auto';
 774     image.runtimeStyle.height = 'auto';
 775
 776     // get the original size
 777     var w = image.width;
 778     var h = image.height;
 779
 780     // and remove overides
 781     image.runtimeStyle.width = oldRuntimeWidth;
 782     image.runtimeStyle.height = oldRuntimeHeight;
 783
 784     if (arguments.length == 3) {
 785       dx = arguments[1];
 786       dy = arguments[2];
 787       sx = sy = 0;
 788       sw = dw = w;
 789       sh = dh = h;
 790     } else if (arguments.length == 5) {
 791       dx = arguments[1];
 792       dy = arguments[2];
 793       dw = arguments[3];
 794       dh = arguments[4];
 795       sx = sy = 0;
 796       sw = w;
 797       sh = h;
 798     } else if (arguments.length == 9) {
 799       sx = arguments[1];
 800       sy = arguments[2];
 801       sw = arguments[3];
 802       sh = arguments[4];
 803       dx = arguments[5];
 804       dy = arguments[6];
 805       dw = arguments[7];
 806       dh = arguments[8];
 807     } else {
 808       throw Error('Invalid number of arguments');
 809     }
 810
 811     var d = this.getCoords_(dx, dy);
 812
 813     var w2 = sw / 2;
 814     var h2 = sh / 2;
 815
 816     var vmlStr = [];
 817
 818     var W = 10;
 819     var H = 10;
 820
 821     // For some reason that I've now forgotten, using divs didn't work
 822     vmlStr.push(' <g_vml_:group',
 823                 ' coordsize="', Z * W, ',', Z * H, '"',
 824                 ' coordorigin="0,0"' ,
 825                 ' style="width:', W, 'px;height:', H, 'px;position:absolute;');
 826
 827     // If filters are necessary (rotation exists), create them
 828     // filters are bog-slow, so only create them if abbsolutely necessary
 829     // The following check doesn't account for skews (which don't exist
 830     // in the canvas spec (yet) anyway.
 831
 832     if (this.m_[0][0] != 1 || this.m_[0][1] ||
 833         this.m_[1][1] != 1 || this.m_[1][0]) {
 834       var filter = [];
 835
 836       // Note the 12/21 reversal
 837       filter.push('M11=', this.m_[0][0], ',',
 838                   'M12=', this.m_[1][0], ',',
 839                   'M21=', this.m_[0][1], ',',
 840                   'M22=', this.m_[1][1], ',',
 841                   'Dx=', mr(d.x / Z), ',',
 842                   'Dy=', mr(d.y / Z), '');
 843
 844       // Bounding box calculation (need to minimize displayed area so that
 845       // filters don't waste time on unused pixels.
 846       var max = d;
 847       var c2 = this.getCoords_(dx + dw, dy);
 848       var c3 = this.getCoords_(dx, dy + dh);
 849       var c4 = this.getCoords_(dx + dw, dy + dh);
 850
 851       max.x = m.max(max.x, c2.x, c3.x, c4.x);
 852       max.y = m.max(max.y, c2.y, c3.y, c4.y);
 853
 854       vmlStr.push('padding:0 ', mr(max.x / Z), 'px ', mr(max.y / Z),
 855                   'px 0;filter:progid:DXImageTransform.Microsoft.Matrix(',
 856                   filter.join(''), ", sizingmethod='clip');");
 857
 858     } else {
 859       vmlStr.push('top:', mr(d.y / Z), 'px;left:', mr(d.x / Z), 'px;');
 860     }
 861
 862     vmlStr.push(' ">' ,
 863                 '<g_vml_:image src="', image.src, '"',
 864                 ' style="width:', Z * dw, 'px;',
 865                 ' height:', Z * dh, 'px"',
 866                 ' cropleft="', sx / w, '"',
 867                 ' croptop="', sy / h, '"',
 868                 ' cropright="', (w - sx - sw) / w, '"',
 869                 ' cropbottom="', (h - sy - sh) / h, '"',
 870                 ' />',
 871                 '</g_vml_:group>');
 872
 873     this.element_.insertAdjacentHTML('BeforeEnd', vmlStr.join(''));
 874   };
 875
 876   contextPrototype.stroke = function(aFill) {
 877     var W = 10;
 878     var H = 10;
 879     // Divide the shape into chunks if it's too long because IE has a limit
 880     // somewhere for how long a VML shape can be. This simple division does
 881     // not work with fills, only strokes, unfortunately.
 882     var chunkSize = 5000;
 883
 884     var min = {x: null, y: null};
 885     var max = {x: null, y: null};
 886
 887     for (var j = 0; j < this.currentPath_.length; j += chunkSize) {
 888       var lineStr = [];
 889       var lineOpen = false;
 890
 891       lineStr.push('<g_vml_:shape',
 892                    ' filled="', !!aFill, '"',
 893                    ' style="position:absolute;width:', W, 'px;height:', H, 'px;"',
 894                    ' coordorigin="0,0"',
 895                    ' coordsize="', Z * W, ',', Z * H, '"',
 896                    ' stroked="', !aFill, '"',
 897                    ' path="');
 898
 899       var newSeq = false;
 900
 901       for (var i = j; i < Math.min(j + chunkSize, this.currentPath_.length); i++) {
 902         if (i % chunkSize == 0 && i > 0) { // move into position for next chunk
 903           lineStr.push(' m ', mr(this.currentPath_[i-1].x), ',', mr(this.currentPath_[i-1].y));
 904         }
 905
 906         var p = this.currentPath_[i];
 907         var c;
 908
 909         switch (p.type) {
 910           case 'moveTo':
 911             c = p;
 912             lineStr.push(' m ', mr(p.x), ',', mr(p.y));
 913             break;
 914           case 'lineTo':
 915             lineStr.push(' l ', mr(p.x), ',', mr(p.y));
 916             break;
 917           case 'close':
 918             lineStr.push(' x ');
 919             p = null;
 920             break;
 921           case 'bezierCurveTo':
 922             lineStr.push(' c ',
 923                          mr(p.cp1x), ',', mr(p.cp1y), ',',
 924                          mr(p.cp2x), ',', mr(p.cp2y), ',',
 925                          mr(p.x), ',', mr(p.y));
 926             break;
 927           case 'at':
 928           case 'wa':
 929             lineStr.push(' ', p.type, ' ',
 930                          mr(p.x - this.arcScaleX_ * p.radius), ',',
 931                          mr(p.y - this.arcScaleY_ * p.radius), ' ',
 932                          mr(p.x + this.arcScaleX_ * p.radius), ',',
 933                          mr(p.y + this.arcScaleY_ * p.radius), ' ',
 934                          mr(p.xStart), ',', mr(p.yStart), ' ',
 935                          mr(p.xEnd), ',', mr(p.yEnd));
 936             break;
 937         }
 938
 939
 940         // TODO: Following is broken for curves due to
 941         //       move to proper paths.
 942
 943         // Figure out dimensions so we can do gradient fills
 944         // properly
 945         if (p) {
 946           if (min.x == null || p.x < min.x) {
 947             min.x = p.x;
 948           }
 949           if (max.x == null || p.x > max.x) {
 950             max.x = p.x;
 951           }
 952           if (min.y == null || p.y < min.y) {
 953             min.y = p.y;
 954           }
 955           if (max.y == null || p.y > max.y) {
 956             max.y = p.y;
 957           }
 958         }
 959       }
 960       lineStr.push(' ">');
 961
 962       if (!aFill) {
 963         appendStroke(this, lineStr);
 964       } else {
 965         appendFill(this, lineStr, min, max);
 966       }
 967
 968       lineStr.push('</g_vml_:shape>');
 969
 970       this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
 971     }
 972   };
 973
 974   function appendStroke(ctx, lineStr) {
 975     var a = processStyle(ctx.strokeStyle);
 976     var color = a.color;
 977     var opacity = a.alpha * ctx.globalAlpha;
 978     var lineWidth = ctx.lineScale_ * ctx.lineWidth;
 979
 980     // VML cannot correctly render a line if the width is less than 1px.
 981     // In that case, we dilute the color to make the line look thinner.
 982     if (lineWidth < 1) {
 983       opacity *= lineWidth;
 984     }
 985
 986     lineStr.push(
 987       '<g_vml_:stroke',
 988       ' opacity="', opacity, '"',
 989       ' joinstyle="', ctx.lineJoin, '"',
 990       ' miterlimit="', ctx.miterLimit, '"',
 991       ' endcap="', processLineCap(ctx.lineCap), '"',
 992       ' weight="', lineWidth, 'px"',
 993       ' color="', color, '" />'
 994     );
 995   }
 996
 997   function appendFill(ctx, lineStr, min, max) {
 998     var fillStyle = ctx.fillStyle;
 999     var arcScaleX = ctx.arcScaleX_;
1000     var arcScaleY = ctx.arcScaleY_;
1001     var width = max.x - min.x;
1002     var height = max.y - min.y;
1003     if (fillStyle instanceof CanvasGradient_) {
1004       // TODO: Gradients transformed with the transformation matrix.
1005       var angle = 0;
1006       var focus = {x: 0, y: 0};
1007
1008       // additional offset
1009       var shift = 0;
1010       // scale factor for offset
1011       var expansion = 1;
1012
1013       if (fillStyle.type_ == 'gradient') {
1014         var x0 = fillStyle.x0_ / arcScaleX;
1015         var y0 = fillStyle.y0_ / arcScaleY;
1016         var x1 = fillStyle.x1_ / arcScaleX;
1017         var y1 = fillStyle.y1_ / arcScaleY;
1018         var p0 = ctx.getCoords_(x0, y0);
1019         var p1 = ctx.getCoords_(x1, y1);
1020         var dx = p1.x - p0.x;
1021         var dy = p1.y - p0.y;
1022         angle = Math.atan2(dx, dy) * 180 / Math.PI;
1023
1024         // The angle should be a non-negative number.
1025         if (angle < 0) {
1026           angle += 360;
1027         }
1028
1029         // Very small angles produce an unexpected result because they are
1030         // converted to a scientific notation string.
1031         if (angle < 1e-6) {
1032           angle = 0;
1033         }
1034       } else {
1035         var p0 = ctx.getCoords_(fillStyle.x0_, fillStyle.y0_);
1036         focus = {
1037           x: (p0.x - min.x) / width,
1038           y: (p0.y - min.y) / height
1039         };
1040
1041         width  /= arcScaleX * Z;
1042         height /= arcScaleY * Z;
1043         var dimension = m.max(width, height);
1044         shift = 2 * fillStyle.r0_ / dimension;
1045         expansion = 2 * fillStyle.r1_ / dimension - shift;
1046       }
1047
1048       // We need to sort the color stops in ascending order by offset,
1049       // otherwise IE won't interpret it correctly.
1050       var stops = fillStyle.colors_;
1051       stops.sort(function(cs1, cs2) {
1052         return cs1.offset - cs2.offset;
1053       });
1054
1055       var length = stops.length;
1056       var color1 = stops[0].color;
1057       var color2 = stops[length - 1].color;
1058       var opacity1 = stops[0].alpha * ctx.globalAlpha;
1059       var opacity2 = stops[length - 1].alpha * ctx.globalAlpha;
1060
1061       var colors = [];
1062       for (var i = 0; i < length; i++) {
1063         var stop = stops[i];
1064         colors.push(stop.offset * expansion + shift + ' ' + stop.color);
1065       }
1066
1067       // When colors attribute is used, the meanings of opacity and o:opacity2
1068       // are reversed.
1069       lineStr.push('<g_vml_:fill type="', fillStyle.type_, '"',
1070                    ' method="none" focus="100%"',
1071                    ' color="', color1, '"',
1072                    ' color2="', color2, '"',
1073                    ' colors="', colors.join(','), '"',
1074                    ' opacity="', opacity2, '"',
1075                    ' g_o_:opacity2="', opacity1, '"',
1076                    ' angle="', angle, '"',
1077                    ' focusposition="', focus.x, ',', focus.y, '" />');
1078     } else if (fillStyle instanceof CanvasPattern_) {
1079       if (width && height) {
1080         var deltaLeft = -min.x;
1081         var deltaTop = -min.y;
1082         lineStr.push('<g_vml_:fill',
1083                      ' position="',
1084                      deltaLeft / width * arcScaleX * arcScaleX, ',',
1085                      deltaTop / height * arcScaleY * arcScaleY, '"',
1086                      ' type="tile"',
1087                      // TODO: Figure out the correct size to fit the scale.
1088                      //' size="', w, 'px ', h, 'px"',
1089                      ' src="', fillStyle.src_, '" />');
1090        }
1091     } else {
1092       var a = processStyle(ctx.fillStyle);
1093       var color = a.color;
1094       var opacity = a.alpha * ctx.globalAlpha;
1095       lineStr.push('<g_vml_:fill color="', color, '" opacity="', opacity,
1096                    '" />');
1097     }
1098   }
1099
1100   contextPrototype.fill = function() {
1101     this.stroke(true);
1102   };
1103
1104   contextPrototype.closePath = function() {
1105     this.currentPath_.push({type: 'close'});
1106   };
1107
1108   /**
1109    * @private
1110    */
1111   contextPrototype.getCoords_ = function(aX, aY) {
1112     var m = this.m_;
1113     return {
1114       x: Z * (aX * m[0][0] + aY * m[1][0] + m[2][0]) - Z2,
1115       y: Z * (aX * m[0][1] + aY * m[1][1] + m[2][1]) - Z2
1116     };
1117   };
1118
1119   contextPrototype.save = function() {
1120     var o = {};
1121     copyState(this, o);
1122     this.aStack_.push(o);
1123     this.mStack_.push(this.m_);
1124     this.m_ = matrixMultiply(createMatrixIdentity(), this.m_);
1125   };
1126
1127   contextPrototype.restore = function() {
1128     if (this.aStack_.length) {
1129       copyState(this.aStack_.pop(), this);
1130       this.m_ = this.mStack_.pop();
1131     }
1132   };
1133
1134   function matrixIsFinite(m) {
1135     return isFinite(m[0][0]) && isFinite(m[0][1]) &&
1136         isFinite(m[1][0]) && isFinite(m[1][1]) &&
1137         isFinite(m[2][0]) && isFinite(m[2][1]);
1138   }
1139
1140   function setM(ctx, m, updateLineScale) {
1141     if (!matrixIsFinite(m)) {
1142       return;
1143     }
1144     ctx.m_ = m;
1145
1146     if (updateLineScale) {
1147       // Get the line scale.
1148       // Determinant of this.m_ means how much the area is enlarged by the
1149       // transformation. So its square root can be used as a scale factor
1150       // for width.
1151       var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
1152       ctx.lineScale_ = sqrt(abs(det));
1153     }
1154   }
1155
1156   contextPrototype.translate = function(aX, aY) {
1157     var m1 = [
1158       [1,  0,  0],
1159       [0,  1,  0],
1160       [aX, aY, 1]
1161     ];
1162
1163     setM(this, matrixMultiply(m1, this.m_), false);
1164   };
1165
1166   contextPrototype.rotate = function(aRot) {
1167     var c = mc(aRot);
1168     var s = ms(aRot);
1169
1170     var m1 = [
1171       [c,  s, 0],
1172       [-s, c, 0],
1173       [0,  0, 1]
1174     ];
1175
1176     setM(this, matrixMultiply(m1, this.m_), false);
1177   };
1178
1179   contextPrototype.scale = function(aX, aY) {
1180     this.arcScaleX_ *= aX;
1181     this.arcScaleY_ *= aY;
1182     var m1 = [
1183       [aX, 0,  0],
1184       [0,  aY, 0],
1185       [0,  0,  1]
1186     ];
1187
1188     setM(this, matrixMultiply(m1, this.m_), true);
1189   };
1190
1191   contextPrototype.transform = function(m11, m12, m21, m22, dx, dy) {
1192     var m1 = [
1193       [m11, m12, 0],
1194       [m21, m22, 0],
1195       [dx,  dy,  1]
1196     ];
1197
1198     setM(this, matrixMultiply(m1, this.m_), true);
1199   };
1200
1201   contextPrototype.setTransform = function(m11, m12, m21, m22, dx, dy) {
1202     var m = [
1203       [m11, m12, 0],
1204       [m21, m22, 0],
1205       [dx,  dy,  1]
1206     ];
1207
1208     setM(this, m, true);
1209   };
1210
1211   /**
1212    * The text drawing function.
1213    * The maxWidth argument isn't taken in account, since no browser supports
1214    * it yet.
1215    */
1216   contextPrototype.drawText_ = function(text, x, y, maxWidth, stroke) {
1217     var m = this.m_,
1218         delta = 1000,
1219         left = 0,
1220         right = delta,
1221         offset = {x: 0, y: 0},
1222         lineStr = [];
1223
1224     var fontStyle = getComputedStyle(processFontStyle(this.font),
1225                                      this.element_);
1226
1227     var fontStyleString = buildStyle(fontStyle);
1228
1229     var elementStyle = this.element_.currentStyle;
1230     var textAlign = this.textAlign.toLowerCase();
1231     switch (textAlign) {
1232       case 'left':
1233       case 'center':
1234       case 'right':
1235         break;
1236       case 'end':
1237         textAlign = elementStyle.direction == 'ltr' ? 'right' : 'left';
1238         break;
1239       case 'start':
1240         textAlign = elementStyle.direction == 'rtl' ? 'right' : 'left';
1241         break;
1242       default:
1243         textAlign = 'left';
1244     }
1245
1246     // 1.75 is an arbitrary number, as there is no info about the text baseline
1247     switch (this.textBaseline) {
1248       case 'hanging':
1249       case 'top':
1250         offset.y = fontStyle.size / 1.75;
1251         break;
1252       case 'middle':
1253         break;
1254       default:
1255       case null:
1256       case 'alphabetic':
1257       case 'ideographic':
1258       case 'bottom':
1259         offset.y = -fontStyle.size / 2.25;
1260         break;
1261     }
1262
1263     switch(textAlign) {
1264       case 'right':
1265         left = delta;
1266         right = 0.05;
1267         break;
1268       case 'center':
1269         left = right = delta / 2;
1270         break;
1271     }
1272
1273     var d = this.getCoords_(x + offset.x, y + offset.y);
1274
1275     lineStr.push('<g_vml_:line from="', -left ,' 0" to="', right ,' 0.05" ',
1276                  ' coordsize="100 100" coordorigin="0 0"',
1277                  ' filled="', !stroke, '" stroked="', !!stroke,
1278                  '" style="position:absolute;width:1px;height:1px;">');
1279
1280     if (stroke) {
1281       appendStroke(this, lineStr);
1282     } else {
1283       // TODO: Fix the min and max params.
1284       appendFill(this, lineStr, {x: -left, y: 0},
1285                  {x: right, y: fontStyle.size});
1286     }
1287
1288     var skewM = m[0][0].toFixed(3) + ',' + m[1][0].toFixed(3) + ',' +
1289                 m[0][1].toFixed(3) + ',' + m[1][1].toFixed(3) + ',0,0';
1290
1291     var skewOffset = mr(d.x / Z) + ',' + mr(d.y / Z);
1292
1293     lineStr.push('<g_vml_:skew on="t" matrix="', skewM ,'" ',
1294                  ' offset="', skewOffset, '" origin="', left ,' 0" />',
1295                  '<g_vml_:path textpathok="true" />',
1296                  '<g_vml_:textpath on="true" string="',
1297                  encodeHtmlAttribute(text),
1298                  '" style="v-text-align:', textAlign,
1299                  ';font:', encodeHtmlAttribute(fontStyleString),
1300                  '" /></g_vml_:line>');
1301
1302     this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
1303   };
1304
1305   contextPrototype.fillText = function(text, x, y, maxWidth) {
1306     this.drawText_(text, x, y, maxWidth, false);
1307   };
1308
1309   contextPrototype.strokeText = function(text, x, y, maxWidth) {
1310     this.drawText_(text, x, y, maxWidth, true);
1311   };
1312
1313   contextPrototype.measureText = function(text) {
1314     if (!this.textMeasureEl_) {
1315       var s = '<span style="position:absolute;' +
1316           'top:-20000px;left:0;padding:0;margin:0;border:none;' +
1317           'white-space:pre;"></span>';
1318       this.element_.insertAdjacentHTML('beforeEnd', s);
1319       this.textMeasureEl_ = this.element_.lastChild;
1320     }
1321     var doc = this.element_.ownerDocument;
1322     this.textMeasureEl_.innerHTML = '';
1323     this.textMeasureEl_.style.font = this.font;
1324     // Don't use innerHTML or innerText because they allow markup/whitespace.
1325     this.textMeasureEl_.appendChild(doc.createTextNode(text));
1326     return {width: this.textMeasureEl_.offsetWidth};
1327   };
1328
1329   /******** STUBS ********/
1330   contextPrototype.clip = function() {
1331     // TODO: Implement
1332   };
1333
1334   contextPrototype.arcTo = function() {
1335     // TODO: Implement
1336   };
1337
1338   contextPrototype.createPattern = function(image, repetition) {
1339     return new CanvasPattern_(image, repetition);
1340   };
1341
1342   // Gradient / Pattern Stubs
1343   function CanvasGradient_(aType) {
1344     this.type_ = aType;
1345     this.x0_ = 0;
1346     this.y0_ = 0;
1347     this.r0_ = 0;
1348     this.x1_ = 0;
1349     this.y1_ = 0;
1350     this.r1_ = 0;
1351     this.colors_ = [];
1352   }
1353
1354   CanvasGradient_.prototype.addColorStop = function(aOffset, aColor) {
1355     aColor = processStyle(aColor);
1356     this.colors_.push({offset: aOffset,
1357                        color: aColor.color,
1358                        alpha: aColor.alpha});
1359   };
1360
1361   function CanvasPattern_(image, repetition) {
1362     assertImageIsValid(image);
1363     switch (repetition) {
1364       case 'repeat':
1365       case null:
1366       case '':
1367         this.repetition_ = 'repeat';
1368         break
1369       case 'repeat-x':
1370       case 'repeat-y':
1371       case 'no-repeat':
1372         this.repetition_ = repetition;
1373         break;
1374       default:
1375         throwException('SYNTAX_ERR');
1376     }
1377
1378     this.src_ = image.src;
1379     this.width_ = image.width;
1380     this.height_ = image.height;
1381   }
1382
1383   function throwException(s) {
1384     throw new DOMException_(s);
1385   }
1386
1387   function assertImageIsValid(img) {
1388     if (!img || img.nodeType != 1 || img.tagName != 'IMG') {
1389       throwException('TYPE_MISMATCH_ERR');
1390     }
1391     if (img.readyState != 'complete') {
1392       throwException('INVALID_STATE_ERR');
1393     }
1394   }
1395
1396   function DOMException_(s) {
1397     this.code = this[s];
1398     this.message = s +': DOM Exception ' + this.code;
1399   }
1400   var p = DOMException_.prototype = new Error;
1401   p.INDEX_SIZE_ERR = 1;
1402   p.DOMSTRING_SIZE_ERR = 2;
1403   p.HIERARCHY_REQUEST_ERR = 3;
1404   p.WRONG_DOCUMENT_ERR = 4;
1405   p.INVALID_CHARACTER_ERR = 5;
1406   p.NO_DATA_ALLOWED_ERR = 6;
1407   p.NO_MODIFICATION_ALLOWED_ERR = 7;
1408   p.NOT_FOUND_ERR = 8;
1409   p.NOT_SUPPORTED_ERR = 9;
1410   p.INUSE_ATTRIBUTE_ERR = 10;
1411   p.INVALID_STATE_ERR = 11;
1412   p.SYNTAX_ERR = 12;
1413   p.INVALID_MODIFICATION_ERR = 13;
1414   p.NAMESPACE_ERR = 14;
1415   p.INVALID_ACCESS_ERR = 15;
1416   p.VALIDATION_ERR = 16;
1417   p.TYPE_MISMATCH_ERR = 17;
1418
1419   // set up externs
1420   G_vmlCanvasManager = G_vmlCanvasManager_;
1421   CanvasRenderingContext2D = CanvasRenderingContext2D_;
1422   CanvasGradient = CanvasGradient_;
1423   CanvasPattern = CanvasPattern_;
1424   DOMException = DOMException_;
1425 })();
1426
1427 } // if