excanvas.js

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// Copyright 2006 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// TODO: Patterns
// TODO: Radial gradient
// TODO: Clipping paths
// TODO: Coordsize (still need to support stretching)
// TODO: Painting mode
// TODO: Optimize
// TODO: canvas width/height sets content size in moz, border size in ie

// only add this code if we do not already have a canvas implementation
if (!window.CanvasRenderingContext2D) {

(function () {

  // alias some functions to make (compiled) code shorter
  var m = Math;
  var mr = m.round;
  var ms = m.sin;
  var mc = m.cos;

  var G_vmlCanvasManager_ = {
    init: function (opt_doc) {
      var doc = opt_doc || document;
      if (/MSIE/.test(navigator.userAgent) && !window.opera) {
        var self = this;
        doc.attachEvent("onreadystatechange", function () {
          self.init_(doc);
        });
      }
    },

    init_: function (doc, e) {
      if (doc.readyState == "complete") {
        // create xmlns
        if (!doc.namespaces["g_vml_"]) {
          doc.namespaces.add("g_vml_", "urn:schemas-microsoft-com:vml");
        }

        // setup default css
        var ss = doc.createStyleSheet();
        ss.cssText = "canvas{display:inline-block;overflow:hidden;" +
            "text-align:left;}" +
            "g_vml_\\:*{behavior:url(#default#VML)}";

        // find all canvas elements
        var els = doc.getElementsByTagName("canvas");
        for (var i = 0; i < els.length; i++) {
          if (!els[i].getContext) {
            this.initElement(els[i]);
          }
        }
      }
    },

    fixElement_: function (el) {
      // in IE before version 5.5 we would need to add HTML: to the tag name
      // but we do not care about IE before version 6
      var outerHTML = el.outerHTML;
      var newEl = document.createElement(outerHTML);
      // if the tag is still open IE has created the children as siblings and
      // it has also created a tag with the name "/FOO"
      if (outerHTML.slice(-2) != "/>") {
        var tagName = "/" + el.tagName;
        var ns;
        // remove content
        while ((ns = el.nextSibling) && ns.tagName != tagName) {
          ns.removeNode();
        }
        // remove the incorrect closing tag
        if (ns) {
          ns.removeNode();
        }
      }
      el.parentNode.replaceChild(newEl, el);
      return newEl;
    },

    /**
     * Public initializes a canvas element so that it can be used as canvas
     * element from now on. This is called automatically before the page is
     * loaded but if you are creating elements using createElement you need to
     * make sure this is called on the element.
     * @param {HTMLElement} el The canvas element to initialize.
     * @return {HTMLElement} the element that was created.
     */
    initElement: function (el) {
      el = this.fixElement_(el);
      el.getContext = function () {
        if (this.context_) {
          return this.context_;
        }
        return this.context_ = new CanvasRenderingContext2D_(this);
      };

      // do not use inline function because that will leak memory
      // el.attachEvent('onpropertychange', onPropertyChange)
      el.attachEvent('onresize', onResize);

      var attrs = el.attributes;
      if (attrs.width && attrs.width.specified) {
        // TODO: use runtimeStyle and coordsize
        // el.getContext().setWidth_(attrs.width.nodeValue);
        el.style.width = attrs.width.nodeValue + "px";
      }
      if (attrs.height && attrs.height.specified) {
        // TODO: use runtimeStyle and coordsize
        // el.getContext().setHeight_(attrs.height.nodeValue);
        el.style.height = attrs.height.nodeValue + "px";
      }
      //el.getContext().setCoordsize_()
      return el;
    }
  };

  function onPropertyChange(e) {
    // we need to watch changes to width and height
    switch (e.propertyName) {
      case 'width':
      case 'height':
        // TODO: coordsize and size
        break;
    }
  }

  function onResize(e) {
    var el = e.srcElement;
    if (el.firstChild) {
      el.firstChild.style.width =  el.clientWidth + 'px';
      el.firstChild.style.height = el.clientHeight + 'px';
    }
  }

  G_vmlCanvasManager_.init();

  // precompute "00" to "FF"
  var dec2hex = [];
  for (var i = 0; i < 16; i++) {
    for (var j = 0; j < 16; j++) {
      dec2hex[i * 16 + j] = i.toString(16) + j.toString(16);
    }
  }

  function createMatrixIdentity() {
    return [
      [1, 0, 0],
      [0, 1, 0],
      [0, 0, 1]
    ];
  }

  function matrixMultiply(m1, m2) {
    var result = createMatrixIdentity();

    for (var x = 0; x < 3; x++) {
      for (var y = 0; y < 3; y++) {
        var sum = 0;

        for (var z = 0; z < 3; z++) {
          sum += m1[x][z] * m2[z][y];
        }

        result[x][y] = sum;
      }
    }
    return result;
  }

  function copyState(o1, o2) {
    o2.fillStyle     = o1.fillStyle;
    o2.lineCap       = o1.lineCap;
    o2.lineJoin      = o1.lineJoin;
    o2.lineWidth     = o1.lineWidth;
    o2.miterLimit    = o1.miterLimit;
    o2.shadowBlur    = o1.shadowBlur;
    o2.shadowColor   = o1.shadowColor;
    o2.shadowOffsetX = o1.shadowOffsetX;
    o2.shadowOffsetY = o1.shadowOffsetY;
    o2.strokeStyle   = o1.strokeStyle;
  }

  function processStyle(styleString) {
    var str, alpha = 1;

    styleString = String(styleString);
    if (styleString.substring(0, 3) == "rgb") {
      var start = styleString.indexOf("(", 3);
      var end = styleString.indexOf(")", start + 1);
      var guts = styleString.substring(start + 1, end).split(",");

      str = "#";
      for (var i = 0; i < 3; i++) {
        str += dec2hex[parseInt(guts[i])];
      }

      if ((guts.length == 4) && (styleString.substr(3, 1) == "a")) {
        alpha = guts[3];
      }
    } else {
      str = styleString;
    }

    return [str, alpha];
  }

  function processLineCap(lineCap) {
    switch (lineCap) {
      case "butt":
        return "flat";
      case "round":
        return "round";
      case "square":
      default:
        return "square";
    }
  }

  /**
   * This class implements CanvasRenderingContext2D interface as described by
   * the WHATWG.
   * @param {HTMLElement} surfaceElement The element that the 2D context should
   * be associated with
   */
   function CanvasRenderingContext2D_(surfaceElement) {
    this.m_ = createMatrixIdentity();

    this.mStack_ = [];
    this.aStack_ = [];
    this.currentPath_ = [];

    // Canvas context properties
    this.strokeStyle = "#000";
    this.fillStyle = "#ccc";

    this.lineWidth = 1;
    this.lineJoin = "miter";
    this.lineCap = "butt";
    this.miterLimit = 10;
    this.globalAlpha = 1;

    var el = document.createElement('div');
    el.style.width =  surfaceElement.clientWidth + 'px';
    el.style.height = surfaceElement.clientHeight + 'px';
    el.style.overflow = 'hidden';
    el.style.position = 'absolute';
    surfaceElement.appendChild(el);

    this.element_ = el;
    this.arcScaleX_ = 1;
    this.arcScaleY_ = 1;
  };

  var contextPrototype = CanvasRenderingContext2D_.prototype;
  contextPrototype.clearRect = function() {
    this.element_.innerHTML = "";
    this.currentPath_ = [];
  };

  contextPrototype.beginPath = function() {
    // TODO: Branch current matrix so that save/restore has no effect
    //       as per safari docs.

    this.currentPath_ = [];
  };

  contextPrototype.moveTo = function(aX, aY) {
    this.currentPath_.push({type: "moveTo", x: aX, y: aY});
  };

  contextPrototype.lineTo = function(aX, aY) {
    this.currentPath_.push({type: "lineTo", x: aX, y: aY});
  };

  contextPrototype.bezierCurveTo = function(aCP1x, aCP1y,
                                            aCP2x, aCP2y,
                                            aX, aY) {
    this.currentPath_.push({type: "bezierCurveTo",
                           cp1x: aCP1x,
                           cp1y: aCP1y,
                           cp2x: aCP2x,
                           cp2y: aCP2y,
                           x: aX,
                           y: aY});
  };

  contextPrototype.quadraticCurveTo = function(aCPx, aCPy, aX, aY) {
    // VML's qb produces different output to Firefox's
    // FF's behaviour seems to have changed in 1.5.0.1, check this
    this.bezierCurveTo(aCPx, aCPy, aCPx, aCPy, aX, aY);
  };

  contextPrototype.arc = function(aX, aY, aRadius,
                                  aStartAngle, aEndAngle, aClockwise) {
    aRadius *= 10;
    var arcType = aClockwise ? "at" : "wa";

    var xStart = aX + (mc(aStartAngle) * aRadius) - 5;
    var yStart = aY + (ms(aStartAngle) * aRadius) - 5;

    var xEnd = aX + (mc(aEndAngle) * aRadius) - 5;
    var yEnd = aY + (ms(aEndAngle) * aRadius) - 5;

    this.currentPath_.push({type: arcType,
                           x: aX,
                           y: aY,
                           radius: aRadius,
                           xStart: xStart,
                           yStart: yStart,
                           xEnd: xEnd,
                           yEnd: yEnd});

  };

  contextPrototype.rect = function(aX, aY, aWidth, aHeight) {
    this.moveTo(aX, aY);
    this.lineTo(aX + aWidth, aY);
    this.lineTo(aX + aWidth, aY + aHeight);
    this.lineTo(aX, aY + aHeight);
    this.closePath();
  };

  contextPrototype.strokeRect = function(aX, aY, aWidth, aHeight) {
    // Will destroy any existing path (same as FF behaviour)
    this.beginPath();
    this.moveTo(aX, aY);
    this.lineTo(aX + aWidth, aY);
    this.lineTo(aX + aWidth, aY + aHeight);
    this.lineTo(aX, aY + aHeight);
    this.closePath();
    this.stroke();
  };

  contextPrototype.fillRect = function(aX, aY, aWidth, aHeight) {
    // Will destroy any existing path (same as FF behaviour)
    this.beginPath();
    this.moveTo(aX, aY);
    this.lineTo(aX + aWidth, aY);
    this.lineTo(aX + aWidth, aY + aHeight);
    this.lineTo(aX, aY + aHeight);
    this.closePath();
    this.fill();
  };

  contextPrototype.createLinearGradient = function(aX0, aY0, aX1, aY1) {
    var gradient = new CanvasGradient_("gradient");
    return gradient;
  };

  contextPrototype.createRadialGradient = function(aX0, aY0,
                                                   aR0, aX1,