Experiment about making graphs of route trips
[busui.git] / js / flotr / lib / excanvas.js
blob:a/js/flotr/lib/excanvas.js -> blob:b/js/flotr/lib/excanvas.js
--- a/js/flotr/lib/excanvas.js
+++ b/js/flotr/lib/excanvas.js
@@ -1,1 +1,885 @@
-
+// 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.
+
+
+// Known Issues:
+//
+// * Patterns are not implemented.
+// * Radial gradient are not implemented. The VML version of these look very
+//   different from the canvas one.
+// * Clipping paths are not implemented.
+// * Coordsize. The width and height attribute have higher priority than the
+//   width and height style values which isn't correct.
+// * Painting mode isn't implemented.
+// * Canvas width/height should is using content-box by default. IE in
+//   Quirks mode will draw the canvas using border-box. Either change your
+//   doctype to HTML5
+//   (http://www.whatwg.org/specs/web-apps/current-work/#the-doctype)
+//   or use Box Sizing Behavior from WebFX
+//   (http://webfx.eae.net/dhtml/boxsizing/boxsizing.html)
+// * Non uniform scaling does not correctly scale strokes.
+// * Optimize. There is always room for speed improvements.
+
+// Only add this code if we do not already have a canvas implementation
+if (!document.createElement('canvas').getContext) {
+
+(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 abs = m.abs;
+  var sqrt = m.sqrt;
+
+  // this is used for sub pixel precision
+  var Z = 10;
+  var Z2 = Z / 2;
+
+  /**
+   * This funtion is assigned to the <canvas> elements as element.getContext().
+   * @this {HTMLElement}
+   * @return {CanvasRenderingContext2D_}
+   */
+  function getContext() {
+    return this.context_ ||
+        (this.context_ = new CanvasRenderingContext2D_(this));
+  }
+
+  var slice = Array.prototype.slice;
+
+  /**
+   * Binds a function to an object. The returned function will always use the
+   * passed in {@code obj} as {@code this}.
+   *
+   * Example:
+   *
+   *   g = bind(f, obj, a, b)
+   *   g(c, d) // will do f.call(obj, a, b, c, d)
+   *
+   * @param {Function} f The function to bind the object to
+   * @param {Object} obj The object that should act as this when the function
+   *     is called
+   * @param {*} var_args Rest arguments that will be used as the initial
+   *     arguments when the function is called
+   * @return {Function} A new function that has bound this
+   */
+  function bind(f, obj, var_args) {
+    var a = slice.call(arguments, 2);
+    return function() {
+      return f.apply(obj, a.concat(slice.call(arguments)));
+    };
+  }
+
+  var G_vmlCanvasManager_ = {
+    init: function(opt_doc) {
+      if (/MSIE/.test(navigator.userAgent) && !window.opera) {
+        var doc = opt_doc || document;
+        // Create a dummy element so that IE will allow canvas elements to be
+        // recognized.
+        doc.createElement('canvas');
+        doc.attachEvent('onreadystatechange', bind(this.init_, this, doc));
+      }
+    },
+
+    init_: function(doc) {
+      // create xmlns
+      if (!doc.namespaces['g_vml_']) {
+        doc.namespaces.add('g_vml_', 'urn:schemas-microsoft-com:vml',
+                           '#default#VML');
+
+      }
+      if (!doc.namespaces['g_o_']) {
+        doc.namespaces.add('g_o_', 'urn:schemas-microsoft-com:office:office',
+                           '#default#VML');
+      }
+
+      // Setup default CSS.  Only add one style sheet per document
+      if (!doc.styleSheets['ex_canvas_']) {
+        var ss = doc.createStyleSheet();
+        ss.owningElement.id = 'ex_canvas_';
+        ss.cssText = 'canvas{display:inline-block;overflow:hidden;' +
+            // default size is 300x150 in Gecko and Opera
+            'text-align:left;width:300px;height:150px}' +
+            'g_vml_\\:*{behavior:url(#default#VML)}' +
+            'g_o_\\:*{behavior:url(#default#VML)}';
+
+      }
+
+      // find all canvas elements
+      var els = doc.getElementsByTagName('canvas');
+      for (var i = 0; i < els.length; i++) {
+        this.initElement(els[i]);
+      }
+    },
+
+    /**
+     * 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) {
+      if (!el.getContext) {
+
+        el.getContext = getContext;
+
+        // Remove fallback content. There is no way to hide text nodes so we
+        // just remove all childNodes. We could hide all elements and remove
+        // text nodes but who really cares about the fallback content.
+        el.innerHTML = '';
+
+        // 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';
+        } else {
+          el.width = el.clientWidth;
+        }
+        if (attrs.height && attrs.height.specified) {
+          // TODO: use runtimeStyle and coordsize
+          // el.getContext().setHeight_(attrs.height.nodeValue);
+          el.style.height = attrs.height.nodeValue + 'px';
+        } else {
+          el.height = el.clientHeight;
+        }
+        //el.getContext().setCoordsize_()
+      }
+      return el;
+    }
+  };
+
+  function onPropertyChange(e) {
+    var el = e.srcElement;
+
+    switch (e.propertyName) {
+      case 'width':
+        el.style.width = el.attributes.width.nodeValue + 'px';
+        el.getContext().clearRect();
+        break;
+      case 'height':
+        el.style.height = el.attributes.height.nodeValue + 'px';
+        el.getContext().clearRect();
+        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;
+    o2.globalAlpha   = o1.globalAlpha;
+    o2.arcScaleX_    = o1.arcScaleX_;
+    o2.arcScaleY_    = o1.arcScaleY_;
+    o2.lineScale_    = o1.lineScale_;
+  }
+
+  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[Number(guts[i])];
+      }
+
+      if (guts.length == 4 && styleString.substr(3, 1) == 'a') {
+        alpha = guts[3];
+      }
+    } else {
+      str = styleString;
+    }
+
+    return {color: str, alpha: 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 = '#000';
+
+    this.lineWidth = 1;
+    this.lineJoin = 'miter';
+    this.lineCap = 'butt';
+    this.miterLimit = Z * 1;
+    this.globalAlpha = 1;
+    this.canvas = surfaceElement;
+
+    var el = surfaceElement.ownerDocument.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;
+    this.lineScale_ = 1;
+  }
+
+  var contextPrototype = CanvasRenderingContext2D_.prototype;
+  contextPrototype.clearRect = function() {
+    this.element_.innerHTML = '';
+  };
+
+  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) {
+    var p = this.getCoords_(aX, aY);
+    this.currentPath_.push({type: 'moveTo', x: p.x, y: p.y});
+    this.currentX_ = p.x;
+    this.currentY_ = p.y;
+  };
+
+  contextPrototype.lineTo = function(aX, aY) {
+    var p = this.getCoords_(aX, aY);
+    this.currentPath_.push({type: 'lineTo', x: p.x, y: p.y});
+
+    this.currentX_ = p.x;
+    this.currentY_ = p.y;
+  };
+
+  contextPrototype.bezierCurveTo = function(aCP1x, aCP1y,
+                                            aCP2x, aCP2y,
+                                            aX, aY) {
+    var p = this.getCoords_(aX, aY);
+    var cp1 = this.getCoords_(aCP1x, aCP1y);
+    var cp2 = this.getCoords_(aCP2x, aCP2y);
+    bezierCurveTo(this, cp1, cp2, p);
+  };
+
+  // Helper function that takes the already fixed cordinates.
+  function bezierCurveTo(self, cp1, cp2, p) {
+    self.currentPath_.push({
+      type: 'bezierCurveTo',
+      cp1x: cp1.x,
+      cp1y: cp1.y,
+      cp2x: cp2.x,
+      cp2y: cp2.y,
+      x: p.x,
+      y: p.y
+    });
+    self.currentX_ = p.x;
+    self.currentY_ = p.y;
+  }
+
+  contextPrototype.quadraticCurveTo = function(aCPx, aCPy, aX, aY) {
+    // the following is lifted almost directly from
+    // http://developer.mozilla.org/en/docs/Canvas_tutorial:Drawing_shapes
+
+    var cp = this.getCoords_(aCPx, aCPy);
+    var p = this.getCoords_(aX, aY);
+
+    var cp1 = {
+      x: this.currentX_ + 2.0 / 3.0 * (cp.x - this.currentX_),
+      y: this.currentY_ + 2.0 / 3.0 * (cp.y - this.currentY_)
+    };
+    var cp2 = {
+      x: cp1.x + (p.x - this.currentX_) / 3.0,
+      y: cp1.y + (p.y - this.currentY_) / 3.0
+    };
+
+    bezierCurveTo(this, cp1, cp2, p);
+  };
+
+  contextPrototype.arc = function(aX, aY, aRadius,
+                                  aStartAngle, aEndAngle, aClockwise) {
+    aRadius *= Z;
+    var arcType = aClockwise ? 'at' : 'wa';
+
+    var xStart = aX + mc(aStartAngle) * aRadius - Z2;
+    var yStart = aY + ms(aStartAngle) * aRadius - Z2;
+
+    var xEnd = aX + mc(aEndAngle) * aRadius - Z2;
+    var yEnd = aY + ms(aEndAngle) * aRadius - Z2;
+
+    // IE won't render arches drawn counter clockwise if xStart == xEnd.
+    if (xStart == xEnd && !aClockwise) {
+      xStart += 0.125; // Offset xStart by 1/80 of a pixel. Use something
+                       // that can be represented in binary
+    }
+
+    var p = this.getCoords_(aX, aY);
+    var pStart = this.getCoords_(xStart, yStart);
+    var pEnd = this.getCoords_(xEnd, yEnd);
+
+    this.currentPath_.push({type: arcType,
+                           x: p.x,
+                           y: p.y,
+                           radius: aRadius,
+                           xStart: pStart.x,
+                           yStart: pStart.y,
+                           xEnd: pEnd.x,
+                           yEnd: pEnd.y});
+
+  };
+
+  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) {
+    var oldPath = this.currentPath_;
+    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();
+
+    this.currentPath_ = oldPath;
+  };
+
+  contextPrototype.fillRect = function(aX, aY, aWidth, aHeight) {
+    var oldPath = this.currentPath_;
+    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();
+
+    this.currentPath_ = oldPath;
+  };
+
+  contextPrototype.createLinearGradient = function(aX0, aY0, aX1, aY1) {
+    var gradient = new CanvasGradient_('gradient');
+    gradient.x0_ = aX0;
+    gradient.y0_ = aY0;
+    gradient.x1_ = aX1;
+    gradient.y1_ = aY1;
+    return gradient;
+  };
+
+  contextPrototype.createRadialGradient = function(aX0, aY0, aR0,
+                                                   aX1, aY1, aR1) {
+    var gradient = new CanvasGradient_('gradientradial');
+    gradient.x0_ = aX0;
+    gradient.y0_ = aY0;
+    gradient.r0_ = aR0;
+    gradient.x1_ = aX1;
+    gradient.y1_ = aY1;
+    gradient.r1_ = aR1;
+    return gradient;
+  };
+
+  contextPrototype.drawImage = function(image, var_args) {
+    var dx, dy, dw, dh, sx, sy, sw, sh;
+
+    // to find the original width we overide the width and height
+    var oldRuntimeWidth = image.runtimeStyle.width;
+    var oldRuntimeHeight = image.runtimeStyle.height;
+    image.runtimeStyle.width = 'auto';
+    image.runtimeStyle.height = 'auto';
+
+    // get the original size
+    var w = image.width;
+    var h = image.height;
+
+    // and remove overides
+    image.runtimeStyle.width = oldRuntimeWidth;
+    image.runtimeStyle.height = oldRuntimeHeight;
+
+    if (arguments.length == 3) {
+      dx = arguments[1];
+      dy = arguments[2];
+      sx = sy = 0;
+      sw = dw = w;
+      sh = dh = h;
+    } else if (arguments.length == 5) {
+      dx = arguments[1];
+      dy = arguments[2];
+      dw = arguments[3];
+      dh = arguments[4];
+      sx = sy = 0;
+      sw = w;
+      sh = h;
+    } else if (arguments.length == 9) {
+      sx = arguments[1];
+      sy = arguments[2];
+      sw = arguments[3];
+      sh = arguments[4];
+      dx = arguments[5];
+      dy = arguments[6];
+      dw = arguments[7];
+      dh = arguments[8];
+    } else {
+      throw Error('Invalid number of arguments');
+    }
+
+    var d = this.getCoords_(dx, dy);
+
+    var w2 = sw / 2;
+    var h2 = sh / 2;
+
+    var vmlStr = [];
+
+    var W = 10;
+    var H = 10;
+
+    // For some reason that I've now forgotten, using divs didn't work
+    vmlStr.push(' <g_vml_:group',
+                ' coordsize="', Z * W, ',', Z * H, '"',
+                ' coordorigin="0,0"' ,
+                ' style="width:', W, 'px;height:', H, 'px;position:absolute;');
+
+    // If filters are necessary (rotation exists), create them
+    // filters are bog-slow, so only create them if abbsolutely necessary
+    // The following check doesn't account for skews (which don't exist
+    // in the canvas spec (yet) anyway.
+
+    if (this.m_[0][0] != 1 || this.m_[0][1]) {
+      var filter = [];
+
+      // Note the 12/21 reversal
+      filter.push('M11=', this.m_[0][0], ',',
+                  'M12=', this.m_[1][0], ',',
+                  'M21=', this.m_[0][1], ',',
+                  'M22=', this.m_[1][1], ',',
+                  'Dx=', mr(d.x / Z), ',',
+                  'Dy=', mr(d.y / Z), '');
+
+      // Bounding box calculation (need to minimize displayed area so that
+      // filters don't waste time on unused pixels.
+      var max = d;
+      var c2 = this.getCoords_(dx + dw, dy);
+      var c3 = this.getCoords_(dx, dy + dh);
+      var c4 = this.getCoords_(dx + dw, dy + dh);
+
+      max.x = m.max(max.x, c2.x, c3.x, c4.x);
+      max.y = m.max(max.y, c2.y, c3.y, c4.y);
+
+      vmlStr.push('padding:0 ', mr(max.x / Z), 'px ', mr(max.y / Z),
+                  'px 0;filter:progid:DXImageTransform.Microsoft.Matrix(',
+                  filter.join(''), ", sizingmethod='clip');")
+    } else {
+      vmlStr.push('top:', mr(d.y / Z), 'px;left:', mr(d.x / Z), 'px;');
+    }
+
+    vmlStr.push(' ">' ,
+                '<g_vml_:image src="', image.src, '"',
+                ' style="width:', Z * dw, 'px;',
+                ' height:', Z * dh, 'px;"',
+                ' cropleft="', sx / w, '"',
+                ' croptop="', sy / h, '"',
+                ' cropright="', (w - sx - sw) / w, '"',
+                ' cropbottom="', (h - sy - sh) / h, '"',
+                ' />',
+                '</g_vml_:group>');
+
+    this.element_.insertAdjacentHTML('BeforeEnd',
+                                    vmlStr.join(''));
+  };
+
+  contextPrototype.stroke = function(aFill) {
+    var lineStr = [];
+    var lineOpen = false;
+    var a = processStyle(aFill ? this.fillStyle : this.strokeStyle);
+    var color = a.color;
+    var opacity = a.alpha * this.globalAlpha;
+
+    var W = 10;
+    var H = 10;
+
+    lineStr.push('<g_vml_:shape',
+                 ' filled="', !!aFill, '"',
+                 ' style="position:absolute;width:', W, 'px;height:', H, 'px;"',
+                 ' coordorigin="0 0" coordsize="', Z * W, ' ', Z * H, '"',
+                 ' stroked="', !aFill, '"',
+                 ' path="');
+
+    var newSeq = false;
+    var min = {x: null, y: null};
+    var max = {x: null, y: null};
+
+    for (var i = 0; i < this.currentPath_.length; i++) {
+      var p = this.currentPath_[i];
+      var c;
+
+      switch (p.type) {
+        case 'moveTo':
+          c = p;
+          lineStr.push(' m ', mr(p.x), ',', mr(p.y));
+          break;
+        case 'lineTo':
+          lineStr.push(' l ', mr(p.x), ',', mr(p.y));
+          break;
+        case 'close':
+          lineStr.push(' x ');
+          p = null;
+          break;
+        case 'bezierCurveTo':
+          lineStr.push(' c ',
+                       mr(p.cp1x), ',', mr(p.cp1y), ',',
+                       mr(p.cp2x), ',', mr(p.cp2y), ',',
+                       mr(p.x), ',', mr(p.y));
+          break;
+        case 'at':
+        case 'wa':
+          lineStr.push(' ', p.type, ' ',
+                       mr(p.x - this.arcScaleX_ * p.radius), ',',
+                       mr(p.y - this.arcScaleY_ * p.radius), ' ',
+                       mr(p.x + this.arcScaleX_ * p.radius), ',',
+                       mr(p.y + this.arcScaleY_ * p.radius), ' ',
+                       mr(p.xStart), ',', mr(p.yStart), ' ',
+                       mr(p.xEnd), ',', mr(p.yEnd));
+          break;
+      }
+
+
+      // TODO: Following is broken for curves due to
+      //       move to proper paths.
+
+      // Figure out dimensions so we can do gradient fills
+      // properly
+      if (p) {
+        if (min.x == null || p.x < min.x) {
+          min.x = p.x;
+        }
+        if (max.x == null || p.x > max.x) {
+          max.x = p.x;
+        }
+        if (min.y == null || p.y < min.y) {
+          min.y = p.y;
+        }
+        if (max.y == null || p.y > max.y) {
+          max.y = p.y;
+        }
+      }
+    }
+    lineStr.push(' ">');
+
+    if (!aFill) {
+      var lineWidth = this.lineScale_ * this.lineWidth;
+
+      // VML cannot correctly render a line if the width is less than 1px.
+      // In that case, we dilute the color to make the line look thinner.
+      if (lineWidth < 1) {
+        opacity *= lineWidth;
+      }
+
+      lineStr.push(
+        '<g_vml_:stroke',
+        ' opacity="', opacity, '"',
+        ' joinstyle="', this.lineJoin, '"',
+        ' miterlimit="', this.miterLimit, '"',
+        ' endcap="', processLineCap(this.lineCap), '"',
+        ' weight="', lineWidth, 'px"',
+        ' color="', color, '" />'
+      );
+    } else if (typeof this.fillStyle == 'object') {
+      var fillStyle = this.fillStyle;
+      var angle = 0;
+      var focus = {x: 0, y: 0};
+
+      // additional offset
+      var shift = 0;
+      // scale factor for offset
+      var expansion = 1;
+
+      if (fillStyle.type_ == 'gradient') {
+        var x0 = fillStyle.x0_ / this.arcScaleX_;
+        var y0 = fillStyle.y0_ / this.arcScaleY_;
+        var x1 = fillStyle.x1_ / this.arcScaleX_;
+        var y1 = fillStyle.y1_ / this.arcScaleY_;
+        var p0 = this.getCoords_(x0, y0);
+        var p1 = this.getCoords_(x1, y1);
+        var dx = p1.x - p0.x;
+        var dy = p1.y - p0.y;
+        angle = Math.atan2(dx, dy) * 180 / Math.PI;
+
+        // The angle should be a non-negative number.
+        if (angle < 0) {
+          angle += 360;
+        }
+
+        // Very small angles produce an unexpected result because they are
+        // converted to a scientific notation string.
+        if (angle < 1e-6) {
+          angle = 0;
+        }
+      } else {
+        var p0 = this.getCoords_(fillStyle.x0_, fillStyle.y0_);
+        var width  = max.x - min.x;
+        var height = max.y - min.y;
+        focus = {
+          x: (p0.x - min.x) / width,
+          y: (p0.y - min.y) / height
+        };
+
+        width  /= this.arcScaleX_ * Z;
+        height /= this.arcScaleY_ * Z;
+        var dimension = m.max(width, height);
+        shift = 2 * fillStyle.r0_ / dimension;
+        expansion = 2 * fillStyle.r1_ / dimension - shift;
+      }
+
+      // We need to sort the color stops in ascending order by offset,
+      // otherwise IE won't interpret it correctly.
+      var stops = fillStyle.colors_;
+      stops.sort(function(cs1, cs2) {
+        return cs1.offset - cs2.offset;
+      });
+
+      var length = stops.length;
+      var color1 = stops[0].color;
+      var color2 = stops[length - 1].color;
+      var opacity1 = stops[0].alpha * this.globalAlpha;
+      var opacity2 = stops[length - 1].alpha * this.globalAlpha;
+
+      var colors = [];
+      for (var i = 0; i < length; i++) {
+        var stop = stops[i];
+        colors.push(stop.offset * expansion + shift + ' ' + stop.color);
+      }
+
+      // When colors attribute is used, the meanings of opacity and o:opacity2
+      // are reversed.
+      lineStr.push('<g_vml_:fill type="', fillStyle.type_, '"',
+                   ' method="none" focus="100%"',
+                   ' color="', color1, '"',
+                   ' color2="', color2, '"',
+                   ' colors="', colors.join(','), '"',
+                   ' opacity="', opacity2, '"',
+                   ' g_o_:opacity2="', opacity1, '"',
+                   ' angle="', angle, '"',
+                   ' focusposition="', focus.x, ',', focus.y, '" />');
+    } else {
+      lineStr.push('<g_vml_:fill color="', color, '" opacity="', opacity,
+                   '" />');
+    }
+
+    lineStr.push('</g_vml_:shape>');
+
+    this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
+  };
+
+  contextPrototype.fill = function() {
+    this.stroke(true);
+  }
+
+  contextPrototype.closePath = function() {
+    this.currentPath_.push({type: 'close'});
+  };
+
+  /**
+   * @private
+   */
+  contextPrototype.getCoords_ = function(aX, aY) {
+    var m = this.m_;
+    return {
+      x: Z * (aX * m[0][0] + aY * m[1][0] + m[2][0]) - Z2,
+      y: Z * (aX * m[0][1] + aY * m[1][1] + m[2][1]) - Z2
+    }
+  };
+
+  contextPrototype.save = function() {
+    var o = {};
+    copyState(this, o);
+    this.aStack_.push(o);
+    this.mStack_.push(this.m_);
+    this.m_ = matrixMultiply(createMatrixIdentity(), this.m_);
+  };
+
+  contextPrototype.restore = function() {
+    copyState(this.aStack_.pop(), this);
+    this.m_ = this.mStack_.pop();
+  };
+
+  contextPrototype.translate = function(aX, aY) {
+    var m1 = [
+      [1,  0,  0],
+      [0,  1,  0],
+      [aX, aY, 1]
+    ];
+
+    this.m_ = matrixMultiply(m1, this.m_);
+  };
+
+  contextPrototype.rotate = function(aRot) {
+    var c = mc(aRot);
+    var s = ms(aRot);
+
+    var m1 = [
+      [c,  s, 0],
+      [-s, c, 0],
+      [0,  0, 1]
+    ];
+
+    this.m_ = matrixMultiply(m1, this.m_);
+  };
+
+  contextPrototype.scale = function(aX, aY) {
+    this.arcScaleX_ *= aX;
+    this.arcScaleY_ *= aY;
+    var m1 = [
+      [aX, 0,  0],
+      [0,  aY, 0],
+      [0,  0,  1]
+    ];
+
+    var m = this.m_ = matrixMultiply(m1, this.m_);
+
+    // Get the line scale.
+    // Determinant of this.m_ means how much the area is enlarged by the
+    // transformation. So its square root can be used as a scale factor
+    // for width.
+    var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
+    this.lineScale_ = sqrt(abs(det));
+  };
+
+  /******** STUBS ********/
+  contextPrototype.clip = function() {
+    // TODO: Implement
+  };
+
+  contextPrototype.arcTo = function() {
+    // TODO: Implement
+  };
+
+  contextPrototype.createPattern = function() {
+    return new CanvasPattern_;
+  };
+
+  // Gradient / Pattern Stubs
+  function CanvasGradient_(aType) {
+    this.type_ = aType;
+    this.x0_ = 0;
+    this.y0_ = 0;
+    this.r0_ = 0;
+    this.x1_ = 0;
+    this.y1_ = 0;
+    this.r1_ = 0;
+    this.colors_ = [];
+  }
+
+  CanvasGradient_.prototype.addColorStop = function(aOffset, aColor) {
+    aColor = processStyle(aColor);
+    this.colors_.push({offset: aOffset,
+                       color: aColor.color,
+                       alpha: aColor.alpha});
+  };
+
+  function CanvasPattern_() {}
+
+  // set up externs
+  G_vmlCanvasManager = G_vmlCanvasManager_;
+  CanvasRenderingContext2D = CanvasRenderingContext2D_;
+  CanvasGradient = CanvasGradient_;
+  CanvasPattern = CanvasPattern_;
+
+})();
+
+} // if
+