annotate mercurial/templates/static/excanvas.js @ 33390:32331f54930c

hgweb: re-implement followlines UI selection using buttons

This changeset attempts to solve two issues with the "followlines" UI in
hgweb. First the "followlines" action is currently not easily discoverable
(one has to hover on a line for some time, wait for the invite message to
appear and then perform some action). Second, it gets in the way of natural
line selection, especially in filerevision view.

This changeset introduces an additional markup element (a <button
class="btn-followlines">) alongside each content line of the view. This button
now holds events for line selection that were previously plugged onto content
lines directly. Consequently, there's no more action on content lines, hence
restoring the "natural line selection" behavior (solving the second problem).
These buttons are hidden by default and get displayed upon hover of content
lines; then upon hover of a button itself, a text inviting followlines section
shows up. This solves the first problem (discoverability) as we now have a
clear visual element indicating that "some action could be perform" (i.e. a
button) and that is self-documented.

In followlines.js, all event listeners are now attached to these <button>
elements. The custom "floating tooltip" element is dropped as <button>
elements are now self-documented through a "title" attribute that changes
depending on preceding actions (selection started or not, in particular).

The new <button> element is inserted in followlines.js script (thus only
visible if JavaScript is activated); it contains a "+" and "-" with a
"diff-semantics" style; upon hover, it scales up.

To find the parent element under which to insert the <button> we either rely
on the "data-selectabletag" attribute (which defines the HTML tag of children
of class="sourcelines" element e.g. <span> for filerevision view and <tr> for
annotate view) or use a child of the latter elements if we find an element
with class="followlines-btn-parent" (useful for annotate view, for which we
have to find the <td> in which to insert the <button>).

On noticeable change in CSS concerns the "margin-left" of span:before
pseudo-elements in filelog view that has been increased a bit in order to
leave space for the new button to appear between line number column and
line content one.
Also note the "z-index" addition for "annotate-info" box so that the latter
appears on top of new buttons (instead of getting hidden).

In some respect, the UI similar to line commenting feature that is implemented
in popular code hosting site like GitHub, BitBucket or Kallithea.

// 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();
  };

  function matrixIsFinite(m) {
    for (var j = 0; j < 3; j++) {
      for (var k = 0; k < 2; k++) {
        if (!isFinite(m[j][k]) || isNaN(m[j][k])) {
          return false;
        }
      }
    }
    return true;
  }

  function setM(ctx, m, updateLineScale) {
    if (!matrixIsFinite(m)) {
      return;
    }
    ctx.m_ = m;

    if (updateLineScale) {
      // 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];
      ctx.lineScale_ = sqrt(abs(det));
    }
  }

  contextPrototype.translate = function(aX, aY) {
    var m1 = [
      [1,  0,  0],
      [0,  1,  0],
      [aX, aY, 1]
    ];

    setM(this, matrixMultiply(m1, this.m_), false);
  };

  contextPrototype.rotate = function(aRot) {
    var c = mc(aRot);
    var s = ms(aRot);

    var m1 = [
      [c,  s, 0],
      [-s, c, 0],
      [0,  0, 1]
    ];

    setM(this, matrixMultiply(m1, this.m_), false);
  };

  contextPrototype.scale = function(aX, aY) {
    this.arcScaleX_ *= aX;
    this.arcScaleY_ *= aY;
    var m1 = [
      [aX, 0,  0],
      [0,  aY, 0],
      [0,  0,  1]
    ];

    setM(this, matrixMultiply(m1, this.m_), true);
  };

  contextPrototype.transform = function(m11, m12, m21, m22, dx, dy) {
    var m1 = [
      [m11, m12, 0],
      [m21, m22, 0],
      [dx,  dy,  1]
    ];

    setM(this, matrixMultiply(m1, this.m_), true);
  };

  contextPrototype.setTransform = function(m11, m12, m21, m22, dx, dy) {
    var m = [
      [m11, m12, 0],
      [m21, m22, 0],
      [dx,  dy,  1]
    ];

    setM(this, m, true);
  };

  /******** 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