dygraph-canvas.js

   1 /**
   2  * @license
   3  * Copyright 2006 Dan Vanderkam (danvdk@gmail.com)
   4  * MIT-licensed (http://opensource.org/licenses/MIT)
   5  */
   6
   7 /**
   8  * @fileoverview Based on PlotKit.CanvasRenderer, but modified to meet the
   9  * needs of dygraphs.
  10  *
  11  * In particular, support for:
  12  * - grid overlays
  13  * - error bars
  14  * - dygraphs attribute system
  15  */
  16
  17 /**
  18  * The DygraphCanvasRenderer class does the actual rendering of the chart onto
  19  * a canvas. It's based on PlotKit.CanvasRenderer.
  20  * @param {Object} element The canvas to attach to
  21  * @param {Object} elementContext The 2d context of the canvas (injected so it
  22  * can be mocked for testing.)
  23  * @param {Layout} layout The DygraphLayout object for this graph.
  24  * @constructor
  25  */
  26
  27 /*jshint globalstrict: true */
  28 /*global Dygraph:false,RGBColor:false */
  29 "use strict";
  30
  31 var DygraphCanvasRenderer = function(dygraph, element, elementContext, layout) {
  32   this.dygraph_ = dygraph;
  33
  34   this.layout = layout;
  35   this.element = element;
  36   this.elementContext = elementContext;
  37   this.container = this.element.parentNode;
  38
  39   this.height = this.element.height;
  40   this.width = this.element.width;
  41
  42   // --- check whether everything is ok before we return
  43   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
  44       throw "Canvas is not supported.";
  45
  46   // internal state
  47   this.xlabels = [];
  48   this.ylabels = [];
  49   this.annotations = [];
  50   this.chartLabels = {};
  51
  52   this.area = layout.getPlotArea();
  53   this.container.style.position = "relative";
  54   this.container.style.width = this.width + "px";
  55
  56   // Set up a clipping area for the canvas (and the interaction canvas).
  57   // This ensures that we don't overdraw.
  58   if (this.dygraph_.isUsingExcanvas_) {
  59     this._createIEClipArea();
  60   } else {
  61     // on Android 3 and 4, setting a clipping area on a canvas prevents it from
  62     // displaying anything.
  63     if (!Dygraph.isAndroid()) {
  64       var ctx = this.dygraph_.canvas_ctx_;
  65       ctx.beginPath();
  66       ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h);
  67       ctx.clip();
  68
  69       ctx = this.dygraph_.hidden_ctx_;
  70       ctx.beginPath();
  71       ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h);
  72       ctx.clip();
  73     }
  74   }
  75 };
  76
  77 DygraphCanvasRenderer.prototype.attr_ = function(x) {
  78   return this.dygraph_.attr_(x);
  79 };
  80
  81 DygraphCanvasRenderer.prototype.clear = function() {
  82   var context;
  83   if (this.isIE) {
  84     // VML takes a while to start up, so we just poll every this.IEDelay
  85     try {
  86       if (this.clearDelay) {
  87         this.clearDelay.cancel();
  88         this.clearDelay = null;
  89       }
  90       context = this.elementContext;
  91     }
  92     catch (e) {
  93       // TODO(danvk): this is broken, since MochiKit.Async is gone.
  94       // this.clearDelay = MochiKit.Async.wait(this.IEDelay);
  95       // this.clearDelay.addCallback(bind(this.clear, this));
  96       return;
  97     }
  98   }
  99
 100   context = this.elementContext;
 101   context.clearRect(0, 0, this.width, this.height);
 102
 103   function removeArray(ary) {
 104     for (var i = 0; i < ary.length; i++) {
 105       var el = ary[i];
 106       if (el.parentNode) el.parentNode.removeChild(el);
 107     }
 108   }
 109
 110   removeArray(this.xlabels);
 111   removeArray(this.ylabels);
 112   removeArray(this.annotations);
 113
 114   for (var k in this.chartLabels) {
 115     if (!this.chartLabels.hasOwnProperty(k)) continue;
 116     var el = this.chartLabels[k];
 117     if (el.parentNode) el.parentNode.removeChild(el);
 118   }
 119   this.xlabels = [];
 120   this.ylabels = [];
 121   this.annotations = [];
 122   this.chartLabels = {};
 123 };
 124
 125
 126 DygraphCanvasRenderer.isSupported = function(canvasName) {
 127   var canvas = null;
 128   try {
 129     if (typeof(canvasName) == 'undefined' || canvasName === null) {
 130       canvas = document.createElement("canvas");
 131     } else {
 132       canvas = canvasName;
 133     }
 134     canvas.getContext("2d");
 135   }
 136   catch (e) {
 137     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 138     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 139     if ((!ie) || (ie[1] < 6) || (opera))
 140       return false;
 141     return true;
 142   }
 143   return true;
 144 };
 145
 146 /**
 147  * @param { [String] } colors Array of color strings. Should have one entry for
 148  * each series to be rendered.
 149  */
 150 DygraphCanvasRenderer.prototype.setColors = function(colors) {
 151   this.colorScheme_ = colors;
 152 };
 153
 154 /**
 155  * Draw an X/Y grid on top of the existing plot
 156  */
 157 DygraphCanvasRenderer.prototype.render = function() {
 158   // Draw the new X/Y grid. Lines appear crisper when pixels are rounded to
 159   // half-integers. This prevents them from drawing in two rows/cols.
 160   var ctx = this.elementContext;
 161   function halfUp(x)  { return Math.round(x) + 0.5; }
 162   function halfDown(y){ return Math.round(y) - 0.5; }
 163
 164   if (this.attr_('underlayCallback')) {
 165     // NOTE: we pass the dygraph object to this callback twice to avoid breaking
 166     // users who expect a deprecated form of this callback.
 167     this.attr_('underlayCallback')(ctx, this.area, this.dygraph_, this.dygraph_);
 168   }
 169
 170   var x, y, i, ticks;
 171   if (this.attr_('drawYGrid')) {
 172     ticks = this.layout.yticks;
 173     // TODO(konigsberg): I don't think these calls to save() have a corresponding restore().
 174     ctx.save();
 175     ctx.strokeStyle = this.attr_('gridLineColor');
 176     ctx.lineWidth = this.attr_('gridLineWidth');
 177     for (i = 0; i < ticks.length; i++) {
 178       // TODO(danvk): allow secondary axes to draw a grid, too.
 179       if (ticks[i][0] !== 0) continue;
 180       x = halfUp(this.area.x);
 181       y = halfDown(this.area.y + ticks[i][1] * this.area.h);
 182       ctx.beginPath();
 183       ctx.moveTo(x, y);
 184       ctx.lineTo(x + this.area.w, y);
 185       ctx.closePath();
 186       ctx.stroke();
 187     }
 188   }
 189
 190   if (this.attr_('drawXGrid')) {
 191     ticks = this.layout.xticks;
 192     ctx.save();
 193     ctx.strokeStyle = this.attr_('gridLineColor');
 194     ctx.lineWidth = this.attr_('gridLineWidth');
 195     for (i=0; i<ticks.length; i++) {
 196       x = halfUp(this.area.x + ticks[i][0] * this.area.w);
 197       y = halfDown(this.area.y + this.area.h);
 198       ctx.beginPath();
 199       ctx.moveTo(x, y);
 200       ctx.lineTo(x, this.area.y);
 201       ctx.closePath();
 202       ctx.stroke();
 203     }
 204   }
 205
 206   // Do the ordinary rendering, as before
 207   this._renderLineChart();
 208   this._renderAxis();
 209   this._renderChartLabels();
 210   this._renderAnnotations();
 211 };
 212
 213 DygraphCanvasRenderer.prototype._createIEClipArea = function() {
 214   var className = 'dygraph-clip-div';
 215   var graphDiv = this.dygraph_.graphDiv;
 216
 217   // Remove old clip divs.
 218   for (var i = graphDiv.childNodes.length-1; i >= 0; i--) {
 219     if (graphDiv.childNodes[i].className == className) {
 220       graphDiv.removeChild(graphDiv.childNodes[i]);
 221     }
 222   }
 223
 224   // Determine background color to give clip divs.
 225   var backgroundColor = document.bgColor;
 226   var element = this.dygraph_.graphDiv;
 227   while (element != document) {
 228     var bgcolor = element.currentStyle.backgroundColor;
 229     if (bgcolor && bgcolor != 'transparent') {
 230       backgroundColor = bgcolor;
 231       break;
 232     }
 233     element = element.parentNode;
 234   }
 235
 236   function createClipDiv(area) {
 237     if (area.w === 0 || area.h === 0) {
 238       return;
 239     }
 240     var elem = document.createElement('div');
 241     elem.className = className;
 242     elem.style.backgroundColor = backgroundColor;
 243     elem.style.position = 'absolute';
 244     elem.style.left = area.x + 'px';
 245     elem.style.top = area.y + 'px';
 246     elem.style.width = area.w + 'px';
 247     elem.style.height = area.h + 'px';
 248     graphDiv.appendChild(elem);
 249   }
 250
 251   var plotArea = this.area;
 252   // Left side
 253   createClipDiv({
 254     x:0, y:0,
 255     w:plotArea.x,
 256     h:this.height
 257   });
 258
 259   // Top
 260   createClipDiv({
 261     x: plotArea.x, y: 0,
 262     w: this.width - plotArea.x,
 263     h: plotArea.y
 264   });
 265
 266   // Right side
 267   createClipDiv({
 268     x: plotArea.x + plotArea.w, y: 0,
 269     w: this.width-plotArea.x - plotArea.w,
 270     h: this.height
 271   });
 272
 273   // Bottom
 274   createClipDiv({
 275     x: plotArea.x,
 276     y: plotArea.y + plotArea.h,
 277     w: this.width - plotArea.x,
 278     h: this.height - plotArea.h - plotArea.y
 279   });
 280 };
 281
 282 DygraphCanvasRenderer.prototype._renderAxis = function() {
 283   if (!this.attr_('drawXAxis') && !this.attr_('drawYAxis')) return;
 284
 285   // Round pixels to half-integer boundaries for crisper drawing.
 286   function halfUp(x)  { return Math.round(x) + 0.5; }
 287   function halfDown(y){ return Math.round(y) - 0.5; }
 288
 289   var context = this.elementContext;
 290
 291   var label, x, y, tick, i;
 292
 293   var labelStyle = {
 294     position: "absolute",
 295     fontSize: this.attr_('axisLabelFontSize') + "px",
 296     zIndex: 10,
 297     color: this.attr_('axisLabelColor'),
 298     width: this.attr_('axisLabelWidth') + "px",
 299     // height: this.attr_('axisLabelFontSize') + 2 + "px",
 300     lineHeight: "normal",  // Something other than "normal" line-height screws up label positioning.
 301     overflow: "hidden"
 302   };
 303   var makeDiv = function(txt, axis, prec_axis) {
 304     var div = document.createElement("div");
 305     for (var name in labelStyle) {
 306       if (labelStyle.hasOwnProperty(name)) {
 307         div.style[name] = labelStyle[name];
 308       }
 309     }
 310     var inner_div = document.createElement("div");
 311     inner_div.className = 'dygraph-axis-label' +
 312                           ' dygraph-axis-label-' + axis +
 313                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 314     inner_div.appendChild(document.createTextNode(txt));
 315     div.appendChild(inner_div);
 316     return div;
 317   };
 318
 319   // axis lines
 320   context.save();
 321   context.strokeStyle = this.attr_('axisLineColor');
 322   context.lineWidth = this.attr_('axisLineWidth');
 323
 324   if (this.attr_('drawYAxis')) {
 325     if (this.layout.yticks && this.layout.yticks.length > 0) {
 326       var num_axes = this.dygraph_.numAxes();
 327       for (i = 0; i < this.layout.yticks.length; i++) {
 328         tick = this.layout.yticks[i];
 329         if (typeof(tick) == "function") return;
 330         x = this.area.x;
 331         var sgn = 1;
 332         var prec_axis = 'y1';
 333         if (tick[0] == 1) {  // right-side y-axis
 334           x = this.area.x + this.area.w;
 335           sgn = -1;
 336           prec_axis = 'y2';
 337         }
 338         y = this.area.y + tick[1] * this.area.h;
 339
 340         /* Tick marks are currently clipped, so don't bother drawing them.
 341         context.beginPath();
 342         context.moveTo(halfUp(x), halfDown(y));
 343         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 344         context.closePath();
 345         context.stroke();
 346         */
 347
 348         label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null);
 349         var top = (y - this.attr_('axisLabelFontSize') / 2);
 350         if (top < 0) top = 0;
 351
 352         if (top + this.attr_('axisLabelFontSize') + 3 > this.height) {
 353           label.style.bottom = "0px";
 354         } else {
 355           label.style.top = top + "px";
 356         }
 357         if (tick[0] === 0) {
 358           label.style.left = (this.area.x - this.attr_('yAxisLabelWidth') - this.attr_('axisTickSize')) + "px";
 359           label.style.textAlign = "right";
 360         } else if (tick[0] == 1) {
 361           label.style.left = (this.area.x + this.area.w +
 362                               this.attr_('axisTickSize')) + "px";
 363           label.style.textAlign = "left";
 364         }
 365         label.style.width = this.attr_('yAxisLabelWidth') + "px";
 366         this.container.appendChild(label);
 367         this.ylabels.push(label);
 368       }
 369
 370       // The lowest tick on the y-axis often overlaps with the leftmost
 371       // tick on the x-axis. Shift the bottom tick up a little bit to
 372       // compensate if necessary.
 373       var bottomTick = this.ylabels[0];
 374       var fontSize = this.attr_('axisLabelFontSize');
 375       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 376       if (bottom > this.height - fontSize) {
 377         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 378             fontSize / 2) + "px";
 379       }
 380     }
 381
 382     // draw a vertical line on the left to separate the chart from the labels.
 383     context.beginPath();
 384     context.moveTo(halfUp(this.area.x), halfDown(this.area.y));
 385     context.lineTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 386     context.closePath();
 387     context.stroke();
 388
 389     // if there's a secondary y-axis, draw a vertical line for that, too.
 390     if (this.dygraph_.numAxes() == 2) {
 391       context.beginPath();
 392       context.moveTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y));
 393       context.lineTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 394       context.closePath();
 395       context.stroke();
 396     }
 397   }
 398
 399   if (this.attr_('drawXAxis')) {
 400     if (this.layout.xticks) {
 401       for (i = 0; i < this.layout.xticks.length; i++) {
 402         tick = this.layout.xticks[i];
 403         x = this.area.x + tick[0] * this.area.w;
 404         y = this.area.y + this.area.h;
 405
 406         /* Tick marks are currently clipped, so don't bother drawing them.
 407         context.beginPath();
 408         context.moveTo(halfUp(x), halfDown(y));
 409         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 410         context.closePath();
 411         context.stroke();
 412         */
 413
 414         label = makeDiv(tick[1], 'x');
 415         label.style.textAlign = "center";
 416         label.style.top = (y + this.attr_('axisTickSize')) + 'px';
 417
 418         var left = (x - this.attr_('axisLabelWidth')/2);
 419         if (left + this.attr_('axisLabelWidth') > this.width) {
 420           left = this.width - this.attr_('xAxisLabelWidth');
 421           label.style.textAlign = "right";
 422         }
 423         if (left < 0) {
 424           left = 0;
 425           label.style.textAlign = "left";
 426         }
 427
 428         label.style.left = left + "px";
 429         label.style.width = this.attr_('xAxisLabelWidth') + "px";
 430         this.container.appendChild(label);
 431         this.xlabels.push(label);
 432       }
 433     }
 434
 435     context.beginPath();
 436     context.moveTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 437     context.lineTo(halfUp(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 438     context.closePath();
 439     context.stroke();
 440   }
 441
 442   context.restore();
 443 };
 444
 445
 446 DygraphCanvasRenderer.prototype._renderChartLabels = function() {
 447   var div, class_div;
 448
 449   // Generate divs for the chart title, xlabel and ylabel.
 450   // Space for these divs has already been taken away from the charting area in
 451   // the DygraphCanvasRenderer constructor.
 452   if (this.attr_('title')) {
 453     div = document.createElement("div");
 454     div.style.position = 'absolute';
 455     div.style.top = '0px';
 456     div.style.left = this.area.x + 'px';
 457     div.style.width = this.area.w + 'px';
 458     div.style.height = this.attr_('titleHeight') + 'px';
 459     div.style.textAlign = 'center';
 460     div.style.fontSize = (this.attr_('titleHeight') - 8) + 'px';
 461     div.style.fontWeight = 'bold';
 462     class_div = document.createElement("div");
 463     class_div.className = 'dygraph-label dygraph-title';
 464     class_div.innerHTML = this.attr_('title');
 465     div.appendChild(class_div);
 466     this.container.appendChild(div);
 467     this.chartLabels.title = div;
 468   }
 469
 470   if (this.attr_('xlabel')) {
 471     div = document.createElement("div");
 472     div.style.position = 'absolute';
 473     div.style.bottom = 0;  // TODO(danvk): this is lazy. Calculate style.top.
 474     div.style.left = this.area.x + 'px';
 475     div.style.width = this.area.w + 'px';
 476     div.style.height = this.attr_('xLabelHeight') + 'px';
 477     div.style.textAlign = 'center';
 478     div.style.fontSize = (this.attr_('xLabelHeight') - 2) + 'px';
 479
 480     class_div = document.createElement("div");
 481     class_div.className = 'dygraph-label dygraph-xlabel';
 482     class_div.innerHTML = this.attr_('xlabel');
 483     div.appendChild(class_div);
 484     this.container.appendChild(div);
 485     this.chartLabels.xlabel = div;
 486   }
 487
 488   var that = this;
 489   function createRotatedDiv(axis, classes, html) {
 490     var box = {
 491       left: 0,
 492       top: that.area.y,
 493       width: that.attr_('yLabelWidth'),
 494       height: that.area.h
 495     };
 496     // TODO(danvk): is this outer div actually necessary?
 497     div = document.createElement("div");
 498     div.style.position = 'absolute';
 499     if (axis == 1) {
 500       div.style.left = box.left;
 501     } else {
 502       div.style.right = box.left;
 503     }
 504     div.style.top = box.top + 'px';
 505     div.style.width = box.width + 'px';
 506     div.style.height = box.height + 'px';
 507     div.style.fontSize = (that.attr_('yLabelWidth') - 2) + 'px';
 508
 509     var inner_div = document.createElement("div");
 510     inner_div.style.position = 'absolute';
 511     inner_div.style.width = box.height + 'px';
 512     inner_div.style.height = box.width + 'px';
 513     inner_div.style.top = (box.height / 2 - box.width / 2) + 'px';
 514     inner_div.style.left = (box.width / 2 - box.height / 2) + 'px';
 515     inner_div.style.textAlign = 'center';
 516
 517     // CSS rotation is an HTML5 feature which is not standardized. Hence every
 518     // browser has its own name for the CSS style.
 519     var val = 'rotate(' + (axis == 1 ? '-' : '') + '90deg)';
 520     inner_div.style.transform = val;        // HTML5
 521     inner_div.style.WebkitTransform = val;  // Safari/Chrome
 522     inner_div.style.MozTransform = val;     // Firefox
 523     inner_div.style.OTransform = val;       // Opera
 524     inner_div.style.msTransform = val;      // IE9
 525
 526     if (typeof(document.documentMode) !== 'undefined' &&
 527         document.documentMode < 9) {
 528       // We're dealing w/ an old version of IE, so we have to rotate the text
 529       // using a BasicImage transform. This uses a different origin of rotation
 530       // than HTML5 rotation (top left of div vs. its center).
 531       inner_div.style.filter =
 532           'progid:DXImageTransform.Microsoft.BasicImage(rotation=' +
 533           (axis == 1 ? '3' : '1') + ')';
 534       inner_div.style.left = '0px';
 535       inner_div.style.top = '0px';
 536     }
 537
 538     class_div = document.createElement("div");
 539     class_div.className = classes;
 540     class_div.innerHTML = html;
 541
 542     inner_div.appendChild(class_div);
 543     div.appendChild(inner_div);
 544     return div;
 545   }
 546
 547   var div;
 548   if (this.attr_('ylabel')) {
 549     div = createRotatedDiv(1, 'dygraph-label dygraph-ylabel',
 550                            this.attr_('ylabel'));
 551     this.container.appendChild(div);
 552     this.chartLabels.ylabel = div;
 553   }
 554   if (this.attr_('y2label') && this.dygraph_.numAxes() == 2) {
 555     div = createRotatedDiv(2, 'dygraph-label dygraph-y2label',
 556                            this.attr_('y2label'));
 557     this.container.appendChild(div);
 558     this.chartLabels.y2label = div;
 559   }
 560 };
 561
 562
 563 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 564   var annotationStyle = {
 565     "position": "absolute",
 566     "fontSize": this.attr_('axisLabelFontSize') + "px",
 567     "zIndex": 10,
 568     "overflow": "hidden"
 569   };
 570
 571   var bindEvt = function(eventName, classEventName, p, self) {
 572     return function(e) {
 573       var a = p.annotation;
 574       if (a.hasOwnProperty(eventName)) {
 575         a[eventName](a, p, self.dygraph_, e);
 576       } else if (self.dygraph_.attr_(classEventName)) {
 577         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 578       }
 579     };
 580   };
 581
 582   // Get a list of point with annotations.
 583   var points = this.layout.annotated_points;
 584   for (var i = 0; i < points.length; i++) {
 585     var p = points[i];
 586     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 587       continue;
 588     }
 589
 590     var a = p.annotation;
 591     var tick_height = 6;
 592     if (a.hasOwnProperty("tickHeight")) {
 593       tick_height = a.tickHeight;
 594     }
 595
 596     var div = document.createElement("div");
 597     for (var name in annotationStyle) {
 598       if (annotationStyle.hasOwnProperty(name)) {
 599         div.style[name] = annotationStyle[name];
 600       }
 601     }
 602     if (!a.hasOwnProperty('icon')) {
 603       div.className = "dygraphDefaultAnnotation";
 604     }
 605     if (a.hasOwnProperty('cssClass')) {
 606       div.className += " " + a.cssClass;
 607     }
 608
 609     var width = a.hasOwnProperty('width') ? a.width : 16;
 610     var height = a.hasOwnProperty('height') ? a.height : 16;
 611     if (a.hasOwnProperty('icon')) {
 612       var img = document.createElement("img");
 613       img.src = a.icon;
 614       img.width = width;
 615       img.height = height;
 616       div.appendChild(img);
 617     } else if (p.annotation.hasOwnProperty('shortText')) {
 618       div.appendChild(document.createTextNode(p.annotation.shortText));
 619     }
 620     div.style.left = (p.canvasx - width / 2) + "px";
 621     if (a.attachAtBottom) {
 622       div.style.top = (this.area.h - height - tick_height) + "px";
 623     } else {
 624       div.style.top = (p.canvasy - height - tick_height) + "px";
 625     }
 626     div.style.width = width + "px";
 627     div.style.height = height + "px";
 628     div.title = p.annotation.text;
 629     div.style.color = this.colors[p.name];
 630     div.style.borderColor = this.colors[p.name];
 631     a.div = div;
 632
 633     Dygraph.addEvent(div, 'click',
 634         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 635     Dygraph.addEvent(div, 'mouseover',
 636         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 637     Dygraph.addEvent(div, 'mouseout',
 638         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 639     Dygraph.addEvent(div, 'dblclick',
 640         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 641
 642     this.container.appendChild(div);
 643     this.annotations.push(div);
 644
 645     var ctx = this.elementContext;
 646     ctx.strokeStyle = this.colors[p.name];
 647     ctx.beginPath();
 648     if (!a.attachAtBottom) {
 649       ctx.moveTo(p.canvasx, p.canvasy);
 650       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 651     } else {
 652       ctx.moveTo(p.canvasx, this.area.h);
 653       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 654     }
 655     ctx.closePath();
 656     ctx.stroke();
 657   }
 658 };
 659
 660
 661 /**
 662  * Actually draw the lines chart, including error bars.
 663  * TODO(danvk): split this into several smaller functions.
 664  * @private
 665  */
 666 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 667   var isNullOrNaN = function(x) {
 668     return (x === null || isNaN(x));
 669   };
 670
 671   // TODO(danvk): use this.attr_ for many of these.
 672   var context = this.elementContext;
 673   var fillAlpha = this.attr_('fillAlpha');
 674   var errorBars = this.attr_("errorBars") || this.attr_("customBars");
 675   var fillGraph = this.attr_("fillGraph");
 676   var stackedGraph = this.attr_("stackedGraph");
 677   var stepPlot = this.attr_("stepPlot");
 678   var points = this.layout.points;
 679   var pointsLength = points.length;
 680   var point, i, j, prevX, prevY, prevYs, color, setName, newYs, err_color, rgb, yscale, axis;
 681
 682   var setNames = [];
 683   for (var name in this.layout.datasets) {
 684     if (this.layout.datasets.hasOwnProperty(name)) {
 685       setNames.push(name);
 686     }
 687   }
 688   var setCount = setNames.length;
 689
 690   // TODO(danvk): Move this mapping into Dygraph and get it out of here.
 691   this.colors = {};
 692   for (i = 0; i < setCount; i++) {
 693     this.colors[setNames[i]] = this.colorScheme_[i % this.colorScheme_.length];
 694   }
 695
 696   // Update Points
 697   // TODO(danvk): here
 698   for (i = pointsLength; i--;) {
 699     point = points[i];
 700     point.canvasx = this.area.w * point.x + this.area.x;
 701     point.canvasy = this.area.h * point.y + this.area.y;
 702   }
 703
 704   // create paths
 705   var ctx = context;
 706   if (errorBars) {
 707     if (fillGraph) {
 708       this.dygraph_.warn("Can't use fillGraph option with error bars");
 709     }
 710
 711     for (i = 0; i < setCount; i++) {
 712       setName = setNames[i];
 713       axis = this.dygraph_.axisPropertiesForSeries(setName);
 714       color = this.colors[setName];
 715
 716       // setup graphics context
 717       ctx.save();
 718       prevX = NaN;
 719       prevY = NaN;
 720       prevYs = [-1, -1];
 721       yscale = axis.yscale;
 722       // should be same color as the lines but only 15% opaque.
 723       rgb = new RGBColor(color);
 724       err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 725                             fillAlpha + ')';
 726       ctx.fillStyle = err_color;
 727       ctx.beginPath();
 728       for (j = 0; j < pointsLength; j++) {
 729         point = points[j];
 730         if (point.name == setName) {
 731           if (!Dygraph.isOK(point.y)) {
 732             prevX = NaN;
 733             continue;
 734           }
 735
 736           // TODO(danvk): here
 737           if (stepPlot) {
 738             newYs = [ point.y_bottom, point.y_top ];
 739             prevY = point.y;
 740           } else {
 741             newYs = [ point.y_bottom, point.y_top ];
 742           }
 743           newYs[0] = this.area.h * newYs[0] + this.area.y;
 744           newYs[1] = this.area.h * newYs[1] + this.area.y;
 745           if (!isNaN(prevX)) {
 746             if (stepPlot) {
 747               ctx.moveTo(prevX, newYs[0]);
 748             } else {
 749               ctx.moveTo(prevX, prevYs[0]);
 750             }
 751             ctx.lineTo(point.canvasx, newYs[0]);
 752             ctx.lineTo(point.canvasx, newYs[1]);
 753             if (stepPlot) {
 754               ctx.lineTo(prevX, newYs[1]);
 755             } else {
 756               ctx.lineTo(prevX, prevYs[1]);
 757             }
 758             ctx.closePath();
 759           }
 760           prevYs = newYs;
 761           prevX = point.canvasx;
 762         }
 763       }
 764       ctx.fill();
 765     }
 766   } else if (fillGraph) {
 767     var baseline = [];  // for stacked graphs: baseline for filling
 768
 769     // process sets in reverse order (needed for stacked graphs)
 770     for (i = setCount - 1; i >= 0; i--) {
 771       setName = setNames[i];
 772       color = this.colors[setName];
 773       axis = this.dygraph_.axisPropertiesForSeries(setName);
 774       var axisY = 1.0 + axis.minyval * axis.yscale;
 775       if (axisY < 0.0) axisY = 0.0;
 776       else if (axisY > 1.0) axisY = 1.0;
 777       axisY = this.area.h * axisY + this.area.y;
 778
 779       // setup graphics context
 780       ctx.save();
 781       prevX = NaN;
 782       prevYs = [-1, -1];
 783       yscale = axis.yscale;
 784       // should be same color as the lines but only 15% opaque.
 785       rgb = new RGBColor(color);
 786       err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 787                             fillAlpha + ')';
 788       ctx.fillStyle = err_color;
 789       ctx.beginPath();
 790       for (j = 0; j < pointsLength; j++) {
 791         point = points[j];
 792         if (point.name == setName) {
 793           if (!Dygraph.isOK(point.y)) {
 794             prevX = NaN;
 795             continue;
 796           }
 797           if (stackedGraph) {
 798             var lastY = baseline[point.canvasx];
 799             if (lastY === undefined) lastY = axisY;
 800             baseline[point.canvasx] = point.canvasy;
 801             newYs = [ point.canvasy, lastY ];
 802           } else {
 803             newYs = [ point.canvasy, axisY ];
 804           }
 805           if (!isNaN(prevX)) {
 806             ctx.moveTo(prevX, prevYs[0]);
 807             if (stepPlot) {
 808               ctx.lineTo(point.canvasx, prevYs[0]);
 809             } else {
 810               ctx.lineTo(point.canvasx, newYs[0]);
 811             }
 812             ctx.lineTo(point.canvasx, newYs[1]);
 813             ctx.lineTo(prevX, prevYs[1]);
 814             ctx.closePath();
 815           }
 816           prevYs = newYs;
 817           prevX = point.canvasx;
 818         }
 819       }
 820       ctx.fill();
 821     }
 822   }
 823
 824   // Drawing the lines.
 825   var firstIndexInSet = 0;
 826   var afterLastIndexInSet = 0;
 827   var setLength = 0;
 828   for (i = 0; i < setCount; i += 1) {
 829     setLength = this.layout.setPointsLengths[i];
 830     afterLastIndexInSet += setLength;
 831     setName = setNames[i];
 832     color = this.colors[setName];
 833     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 834
 835     // setup graphics context
 836     // TODO(konigsberg): This function has ctx and context. Clarify the difference.
 837     context.save();
 838     var pointSize = this.dygraph_.attr_("pointSize", setName);
 839     prevX = null;
 840     prevY = null;
 841     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 842     var drawPointCallback = this.dygraph_.attr_("drawPointCallback", setName);
 843     if (!drawPointCallback) {
 844       drawPointCallback = Dygraph.Circles.DEFAULT;
 845     }
 846     var pointsOnLine = []; // Array of [canvasx, canvasy] pairs.
 847     for (j = firstIndexInSet; j < afterLastIndexInSet; j++) {
 848       point = points[j];
 849       if (isNullOrNaN(point.canvasy)) {
 850         if (stepPlot && prevX !== null) {
 851           // Draw a horizontal line to the start of the missing data
 852           ctx.beginPath();
 853           ctx.strokeStyle = color;
 854           ctx.lineWidth = this.attr_('strokeWidth');
 855           ctx.moveTo(prevX, prevY);
 856           ctx.lineTo(point.canvasx, prevY);
 857           ctx.stroke();
 858         }
 859         // this will make us move to the next point, not draw a line to it.
 860         prevX = prevY = null;
 861       } else {
 862         // A point is "isolated" if it is non-null but both the previous
 863         // and next points are null.
 864         var isIsolated = (!prevX && (j == points.length - 1 ||
 865                                      isNullOrNaN(points[j+1].canvasy)));
 866         if (prevX === null) {
 867           prevX = point.canvasx;
 868           prevY = point.canvasy;
 869         } else {
 870           // Skip over points that will be drawn in the same pixel.
 871           if (Math.round(prevX) == Math.round(point.canvasx) &&
 872               Math.round(prevY) == Math.round(point.canvasy)) {
 873             continue;
 874           }
 875           // TODO(antrob): skip over points that lie on a line that is already
 876           // going to be drawn. There is no need to have more than 2
 877           // consecutive points that are collinear.
 878           if (strokeWidth) {
 879             ctx.beginPath();
 880             ctx.strokeStyle = color;
 881             ctx.lineWidth = strokeWidth;
 882             ctx.moveTo(prevX, prevY);
 883             if (stepPlot) {
 884               ctx.lineTo(point.canvasx, prevY);
 885             }
 886             prevX = point.canvasx;
 887             prevY = point.canvasy;
 888             ctx.lineTo(prevX, prevY);
 889             ctx.stroke();
 890           }
 891         }
 892
 893         if (drawPoints || isIsolated) {
 894           pointsOnLine.push([point.canvasx, point.canvasy]);
 895         }
 896       }
 897     }
 898     for (var idx = 0; idx < pointsOnLine.length; idx++) {
 899       var cb = pointsOnLine[idx];
 900       ctx.save();
 901       drawPointCallback(
 902           this.dygraph_, setName, ctx, cb[0], cb[1], color, pointSize);
 903       ctx.restore();
 904
 905     }
 906     firstIndexInSet = afterLastIndexInSet;
 907   }
 908
 909   context.restore();
 910 };