dygraph-canvas.js

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