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) {
 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     // TODO(danvk): separate class for secondary y-axis
 272     inner_div.className = 'dygraph-axis-label dygraph-axis-label-' + axis;
 273     inner_div.appendChild(document.createTextNode(txt));
 274     div.appendChild(inner_div);
 275     return div;
 276   };
 277
 278   // axis lines
 279   context.save();
 280   context.strokeStyle = this.attr_('axisLineColor');
 281   context.lineWidth = this.attr_('axisLineWidth');
 282
 283   if (this.attr_('drawYAxis')) {
 284     if (this.layout.yticks && this.layout.yticks.length > 0) {
 285       for (var i = 0; i < this.layout.yticks.length; i++) {
 286         var tick = this.layout.yticks[i];
 287         if (typeof(tick) == "function") return;
 288         var x = this.area.x;
 289         var sgn = 1;
 290         if (tick[0] == 1) {  // right-side y-axis
 291           x = this.area.x + this.area.w;
 292           sgn = -1;
 293         }
 294         var y = this.area.y + tick[1] * this.area.h;
 295         context.beginPath();
 296         context.moveTo(halfUp(x), halfDown(y));
 297         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 298         context.closePath();
 299         context.stroke();
 300
 301         var label = makeDiv(tick[2], 'y');
 302         var top = (y - this.attr_('axisLabelFontSize') / 2);
 303         if (top < 0) top = 0;
 304
 305         if (top + this.attr_('axisLabelFontSize') + 3 > this.height) {
 306           label.style.bottom = "0px";
 307         } else {
 308           label.style.top = top + "px";
 309         }
 310         if (tick[0] == 0) {
 311           label.style.left = (this.area.x - this.attr_('yAxisLabelWidth') - this.attr_('axisTickSize')) + "px";
 312           label.style.textAlign = "right";
 313         } else if (tick[0] == 1) {
 314           label.style.left = (this.area.x + this.area.w +
 315                               this.attr_('axisTickSize')) + "px";
 316           label.style.textAlign = "left";
 317         }
 318         label.style.width = this.attr_('yAxisLabelWidth') + "px";
 319         this.container.appendChild(label);
 320         this.ylabels.push(label);
 321       }
 322
 323       // The lowest tick on the y-axis often overlaps with the leftmost
 324       // tick on the x-axis. Shift the bottom tick up a little bit to
 325       // compensate if necessary.
 326       var bottomTick = this.ylabels[0];
 327       var fontSize = this.attr_('axisLabelFontSize');
 328       var bottom = parseInt(bottomTick.style.top) + fontSize;
 329       if (bottom > this.height - fontSize) {
 330         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 331             fontSize / 2) + "px";
 332       }
 333     }
 334
 335     // draw a vertical line on the left to separate the chart from the labels.
 336     context.beginPath();
 337     context.moveTo(halfUp(this.area.x), halfDown(this.area.y));
 338     context.lineTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 339     context.closePath();
 340     context.stroke();
 341
 342     // if there's a secondary y-axis, draw a vertical line for that, too.
 343     if (this.dygraph_.numAxes() == 2) {
 344       context.beginPath();
 345       context.moveTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y));
 346       context.lineTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 347       context.closePath();
 348       context.stroke();
 349     }
 350   }
 351
 352   if (this.attr_('drawXAxis')) {
 353     if (this.layout.xticks) {
 354       for (var i = 0; i < this.layout.xticks.length; i++) {
 355         var tick = this.layout.xticks[i];
 356         if (typeof(dataset) == "function") return;
 357
 358         var x = this.area.x + tick[0] * this.area.w;
 359         var y = this.area.y + this.area.h;
 360         context.beginPath();
 361         context.moveTo(halfUp(x), halfDown(y));
 362         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 363         context.closePath();
 364         context.stroke();
 365
 366         var label = makeDiv(tick[1], 'x');
 367         label.style.textAlign = "center";
 368         label.style.top = (y + this.attr_('axisTickSize')) + 'px';
 369
 370         var left = (x - this.attr_('axisLabelWidth')/2);
 371         if (left + this.attr_('axisLabelWidth') > this.width) {
 372           left = this.width - this.attr_('xAxisLabelWidth');
 373           label.style.textAlign = "right";
 374         }
 375         if (left < 0) {
 376           left = 0;
 377           label.style.textAlign = "left";
 378         }
 379
 380         label.style.left = left + "px";
 381         label.style.width = this.attr_('xAxisLabelWidth') + "px";
 382         this.container.appendChild(label);
 383         this.xlabels.push(label);
 384       }
 385     }
 386
 387     context.beginPath();
 388     context.moveTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 389     context.lineTo(halfUp(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 390     context.closePath();
 391     context.stroke();
 392   }
 393
 394   context.restore();
 395 };
 396
 397
 398 DygraphCanvasRenderer.prototype._renderChartLabels = function() {
 399   // Generate divs for the chart title, xlabel and ylabel.
 400   // Space for these divs has already been taken away from the charting area in
 401   // the DygraphCanvasRenderer constructor.
 402   if (this.attr_('title')) {
 403     var div = document.createElement("div");
 404     div.style.position = 'absolute';
 405     div.style.top = '0px';
 406     div.style.left = this.area.x + 'px';
 407     div.style.width = this.area.w + 'px';
 408     div.style.height = this.attr_('titleHeight') + 'px';
 409     div.style.textAlign = 'center';
 410     div.style.fontSize = (this.attr_('titleHeight') - 8) + 'px';
 411     div.style.fontWeight = 'bold';
 412     var class_div = document.createElement("div");
 413     class_div.className = 'dygraph-label dygraph-title';
 414     class_div.innerHTML = this.attr_('title');
 415     div.appendChild(class_div);
 416     this.container.appendChild(div);
 417     this.chartLabels.title = div;
 418   }
 419
 420   if (this.attr_('xlabel')) {
 421     var div = document.createElement("div");
 422     div.style.position = 'absolute';
 423     div.style.bottom = 0;  // TODO(danvk): this is lazy. Calculate style.top.
 424     div.style.left = this.area.x + 'px';
 425     div.style.width = this.area.w + 'px';
 426     div.style.height = this.attr_('xLabelHeight') + 'px';
 427     div.style.textAlign = 'center';
 428     div.style.fontSize = (this.attr_('xLabelHeight') - 2) + 'px';
 429
 430     var class_div = document.createElement("div");
 431     class_div.className = 'dygraph-label dygraph-xlabel';
 432     class_div.innerHTML = this.attr_('xlabel');
 433     div.appendChild(class_div);
 434     this.container.appendChild(div);
 435     this.chartLabels.xlabel = div;
 436   }
 437
 438   if (this.attr_('ylabel')) {
 439     var box = {
 440       left: 0,
 441       top: this.area.y,
 442       width: this.attr_('yLabelWidth'),
 443       height: this.area.h
 444     };
 445     // TODO(danvk): is this outer div actually necessary?
 446     var div = document.createElement("div");
 447     div.style.position = 'absolute';
 448     div.style.left = box.left;
 449     div.style.top = box.top + 'px';
 450     div.style.width = box.width + 'px';
 451     div.style.height = box.height + 'px';
 452     div.style.fontSize = (this.attr_('yLabelWidth') - 2) + 'px';
 453
 454     var inner_div = document.createElement("div");
 455     inner_div.style.position = 'absolute';
 456     inner_div.style.width = box.height + 'px';
 457     inner_div.style.height = box.width + 'px';
 458     inner_div.style.top = (box.height / 2 - box.width / 2) + 'px';
 459     inner_div.style.left = (box.width / 2 - box.height / 2) + 'px';
 460     inner_div.style.textAlign = 'center';
 461
 462     // CSS rotation is an HTML5 feature which is not standardized. Hence every
 463     // browser has its own name for the CSS style.
 464     inner_div.style.transform = 'rotate(-90deg)';        // HTML5
 465     inner_div.style.WebkitTransform = 'rotate(-90deg)';  // Safari/Chrome
 466     inner_div.style.MozTransform = 'rotate(-90deg)';     // Firefox
 467     inner_div.style.OTransform = 'rotate(-90deg)';       // Opera
 468     inner_div.style.msTransform = 'rotate(-90deg)';      // IE9
 469
 470     if (typeof(document.documentMode) !== 'undefined' &&
 471         document.documentMode < 9) {
 472       // We're dealing w/ an old version of IE, so we have to rotate the text
 473       // using a BasicImage transform. This uses a different origin of rotation
 474       // than HTML5 rotation (top left of div vs. its center).
 475       inner_div.style.filter =
 476        'progid:DXImageTransform.Microsoft.BasicImage(rotation=3)';
 477       inner_div.style.left = '0px';
 478       inner_div.style.top = '0px';
 479     }
 480
 481     var class_div = document.createElement("div");
 482     class_div.className = 'dygraph-label dygraph-ylabel';
 483     class_div.innerHTML = this.attr_('ylabel');
 484
 485     inner_div.appendChild(class_div);
 486     div.appendChild(inner_div);
 487     this.container.appendChild(div);
 488     this.chartLabels.ylabel = div;
 489   }
 490 };
 491
 492
 493 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 494   var annotationStyle = {
 495     "position": "absolute",
 496     "fontSize": this.attr_('axisLabelFontSize') + "px",
 497     "zIndex": 10,
 498     "overflow": "hidden"
 499   };
 500
 501   var bindEvt = function(eventName, classEventName, p, self) {
 502     return function(e) {
 503       var a = p.annotation;
 504       if (a.hasOwnProperty(eventName)) {
 505         a[eventName](a, p, self.dygraph_, e);
 506       } else if (self.dygraph_.attr_(classEventName)) {
 507         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 508       }
 509     };
 510   }
 511
 512   // Get a list of point with annotations.
 513   var points = this.layout.annotated_points;
 514   for (var i = 0; i < points.length; i++) {
 515     var p = points[i];
 516     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 517       continue;
 518     }
 519
 520     var a = p.annotation;
 521     var tick_height = 6;
 522     if (a.hasOwnProperty("tickHeight")) {
 523       tick_height = a.tickHeight;
 524     }
 525
 526     var div = document.createElement("div");
 527     for (var name in annotationStyle) {
 528       if (annotationStyle.hasOwnProperty(name)) {
 529         div.style[name] = annotationStyle[name];
 530       }
 531     }
 532     if (!a.hasOwnProperty('icon')) {
 533       div.className = "dygraphDefaultAnnotation";
 534     }
 535     if (a.hasOwnProperty('cssClass')) {
 536       div.className += " " + a.cssClass;
 537     }
 538
 539     var width = a.hasOwnProperty('width') ? a.width : 16;
 540     var height = a.hasOwnProperty('height') ? a.height : 16;
 541     if (a.hasOwnProperty('icon')) {
 542       var img = document.createElement("img");
 543       img.src = a.icon;
 544       img.width = width;
 545       img.height = height;
 546       div.appendChild(img);
 547     } else if (p.annotation.hasOwnProperty('shortText')) {
 548       div.appendChild(document.createTextNode(p.annotation.shortText));
 549     }
 550     div.style.left = (p.canvasx - width / 2) + "px";
 551     if (a.attachAtBottom) {
 552       div.style.top = (this.area.h - height - tick_height) + "px";
 553     } else {
 554       div.style.top = (p.canvasy - height - tick_height) + "px";
 555     }
 556     div.style.width = width + "px";
 557     div.style.height = height + "px";
 558     div.title = p.annotation.text;
 559     div.style.color = this.colors[p.name];
 560     div.style.borderColor = this.colors[p.name];
 561     a.div = div;
 562
 563     Dygraph.addEvent(div, 'click',
 564         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 565     Dygraph.addEvent(div, 'mouseover',
 566         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 567     Dygraph.addEvent(div, 'mouseout',
 568         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 569     Dygraph.addEvent(div, 'dblclick',
 570         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 571
 572     this.container.appendChild(div);
 573     this.annotations.push(div);
 574
 575     var ctx = this.elementContext;
 576     ctx.strokeStyle = this.colors[p.name];
 577     ctx.beginPath();
 578     if (!a.attachAtBottom) {
 579       ctx.moveTo(p.canvasx, p.canvasy);
 580       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 581     } else {
 582       ctx.moveTo(p.canvasx, this.area.h);
 583       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 584     }
 585     ctx.closePath();
 586     ctx.stroke();
 587   }
 588 };
 589
 590
 591 /**
 592  * Overrides the CanvasRenderer method to draw error bars
 593  */
 594 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 595   // TODO(danvk): use this.attr_ for many of these.
 596   var context = this.elementContext;
 597   var fillAlpha = this.attr_('fillAlpha');
 598   var errorBars = this.attr_("errorBars") || this.attr_("customBars");
 599   var fillGraph = this.attr_("fillGraph");
 600   var stackedGraph = this.attr_("stackedGraph");
 601   var stepPlot = this.attr_("stepPlot");
 602
 603   var setNames = [];
 604   for (var name in this.layout.datasets) {
 605     if (this.layout.datasets.hasOwnProperty(name)) {
 606       setNames.push(name);
 607     }
 608   }
 609   var setCount = setNames.length;
 610
 611   // TODO(danvk): Move this mapping into Dygraph and get it out of here.
 612   this.colors = {}
 613   for (var i = 0; i < setCount; i++) {
 614     this.colors[setNames[i]] = this.colorScheme_[i % this.colorScheme_.length];
 615   }
 616
 617   // Update Points
 618   // TODO(danvk): here
 619   for (var i = 0; i < this.layout.points.length; i++) {
 620     var point = this.layout.points[i];
 621     point.canvasx = this.area.w * point.x + this.area.x;
 622     point.canvasy = this.area.h * point.y + this.area.y;
 623   }
 624
 625   // create paths
 626   var ctx = context;
 627   if (errorBars) {
 628     if (fillGraph) {
 629       this.dygraph_.warn("Can't use fillGraph option with error bars");
 630     }
 631
 632     for (var i = 0; i < setCount; i++) {
 633       var setName = setNames[i];
 634       var axis = this.dygraph_.axisPropertiesForSeries(setName);
 635       var color = this.colors[setName];
 636
 637       // setup graphics context
 638       ctx.save();
 639       var prevX = NaN;
 640       var prevY = NaN;
 641       var prevYs = [-1, -1];
 642       var yscale = axis.yscale;
 643       // should be same color as the lines but only 15% opaque.
 644       var rgb = new RGBColor(color);
 645       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 646                             fillAlpha + ')';
 647       ctx.fillStyle = err_color;
 648       ctx.beginPath();
 649       for (var j = 0; j < this.layout.points.length; j++) {
 650         var point = this.layout.points[j];
 651         if (point.name == setName) {
 652           if (!Dygraph.isOK(point.y)) {
 653             prevX = NaN;
 654             continue;
 655           }
 656
 657           // TODO(danvk): here
 658           if (stepPlot) {
 659             var newYs = [ prevY - point.errorPlus * yscale,
 660                           prevY + point.errorMinus * yscale ];
 661             prevY = point.y;
 662           } else {
 663             var newYs = [ point.y - point.errorPlus * yscale,
 664                           point.y + point.errorMinus * yscale ];
 665           }
 666           newYs[0] = this.area.h * newYs[0] + this.area.y;
 667           newYs[1] = this.area.h * newYs[1] + this.area.y;
 668           if (!isNaN(prevX)) {
 669             if (stepPlot) {
 670               ctx.moveTo(prevX, newYs[0]);
 671             } else {
 672               ctx.moveTo(prevX, prevYs[0]);
 673             }
 674             ctx.lineTo(point.canvasx, newYs[0]);
 675             ctx.lineTo(point.canvasx, newYs[1]);
 676             if (stepPlot) {
 677               ctx.lineTo(prevX, newYs[1]);
 678             } else {
 679               ctx.lineTo(prevX, prevYs[1]);
 680             }
 681             ctx.closePath();
 682           }
 683           prevYs = newYs;
 684           prevX = point.canvasx;
 685         }
 686       }
 687       ctx.fill();
 688     }
 689   } else if (fillGraph) {
 690     var baseline = []  // for stacked graphs: baseline for filling
 691
 692     // process sets in reverse order (needed for stacked graphs)
 693     for (var i = setCount - 1; i >= 0; i--) {
 694       var setName = setNames[i];
 695       var color = this.colors[setName];
 696       var axis = this.dygraph_.axisPropertiesForSeries(setName);
 697       var axisY = 1.0 + axis.minyval * axis.yscale;
 698       if (axisY < 0.0) axisY = 0.0;
 699       else if (axisY > 1.0) axisY = 1.0;
 700       axisY = this.area.h * axisY + this.area.y;
 701
 702       // setup graphics context
 703       ctx.save();
 704       var prevX = NaN;
 705       var prevYs = [-1, -1];
 706       var yscale = axis.yscale;
 707       // should be same color as the lines but only 15% opaque.
 708       var rgb = new RGBColor(color);
 709       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 710                             fillAlpha + ')';
 711       ctx.fillStyle = err_color;
 712       ctx.beginPath();
 713       for (var j = 0; j < this.layout.points.length; j++) {
 714         var point = this.layout.points[j];
 715         if (point.name == setName) {
 716           if (!Dygraph.isOK(point.y)) {
 717             prevX = NaN;
 718             continue;
 719           }
 720           var newYs;
 721           if (stackedGraph) {
 722             lastY = baseline[point.canvasx];
 723             if (lastY === undefined) lastY = axisY;
 724             baseline[point.canvasx] = point.canvasy;
 725             newYs = [ point.canvasy, lastY ];
 726           } else {
 727             newYs = [ point.canvasy, axisY ];
 728           }
 729           if (!isNaN(prevX)) {
 730             ctx.moveTo(prevX, prevYs[0]);
 731             if (stepPlot) {
 732               ctx.lineTo(point.canvasx, prevYs[0]);
 733             } else {
 734               ctx.lineTo(point.canvasx, newYs[0]);
 735             }
 736             ctx.lineTo(point.canvasx, newYs[1]);
 737             ctx.lineTo(prevX, prevYs[1]);
 738             ctx.closePath();
 739           }
 740           prevYs = newYs;
 741           prevX = point.canvasx;
 742         }
 743       }
 744       ctx.fill();
 745     }
 746   }
 747
 748   var isNullOrNaN = function(x) {
 749     return (x === null || isNaN(x));
 750   };
 751
 752   for (var i = 0; i < setCount; i++) {
 753     var setName = setNames[i];
 754     var color = this.colors[setName];
 755     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 756
 757     // setup graphics context
 758     context.save();
 759     var point = this.layout.points[0];
 760     var pointSize = this.dygraph_.attr_("pointSize", setName);
 761     var prevX = null, prevY = null;
 762     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 763     var points = this.layout.points;
 764     for (var j = 0; j < points.length; j++) {
 765       var point = points[j];
 766       if (point.name == setName) {
 767         if (isNullOrNaN(point.canvasy)) {
 768           if (stepPlot && prevX != null) {
 769             // Draw a horizontal line to the start of the missing data
 770             ctx.beginPath();
 771             ctx.strokeStyle = color;
 772             ctx.lineWidth = this.attr_('strokeWidth');
 773             ctx.moveTo(prevX, prevY);
 774             ctx.lineTo(point.canvasx, prevY);
 775             ctx.stroke();
 776           }
 777           // this will make us move to the next point, not draw a line to it.
 778           prevX = prevY = null;
 779         } else {
 780           // A point is "isolated" if it is non-null but both the previous
 781           // and next points are null.
 782           var isIsolated = (!prevX && (j == points.length - 1 ||
 783                                        isNullOrNaN(points[j+1].canvasy)));
 784
 785           if (prevX === null) {
 786             prevX = point.canvasx;
 787             prevY = point.canvasy;
 788           } else {
 789             // TODO(danvk): figure out why this conditional is necessary.
 790             if (strokeWidth) {
 791               ctx.beginPath();
 792               ctx.strokeStyle = color;
 793               ctx.lineWidth = strokeWidth;
 794               ctx.moveTo(prevX, prevY);
 795               if (stepPlot) {
 796                 ctx.lineTo(point.canvasx, prevY);
 797               }
 798               prevX = point.canvasx;
 799               prevY = point.canvasy;
 800               ctx.lineTo(prevX, prevY);
 801               ctx.stroke();
 802             }
 803           }
 804
 805           if (drawPoints || isIsolated) {
 806            ctx.beginPath();
 807            ctx.fillStyle = color;
 808            ctx.arc(point.canvasx, point.canvasy, pointSize,
 809                    0, 2 * Math.PI, false);
 810            ctx.fill();
 811           }
 812         }
 813       }
 814     }
 815   }
 816
 817   context.restore();
 818 };