dygraph-canvas.js

   1 // Copyright 2006 Dan Vanderkam (danvdk@gmail.com)
   2 // All Rights Reserved.
   3
   4 /**
   5  * @fileoverview Based on PlotKit, but modified to meet the needs of dygraphs.
   6  * In particular, support for:
   7  * - grid overlays
   8  * - error bars
   9  * - dygraphs attribute system
  10  */
  11
  12 /**
  13  * Creates a new DygraphLayout object.
  14  * @param {Object} options Options for PlotKit.Layout
  15  * @return {Object} The DygraphLayout object
  16  */
  17 DygraphLayout = function(dygraph, options) {
  18   this.dygraph_ = dygraph;
  19   this.options = {};  // TODO(danvk): remove, use attr_ instead.
  20   Dygraph.update(this.options, options ? options : {});
  21   this.datasets = new Array();
  22   this.annotations = new Array();
  23 };
  24
  25 DygraphLayout.prototype.attr_ = function(name) {
  26   return this.dygraph_.attr_(name);
  27 };
  28
  29 DygraphLayout.prototype.addDataset = function(setname, set_xy) {
  30   this.datasets[setname] = set_xy;
  31 };
  32
  33 DygraphLayout.prototype.setAnnotations = function(ann) {
  34   // The Dygraph object's annotations aren't parsed. We parse them here and
  35   // save a copy.
  36   var parse = this.attr_('xValueParser');
  37   for (var i = 0; i < ann.length; i++) {
  38     var a = {};
  39     if (!ann[i].xval && !ann[i].x) {
  40       this.dygraph_.error("Annotations must have an 'x' property");
  41       return;
  42     }
  43     if (ann[i].icon &&
  44         !(ann[i].hasOwnProperty('width') &&
  45           ann[i].hasOwnProperty('height'))) {
  46       this.dygraph_.error("Must set width and height when setting " +
  47                           "annotation.icon property");
  48       return;
  49     }
  50     Dygraph.update(a, ann[i]);
  51     if (!a.xval) a.xval = parse(a.x);
  52     this.annotations.push(a);
  53   }
  54 };
  55
  56 DygraphLayout.prototype.evaluate = function() {
  57   this._evaluateLimits();
  58   this._evaluateLineCharts();
  59   this._evaluateLineTicks();
  60   this._evaluateAnnotations();
  61 };
  62
  63 DygraphLayout.prototype._evaluateLimits = function() {
  64   this.minxval = this.maxxval = null;
  65   if (this.options.dateWindow) {
  66     this.minxval = this.options.dateWindow[0];
  67     this.maxxval = this.options.dateWindow[1];
  68   } else {
  69     for (var name in this.datasets) {
  70       if (!this.datasets.hasOwnProperty(name)) continue;
  71       var series = this.datasets[name];
  72       var x1 = series[0][0];
  73       if (!this.minxval || x1 < this.minxval) this.minxval = x1;
  74
  75       var x2 = series[series.length - 1][0];
  76       if (!this.maxxval || x2 > this.maxxval) this.maxxval = x2;
  77     }
  78   }
  79   this.xrange = this.maxxval - this.minxval;
  80   this.xscale = (this.xrange != 0 ? 1/this.xrange : 1.0);
  81
  82   this.minyval = this.options.yAxis[0];
  83   this.maxyval = this.options.yAxis[1];
  84   this.yrange = this.maxyval - this.minyval;
  85   this.yscale = (this.yrange != 0 ? 1/this.yrange : 1.0);
  86 };
  87
  88 DygraphLayout.prototype._evaluateLineCharts = function() {
  89   // add all the rects
  90   this.points = new Array();
  91   for (var setName in this.datasets) {
  92     if (!this.datasets.hasOwnProperty(setName)) continue;
  93
  94     var dataset = this.datasets[setName];
  95     for (var j = 0; j < dataset.length; j++) {
  96       var item = dataset[j];
  97       var point = {
  98         // TODO(danvk): here
  99         x: ((parseFloat(item[0]) - this.minxval) * this.xscale),
 100         y: 1.0 - ((parseFloat(item[1]) - this.minyval) * this.yscale),
 101         xval: parseFloat(item[0]),
 102         yval: parseFloat(item[1]),
 103         name: setName
 104       };
 105
 106       this.points.push(point);
 107     }
 108   }
 109 };
 110
 111 DygraphLayout.prototype._evaluateLineTicks = function() {
 112   this.xticks = new Array();
 113   for (var i = 0; i < this.options.xTicks.length; i++) {
 114     var tick = this.options.xTicks[i];
 115     var label = tick.label;
 116     var pos = this.xscale * (tick.v - this.minxval);
 117     if ((pos >= 0.0) && (pos <= 1.0)) {
 118       this.xticks.push([pos, label]);
 119     }
 120   }
 121
 122   this.yticks = new Array();
 123   for (var i = 0; i < this.options.yTicks.length; i++) {
 124     var tick = this.options.yTicks[i];
 125     var label = tick.label;
 126     var pos = 1.0 - (this.yscale * (tick.v - this.minyval));
 127     if ((pos >= 0.0) && (pos <= 1.0)) {
 128       this.yticks.push([pos, label]);
 129     }
 130   }
 131 };
 132
 133
 134 /**
 135  * Behaves the same way as PlotKit.Layout, but also copies the errors
 136  * @private
 137  */
 138 DygraphLayout.prototype.evaluateWithError = function() {
 139   this.evaluate();
 140   if (!this.options.errorBars) return;
 141
 142   // Copy over the error terms
 143   var i = 0; // index in this.points
 144   for (var setName in this.datasets) {
 145     if (!this.datasets.hasOwnProperty(setName)) continue;
 146     var j = 0;
 147     var dataset = this.datasets[setName];
 148     for (var j = 0; j < dataset.length; j++, i++) {
 149       var item = dataset[j];
 150       var xv = parseFloat(item[0]);
 151       var yv = parseFloat(item[1]);
 152
 153       if (xv == this.points[i].xval &&
 154           yv == this.points[i].yval) {
 155         this.points[i].errorMinus = parseFloat(item[2]);
 156         this.points[i].errorPlus = parseFloat(item[3]);
 157       }
 158     }
 159   }
 160 };
 161
 162 DygraphLayout.prototype._evaluateAnnotations = function() {
 163   // Add the annotations to the point to which they belong.
 164   // Make a map from (setName, xval) to annotation for quick lookups.
 165   var annotations = {};
 166   for (var i = 0; i < this.annotations.length; i++) {
 167     var a = this.annotations[i];
 168     annotations[a.xval + "," + a.series] = a;
 169   }
 170
 171   this.annotated_points = [];
 172   for (var i = 0; i < this.points.length; i++) {
 173     var p = this.points[i];
 174     var k = p.xval + "," + p.name;
 175     if (k in annotations) {
 176       p.annotation = annotations[k];
 177       this.annotated_points.push(p);
 178     }
 179   }
 180 };
 181
 182 /**
 183  * Convenience function to remove all the data sets from a graph
 184  */
 185 DygraphLayout.prototype.removeAllDatasets = function() {
 186   delete this.datasets;
 187   this.datasets = new Array();
 188 };
 189
 190 /**
 191  * Change the values of various layout options
 192  * @param {Object} new_options an associative array of new properties
 193  */
 194 DygraphLayout.prototype.updateOptions = function(new_options) {
 195   Dygraph.update(this.options, new_options ? new_options : {});
 196 };
 197
 198 /**
 199  * Return a copy of the point at the indicated index, with its yval unstacked.
 200  * @param int index of point in layout_.points
 201  */
 202 DygraphLayout.prototype.unstackPointAtIndex = function(idx) {
 203   var point = this.points[idx];
 204
 205   // Clone the point since we modify it
 206   var unstackedPoint = {};
 207   for (var i in point) {
 208     unstackedPoint[i] = point[i];
 209   }
 210
 211   if (!this.attr_("stackedGraph")) {
 212     return unstackedPoint;
 213   }
 214
 215   // The unstacked yval is equal to the current yval minus the yval of the
 216   // next point at the same xval.
 217   for (var i = idx+1; i < this.points.length; i++) {
 218     if (this.points[i].xval == point.xval) {
 219       unstackedPoint.yval -= this.points[i].yval;
 220       break;
 221     }
 222   }
 223
 224   return unstackedPoint;
 225 }
 226
 227 // Subclass PlotKit.CanvasRenderer to add:
 228 // 1. X/Y grid overlay
 229 // 2. Ability to draw error bars (if required)
 230
 231 /**
 232  * Sets some PlotKit.CanvasRenderer options
 233  * @param {Object} element The canvas to attach to
 234  * @param {Layout} layout The DygraphLayout object for this graph.
 235  * @param {Object} options Options to pass on to CanvasRenderer
 236  */
 237 DygraphCanvasRenderer = function(dygraph, element, layout, options) {
 238   // TODO(danvk): remove options, just use dygraph.attr_.
 239   this.dygraph_ = dygraph;
 240
 241   // default options
 242   this.options = {
 243     "strokeWidth": 0.5,
 244     "drawXAxis": true,
 245     "drawYAxis": true,
 246     "axisLineColor": "black",
 247     "axisLineWidth": 0.5,
 248     "axisTickSize": 3,
 249     "axisLabelColor": "black",
 250     "axisLabelFont": "Arial",
 251     "axisLabelFontSize": 9,
 252     "axisLabelWidth": 50,
 253     "drawYGrid": true,
 254     "drawXGrid": true,
 255     "gridLineColor": "rgb(128,128,128)",
 256     "fillAlpha": 0.15,
 257     "underlayCallback": null
 258   };
 259   Dygraph.update(this.options, options);
 260
 261   this.layout = layout;
 262   this.element = element;
 263   this.container = this.element.parentNode;
 264
 265   this.height = this.element.height;
 266   this.width = this.element.width;
 267
 268   // --- check whether everything is ok before we return
 269   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
 270       throw "Canvas is not supported.";
 271
 272   // internal state
 273   this.xlabels = new Array();
 274   this.ylabels = new Array();
 275   this.annotations = new Array();
 276
 277   this.area = {
 278     x: this.options.yAxisLabelWidth + 2 * this.options.axisTickSize,
 279     y: 0
 280   };
 281   this.area.w = this.width - this.area.x - this.options.rightGap;
 282   this.area.h = this.height - this.options.axisLabelFontSize -
 283                 2 * this.options.axisTickSize;
 284
 285   this.container.style.position = "relative";
 286   this.container.style.width = this.width + "px";
 287 };
 288
 289 DygraphCanvasRenderer.prototype.clear = function() {
 290   if (this.isIE) {
 291     // VML takes a while to start up, so we just poll every this.IEDelay
 292     try {
 293       if (this.clearDelay) {
 294         this.clearDelay.cancel();
 295         this.clearDelay = null;
 296       }
 297       var context = this.element.getContext("2d");
 298     }
 299     catch (e) {
 300       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 301       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 302       this.clearDelay.addCallback(bind(this.clear, this));
 303       return;
 304     }
 305   }
 306
 307   var context = this.element.getContext("2d");
 308   context.clearRect(0, 0, this.width, this.height);
 309
 310   for (var i = 0; i < this.xlabels.length; i++) {
 311     var el = this.xlabels[i];
 312     el.parentNode.removeChild(el);
 313   }
 314   for (var i = 0; i < this.ylabels.length; i++) {
 315     var el = this.ylabels[i];
 316     el.parentNode.removeChild(el);
 317   }
 318   for (var i = 0; i < this.annotations.length; i++) {
 319     var el = this.annotations[i];
 320     el.parentNode.removeChild(el);
 321   }
 322   this.xlabels = new Array();
 323   this.ylabels = new Array();
 324   this.annotations = new Array();
 325 };
 326
 327
 328 DygraphCanvasRenderer.isSupported = function(canvasName) {
 329   var canvas = null;
 330   try {
 331     if (typeof(canvasName) == 'undefined' || canvasName == null)
 332       canvas = document.createElement("canvas");
 333     else
 334       canvas = canvasName;
 335     var context = canvas.getContext("2d");
 336   }
 337   catch (e) {
 338     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 339     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 340     if ((!ie) || (ie[1] < 6) || (opera))
 341       return false;
 342     return true;
 343   }
 344   return true;
 345 };
 346
 347 /**
 348  * Draw an X/Y grid on top of the existing plot
 349  */
 350 DygraphCanvasRenderer.prototype.render = function() {
 351   // Draw the new X/Y grid
 352   var ctx = this.element.getContext("2d");
 353
 354   if (this.options.underlayCallback) {
 355     this.options.underlayCallback(ctx, this.area, this.layout, this.dygraph_);
 356   }
 357
 358   if (this.options.drawYGrid) {
 359     var ticks = this.layout.yticks;
 360     ctx.save();
 361     ctx.strokeStyle = this.options.gridLineColor;
 362     ctx.lineWidth = this.options.axisLineWidth;
 363     for (var i = 0; i < ticks.length; i++) {
 364       var x = this.area.x;
 365       var y = this.area.y + ticks[i][0] * this.area.h;
 366       ctx.beginPath();
 367       ctx.moveTo(x, y);
 368       ctx.lineTo(x + this.area.w, y);
 369       ctx.closePath();
 370       ctx.stroke();
 371     }
 372   }
 373
 374   if (this.options.drawXGrid) {
 375     var ticks = this.layout.xticks;
 376     ctx.save();
 377     ctx.strokeStyle = this.options.gridLineColor;
 378     ctx.lineWidth = this.options.axisLineWidth;
 379     for (var i=0; i<ticks.length; i++) {
 380       var x = this.area.x + ticks[i][0] * this.area.w;
 381       var y = this.area.y + this.area.h;
 382       ctx.beginPath();
 383       ctx.moveTo(x, y);
 384       ctx.lineTo(x, this.area.y);
 385       ctx.closePath();
 386       ctx.stroke();
 387     }
 388   }
 389
 390   // Do the ordinary rendering, as before
 391   this._renderLineChart();
 392   this._renderAxis();
 393   this._renderAnnotations();
 394 };
 395
 396
 397 DygraphCanvasRenderer.prototype._renderAxis = function() {
 398   if (!this.options.drawXAxis && !this.options.drawYAxis)
 399     return;
 400
 401   var context = this.element.getContext("2d");
 402
 403   var labelStyle = {
 404     "position": "absolute",
 405     "fontSize": this.options.axisLabelFontSize + "px",
 406     "zIndex": 10,
 407     "color": this.options.axisLabelColor,
 408     "width": this.options.axisLabelWidth + "px",
 409     "overflow": "hidden"
 410   };
 411   var makeDiv = function(txt) {
 412     var div = document.createElement("div");
 413     for (var name in labelStyle) {
 414       if (labelStyle.hasOwnProperty(name)) {
 415         div.style[name] = labelStyle[name];
 416       }
 417     }
 418     div.appendChild(document.createTextNode(txt));
 419     return div;
 420   };
 421
 422   // axis lines
 423   context.save();
 424   context.strokeStyle = this.options.axisLineColor;
 425   context.lineWidth = this.options.axisLineWidth;
 426
 427   if (this.options.drawYAxis) {
 428     if (this.layout.yticks && this.layout.yticks.length > 0) {
 429       for (var i = 0; i < this.layout.yticks.length; i++) {
 430         var tick = this.layout.yticks[i];
 431         if (typeof(tick) == "function") return;
 432         var x = this.area.x;
 433         var y = this.area.y + tick[0] * this.area.h;
 434         context.beginPath();
 435         context.moveTo(x, y);
 436         context.lineTo(x - this.options.axisTickSize, y);
 437         context.closePath();
 438         context.stroke();
 439
 440         var label = makeDiv(tick[1]);
 441         var top = (y - this.options.axisLabelFontSize / 2);
 442         if (top < 0) top = 0;
 443
 444         if (top + this.options.axisLabelFontSize + 3 > this.height) {
 445           label.style.bottom = "0px";
 446         } else {
 447           label.style.top = top + "px";
 448         }
 449         label.style.left = "0px";
 450         label.style.textAlign = "right";
 451         label.style.width = this.options.yAxisLabelWidth + "px";
 452         this.container.appendChild(label);
 453         this.ylabels.push(label);
 454       }
 455
 456       // The lowest tick on the y-axis often overlaps with the leftmost
 457       // tick on the x-axis. Shift the bottom tick up a little bit to
 458       // compensate if necessary.
 459       var bottomTick = this.ylabels[0];
 460       var fontSize = this.options.axisLabelFontSize;
 461       var bottom = parseInt(bottomTick.style.top) + fontSize;
 462       if (bottom > this.height - fontSize) {
 463         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 464             fontSize / 2) + "px";
 465       }
 466     }
 467
 468     context.beginPath();
 469     context.moveTo(this.area.x, this.area.y);
 470     context.lineTo(this.area.x, this.area.y + this.area.h);
 471     context.closePath();
 472     context.stroke();
 473   }
 474
 475   if (this.options.drawXAxis) {
 476     if (this.layout.xticks) {
 477       for (var i = 0; i < this.layout.xticks.length; i++) {
 478         var tick = this.layout.xticks[i];
 479         if (typeof(dataset) == "function") return;
 480
 481         var x = this.area.x + tick[0] * this.area.w;
 482         var y = this.area.y + this.area.h;
 483         context.beginPath();
 484         context.moveTo(x, y);
 485         context.lineTo(x, y + this.options.axisTickSize);
 486         context.closePath();
 487         context.stroke();
 488
 489         var label = makeDiv(tick[1]);
 490         label.style.textAlign = "center";
 491         label.style.bottom = "0px";
 492
 493         var left = (x - this.options.axisLabelWidth/2);
 494         if (left + this.options.axisLabelWidth > this.width) {
 495           left = this.width - this.options.xAxisLabelWidth;
 496           label.style.textAlign = "right";
 497         }
 498         if (left < 0) {
 499           left = 0;
 500           label.style.textAlign = "left";
 501         }
 502
 503         label.style.left = left + "px";
 504         label.style.width = this.options.xAxisLabelWidth + "px";
 505         this.container.appendChild(label);
 506         this.xlabels.push(label);
 507       }
 508     }
 509
 510     context.beginPath();
 511     context.moveTo(this.area.x, this.area.y + this.area.h);
 512     context.lineTo(this.area.x + this.area.w, this.area.y + this.area.h);
 513     context.closePath();
 514     context.stroke();
 515   }
 516
 517   context.restore();
 518 };
 519
 520
 521 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 522   var annotationStyle = {
 523     "position": "absolute",
 524     "fontSize": this.options.axisLabelFontSize + "px",
 525     "zIndex": 10,
 526     "overflow": "hidden"
 527   };
 528
 529   var bindEvt = function(eventName, classEventName, p, self) {
 530     return function(e) {
 531       var a = p.annotation;
 532       if (a.hasOwnProperty(eventName)) {
 533         a[eventName](a, p, self.dygraph_, e);
 534       } else if (self.dygraph_.attr_(classEventName)) {
 535         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 536       }
 537     };
 538   }
 539
 540   // Get a list of point with annotations.
 541   var points = this.layout.annotated_points;
 542   for (var i = 0; i < points.length; i++) {
 543     var p = points[i];
 544     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 545       continue;
 546     }
 547
 548     var a = p.annotation;
 549     var tick_height = 6;
 550     if (a.hasOwnProperty("tickHeight")) {
 551       tick_height = a.tickHeight;
 552     }
 553
 554     var div = document.createElement("div");
 555     for (var name in annotationStyle) {
 556       if (annotationStyle.hasOwnProperty(name)) {
 557         div.style[name] = annotationStyle[name];
 558       }
 559     }
 560     if (!a.hasOwnProperty('icon')) {
 561       div.className = "dygraphDefaultAnnotation";
 562     }
 563     if (a.hasOwnProperty('cssClass')) {
 564       div.className += " " + a.cssClass;
 565     }
 566
 567     var width = a.hasOwnProperty('width') ? a.width : 16;
 568     var height = a.hasOwnProperty('height') ? a.height : 16;
 569     if (a.hasOwnProperty('icon')) {
 570       var img = document.createElement("img");
 571       img.src = a.icon;
 572       img.width = width;
 573       img.height = height;
 574       div.appendChild(img);
 575     } else if (p.annotation.hasOwnProperty('shortText')) {
 576       div.appendChild(document.createTextNode(p.annotation.shortText));
 577     }
 578     div.style.left = (p.canvasx - width / 2) + "px";
 579     if (a.attachAtBottom) {
 580       div.style.top = (this.area.h - height - tick_height) + "px";
 581     } else {
 582       div.style.top = (p.canvasy - height - tick_height) + "px";
 583     }
 584     div.style.width = width + "px";
 585     div.style.height = height + "px";
 586     div.title = p.annotation.text;
 587     div.style.color = this.colors[p.name];
 588     div.style.borderColor = this.colors[p.name];
 589     a.div = div;
 590
 591     Dygraph.addEvent(div, 'click',
 592         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 593     Dygraph.addEvent(div, 'mouseover',
 594         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 595     Dygraph.addEvent(div, 'mouseout',
 596         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 597     Dygraph.addEvent(div, 'dblclick',
 598         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 599
 600     this.container.appendChild(div);
 601     this.annotations.push(div);
 602
 603     var ctx = this.element.getContext("2d");
 604     ctx.strokeStyle = this.colors[p.name];
 605     ctx.beginPath();
 606     if (!a.attachAtBottom) {
 607       ctx.moveTo(p.canvasx, p.canvasy);
 608       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 609     } else {
 610       ctx.moveTo(p.canvasx, this.area.h);
 611       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 612     }
 613     ctx.closePath();
 614     ctx.stroke();
 615   }
 616 };
 617
 618
 619 /**
 620  * Overrides the CanvasRenderer method to draw error bars
 621  */
 622 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 623   var context = this.element.getContext("2d");
 624   var colorCount = this.options.colorScheme.length;
 625   var colorScheme = this.options.colorScheme;
 626   var fillAlpha = this.options.fillAlpha;
 627   var errorBars = this.layout.options.errorBars;
 628   var fillGraph = this.layout.options.fillGraph;
 629   var stackedGraph = this.layout.options.stackedGraph;
 630   var stepPlot = this.layout.options.stepPlot;
 631
 632   var setNames = [];
 633   for (var name in this.layout.datasets) {
 634     if (this.layout.datasets.hasOwnProperty(name)) {
 635       setNames.push(name);
 636     }
 637   }
 638   var setCount = setNames.length;
 639
 640   this.colors = {}
 641   for (var i = 0; i < setCount; i++) {
 642     this.colors[setNames[i]] = colorScheme[i % colorCount];
 643   }
 644
 645   // Update Points
 646   // TODO(danvk): here
 647   for (var i = 0; i < this.layout.points.length; i++) {
 648     var point = this.layout.points[i];
 649     point.canvasx = this.area.w * point.x + this.area.x;
 650     point.canvasy = this.area.h * point.y + this.area.y;
 651   }
 652
 653   // create paths
 654   var isOK = function(x) { return x && !isNaN(x); };
 655
 656   var ctx = context;
 657   if (errorBars) {
 658     if (fillGraph) {
 659       this.dygraph_.warn("Can't use fillGraph option with error bars");
 660     }
 661
 662     for (var i = 0; i < setCount; i++) {
 663       var setName = setNames[i];
 664       var color = this.colors[setName];
 665
 666       // setup graphics context
 667       ctx.save();
 668       var prevX = NaN;
 669       var prevY = NaN;
 670       var prevYs = [-1, -1];
 671       var yscale = this.layout.yscale;
 672       // should be same color as the lines but only 15% opaque.
 673       var rgb = new RGBColor(color);
 674       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 675                             fillAlpha + ')';
 676       ctx.fillStyle = err_color;
 677       ctx.beginPath();
 678       for (var j = 0; j < this.layout.points.length; j++) {
 679         var point = this.layout.points[j];
 680         if (point.name == setName) {
 681           if (!isOK(point.y)) {
 682             prevX = NaN;
 683             continue;
 684           }
 685
 686           // TODO(danvk): here
 687           if (stepPlot) {
 688             var newYs = [ prevY - point.errorPlus * yscale,
 689                           prevY + point.errorMinus * yscale ];
 690             prevY = point.y;
 691           } else {
 692             var newYs = [ point.y - point.errorPlus * yscale,
 693                           point.y + point.errorMinus * yscale ];
 694           }
 695           newYs[0] = this.area.h * newYs[0] + this.area.y;
 696           newYs[1] = this.area.h * newYs[1] + this.area.y;
 697           if (!isNaN(prevX)) {
 698             if (stepPlot) {
 699               ctx.moveTo(prevX, newYs[0]);
 700             } else {
 701               ctx.moveTo(prevX, prevYs[0]);
 702             }
 703             ctx.lineTo(point.canvasx, newYs[0]);
 704             ctx.lineTo(point.canvasx, newYs[1]);
 705             if (stepPlot) {
 706               ctx.lineTo(prevX, newYs[1]);
 707             } else {
 708               ctx.lineTo(prevX, prevYs[1]);
 709             }
 710             ctx.closePath();
 711           }
 712           prevYs = newYs;
 713           prevX = point.canvasx;
 714         }
 715       }
 716       ctx.fill();
 717     }
 718   } else if (fillGraph) {
 719     var axisY = 1.0 + this.layout.minyval * this.layout.yscale;
 720     if (axisY < 0.0) axisY = 0.0;
 721     else if (axisY > 1.0) axisY = 1.0;
 722     axisY = this.area.h * axisY + this.area.y;
 723
 724     var baseline = []  // for stacked graphs: baseline for filling
 725
 726     // process sets in reverse order (needed for stacked graphs)
 727     for (var i = setCount - 1; i >= 0; i--) {
 728       var setName = setNames[i];
 729       var color = this.colors[setName];
 730
 731       // setup graphics context
 732       ctx.save();
 733       var prevX = NaN;
 734       var prevYs = [-1, -1];
 735       var yscale = this.layout.yscale;
 736       // should be same color as the lines but only 15% opaque.
 737       var rgb = new RGBColor(color);
 738       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 739                             fillAlpha + ')';
 740       ctx.fillStyle = err_color;
 741       ctx.beginPath();
 742       for (var j = 0; j < this.layout.points.length; j++) {
 743         var point = this.layout.points[j];
 744         if (point.name == setName) {
 745           if (!isOK(point.y)) {
 746             prevX = NaN;
 747             continue;
 748           }
 749           var newYs;
 750           if (stackedGraph) {
 751             lastY = baseline[point.canvasx];
 752             if (lastY === undefined) lastY = axisY;
 753             baseline[point.canvasx] = point.canvasy;
 754             newYs = [ point.canvasy, lastY ];
 755           } else {
 756             newYs = [ point.canvasy, axisY ];
 757           }
 758           if (!isNaN(prevX)) {
 759             ctx.moveTo(prevX, prevYs[0]);
 760             if (stepPlot) {
 761               ctx.lineTo(point.canvasx, prevYs[0]);
 762             } else {
 763               ctx.lineTo(point.canvasx, newYs[0]);
 764             }
 765             ctx.lineTo(point.canvasx, newYs[1]);
 766             ctx.lineTo(prevX, prevYs[1]);
 767             ctx.closePath();
 768           }
 769           prevYs = newYs;
 770           prevX = point.canvasx;
 771         }
 772       }
 773       ctx.fill();
 774     }
 775   }
 776
 777   for (var i = 0; i < setCount; i++) {
 778     var setName = setNames[i];
 779     var color = this.colors[setName];
 780     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 781
 782     // setup graphics context
 783     context.save();
 784     var point = this.layout.points[0];
 785     var pointSize = this.dygraph_.attr_("pointSize", setName);
 786     var prevX = null, prevY = null;
 787     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 788     var points = this.layout.points;
 789     for (var j = 0; j < points.length; j++) {
 790       var point = points[j];
 791       if (point.name == setName) {
 792         if (!isOK(point.canvasy)) {
 793           // this will make us move to the next point, not draw a line to it.
 794           prevX = prevY = null;
 795         } else {
 796           // A point is "isolated" if it is non-null but both the previous
 797           // and next points are null.
 798           var isIsolated = (!prevX && (j == points.length - 1 ||
 799                                        !isOK(points[j+1].canvasy)));
 800
 801           if (!prevX) {
 802             prevX = point.canvasx;
 803             prevY = point.canvasy;
 804           } else {
 805             // TODO(danvk): figure out why this conditional is necessary.
 806             if (strokeWidth) {
 807               ctx.beginPath();
 808               ctx.strokeStyle = color;
 809               ctx.lineWidth = strokeWidth;
 810               ctx.moveTo(prevX, prevY);
 811               if (stepPlot) {
 812                 ctx.lineTo(point.canvasx, prevY);
 813               }
 814               prevX = point.canvasx;
 815               prevY = point.canvasy;
 816               ctx.lineTo(prevX, prevY);
 817               ctx.stroke();
 818             }
 819           }
 820
 821           if (drawPoints || isIsolated) {
 822            ctx.beginPath();
 823            ctx.fillStyle = color;
 824            ctx.arc(point.canvasx, point.canvasy, pointSize,
 825                    0, 2 * Math.PI, false);
 826            ctx.fill();
 827           }
 828         }
 829       }
 830     }
 831   }
 832
 833   context.restore();
 834 };