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       // limit the x, y values so they do not overdraw
 107       if (point.y <= 0.0) {
 108         point.y = 0.0;
 109       }
 110       if (point.y >= 1.0) {
 111         point.y = 1.0;
 112       }
 113       this.points.push(point);
 114     }
 115   }
 116 };
 117
 118 DygraphLayout.prototype._evaluateLineTicks = function() {
 119   this.xticks = new Array();
 120   for (var i = 0; i < this.options.xTicks.length; i++) {
 121     var tick = this.options.xTicks[i];
 122     var label = tick.label;
 123     var pos = this.xscale * (tick.v - this.minxval);
 124     if ((pos >= 0.0) && (pos <= 1.0)) {
 125       this.xticks.push([pos, label]);
 126     }
 127   }
 128
 129   this.yticks = new Array();
 130   for (var i = 0; i < this.options.yTicks.length; i++) {
 131     var tick = this.options.yTicks[i];
 132     var label = tick.label;
 133     var pos = 1.0 - (this.yscale * (tick.v - this.minyval));
 134     if ((pos >= 0.0) && (pos <= 1.0)) {
 135       this.yticks.push([pos, label]);
 136     }
 137   }
 138 };
 139
 140
 141 /**
 142  * Behaves the same way as PlotKit.Layout, but also copies the errors
 143  * @private
 144  */
 145 DygraphLayout.prototype.evaluateWithError = function() {
 146   this.evaluate();
 147   if (!this.options.errorBars) return;
 148
 149   // Copy over the error terms
 150   var i = 0; // index in this.points
 151   for (var setName in this.datasets) {
 152     if (!this.datasets.hasOwnProperty(setName)) continue;
 153     var j = 0;
 154     var dataset = this.datasets[setName];
 155     for (var j = 0; j < dataset.length; j++, i++) {
 156       var item = dataset[j];
 157       var xv = parseFloat(item[0]);
 158       var yv = parseFloat(item[1]);
 159
 160       if (xv == this.points[i].xval &&
 161           yv == this.points[i].yval) {
 162         this.points[i].errorMinus = parseFloat(item[2]);
 163         this.points[i].errorPlus = parseFloat(item[3]);
 164       }
 165     }
 166   }
 167 };
 168
 169 DygraphLayout.prototype._evaluateAnnotations = function() {
 170   // Add the annotations to the point to which they belong.
 171   // Make a map from (setName, xval) to annotation for quick lookups.
 172   var annotations = {};
 173   for (var i = 0; i < this.annotations.length; i++) {
 174     var a = this.annotations[i];
 175     annotations[a.xval + "," + a.series] = a;
 176   }
 177
 178   this.annotated_points = [];
 179   for (var i = 0; i < this.points.length; i++) {
 180     var p = this.points[i];
 181     var k = p.xval + "," + p.name;
 182     if (k in annotations) {
 183       p.annotation = annotations[k];
 184       this.annotated_points.push(p);
 185     }
 186   }
 187 };
 188
 189 /**
 190  * Convenience function to remove all the data sets from a graph
 191  */
 192 DygraphLayout.prototype.removeAllDatasets = function() {
 193   delete this.datasets;
 194   this.datasets = new Array();
 195 };
 196
 197 /**
 198  * Change the values of various layout options
 199  * @param {Object} new_options an associative array of new properties
 200  */
 201 DygraphLayout.prototype.updateOptions = function(new_options) {
 202   Dygraph.update(this.options, new_options ? new_options : {});
 203 };
 204
 205 /**
 206  * Return a copy of the point at the indicated index, with its yval unstacked.
 207  * @param int index of point in layout_.points
 208  */
 209 DygraphLayout.prototype.unstackPointAtIndex_ = function(idx) {
 210   var point = this.points[idx];
 211
 212   // Clone the point since we modify it
 213   var unstackedPoint = {};
 214   for (var i in point) {
 215     unstackedPoint[i] = point[i];
 216   }
 217
 218   if (!this.attr_("stackedGraph")) {
 219     return unstackedPoint;
 220   }
 221
 222   // The unstacked yval is equal to the current yval minus the yval of the
 223   // next point at the same xval.
 224   for (var i = idx+1; i < this.points.length; i++) {
 225     if (this.points[i].xval == point.xval) {
 226       unstackedPoint.yval -= this.points[i].yval;
 227       break;
 228     }
 229   }
 230
 231   return unstackedPoint;
 232 }
 233
 234 // Subclass PlotKit.CanvasRenderer to add:
 235 // 1. X/Y grid overlay
 236 // 2. Ability to draw error bars (if required)
 237
 238 /**
 239  * Sets some PlotKit.CanvasRenderer options
 240  * @param {Object} element The canvas to attach to
 241  * @param {Layout} layout The DygraphLayout object for this graph.
 242  * @param {Object} options Options to pass on to CanvasRenderer
 243  */
 244 DygraphCanvasRenderer = function(dygraph, element, layout, options) {
 245   // TODO(danvk): remove options, just use dygraph.attr_.
 246   this.dygraph_ = dygraph;
 247
 248   // default options
 249   this.options = {
 250     "strokeWidth": 0.5,
 251     "drawXAxis": true,
 252     "drawYAxis": true,
 253     "axisLineColor": "black",
 254     "axisLineWidth": 0.5,
 255     "axisTickSize": 3,
 256     "axisLabelColor": "black",
 257     "axisLabelFont": "Arial",
 258     "axisLabelFontSize": 9,
 259     "axisLabelWidth": 50,
 260     "drawYGrid": true,
 261     "drawXGrid": true,
 262     "gridLineColor": "rgb(128,128,128)",
 263     "fillAlpha": 0.15,
 264     "underlayCallback": null
 265   };
 266   Dygraph.update(this.options, options);
 267
 268   this.layout = layout;
 269   this.element = element;
 270   this.container = this.element.parentNode;
 271
 272   this.height = this.element.height;
 273   this.width = this.element.width;
 274
 275   // --- check whether everything is ok before we return
 276   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
 277       throw "Canvas is not supported.";
 278
 279   // internal state
 280   this.xlabels = new Array();
 281   this.ylabels = new Array();
 282   this.annotations = new Array();
 283
 284   this.area = {
 285     x: this.options.yAxisLabelWidth + 2 * this.options.axisTickSize,
 286     y: 0
 287   };
 288   this.area.w = this.width - this.area.x - this.options.rightGap;
 289   this.area.h = this.height - this.options.axisLabelFontSize -
 290                 2 * this.options.axisTickSize;
 291
 292   this.container.style.position = "relative";
 293   this.container.style.width = this.width + "px";
 294 };
 295
 296 DygraphCanvasRenderer.prototype.clear = function() {
 297   if (this.isIE) {
 298     // VML takes a while to start up, so we just poll every this.IEDelay
 299     try {
 300       if (this.clearDelay) {
 301         this.clearDelay.cancel();
 302         this.clearDelay = null;
 303       }
 304       var context = this.element.getContext("2d");
 305     }
 306     catch (e) {
 307       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 308       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 309       this.clearDelay.addCallback(bind(this.clear, this));
 310       return;
 311     }
 312   }
 313
 314   var context = this.element.getContext("2d");
 315   context.clearRect(0, 0, this.width, this.height);
 316
 317   for (var i = 0; i < this.xlabels.length; i++) {
 318     var el = this.xlabels[i];
 319     el.parentNode.removeChild(el);
 320   }
 321   for (var i = 0; i < this.ylabels.length; i++) {
 322     var el = this.ylabels[i];
 323     el.parentNode.removeChild(el);
 324   }
 325   for (var i = 0; i < this.annotations.length; i++) {
 326     var el = this.annotations[i];
 327     el.parentNode.removeChild(el);
 328   }
 329   this.xlabels = new Array();
 330   this.ylabels = new Array();
 331   this.annotations = new Array();
 332 };
 333
 334
 335 DygraphCanvasRenderer.isSupported = function(canvasName) {
 336   var canvas = null;
 337   try {
 338     if (typeof(canvasName) == 'undefined' || canvasName == null)
 339       canvas = document.createElement("canvas");
 340     else
 341       canvas = canvasName;
 342     var context = canvas.getContext("2d");
 343   }
 344   catch (e) {
 345     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 346     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 347     if ((!ie) || (ie[1] < 6) || (opera))
 348       return false;
 349     return true;
 350   }
 351   return true;
 352 };
 353
 354 /**
 355  * Draw an X/Y grid on top of the existing plot
 356  */
 357 DygraphCanvasRenderer.prototype.render = function() {
 358   // Draw the new X/Y grid
 359   var ctx = this.element.getContext("2d");
 360
 361   if (this.options.underlayCallback) {
 362     this.options.underlayCallback(ctx, this.area, this.layout, this.dygraph_);
 363   }
 364
 365   if (this.options.drawYGrid) {
 366     var ticks = this.layout.yticks;
 367     ctx.save();
 368     ctx.strokeStyle = this.options.gridLineColor;
 369     ctx.lineWidth = this.options.axisLineWidth;
 370     for (var i = 0; i < ticks.length; i++) {
 371       var x = this.area.x;
 372       var y = this.area.y + ticks[i][0] * this.area.h;
 373       ctx.beginPath();
 374       ctx.moveTo(x, y);
 375       ctx.lineTo(x + this.area.w, y);
 376       ctx.closePath();
 377       ctx.stroke();
 378     }
 379   }
 380
 381   if (this.options.drawXGrid) {
 382     var ticks = this.layout.xticks;
 383     ctx.save();
 384     ctx.strokeStyle = this.options.gridLineColor;
 385     ctx.lineWidth = this.options.axisLineWidth;
 386     for (var i=0; i<ticks.length; i++) {
 387       var x = this.area.x + ticks[i][0] * this.area.w;
 388       var y = this.area.y + this.area.h;
 389       ctx.beginPath();
 390       ctx.moveTo(x, y);
 391       ctx.lineTo(x, this.area.y);
 392       ctx.closePath();
 393       ctx.stroke();
 394     }
 395   }
 396
 397   // Do the ordinary rendering, as before
 398   this._renderLineChart();
 399   this._renderAxis();
 400   this._renderAnnotations();
 401 };
 402
 403
 404 DygraphCanvasRenderer.prototype._renderAxis = function() {
 405   if (!this.options.drawXAxis && !this.options.drawYAxis)
 406     return;
 407
 408   var context = this.element.getContext("2d");
 409
 410   var labelStyle = {
 411     "position": "absolute",
 412     "fontSize": this.options.axisLabelFontSize + "px",
 413     "zIndex": 10,
 414     "color": this.options.axisLabelColor,
 415     "width": this.options.axisLabelWidth + "px",
 416     "overflow": "hidden"
 417   };
 418   var makeDiv = function(txt) {
 419     var div = document.createElement("div");
 420     for (var name in labelStyle) {
 421       if (labelStyle.hasOwnProperty(name)) {
 422         div.style[name] = labelStyle[name];
 423       }
 424     }
 425     div.appendChild(document.createTextNode(txt));
 426     return div;
 427   };
 428
 429   // axis lines
 430   context.save();
 431   context.strokeStyle = this.options.axisLineColor;
 432   context.lineWidth = this.options.axisLineWidth;
 433
 434   if (this.options.drawYAxis) {
 435     if (this.layout.yticks && this.layout.yticks.length > 0) {
 436       for (var i = 0; i < this.layout.yticks.length; i++) {
 437         var tick = this.layout.yticks[i];
 438         if (typeof(tick) == "function") return;
 439         var x = this.area.x;
 440         var y = this.area.y + tick[0] * this.area.h;
 441         context.beginPath();
 442         context.moveTo(x, y);
 443         context.lineTo(x - this.options.axisTickSize, y);
 444         context.closePath();
 445         context.stroke();
 446
 447         var label = makeDiv(tick[1]);
 448         var top = (y - this.options.axisLabelFontSize / 2);
 449         if (top < 0) top = 0;
 450
 451         if (top + this.options.axisLabelFontSize + 3 > this.height) {
 452           label.style.bottom = "0px";
 453         } else {
 454           label.style.top = top + "px";
 455         }
 456         label.style.left = "0px";
 457         label.style.textAlign = "right";
 458         label.style.width = this.options.yAxisLabelWidth + "px";
 459         this.container.appendChild(label);
 460         this.ylabels.push(label);
 461       }
 462
 463       // The lowest tick on the y-axis often overlaps with the leftmost
 464       // tick on the x-axis. Shift the bottom tick up a little bit to
 465       // compensate if necessary.
 466       var bottomTick = this.ylabels[0];
 467       var fontSize = this.options.axisLabelFontSize;
 468       var bottom = parseInt(bottomTick.style.top) + fontSize;
 469       if (bottom > this.height - fontSize) {
 470         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 471             fontSize / 2) + "px";
 472       }
 473     }
 474
 475     context.beginPath();
 476     context.moveTo(this.area.x, this.area.y);
 477     context.lineTo(this.area.x, this.area.y + this.area.h);
 478     context.closePath();
 479     context.stroke();
 480   }
 481
 482   if (this.options.drawXAxis) {
 483     if (this.layout.xticks) {
 484       for (var i = 0; i < this.layout.xticks.length; i++) {
 485         var tick = this.layout.xticks[i];
 486         if (typeof(dataset) == "function") return;
 487
 488         var x = this.area.x + tick[0] * this.area.w;
 489         var y = this.area.y + this.area.h;
 490         context.beginPath();
 491         context.moveTo(x, y);
 492         context.lineTo(x, y + this.options.axisTickSize);
 493         context.closePath();
 494         context.stroke();
 495
 496         var label = makeDiv(tick[1]);
 497         label.style.textAlign = "center";
 498         label.style.bottom = "0px";
 499
 500         var left = (x - this.options.axisLabelWidth/2);
 501         if (left + this.options.axisLabelWidth > this.width) {
 502           left = this.width - this.options.xAxisLabelWidth;
 503           label.style.textAlign = "right";
 504         }
 505         if (left < 0) {
 506           left = 0;
 507           label.style.textAlign = "left";
 508         }
 509
 510         label.style.left = left + "px";
 511         label.style.width = this.options.xAxisLabelWidth + "px";
 512         this.container.appendChild(label);
 513         this.xlabels.push(label);
 514       }
 515     }
 516
 517     context.beginPath();
 518     context.moveTo(this.area.x, this.area.y + this.area.h);
 519     context.lineTo(this.area.x + this.area.w, this.area.y + this.area.h);
 520     context.closePath();
 521     context.stroke();
 522   }
 523
 524   context.restore();
 525 };
 526
 527
 528 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 529   var annotationStyle = {
 530     "position": "absolute",
 531     "fontSize": this.options.axisLabelFontSize + "px",
 532     "zIndex": 10,
 533     "overflow": "hidden"
 534   };
 535
 536   var bindEvt = function(eventName, classEventName, p, self) {
 537     return function(e) {
 538       var a = p.annotation;
 539       if (a.hasOwnProperty(eventName)) {
 540         a[eventName](a, p, self.dygraph_, e);
 541       } else if (self.dygraph_.attr_(classEventName)) {
 542         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 543       }
 544     };
 545   }
 546
 547   // Get a list of point with annotations.
 548   var points = this.layout.annotated_points;
 549   for (var i = 0; i < points.length; i++) {
 550     var p = points[i];
 551     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 552       continue;
 553     }
 554
 555     var a = p.annotation;
 556     var tick_height = 6;
 557     if (a.hasOwnProperty("tickHeight")) {
 558       tick_height = a.tickHeight;
 559     }
 560
 561     var div = document.createElement("div");
 562     for (var name in annotationStyle) {
 563       if (annotationStyle.hasOwnProperty(name)) {
 564         div.style[name] = annotationStyle[name];
 565       }
 566     }
 567     if (!a.hasOwnProperty('icon')) {
 568       div.className = "dygraphDefaultAnnotation";
 569     }
 570     if (a.hasOwnProperty('cssClass')) {
 571       div.className += " " + a.cssClass;
 572     }
 573
 574     var width = a.hasOwnProperty('width') ? a.width : 16;
 575     var height = a.hasOwnProperty('height') ? a.height : 16;
 576     if (a.hasOwnProperty('icon')) {
 577       var img = document.createElement("img");
 578       img.src = a.icon;
 579       img.width = width;
 580       img.height = height;
 581       div.appendChild(img);
 582     } else if (p.annotation.hasOwnProperty('shortText')) {
 583       div.appendChild(document.createTextNode(p.annotation.shortText));
 584     }
 585     div.style.left = (p.canvasx - width / 2) + "px";
 586     if (a.attachAtBottom) {
 587       div.style.top = (this.area.h - height - tick_height) + "px";
 588     } else {
 589       div.style.top = (p.canvasy - height - tick_height) + "px";
 590     }
 591     div.style.width = width + "px";
 592     div.style.height = height + "px";
 593     div.title = p.annotation.text;
 594     div.style.color = this.colors[p.name];
 595     div.style.borderColor = this.colors[p.name];
 596     a.div = div;
 597
 598     Dygraph.addEvent(div, 'click',
 599         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 600     Dygraph.addEvent(div, 'mouseover',
 601         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 602     Dygraph.addEvent(div, 'mouseout',
 603         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 604     Dygraph.addEvent(div, 'dblclick',
 605         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 606
 607     this.container.appendChild(div);
 608     this.annotations.push(div);
 609
 610     var ctx = this.element.getContext("2d");
 611     ctx.strokeStyle = this.colors[p.name];
 612     ctx.beginPath();
 613     if (!a.attachAtBottom) {
 614       ctx.moveTo(p.canvasx, p.canvasy);
 615       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 616     } else {
 617       ctx.moveTo(p.canvasx, this.area.h);
 618       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 619     }
 620     ctx.closePath();
 621     ctx.stroke();
 622   }
 623 };
 624
 625
 626 /**
 627  * Overrides the CanvasRenderer method to draw error bars
 628  */
 629 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 630   var context = this.element.getContext("2d");
 631   var colorCount = this.options.colorScheme.length;
 632   var colorScheme = this.options.colorScheme;
 633   var fillAlpha = this.options.fillAlpha;
 634   var errorBars = this.layout.options.errorBars;
 635   var fillGraph = this.layout.options.fillGraph;
 636   var stackedGraph = this.layout.options.stackedGraph;
 637   var stepPlot = this.layout.options.stepPlot;
 638
 639   var setNames = [];
 640   for (var name in this.layout.datasets) {
 641     if (this.layout.datasets.hasOwnProperty(name)) {
 642       setNames.push(name);
 643     }
 644   }
 645   var setCount = setNames.length;
 646
 647   this.colors = {}
 648   for (var i = 0; i < setCount; i++) {
 649     this.colors[setNames[i]] = colorScheme[i % colorCount];
 650   }
 651
 652   // Update Points
 653   // TODO(danvk): here
 654   for (var i = 0; i < this.layout.points.length; i++) {
 655     var point = this.layout.points[i];
 656     point.canvasx = this.area.w * point.x + this.area.x;
 657     point.canvasy = this.area.h * point.y + this.area.y;
 658   }
 659
 660   // create paths
 661   var isOK = function(x) { return x && !isNaN(x); };
 662
 663   var ctx = context;
 664   if (errorBars) {
 665     if (fillGraph) {
 666       this.dygraph_.warn("Can't use fillGraph option with error bars");
 667     }
 668
 669     for (var i = 0; i < setCount; i++) {
 670       var setName = setNames[i];
 671       var color = this.colors[setName];
 672
 673       // setup graphics context
 674       ctx.save();
 675       var prevX = NaN;
 676       var prevY = NaN;
 677       var prevYs = [-1, -1];
 678       var yscale = this.layout.yscale;
 679       // should be same color as the lines but only 15% opaque.
 680       var rgb = new RGBColor(color);
 681       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 682                             fillAlpha + ')';
 683       ctx.fillStyle = err_color;
 684       ctx.beginPath();
 685       for (var j = 0; j < this.layout.points.length; j++) {
 686         var point = this.layout.points[j];
 687         if (point.name == setName) {
 688           if (!isOK(point.y)) {
 689             prevX = NaN;
 690             continue;
 691           }
 692
 693           // TODO(danvk): here
 694           if (stepPlot) {
 695             var newYs = [ prevY - point.errorPlus * yscale,
 696                           prevY + point.errorMinus * yscale ];
 697             prevY = point.y;
 698           } else {
 699             var newYs = [ point.y - point.errorPlus * yscale,
 700                           point.y + point.errorMinus * yscale ];
 701           }
 702           newYs[0] = this.area.h * newYs[0] + this.area.y;
 703           newYs[1] = this.area.h * newYs[1] + this.area.y;
 704           if (!isNaN(prevX)) {
 705             if (stepPlot) {
 706               ctx.moveTo(prevX, newYs[0]);
 707             } else {
 708               ctx.moveTo(prevX, prevYs[0]);
 709             }
 710             ctx.lineTo(point.canvasx, newYs[0]);
 711             ctx.lineTo(point.canvasx, newYs[1]);
 712             if (stepPlot) {
 713               ctx.lineTo(prevX, newYs[1]);
 714             } else {
 715               ctx.lineTo(prevX, prevYs[1]);
 716             }
 717             ctx.closePath();
 718           }
 719           prevYs = newYs;
 720           prevX = point.canvasx;
 721         }
 722       }
 723       ctx.fill();
 724     }
 725   } else if (fillGraph) {
 726     var axisY = 1.0 + this.layout.minyval * this.layout.yscale;
 727     if (axisY < 0.0) axisY = 0.0;
 728     else if (axisY > 1.0) axisY = 1.0;
 729     axisY = this.area.h * axisY + this.area.y;
 730
 731     var baseline = []  // for stacked graphs: baseline for filling
 732
 733     // process sets in reverse order (needed for stacked graphs)
 734     for (var i = setCount - 1; i >= 0; i--) {
 735       var setName = setNames[i];
 736       var color = this.colors[setName];
 737
 738       // setup graphics context
 739       ctx.save();
 740       var prevX = NaN;
 741       var prevYs = [-1, -1];
 742       var yscale = this.layout.yscale;
 743       // should be same color as the lines but only 15% opaque.
 744       var rgb = new RGBColor(color);
 745       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 746                             fillAlpha + ')';
 747       ctx.fillStyle = err_color;
 748       ctx.beginPath();
 749       for (var j = 0; j < this.layout.points.length; j++) {
 750         var point = this.layout.points[j];
 751         if (point.name == setName) {
 752           if (!isOK(point.y)) {
 753             prevX = NaN;
 754             continue;
 755           }
 756           var newYs;
 757           if (stackedGraph) {
 758             lastY = baseline[point.canvasx];
 759             if (lastY === undefined) lastY = axisY;
 760             baseline[point.canvasx] = point.canvasy;
 761             newYs = [ point.canvasy, lastY ];
 762           } else {
 763             newYs = [ point.canvasy, axisY ];
 764           }
 765           if (!isNaN(prevX)) {
 766             ctx.moveTo(prevX, prevYs[0]);
 767             if (stepPlot) {
 768               ctx.lineTo(point.canvasx, prevYs[0]);
 769             } else {
 770               ctx.lineTo(point.canvasx, newYs[0]);
 771             }
 772             ctx.lineTo(point.canvasx, newYs[1]);
 773             ctx.lineTo(prevX, prevYs[1]);
 774             ctx.closePath();
 775           }
 776           prevYs = newYs;
 777           prevX = point.canvasx;
 778         }
 779       }
 780       ctx.fill();
 781     }
 782   }
 783
 784   for (var i = 0; i < setCount; i++) {
 785     var setName = setNames[i];
 786     var color = this.colors[setName];
 787
 788     // setup graphics context
 789     context.save();
 790     var point = this.layout.points[0];
 791     var pointSize = this.dygraph_.attr_("pointSize");
 792     var prevX = null, prevY = null;
 793     var drawPoints = this.dygraph_.attr_("drawPoints");
 794     var points = this.layout.points;
 795     for (var j = 0; j < points.length; j++) {
 796       var point = points[j];
 797       if (point.name == setName) {
 798         if (!isOK(point.canvasy)) {
 799           // this will make us move to the next point, not draw a line to it.
 800           prevX = prevY = null;
 801         } else {
 802           // A point is "isolated" if it is non-null but both the previous
 803           // and next points are null.
 804           var isIsolated = (!prevX && (j == points.length - 1 ||
 805                                        !isOK(points[j+1].canvasy)));
 806
 807           if (!prevX) {
 808             prevX = point.canvasx;
 809             prevY = point.canvasy;
 810           } else {
 811             ctx.beginPath();
 812             ctx.strokeStyle = color;
 813             ctx.lineWidth = this.options.strokeWidth;
 814             ctx.moveTo(prevX, prevY);
 815             if (stepPlot) {
 816               ctx.lineTo(point.canvasx, prevY);
 817             }
 818             prevX = point.canvasx;
 819             prevY = point.canvasy;
 820             ctx.lineTo(prevX, prevY);
 821             ctx.stroke();
 822           }
 823
 824           if (drawPoints || isIsolated) {
 825            ctx.beginPath();
 826            ctx.fillStyle = color;
 827            ctx.arc(point.canvasx, point.canvasy, pointSize,
 828                    0, 2 * Math.PI, false);
 829            ctx.fill();
 830           }
 831         }
 832       }
 833     }
 834   }
 835
 836   context.restore();
 837 };