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