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