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