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