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   this.annotations = [];
  37   var parse = this.attr_('xValueParser');
  38   for (var i = 0; i < ann.length; i++) {
  39     var a = {};
  40     if (!ann[i].xval && !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('width') &&
  46           ann[i].hasOwnProperty('height'))) {
  47       this.dygraph_.error("Must set width and height when setting " +
  48                           "annotation.icon property");
  49       return;
  50     }
  51     Dygraph.update(a, ann[i]);
  52     if (!a.xval) 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       if (series.length > 1) {
  74         var x1 = series[0][0];
  75         if (!this.minxval || x1 < this.minxval) this.minxval = x1;
  76
  77         var x2 = series[series.length - 1][0];
  78         if (!this.maxxval || x2 > this.maxxval) this.maxxval = x2;
  79       }
  80     }
  81   }
  82   this.xrange = this.maxxval - this.minxval;
  83   this.xscale = (this.xrange != 0 ? 1/this.xrange : 1.0);
  84
  85   this.minyval = this.options.yAxis[0];
  86   this.maxyval = this.options.yAxis[1];
  87   this.yrange = this.maxyval - this.minyval;
  88   this.yscale = (this.yrange != 0 ? 1/this.yrange : 1.0);
  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     for (var j = 0; j < dataset.length; j++) {
  99       var item = dataset[j];
 100       var point = {
 101         // TODO(danvk): here
 102         x: ((parseFloat(item[0]) - this.minxval) * this.xscale),
 103         y: 1.0 - ((parseFloat(item[1]) - this.minyval) * this.yscale),
 104         xval: parseFloat(item[0]),
 105         yval: parseFloat(item[1]),
 106         name: setName
 107       };
 108
 109       // limit the x, y values so they do not overdraw
 110       if (point.y <= 0.0) {
 111         point.y = 0.0;
 112       }
 113       if (point.y >= 1.0) {
 114         point.y = 1.0;
 115       }
 116       this.points.push(point);
 117     }
 118   }
 119 };
 120
 121 DygraphLayout.prototype._evaluateLineTicks = function() {
 122   this.xticks = new Array();
 123   for (var i = 0; i < this.options.xTicks.length; i++) {
 124     var tick = this.options.xTicks[i];
 125     var label = tick.label;
 126     var pos = this.xscale * (tick.v - this.minxval);
 127     if ((pos >= 0.0) && (pos <= 1.0)) {
 128       this.xticks.push([pos, label]);
 129     }
 130   }
 131
 132   this.yticks = new Array();
 133   for (var i = 0; i < this.options.yTicks.length; i++) {
 134     var tick = this.options.yTicks[i];
 135     var label = tick.label;
 136     var pos = 1.0 - (this.yscale * (tick.v - this.minyval));
 137     if ((pos >= 0.0) && (pos <= 1.0)) {
 138       this.yticks.push([pos, label]);
 139     }
 140   }
 141 };
 142
 143
 144 /**
 145  * Behaves the same way as PlotKit.Layout, but also copies the errors
 146  * @private
 147  */
 148 DygraphLayout.prototype.evaluateWithError = function() {
 149   this.evaluate();
 150   if (!this.options.errorBars) return;
 151
 152   // Copy over the error terms
 153   var i = 0; // index in this.points
 154   for (var setName in this.datasets) {
 155     if (!this.datasets.hasOwnProperty(setName)) continue;
 156     var j = 0;
 157     var dataset = this.datasets[setName];
 158     for (var j = 0; j < dataset.length; j++, i++) {
 159       var item = dataset[j];
 160       var xv = parseFloat(item[0]);
 161       var yv = parseFloat(item[1]);
 162
 163       if (xv == this.points[i].xval &&
 164           yv == this.points[i].yval) {
 165         this.points[i].errorMinus = parseFloat(item[2]);
 166         this.points[i].errorPlus = parseFloat(item[3]);
 167       }
 168     }
 169   }
 170 };
 171
 172 DygraphLayout.prototype._evaluateAnnotations = function() {
 173   // Add the annotations to the point to which they belong.
 174   // Make a map from (setName, xval) to annotation for quick lookups.
 175   var annotations = {};
 176   for (var i = 0; i < this.annotations.length; i++) {
 177     var a = this.annotations[i];
 178     annotations[a.xval + "," + a.series] = a;
 179   }
 180
 181   this.annotated_points = [];
 182   for (var i = 0; i < this.points.length; i++) {
 183     var p = this.points[i];
 184     var k = p.xval + "," + p.name;
 185     if (k in annotations) {
 186       p.annotation = annotations[k];
 187       this.annotated_points.push(p);
 188     }
 189   }
 190 };
 191
 192 /**
 193  * Convenience function to remove all the data sets from a graph
 194  */
 195 DygraphLayout.prototype.removeAllDatasets = function() {
 196   delete this.datasets;
 197   this.datasets = new Array();
 198 };
 199
 200 /**
 201  * Change the values of various layout options
 202  * @param {Object} new_options an associative array of new properties
 203  */
 204 DygraphLayout.prototype.updateOptions = function(new_options) {
 205   Dygraph.update(this.options, new_options ? new_options : {});
 206 };
 207
 208 /**
 209  * Return a copy of the point at the indicated index, with its yval unstacked.
 210  * @param int index of point in layout_.points
 211  */
 212 DygraphLayout.prototype.unstackPointAtIndex = function(idx) {
 213   var point = this.points[idx];
 214
 215   // Clone the point since we modify it
 216   var unstackedPoint = {};
 217   for (var i in point) {
 218     unstackedPoint[i] = point[i];
 219   }
 220
 221   if (!this.attr_("stackedGraph")) {
 222     return unstackedPoint;
 223   }
 224
 225   // The unstacked yval is equal to the current yval minus the yval of the
 226   // next point at the same xval.
 227   for (var i = idx+1; i < this.points.length; i++) {
 228     if (this.points[i].xval == point.xval) {
 229       unstackedPoint.yval -= this.points[i].yval;
 230       break;
 231     }
 232   }
 233
 234   return unstackedPoint;
 235 }
 236
 237 // Subclass PlotKit.CanvasRenderer to add:
 238 // 1. X/Y grid overlay
 239 // 2. Ability to draw error bars (if required)
 240
 241 /**
 242  * Sets some PlotKit.CanvasRenderer options
 243  * @param {Object} element The canvas to attach to
 244  * @param {Layout} layout The DygraphLayout object for this graph.
 245  * @param {Object} options Options to pass on to CanvasRenderer
 246  */
 247 DygraphCanvasRenderer = function(dygraph, element, layout, options) {
 248   // TODO(danvk): remove options, just use dygraph.attr_.
 249   this.dygraph_ = dygraph;
 250
 251   // default options
 252   this.options = {
 253     "strokeWidth": 0.5,
 254     "drawXAxis": true,
 255     "drawYAxis": true,
 256     "axisLineColor": "black",
 257     "axisLineWidth": 0.5,
 258     "axisTickSize": 3,
 259     "axisLabelColor": "black",
 260     "axisLabelFont": "Arial",
 261     "axisLabelFontSize": 9,
 262     "axisLabelWidth": 50,
 263     "drawYGrid": true,
 264     "drawXGrid": true,
 265     "gridLineColor": "rgb(128,128,128)",
 266     "fillAlpha": 0.15,
 267     "underlayCallback": null
 268   };
 269   Dygraph.update(this.options, options);
 270
 271   this.layout = layout;
 272   this.element = element;
 273   this.container = this.element.parentNode;
 274
 275   this.height = this.element.height;
 276   this.width = this.element.width;
 277
 278   // --- check whether everything is ok before we return
 279   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
 280       throw "Canvas is not supported.";
 281
 282   // internal state
 283   this.xlabels = new Array();
 284   this.ylabels = new Array();
 285   this.annotations = new Array();
 286
 287   this.area = {
 288     x: this.options.yAxisLabelWidth + 2 * this.options.axisTickSize,
 289     y: 0
 290   };
 291   this.area.w = this.width - this.area.x - this.options.rightGap;
 292   this.area.h = this.height - this.options.axisLabelFontSize -
 293                 2 * this.options.axisTickSize;
 294
 295   this.container.style.position = "relative";
 296   this.container.style.width = this.width + "px";
 297 };
 298
 299 DygraphCanvasRenderer.prototype.clear = function() {
 300   if (this.isIE) {
 301     // VML takes a while to start up, so we just poll every this.IEDelay
 302     try {
 303       if (this.clearDelay) {
 304         this.clearDelay.cancel();
 305         this.clearDelay = null;
 306       }
 307       var context = this.element.getContext("2d");
 308     }
 309     catch (e) {
 310       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 311       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 312       this.clearDelay.addCallback(bind(this.clear, this));
 313       return;
 314     }
 315   }
 316
 317   var context = this.element.getContext("2d");
 318   context.clearRect(0, 0, this.width, this.height);
 319
 320   for (var i = 0; i < this.xlabels.length; i++) {
 321     var el = this.xlabels[i];
 322     el.parentNode.removeChild(el);
 323   }
 324   for (var i = 0; i < this.ylabels.length; i++) {
 325     var el = this.ylabels[i];
 326     el.parentNode.removeChild(el);
 327   }
 328   for (var i = 0; i < this.annotations.length; i++) {
 329     var el = this.annotations[i];
 330     el.parentNode.removeChild(el);
 331   }
 332   this.xlabels = new Array();
 333   this.ylabels = new Array();
 334   this.annotations = new Array();
 335 };
 336
 337
 338 DygraphCanvasRenderer.isSupported = function(canvasName) {
 339   var canvas = null;
 340   try {
 341     if (typeof(canvasName) == 'undefined' || canvasName == null)
 342       canvas = document.createElement("canvas");
 343     else
 344       canvas = canvasName;
 345     var context = canvas.getContext("2d");
 346   }
 347   catch (e) {
 348     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 349     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 350     if ((!ie) || (ie[1] < 6) || (opera))
 351       return false;
 352     return true;
 353   }
 354   return true;
 355 };
 356
 357 /**
 358  * Draw an X/Y grid on top of the existing plot
 359  */
 360 DygraphCanvasRenderer.prototype.render = function() {
 361   // Draw the new X/Y grid
 362   var ctx = this.element.getContext("2d");
 363
 364   if (this.options.underlayCallback) {
 365     this.options.underlayCallback(ctx, this.area, this.layout, this.dygraph_);
 366   }
 367
 368   if (this.options.drawYGrid) {
 369     var ticks = this.layout.yticks;
 370     ctx.save();
 371     ctx.strokeStyle = this.options.gridLineColor;
 372     ctx.lineWidth = this.options.axisLineWidth;
 373     for (var i = 0; i < ticks.length; i++) {
 374       var x = this.area.x;
 375       var y = this.area.y + ticks[i][0] * this.area.h;
 376       ctx.beginPath();
 377       ctx.moveTo(x, y);
 378       ctx.lineTo(x + this.area.w, y);
 379       ctx.closePath();
 380       ctx.stroke();
 381     }
 382   }
 383
 384   if (this.options.drawXGrid) {
 385     var ticks = this.layout.xticks;
 386     ctx.save();
 387     ctx.strokeStyle = this.options.gridLineColor;
 388     ctx.lineWidth = this.options.axisLineWidth;
 389     for (var i=0; i<ticks.length; i++) {
 390       var x = this.area.x + ticks[i][0] * this.area.w;
 391       var y = this.area.y + this.area.h;
 392       ctx.beginPath();
 393       ctx.moveTo(x, y);
 394       ctx.lineTo(x, this.area.y);
 395       ctx.closePath();
 396       ctx.stroke();
 397     }
 398   }
 399
 400   // Do the ordinary rendering, as before
 401   this._renderLineChart();
 402   this._renderAxis();
 403   this._renderAnnotations();
 404 };
 405
 406
 407 DygraphCanvasRenderer.prototype._renderAxis = function() {
 408   if (!this.options.drawXAxis && !this.options.drawYAxis)
 409     return;
 410
 411   var context = this.element.getContext("2d");
 412
 413   var labelStyle = {
 414     "position": "absolute",
 415     "fontSize": this.options.axisLabelFontSize + "px",
 416     "zIndex": 10,
 417     "color": this.options.axisLabelColor,
 418     "width": this.options.axisLabelWidth + "px",
 419     "overflow": "hidden"
 420   };
 421   var makeDiv = function(txt) {
 422     var div = document.createElement("div");
 423     for (var name in labelStyle) {
 424       if (labelStyle.hasOwnProperty(name)) {
 425         div.style[name] = labelStyle[name];
 426       }
 427     }
 428     div.appendChild(document.createTextNode(txt));
 429     return div;
 430   };
 431
 432   // axis lines
 433   context.save();
 434   context.strokeStyle = this.options.axisLineColor;
 435   context.lineWidth = this.options.axisLineWidth;
 436
 437   if (this.options.drawYAxis) {
 438     if (this.layout.yticks && this.layout.yticks.length > 0) {
 439       for (var i = 0; i < this.layout.yticks.length; i++) {
 440         var tick = this.layout.yticks[i];
 441         if (typeof(tick) == "function") return;
 442         var x = this.area.x;
 443         var y = this.area.y + tick[0] * this.area.h;
 444         context.beginPath();
 445         context.moveTo(x, y);
 446         context.lineTo(x - this.options.axisTickSize, y);
 447         context.closePath();
 448         context.stroke();
 449
 450         var label = makeDiv(tick[1]);
 451         var top = (y - this.options.axisLabelFontSize / 2);
 452         if (top < 0) top = 0;
 453
 454         if (top + this.options.axisLabelFontSize + 3 > this.height) {
 455           label.style.bottom = "0px";
 456         } else {
 457           label.style.top = top + "px";
 458         }
 459         label.style.left = "0px";
 460         label.style.textAlign = "right";
 461         label.style.width = this.options.yAxisLabelWidth + "px";
 462         this.container.appendChild(label);
 463         this.ylabels.push(label);
 464       }
 465
 466       // The lowest tick on the y-axis often overlaps with the leftmost
 467       // tick on the x-axis. Shift the bottom tick up a little bit to
 468       // compensate if necessary.
 469       var bottomTick = this.ylabels[0];
 470       var fontSize = this.options.axisLabelFontSize;
 471       var bottom = parseInt(bottomTick.style.top) + fontSize;
 472       if (bottom > this.height - fontSize) {
 473         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 474             fontSize / 2) + "px";
 475       }
 476     }
 477
 478     context.beginPath();
 479     context.moveTo(this.area.x, this.area.y);
 480     context.lineTo(this.area.x, this.area.y + this.area.h);
 481     context.closePath();
 482     context.stroke();
 483   }
 484
 485   if (this.options.drawXAxis) {
 486     if (this.layout.xticks) {
 487       for (var i = 0; i < this.layout.xticks.length; i++) {
 488         var tick = this.layout.xticks[i];
 489         if (typeof(dataset) == "function") return;
 490
 491         var x = this.area.x + tick[0] * this.area.w;
 492         var y = this.area.y + this.area.h;
 493         context.beginPath();
 494         context.moveTo(x, y);
 495         context.lineTo(x, y + this.options.axisTickSize);
 496         context.closePath();
 497         context.stroke();
 498
 499         var label = makeDiv(tick[1]);
 500         label.style.textAlign = "center";
 501         label.style.bottom = "0px";
 502
 503         var left = (x - this.options.axisLabelWidth/2);
 504         if (left + this.options.axisLabelWidth > this.width) {
 505           left = this.width - this.options.xAxisLabelWidth;
 506           label.style.textAlign = "right";
 507         }
 508         if (left < 0) {
 509           left = 0;
 510           label.style.textAlign = "left";
 511         }
 512
 513         label.style.left = left + "px";
 514         label.style.width = this.options.xAxisLabelWidth + "px";
 515         this.container.appendChild(label);
 516         this.xlabels.push(label);
 517       }
 518     }
 519
 520     context.beginPath();
 521     context.moveTo(this.area.x, this.area.y + this.area.h);
 522     context.lineTo(this.area.x + this.area.w, this.area.y + this.area.h);
 523     context.closePath();
 524     context.stroke();
 525   }
 526
 527   context.restore();
 528 };
 529
 530
 531 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 532   var annotationStyle = {
 533     "position": "absolute",
 534     "fontSize": this.options.axisLabelFontSize + "px",
 535     "zIndex": 10,
 536     "overflow": "hidden"
 537   };
 538
 539   var bindEvt = function(eventName, classEventName, p, self) {
 540     return function(e) {
 541       var a = p.annotation;
 542       if (a.hasOwnProperty(eventName)) {
 543         a[eventName](a, p, self.dygraph_, e);
 544       } else if (self.dygraph_.attr_(classEventName)) {
 545         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 546       }
 547     };
 548   }
 549
 550   // Get a list of point with annotations.
 551   var points = this.layout.annotated_points;
 552   for (var i = 0; i < points.length; i++) {
 553     var p = points[i];
 554     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 555       continue;
 556     }
 557
 558     var a = p.annotation;
 559     var tick_height = 6;
 560     if (a.hasOwnProperty("tickHeight")) {
 561       tick_height = a.tickHeight;
 562     }
 563
 564     var div = document.createElement("div");
 565     for (var name in annotationStyle) {
 566       if (annotationStyle.hasOwnProperty(name)) {
 567         div.style[name] = annotationStyle[name];
 568       }
 569     }
 570     if (!a.hasOwnProperty('icon')) {
 571       div.className = "dygraphDefaultAnnotation";
 572     }
 573     if (a.hasOwnProperty('cssClass')) {
 574       div.className += " " + a.cssClass;
 575     }
 576
 577     var width = a.hasOwnProperty('width') ? a.width : 16;
 578     var height = a.hasOwnProperty('height') ? a.height : 16;
 579     if (a.hasOwnProperty('icon')) {
 580       var img = document.createElement("img");
 581       img.src = a.icon;
 582       img.width = width;
 583       img.height = height;
 584       div.appendChild(img);
 585     } else if (p.annotation.hasOwnProperty('shortText')) {
 586       div.appendChild(document.createTextNode(p.annotation.shortText));
 587     }
 588     div.style.left = (p.canvasx - width / 2) + "px";
 589     if (a.attachAtBottom) {
 590       div.style.top = (this.area.h - height - tick_height) + "px";
 591     } else {
 592       div.style.top = (p.canvasy - height - tick_height) + "px";
 593     }
 594     div.style.width = width + "px";
 595     div.style.height = height + "px";
 596     div.title = p.annotation.text;
 597     div.style.color = this.colors[p.name];
 598     div.style.borderColor = this.colors[p.name];
 599     a.div = div;
 600
 601     Dygraph.addEvent(div, 'click',
 602         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 603     Dygraph.addEvent(div, 'mouseover',
 604         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 605     Dygraph.addEvent(div, 'mouseout',
 606         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 607     Dygraph.addEvent(div, 'dblclick',
 608         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 609
 610     this.container.appendChild(div);
 611     this.annotations.push(div);
 612
 613     var ctx = this.element.getContext("2d");
 614     ctx.strokeStyle = this.colors[p.name];
 615     ctx.beginPath();
 616     if (!a.attachAtBottom) {
 617       ctx.moveTo(p.canvasx, p.canvasy);
 618       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 619     } else {
 620       ctx.moveTo(p.canvasx, this.area.h);
 621       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 622     }
 623     ctx.closePath();
 624     ctx.stroke();
 625   }
 626 };
 627
 628
 629 /**
 630  * Overrides the CanvasRenderer method to draw error bars
 631  */
 632 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 633   var context = this.element.getContext("2d");
 634   var colorCount = this.options.colorScheme.length;
 635   var colorScheme = this.options.colorScheme;
 636   var fillAlpha = this.options.fillAlpha;
 637   var errorBars = this.layout.options.errorBars;
 638   var fillGraph = this.layout.options.fillGraph;
 639   var stackedGraph = this.layout.options.stackedGraph;
 640   var stepPlot = this.layout.options.stepPlot;
 641
 642   var setNames = [];
 643   for (var name in this.layout.datasets) {
 644     if (this.layout.datasets.hasOwnProperty(name)) {
 645       setNames.push(name);
 646     }
 647   }
 648   var setCount = setNames.length;
 649
 650   this.colors = {}
 651   for (var i = 0; i < setCount; i++) {
 652     this.colors[setNames[i]] = colorScheme[i % colorCount];
 653   }
 654
 655   // Update Points
 656   // TODO(danvk): here
 657   for (var i = 0; i < this.layout.points.length; i++) {
 658     var point = this.layout.points[i];
 659     point.canvasx = this.area.w * point.x + this.area.x;
 660     point.canvasy = this.area.h * point.y + this.area.y;
 661   }
 662
 663   // create paths
 664   var isOK = function(x) { return x && !isNaN(x); };
 665
 666   var ctx = context;
 667   if (errorBars) {
 668     if (fillGraph) {
 669       this.dygraph_.warn("Can't use fillGraph option with error bars");
 670     }
 671
 672     for (var i = 0; i < setCount; i++) {
 673       var setName = setNames[i];
 674       var color = this.colors[setName];
 675
 676       // setup graphics context
 677       ctx.save();
 678       var prevX = NaN;
 679       var prevY = NaN;
 680       var prevYs = [-1, -1];
 681       var yscale = this.layout.yscale;
 682       // should be same color as the lines but only 15% opaque.
 683       var rgb = new RGBColor(color);
 684       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 685                             fillAlpha + ')';
 686       ctx.fillStyle = err_color;
 687       ctx.beginPath();
 688       for (var j = 0; j < this.layout.points.length; j++) {
 689         var point = this.layout.points[j];
 690         if (point.name == setName) {
 691           if (!isOK(point.y)) {
 692             prevX = NaN;
 693             continue;
 694           }
 695
 696           // TODO(danvk): here
 697           if (stepPlot) {
 698             var newYs = [ prevY - point.errorPlus * yscale,
 699                           prevY + point.errorMinus * yscale ];
 700             prevY = point.y;
 701           } else {
 702             var newYs = [ point.y - point.errorPlus * yscale,
 703                           point.y + point.errorMinus * yscale ];
 704           }
 705           newYs[0] = this.area.h * newYs[0] + this.area.y;
 706           newYs[1] = this.area.h * newYs[1] + this.area.y;
 707           if (!isNaN(prevX)) {
 708             if (stepPlot) {
 709               ctx.moveTo(prevX, newYs[0]);
 710             } else {
 711               ctx.moveTo(prevX, prevYs[0]);
 712             }
 713             ctx.lineTo(point.canvasx, newYs[0]);
 714             ctx.lineTo(point.canvasx, newYs[1]);
 715             if (stepPlot) {
 716               ctx.lineTo(prevX, newYs[1]);
 717             } else {
 718               ctx.lineTo(prevX, prevYs[1]);
 719             }
 720             ctx.closePath();
 721           }
 722           prevYs = newYs;
 723           prevX = point.canvasx;
 724         }
 725       }
 726       ctx.fill();
 727     }
 728   } else if (fillGraph) {
 729     var axisY = 1.0 + this.layout.minyval * this.layout.yscale;
 730     if (axisY < 0.0) axisY = 0.0;
 731     else if (axisY > 1.0) axisY = 1.0;
 732     axisY = this.area.h * axisY + this.area.y;
 733
 734     var baseline = []  // for stacked graphs: baseline for filling
 735
 736     // process sets in reverse order (needed for stacked graphs)
 737     for (var i = setCount - 1; i >= 0; i--) {
 738       var setName = setNames[i];
 739       var color = this.colors[setName];
 740
 741       // setup graphics context
 742       ctx.save();
 743       var prevX = NaN;
 744       var prevYs = [-1, -1];
 745       var yscale = this.layout.yscale;
 746       // should be same color as the lines but only 15% opaque.
 747       var rgb = new RGBColor(color);
 748       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 749                             fillAlpha + ')';
 750       ctx.fillStyle = err_color;
 751       ctx.beginPath();
 752       for (var j = 0; j < this.layout.points.length; j++) {
 753         var point = this.layout.points[j];
 754         if (point.name == setName) {
 755           if (!isOK(point.y)) {
 756             prevX = NaN;
 757             continue;
 758           }
 759           var newYs;
 760           if (stackedGraph) {
 761             lastY = baseline[point.canvasx];
 762             if (lastY === undefined) lastY = axisY;
 763             baseline[point.canvasx] = point.canvasy;
 764             newYs = [ point.canvasy, lastY ];
 765           } else {
 766             newYs = [ point.canvasy, axisY ];
 767           }
 768           if (!isNaN(prevX)) {
 769             ctx.moveTo(prevX, prevYs[0]);
 770             if (stepPlot) {
 771               ctx.lineTo(point.canvasx, prevYs[0]);
 772             } else {
 773               ctx.lineTo(point.canvasx, newYs[0]);
 774             }
 775             ctx.lineTo(point.canvasx, newYs[1]);
 776             ctx.lineTo(prevX, prevYs[1]);
 777             ctx.closePath();
 778           }
 779           prevYs = newYs;
 780           prevX = point.canvasx;
 781         }
 782       }
 783       ctx.fill();
 784     }
 785   }
 786
 787   for (var i = 0; i < setCount; i++) {
 788     var setName = setNames[i];
 789     var color = this.colors[setName];
 790     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 791
 792     // setup graphics context
 793     context.save();
 794     var point = this.layout.points[0];
 795     var pointSize = this.dygraph_.attr_("pointSize", setName);
 796     var prevX = null, prevY = null;
 797     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 798     var points = this.layout.points;
 799     for (var j = 0; j < points.length; j++) {
 800       var point = points[j];
 801       if (point.name == setName) {
 802         if (!isOK(point.canvasy)) {
 803           if (stepPlot && prevX != null) {
 804             // Draw a horizontal line to the start of the missing data
 805             ctx.beginPath();
 806             ctx.strokeStyle = color;
 807             ctx.lineWidth = this.options.strokeWidth;
 808             ctx.moveTo(prevX, prevY);
 809             ctx.lineTo(point.canvasx, prevY);
 810             ctx.stroke();
 811           }
 812           // this will make us move to the next point, not draw a line to it.
 813           prevX = prevY = null;
 814         } else {
 815           // A point is "isolated" if it is non-null but both the previous
 816           // and next points are null.
 817           var isIsolated = (!prevX && (j == points.length - 1 ||
 818                                        !isOK(points[j+1].canvasy)));
 819
 820           if (!prevX) {
 821             prevX = point.canvasx;
 822             prevY = point.canvasy;
 823           } else {
 824             // TODO(danvk): figure out why this conditional is necessary.
 825             if (strokeWidth) {
 826               ctx.beginPath();
 827               ctx.strokeStyle = color;
 828               ctx.lineWidth = strokeWidth;
 829               ctx.moveTo(prevX, prevY);
 830               if (stepPlot) {
 831                 ctx.lineTo(point.canvasx, prevY);
 832               }
 833               prevX = point.canvasx;
 834               prevY = point.canvasy;
 835               ctx.lineTo(prevX, prevY);
 836               ctx.stroke();
 837             }
 838           }
 839
 840           if (drawPoints || isIsolated) {
 841            ctx.beginPath();
 842            ctx.fillStyle = color;
 843            ctx.arc(point.canvasx, point.canvasy, pointSize,
 844                    0, 2 * Math.PI, false);
 845            ctx.fill();
 846           }
 847         }
 848       }
 849     }
 850   }
 851
 852   context.restore();
 853 };