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   for (var i = 0; i < this.options.yAxes.length; i++) {
  86     var axis = this.options.yAxes[i];
  87     axis.minyval = axis.valueRange[0];
  88     axis.maxyval = axis.valueRange[1];
  89     axis.yrange = axis.maxyval - axis.minyval;
  90     axis.yscale = (axis.yrange != 0 ? 1.0 / axis.yrange : 1.0);
  91   }
  92 };
  93
  94 DygraphLayout.prototype._evaluateLineCharts = function() {
  95   // add all the rects
  96   this.points = new Array();
  97   for (var setName in this.datasets) {
  98     if (!this.datasets.hasOwnProperty(setName)) continue;
  99
 100     var dataset = this.datasets[setName];
 101     var axis = this.options.yAxes[this.options.seriesToAxisMap[setName]];
 102
 103     for (var j = 0; j < dataset.length; j++) {
 104       var item = dataset[j];
 105       var point = {
 106         // TODO(danvk): here
 107         x: ((parseFloat(item[0]) - this.minxval) * this.xscale),
 108         y: 1.0 - ((parseFloat(item[1]) - axis.minyval) * axis.yscale),
 109         xval: parseFloat(item[0]),
 110         yval: parseFloat(item[1]),
 111         name: setName
 112       };
 113
 114       // limit the x, y values so they do not overdraw
 115       if (point.y <= 0.0) {
 116         point.y = 0.0;
 117       }
 118       if (point.y >= 1.0) {
 119         point.y = 1.0;
 120       }
 121       this.points.push(point);
 122     }
 123   }
 124 };
 125
 126 DygraphLayout.prototype._evaluateLineTicks = function() {
 127   this.xticks = new Array();
 128   for (var i = 0; i < this.options.xTicks.length; i++) {
 129     var tick = this.options.xTicks[i];
 130     var label = tick.label;
 131     var pos = this.xscale * (tick.v - this.minxval);
 132     if ((pos >= 0.0) && (pos <= 1.0)) {
 133       this.xticks.push([pos, label]);
 134     }
 135   }
 136
 137   this.yticks = new Array();
 138   for (var i = 0; i < this.options.yAxes.length; i++ ) {
 139     var axis = this.options.yAxes[i];
 140     for (var j = 0; j < axis.ticks.length; j++) {
 141       var tick = axis.ticks[j];
 142       var label = tick.label;
 143       var pos = 1.0 - (axis.yscale * (tick.v - axis.minyval));
 144       if ((pos >= 0.0) && (pos <= 1.0)) {
 145         this.yticks.push([i, pos, label]);
 146       }
 147     }
 148   }
 149 };
 150
 151
 152 /**
 153  * Behaves the same way as PlotKit.Layout, but also copies the errors
 154  * @private
 155  */
 156 DygraphLayout.prototype.evaluateWithError = function() {
 157   this.evaluate();
 158   if (!this.options.errorBars) return;
 159
 160   // Copy over the error terms
 161   var i = 0; // index in this.points
 162   for (var setName in this.datasets) {
 163     if (!this.datasets.hasOwnProperty(setName)) continue;
 164     var j = 0;
 165     var dataset = this.datasets[setName];
 166     for (var j = 0; j < dataset.length; j++, i++) {
 167       var item = dataset[j];
 168       var xv = parseFloat(item[0]);
 169       var yv = parseFloat(item[1]);
 170
 171       if (xv == this.points[i].xval &&
 172           yv == this.points[i].yval) {
 173         this.points[i].errorMinus = parseFloat(item[2]);
 174         this.points[i].errorPlus = parseFloat(item[3]);
 175       }
 176     }
 177   }
 178 };
 179
 180 DygraphLayout.prototype._evaluateAnnotations = function() {
 181   // Add the annotations to the point to which they belong.
 182   // Make a map from (setName, xval) to annotation for quick lookups.
 183   var annotations = {};
 184   for (var i = 0; i < this.annotations.length; i++) {
 185     var a = this.annotations[i];
 186     annotations[a.xval + "," + a.series] = a;
 187   }
 188
 189   this.annotated_points = [];
 190   for (var i = 0; i < this.points.length; i++) {
 191     var p = this.points[i];
 192     var k = p.xval + "," + p.name;
 193     if (k in annotations) {
 194       p.annotation = annotations[k];
 195       this.annotated_points.push(p);
 196     }
 197   }
 198 };
 199
 200 /**
 201  * Convenience function to remove all the data sets from a graph
 202  */
 203 DygraphLayout.prototype.removeAllDatasets = function() {
 204   delete this.datasets;
 205   this.datasets = new Array();
 206 };
 207
 208 /**
 209  * Change the values of various layout options
 210  * @param {Object} new_options an associative array of new properties
 211  */
 212 DygraphLayout.prototype.updateOptions = function(new_options) {
 213   Dygraph.update(this.options, new_options ? new_options : {});
 214 };
 215
 216 /**
 217  * Return a copy of the point at the indicated index, with its yval unstacked.
 218  * @param int index of point in layout_.points
 219  */
 220 DygraphLayout.prototype.unstackPointAtIndex = function(idx) {
 221   var point = this.points[idx];
 222
 223   // Clone the point since we modify it
 224   var unstackedPoint = {};
 225   for (var i in point) {
 226     unstackedPoint[i] = point[i];
 227   }
 228
 229   if (!this.attr_("stackedGraph")) {
 230     return unstackedPoint;
 231   }
 232
 233   // The unstacked yval is equal to the current yval minus the yval of the
 234   // next point at the same xval.
 235   for (var i = idx+1; i < this.points.length; i++) {
 236     if (this.points[i].xval == point.xval) {
 237       unstackedPoint.yval -= this.points[i].yval;
 238       break;
 239     }
 240   }
 241
 242   return unstackedPoint;
 243 }
 244
 245 // Subclass PlotKit.CanvasRenderer to add:
 246 // 1. X/Y grid overlay
 247 // 2. Ability to draw error bars (if required)
 248
 249 /**
 250  * Sets some PlotKit.CanvasRenderer options
 251  * @param {Object} element The canvas to attach to
 252  * @param {Layout} layout The DygraphLayout object for this graph.
 253  * @param {Object} options Options to pass on to CanvasRenderer
 254  */
 255 DygraphCanvasRenderer = function(dygraph, element, layout, options) {
 256   // TODO(danvk): remove options, just use dygraph.attr_.
 257   this.dygraph_ = dygraph;
 258
 259   // default options
 260   this.options = {
 261     "strokeWidth": 0.5,
 262     "drawXAxis": true,
 263     "drawYAxis": true,
 264     "axisLineColor": "black",
 265     "axisLineWidth": 0.5,
 266     "axisTickSize": 3,
 267     "axisLabelColor": "black",
 268     "axisLabelFont": "Arial",
 269     "axisLabelFontSize": 9,
 270     "axisLabelWidth": 50,
 271     "drawYGrid": true,
 272     "drawXGrid": true,
 273     "gridLineColor": "rgb(128,128,128)",
 274     "fillAlpha": 0.15,
 275     "underlayCallback": null
 276   };
 277   Dygraph.update(this.options, options);
 278
 279   this.layout = layout;
 280   this.element = element;
 281   this.container = this.element.parentNode;
 282
 283   this.height = this.element.height;
 284   this.width = this.element.width;
 285
 286   // --- check whether everything is ok before we return
 287   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
 288       throw "Canvas is not supported.";
 289
 290   // internal state
 291   this.xlabels = new Array();
 292   this.ylabels = new Array();
 293   this.annotations = new Array();
 294
 295   // TODO(danvk): consider all axes in this computation.
 296   this.area = {
 297     // TODO(danvk): per-axis setting.
 298     x: this.options.yAxisLabelWidth + 2 * this.options.axisTickSize,
 299     y: 0
 300   };
 301   this.area.w = this.width - this.area.x - this.options.rightGap;
 302   this.area.h = this.height - this.options.axisLabelFontSize -
 303                 2 * this.options.axisTickSize;
 304
 305   this.container.style.position = "relative";
 306   this.container.style.width = this.width + "px";
 307 };
 308
 309 DygraphCanvasRenderer.prototype.clear = function() {
 310   if (this.isIE) {
 311     // VML takes a while to start up, so we just poll every this.IEDelay
 312     try {
 313       if (this.clearDelay) {
 314         this.clearDelay.cancel();
 315         this.clearDelay = null;
 316       }
 317       var context = this.element.getContext("2d");
 318     }
 319     catch (e) {
 320       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 321       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 322       this.clearDelay.addCallback(bind(this.clear, this));
 323       return;
 324     }
 325   }
 326
 327   var context = this.element.getContext("2d");
 328   context.clearRect(0, 0, this.width, this.height);
 329
 330   for (var i = 0; i < this.xlabels.length; i++) {
 331     var el = this.xlabels[i];
 332     el.parentNode.removeChild(el);
 333   }
 334   for (var i = 0; i < this.ylabels.length; i++) {
 335     var el = this.ylabels[i];
 336     el.parentNode.removeChild(el);
 337   }
 338   for (var i = 0; i < this.annotations.length; i++) {
 339     var el = this.annotations[i];
 340     el.parentNode.removeChild(el);
 341   }
 342   this.xlabels = new Array();
 343   this.ylabels = new Array();
 344   this.annotations = new Array();
 345 };
 346
 347
 348 DygraphCanvasRenderer.isSupported = function(canvasName) {
 349   var canvas = null;
 350   try {
 351     if (typeof(canvasName) == 'undefined' || canvasName == null)
 352       canvas = document.createElement("canvas");
 353     else
 354       canvas = canvasName;
 355     var context = canvas.getContext("2d");
 356   }
 357   catch (e) {
 358     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 359     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 360     if ((!ie) || (ie[1] < 6) || (opera))
 361       return false;
 362     return true;
 363   }
 364   return true;
 365 };
 366
 367 /**
 368  * Draw an X/Y grid on top of the existing plot
 369  */
 370 DygraphCanvasRenderer.prototype.render = function() {
 371   // Shrink the drawing area to accomodate additional y-axes.
 372   if (this.layout.options.yAxes.length == 2) {
 373     // TODO(danvk): per-axis setting.
 374     this.area.w -= (this.options.yAxisLabelWidth + 2 * this.options.axisTickSize);
 375   } else if (this.layout.options.yAxes.length > 2) {
 376     this.dygraph_.error("Only two y-axes are supported at this time. (Trying " +
 377                         "to use " + this.layout.yAxes.length + ")");
 378   }
 379
 380   // Draw the new X/Y grid
 381   var ctx = this.element.getContext("2d");
 382
 383   if (this.options.underlayCallback) {
 384     this.options.underlayCallback(ctx, this.area, this.layout, this.dygraph_);
 385   }
 386
 387   if (this.options.drawYGrid) {
 388     var ticks = this.layout.yticks;
 389     ctx.save();
 390     ctx.strokeStyle = this.options.gridLineColor;
 391     ctx.lineWidth = this.options.axisLineWidth;
 392     for (var i = 0; i < ticks.length; i++) {
 393       if (ticks[i][0] != 0) continue;  // TODO(danvk): per-axis property
 394       var x = this.area.x;
 395       var y = this.area.y + ticks[i][1] * this.area.h;
 396       ctx.beginPath();
 397       ctx.moveTo(x, y);
 398       ctx.lineTo(x + this.area.w, y);
 399       ctx.closePath();
 400       ctx.stroke();
 401     }
 402   }
 403
 404   if (this.options.drawXGrid) {
 405     var ticks = this.layout.xticks;
 406     ctx.save();
 407     ctx.strokeStyle = this.options.gridLineColor;
 408     ctx.lineWidth = this.options.axisLineWidth;
 409     for (var i=0; i<ticks.length; i++) {
 410       var x = this.area.x + ticks[i][1] * this.area.w;
 411       var y = this.area.y + this.area.h;
 412       ctx.beginPath();
 413       ctx.moveTo(x, y);
 414       ctx.lineTo(x, this.area.y);
 415       ctx.closePath();
 416       ctx.stroke();
 417     }
 418   }
 419
 420   // Do the ordinary rendering, as before
 421   this._renderLineChart();
 422   this._renderAxis();
 423   this._renderAnnotations();
 424 };
 425
 426
 427 DygraphCanvasRenderer.prototype._renderAxis = function() {
 428   if (!this.options.drawXAxis && !this.options.drawYAxis)
 429     return;
 430
 431   var context = this.element.getContext("2d");
 432
 433   var labelStyle = {
 434     "position": "absolute",
 435     "fontSize": this.options.axisLabelFontSize + "px",
 436     "zIndex": 10,
 437     "color": this.options.axisLabelColor,
 438     "width": this.options.axisLabelWidth + "px",
 439     "overflow": "hidden"
 440   };
 441   var makeDiv = function(txt) {
 442     var div = document.createElement("div");
 443     for (var name in labelStyle) {
 444       if (labelStyle.hasOwnProperty(name)) {
 445         div.style[name] = labelStyle[name];
 446       }
 447     }
 448     div.appendChild(document.createTextNode(txt));
 449     return div;
 450   };
 451
 452   // axis lines
 453   context.save();
 454   context.strokeStyle = this.options.axisLineColor;
 455   context.lineWidth = this.options.axisLineWidth;
 456
 457   if (this.options.drawYAxis) {
 458     if (this.layout.yticks && this.layout.yticks.length > 0) {
 459       for (var i = 0; i < this.layout.yticks.length; i++) {
 460         var tick = this.layout.yticks[i];
 461         if (typeof(tick) == "function") return;
 462         var x = this.area.x;
 463         if (tick[0] == 1) {
 464           x = this.area.x + this.area.w - labelStyle.width;
 465         }
 466         var y = this.area.y + tick[1] * this.area.h;
 467         context.beginPath();
 468         context.moveTo(x, y);
 469         context.lineTo(x - this.options.axisTickSize, y);
 470         context.closePath();
 471         context.stroke();
 472
 473         var label = makeDiv(tick[2]);
 474         var top = (y - this.options.axisLabelFontSize / 2);
 475         if (top < 0) top = 0;
 476
 477         if (top + this.options.axisLabelFontSize + 3 > this.height) {
 478           label.style.bottom = "0px";
 479         } else {
 480           label.style.top = top + "px";
 481         }
 482         if (tick[0] == 0) {
 483           label.style.left = "0px";
 484           label.style.textAlign = "right";
 485         } else if (tick[0] == 1) {
 486           label.style.left = (this.area.x + this.area.w +
 487                               this.options.axisTickSize) + "px";
 488           label.style.textAlign = "left";
 489         }
 490         label.style.width = this.options.yAxisLabelWidth + "px";
 491         this.container.appendChild(label);
 492         this.ylabels.push(label);
 493       }
 494
 495       // The lowest tick on the y-axis often overlaps with the leftmost
 496       // tick on the x-axis. Shift the bottom tick up a little bit to
 497       // compensate if necessary.
 498       var bottomTick = this.ylabels[0];
 499       var fontSize = this.options.axisLabelFontSize;
 500       var bottom = parseInt(bottomTick.style.top) + fontSize;
 501       if (bottom > this.height - fontSize) {
 502         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 503             fontSize / 2) + "px";
 504       }
 505     }
 506
 507     context.beginPath();
 508     context.moveTo(this.area.x, this.area.y);
 509     context.lineTo(this.area.x, this.area.y + this.area.h);
 510     context.closePath();
 511     context.stroke();
 512   }
 513
 514   if (this.options.drawXAxis) {
 515     if (this.layout.xticks) {
 516       for (var i = 0; i < this.layout.xticks.length; i++) {
 517         var tick = this.layout.xticks[i];
 518         if (typeof(dataset) == "function") return;
 519
 520         var x = this.area.x + tick[0] * this.area.w;
 521         var y = this.area.y + this.area.h;
 522         context.beginPath();
 523         context.moveTo(x, y);
 524         context.lineTo(x, y + this.options.axisTickSize);
 525         context.closePath();
 526         context.stroke();
 527
 528         var label = makeDiv(tick[1]);
 529         label.style.textAlign = "center";
 530         label.style.bottom = "0px";
 531
 532         var left = (x - this.options.axisLabelWidth/2);
 533         if (left + this.options.axisLabelWidth > this.width) {
 534           left = this.width - this.options.xAxisLabelWidth;
 535           label.style.textAlign = "right";
 536         }
 537         if (left < 0) {
 538           left = 0;
 539           label.style.textAlign = "left";
 540         }
 541
 542         label.style.left = left + "px";
 543         label.style.width = this.options.xAxisLabelWidth + "px";
 544         this.container.appendChild(label);
 545         this.xlabels.push(label);
 546       }
 547     }
 548
 549     context.beginPath();
 550     context.moveTo(this.area.x, this.area.y + this.area.h);
 551     context.lineTo(this.area.x + this.area.w, this.area.y + this.area.h);
 552     context.closePath();
 553     context.stroke();
 554   }
 555
 556   context.restore();
 557 };
 558
 559
 560 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 561   var annotationStyle = {
 562     "position": "absolute",
 563     "fontSize": this.options.axisLabelFontSize + "px",
 564     "zIndex": 10,
 565     "overflow": "hidden"
 566   };
 567
 568   var bindEvt = function(eventName, classEventName, p, self) {
 569     return function(e) {
 570       var a = p.annotation;
 571       if (a.hasOwnProperty(eventName)) {
 572         a[eventName](a, p, self.dygraph_, e);
 573       } else if (self.dygraph_.attr_(classEventName)) {
 574         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 575       }
 576     };
 577   }
 578
 579   // Get a list of point with annotations.
 580   var points = this.layout.annotated_points;
 581   for (var i = 0; i < points.length; i++) {
 582     var p = points[i];
 583     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 584       continue;
 585     }
 586
 587     var a = p.annotation;
 588     var tick_height = 6;
 589     if (a.hasOwnProperty("tickHeight")) {
 590       tick_height = a.tickHeight;
 591     }
 592
 593     var div = document.createElement("div");
 594     for (var name in annotationStyle) {
 595       if (annotationStyle.hasOwnProperty(name)) {
 596         div.style[name] = annotationStyle[name];
 597       }
 598     }
 599     if (!a.hasOwnProperty('icon')) {
 600       div.className = "dygraphDefaultAnnotation";
 601     }
 602     if (a.hasOwnProperty('cssClass')) {
 603       div.className += " " + a.cssClass;
 604     }
 605
 606     var width = a.hasOwnProperty('width') ? a.width : 16;
 607     var height = a.hasOwnProperty('height') ? a.height : 16;
 608     if (a.hasOwnProperty('icon')) {
 609       var img = document.createElement("img");
 610       img.src = a.icon;
 611       img.width = width;
 612       img.height = height;
 613       div.appendChild(img);
 614     } else if (p.annotation.hasOwnProperty('shortText')) {
 615       div.appendChild(document.createTextNode(p.annotation.shortText));
 616     }
 617     div.style.left = (p.canvasx - width / 2) + "px";
 618     if (a.attachAtBottom) {
 619       div.style.top = (this.area.h - height - tick_height) + "px";
 620     } else {
 621       div.style.top = (p.canvasy - height - tick_height) + "px";
 622     }
 623     div.style.width = width + "px";
 624     div.style.height = height + "px";
 625     div.title = p.annotation.text;
 626     div.style.color = this.colors[p.name];
 627     div.style.borderColor = this.colors[p.name];
 628     a.div = div;
 629
 630     Dygraph.addEvent(div, 'click',
 631         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 632     Dygraph.addEvent(div, 'mouseover',
 633         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 634     Dygraph.addEvent(div, 'mouseout',
 635         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 636     Dygraph.addEvent(div, 'dblclick',
 637         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 638
 639     this.container.appendChild(div);
 640     this.annotations.push(div);
 641
 642     var ctx = this.element.getContext("2d");
 643     ctx.strokeStyle = this.colors[p.name];
 644     ctx.beginPath();
 645     if (!a.attachAtBottom) {
 646       ctx.moveTo(p.canvasx, p.canvasy);
 647       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 648     } else {
 649       ctx.moveTo(p.canvasx, this.area.h);
 650       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 651     }
 652     ctx.closePath();
 653     ctx.stroke();
 654   }
 655 };
 656
 657
 658 /**
 659  * Overrides the CanvasRenderer method to draw error bars
 660  */
 661 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 662   var context = this.element.getContext("2d");
 663   var colorCount = this.options.colorScheme.length;
 664   var colorScheme = this.options.colorScheme;
 665   var fillAlpha = this.options.fillAlpha;
 666   var errorBars = this.layout.options.errorBars;
 667   var fillGraph = this.layout.options.fillGraph;
 668   var stackedGraph = this.layout.options.stackedGraph;
 669   var stepPlot = this.layout.options.stepPlot;
 670
 671   var setNames = [];
 672   for (var name in this.layout.datasets) {
 673     if (this.layout.datasets.hasOwnProperty(name)) {
 674       setNames.push(name);
 675     }
 676   }
 677   var setCount = setNames.length;
 678
 679   this.colors = {}
 680   for (var i = 0; i < setCount; i++) {
 681     this.colors[setNames[i]] = colorScheme[i % colorCount];
 682   }
 683
 684   // Update Points
 685   // TODO(danvk): here
 686   for (var i = 0; i < this.layout.points.length; i++) {
 687     var point = this.layout.points[i];
 688     point.canvasx = this.area.w * point.x + this.area.x;
 689     point.canvasy = this.area.h * point.y + this.area.y;
 690   }
 691
 692   // create paths
 693   var isOK = function(x) { return x && !isNaN(x); };
 694
 695   var ctx = context;
 696   if (errorBars) {
 697     if (fillGraph) {
 698       this.dygraph_.warn("Can't use fillGraph option with error bars");
 699     }
 700
 701     for (var i = 0; i < setCount; i++) {
 702       var setName = setNames[i];
 703       var axis = this.layout.options.yAxes[
 704         this.layout.options.seriesToAxisMap[setName]];
 705       var color = this.colors[setName];
 706
 707       // setup graphics context
 708       ctx.save();
 709       var prevX = NaN;
 710       var prevY = NaN;
 711       var prevYs = [-1, -1];
 712       var yscale = axis.yscale;
 713       // should be same color as the lines but only 15% opaque.
 714       var rgb = new RGBColor(color);
 715       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 716                             fillAlpha + ')';
 717       ctx.fillStyle = err_color;
 718       ctx.beginPath();
 719       for (var j = 0; j < this.layout.points.length; j++) {
 720         var point = this.layout.points[j];
 721         if (point.name == setName) {
 722           if (!isOK(point.y)) {
 723             prevX = NaN;
 724             continue;
 725           }
 726
 727           // TODO(danvk): here
 728           if (stepPlot) {
 729             var newYs = [ prevY - point.errorPlus * yscale,
 730                           prevY + point.errorMinus * yscale ];
 731             prevY = point.y;
 732           } else {
 733             var newYs = [ point.y - point.errorPlus * yscale,
 734                           point.y + point.errorMinus * yscale ];
 735           }
 736           newYs[0] = this.area.h * newYs[0] + this.area.y;
 737           newYs[1] = this.area.h * newYs[1] + this.area.y;
 738           if (!isNaN(prevX)) {
 739             if (stepPlot) {
 740               ctx.moveTo(prevX, newYs[0]);
 741             } else {
 742               ctx.moveTo(prevX, prevYs[0]);
 743             }
 744             ctx.lineTo(point.canvasx, newYs[0]);
 745             ctx.lineTo(point.canvasx, newYs[1]);
 746             if (stepPlot) {
 747               ctx.lineTo(prevX, newYs[1]);
 748             } else {
 749               ctx.lineTo(prevX, prevYs[1]);
 750             }
 751             ctx.closePath();
 752           }
 753           prevYs = newYs;
 754           prevX = point.canvasx;
 755         }
 756       }
 757       ctx.fill();
 758     }
 759   } else if (fillGraph) {
 760     var baseline = []  // for stacked graphs: baseline for filling
 761
 762     // process sets in reverse order (needed for stacked graphs)
 763     for (var i = setCount - 1; i >= 0; i--) {
 764       var setName = setNames[i];
 765       var color = this.colors[setName];
 766       var axis = this.layout.options.yAxes[
 767         this.layout.options.seriesToAxisMap[setName]];
 768       var axisY = 1.0 + axis.minyval * axis.yscale;
 769       if (axisY < 0.0) axisY = 0.0;
 770       else if (axisY > 1.0) axisY = 1.0;
 771       axisY = this.area.h * axisY + this.area.y;
 772
 773       // setup graphics context
 774       ctx.save();
 775       var prevX = NaN;
 776       var prevYs = [-1, -1];
 777       var yscale = axis.yscale;
 778       // should be same color as the lines but only 15% opaque.
 779       var rgb = new RGBColor(color);
 780       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 781                             fillAlpha + ')';
 782       ctx.fillStyle = err_color;
 783       ctx.beginPath();
 784       for (var j = 0; j < this.layout.points.length; j++) {
 785         var point = this.layout.points[j];
 786         if (point.name == setName) {
 787           if (!isOK(point.y)) {
 788             prevX = NaN;
 789             continue;
 790           }
 791           var newYs;
 792           if (stackedGraph) {
 793             lastY = baseline[point.canvasx];
 794             if (lastY === undefined) lastY = axisY;
 795             baseline[point.canvasx] = point.canvasy;
 796             newYs = [ point.canvasy, lastY ];
 797           } else {
 798             newYs = [ point.canvasy, axisY ];
 799           }
 800           if (!isNaN(prevX)) {
 801             ctx.moveTo(prevX, prevYs[0]);
 802             if (stepPlot) {
 803               ctx.lineTo(point.canvasx, prevYs[0]);
 804             } else {
 805               ctx.lineTo(point.canvasx, newYs[0]);
 806             }
 807             ctx.lineTo(point.canvasx, newYs[1]);
 808             ctx.lineTo(prevX, prevYs[1]);
 809             ctx.closePath();
 810           }
 811           prevYs = newYs;
 812           prevX = point.canvasx;
 813         }
 814       }
 815       ctx.fill();
 816     }
 817   }
 818
 819   for (var i = 0; i < setCount; i++) {
 820     var setName = setNames[i];
 821     var color = this.colors[setName];
 822     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 823
 824     // setup graphics context
 825     context.save();
 826     var point = this.layout.points[0];
 827     var pointSize = this.dygraph_.attr_("pointSize", setName);
 828     var prevX = null, prevY = null;
 829     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 830     var points = this.layout.points;
 831     for (var j = 0; j < points.length; j++) {
 832       var point = points[j];
 833       if (point.name == setName) {
 834         if (!isOK(point.canvasy)) {
 835           if (stepPlot && prevX != null) {
 836             // Draw a horizontal line to the start of the missing data
 837             ctx.beginPath();
 838             ctx.strokeStyle = color;
 839             ctx.lineWidth = this.options.strokeWidth;
 840             ctx.moveTo(prevX, prevY);
 841             ctx.lineTo(point.canvasx, prevY);
 842             ctx.stroke();
 843           }
 844           // this will make us move to the next point, not draw a line to it.
 845           prevX = prevY = null;
 846         } else {
 847           // A point is "isolated" if it is non-null but both the previous
 848           // and next points are null.
 849           var isIsolated = (!prevX && (j == points.length - 1 ||
 850                                        !isOK(points[j+1].canvasy)));
 851
 852           if (!prevX) {
 853             prevX = point.canvasx;
 854             prevY = point.canvasy;
 855           } else {
 856             // TODO(danvk): figure out why this conditional is necessary.
 857             if (strokeWidth) {
 858               ctx.beginPath();
 859               ctx.strokeStyle = color;
 860               ctx.lineWidth = strokeWidth;
 861               ctx.moveTo(prevX, prevY);
 862               if (stepPlot) {
 863                 ctx.lineTo(point.canvasx, prevY);
 864               }
 865               prevX = point.canvasx;
 866               prevY = point.canvasy;
 867               ctx.lineTo(prevX, prevY);
 868               ctx.stroke();
 869             }
 870           }
 871
 872           if (drawPoints || isIsolated) {
 873            ctx.beginPath();
 874            ctx.fillStyle = color;
 875            ctx.arc(point.canvasx, point.canvasy, pointSize,
 876                    0, 2 * Math.PI, false);
 877            ctx.fill();
 878           }
 879         }
 880       }
 881     }
 882   }
 883
 884   context.restore();
 885 };