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       if (series.length > 1) {
  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   }
  81   this.xrange = this.maxxval - this.minxval;
  82   this.xscale = (this.xrange != 0 ? 1/this.xrange : 1.0);
  83
  84   this.minyval = this.options.yAxis[0];
  85   this.maxyval = this.options.yAxis[1];
  86   this.yrange = this.maxyval - this.minyval;
  87   this.yscale = (this.yrange != 0 ? 1/this.yrange : 1.0);
  88 };
  89
  90 DygraphLayout.prototype._evaluateLineCharts = function() {
  91   // add all the rects
  92   this.points = new Array();
  93   for (var setName in this.datasets) {
  94     if (!this.datasets.hasOwnProperty(setName)) continue;
  95
  96     var dataset = this.datasets[setName];
  97     for (var j = 0; j < dataset.length; j++) {
  98       var item = dataset[j];
  99       var point = {
 100         // TODO(danvk): here
 101         x: ((parseFloat(item[0]) - this.minxval) * this.xscale),
 102         y: 1.0 - ((parseFloat(item[1]) - this.minyval) * this.yscale),
 103         xval: parseFloat(item[0]),
 104         yval: parseFloat(item[1]),
 105         name: setName
 106       };
 107
 108       // limit the x, y values so they do not overdraw
 109       if (point.y <= 0.0) {
 110         point.y = 0.0;
 111       }
 112       if (point.y >= 1.0) {
 113         point.y = 1.0;
 114       }
 115       this.points.push(point);
 116     }
 117   }
 118 };
 119
 120 DygraphLayout.prototype._evaluateLineTicks = function() {
 121   this.xticks = new Array();
 122   for (var i = 0; i < this.options.xTicks.length; i++) {
 123     var tick = this.options.xTicks[i];
 124     var label = tick.label;
 125     var pos = this.xscale * (tick.v - this.minxval);
 126     if ((pos >= 0.0) && (pos <= 1.0)) {
 127       this.xticks.push([pos, label]);
 128     }
 129   }
 130
 131   this.yticks = new Array();
 132   for (var i = 0; i < this.options.yTicks.length; i++) {
 133     var tick = this.options.yTicks[i];
 134     var label = tick.label;
 135     var pos = 1.0 - (this.yscale * (tick.v - this.minyval));
 136     if ((pos >= 0.0) && (pos <= 1.0)) {
 137       this.yticks.push([pos, label]);
 138     }
 139   }
 140 };
 141
 142
 143 /**
 144  * Behaves the same way as PlotKit.Layout, but also copies the errors
 145  * @private
 146  */
 147 DygraphLayout.prototype.evaluateWithError = function() {
 148   this.evaluate();
 149   if (!this.options.errorBars) return;
 150
 151   // Copy over the error terms
 152   var i = 0; // index in this.points
 153   for (var setName in this.datasets) {
 154     if (!this.datasets.hasOwnProperty(setName)) continue;
 155     var j = 0;
 156     var dataset = this.datasets[setName];
 157     for (var j = 0; j < dataset.length; j++, i++) {
 158       var item = dataset[j];
 159       var xv = parseFloat(item[0]);
 160       var yv = parseFloat(item[1]);
 161
 162       if (xv == this.points[i].xval &&
 163           yv == this.points[i].yval) {
 164         this.points[i].errorMinus = parseFloat(item[2]);
 165         this.points[i].errorPlus = parseFloat(item[3]);
 166       }
 167     }
 168   }
 169 };
 170
 171 DygraphLayout.prototype._evaluateAnnotations = function() {
 172   // Add the annotations to the point to which they belong.
 173   // Make a map from (setName, xval) to annotation for quick lookups.
 174   var annotations = {};
 175   for (var i = 0; i < this.annotations.length; i++) {
 176     var a = this.annotations[i];
 177     annotations[a.xval + "," + a.series] = a;
 178   }
 179
 180   this.annotated_points = [];
 181   for (var i = 0; i < this.points.length; i++) {
 182     var p = this.points[i];
 183     var k = p.xval + "," + p.name;
 184     if (k in annotations) {
 185       p.annotation = annotations[k];
 186       this.annotated_points.push(p);
 187     }
 188   }
 189 };
 190
 191 /**
 192  * Convenience function to remove all the data sets from a graph
 193  */
 194 DygraphLayout.prototype.removeAllDatasets = function() {
 195   delete this.datasets;
 196   this.datasets = new Array();
 197 };
 198
 199 /**
 200  * Change the values of various layout options
 201  * @param {Object} new_options an associative array of new properties
 202  */
 203 DygraphLayout.prototype.updateOptions = function(new_options) {
 204   Dygraph.update(this.options, new_options ? new_options : {});
 205 };
 206
 207 /**
 208  * Return a copy of the point at the indicated index, with its yval unstacked.
 209  * @param int index of point in layout_.points
 210  */
 211 DygraphLayout.prototype.unstackPointAtIndex = function(idx) {
 212   var point = this.points[idx];
 213
 214   // Clone the point since we modify it
 215   var unstackedPoint = {};
 216   for (var i in point) {
 217     unstackedPoint[i] = point[i];
 218   }
 219
 220   if (!this.attr_("stackedGraph")) {
 221     return unstackedPoint;
 222   }
 223
 224   // The unstacked yval is equal to the current yval minus the yval of the
 225   // next point at the same xval.
 226   for (var i = idx+1; i < this.points.length; i++) {
 227     if (this.points[i].xval == point.xval) {
 228       unstackedPoint.yval -= this.points[i].yval;
 229       break;
 230     }
 231   }
 232
 233   return unstackedPoint;
 234 }
 235
 236 // Subclass PlotKit.CanvasRenderer to add:
 237 // 1. X/Y grid overlay
 238 // 2. Ability to draw error bars (if required)
 239
 240 /**
 241  * Sets some PlotKit.CanvasRenderer options
 242  * @param {Object} element The canvas to attach to
 243  * @param {Layout} layout The DygraphLayout object for this graph.
 244  * @param {Object} options Options to pass on to CanvasRenderer
 245  */
 246 DygraphCanvasRenderer = function(dygraph, element, layout, options) {
 247   // TODO(danvk): remove options, just use dygraph.attr_.
 248   this.dygraph_ = dygraph;
 249
 250   // default options
 251   this.options = {
 252     "strokeWidth": 0.5,
 253     "drawXAxis": true,
 254     "drawYAxis": true,
 255     "axisLineColor": "black",
 256     "axisLineWidth": 0.5,
 257     "axisTickSize": 3,
 258     "axisLabelColor": "black",
 259     "axisLabelFont": "Arial",
 260     "axisLabelFontSize": 9,
 261     "axisLabelWidth": 50,
 262     "drawYGrid": true,
 263     "drawXGrid": true,
 264     "gridLineColor": "rgb(128,128,128)",
 265     "fillAlpha": 0.15,
 266     "underlayCallback": null
 267   };
 268   Dygraph.update(this.options, options);
 269
 270   this.layout = layout;
 271   this.element = element;
 272   this.container = this.element.parentNode;
 273
 274   this.height = this.element.height;
 275   this.width = this.element.width;
 276
 277   // --- check whether everything is ok before we return
 278   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
 279       throw "Canvas is not supported.";
 280
 281   // internal state
 282   this.xlabels = new Array();
 283   this.ylabels = new Array();
 284   this.annotations = new Array();
 285
 286   this.area = {
 287     x: this.options.yAxisLabelWidth + 2 * this.options.axisTickSize,
 288     y: 0
 289   };
 290   this.area.w = this.width - this.area.x - this.options.rightGap;
 291   this.area.h = this.height - this.options.axisLabelFontSize -
 292                 2 * this.options.axisTickSize;
 293
 294   this.container.style.position = "relative";
 295   this.container.style.width = this.width + "px";
 296 };
 297
 298 DygraphCanvasRenderer.prototype.clear = function() {
 299   if (this.isIE) {
 300     // VML takes a while to start up, so we just poll every this.IEDelay
 301     try {
 302       if (this.clearDelay) {
 303         this.clearDelay.cancel();
 304         this.clearDelay = null;
 305       }
 306       var context = this.element.getContext("2d");
 307     }
 308     catch (e) {
 309       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 310       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 311       this.clearDelay.addCallback(bind(this.clear, this));
 312       return;
 313     }
 314   }
 315
 316   var context = this.element.getContext("2d");
 317   context.clearRect(0, 0, this.width, this.height);
 318
 319   for (var i = 0; i < this.xlabels.length; i++) {
 320     var el = this.xlabels[i];
 321     el.parentNode.removeChild(el);
 322   }
 323   for (var i = 0; i < this.ylabels.length; i++) {
 324     var el = this.ylabels[i];
 325     el.parentNode.removeChild(el);
 326   }
 327   for (var i = 0; i < this.annotations.length; i++) {
 328     var el = this.annotations[i];
 329     el.parentNode.removeChild(el);
 330   }
 331   this.xlabels = new Array();
 332   this.ylabels = new Array();
 333   this.annotations = new Array();
 334 };
 335
 336
 337 DygraphCanvasRenderer.isSupported = function(canvasName) {
 338   var canvas = null;
 339   try {
 340     if (typeof(canvasName) == 'undefined' || canvasName == null)
 341       canvas = document.createElement("canvas");
 342     else
 343       canvas = canvasName;
 344     var context = canvas.getContext("2d");
 345   }
 346   catch (e) {
 347     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 348     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 349     if ((!ie) || (ie[1] < 6) || (opera))
 350       return false;
 351     return true;
 352   }
 353   return true;
 354 };
 355
 356 /**
 357  * Draw an X/Y grid on top of the existing plot
 358  */
 359 DygraphCanvasRenderer.prototype.render = function() {
 360   // Draw the new X/Y grid
 361   var ctx = this.element.getContext("2d");
 362
 363   if (this.options.underlayCallback) {
 364     this.options.underlayCallback(ctx, this.area, this.layout, this.dygraph_);
 365   }
 366
 367   if (this.options.drawYGrid) {
 368     var ticks = this.layout.yticks;
 369     ctx.save();
 370     ctx.strokeStyle = this.options.gridLineColor;
 371     ctx.lineWidth = this.options.axisLineWidth;
 372     for (var i = 0; i < ticks.length; i++) {
 373       var x = this.area.x;
 374       var y = this.area.y + ticks[i][0] * this.area.h;
 375       ctx.beginPath();
 376       ctx.moveTo(x, y);
 377       ctx.lineTo(x + this.area.w, y);
 378       ctx.closePath();
 379       ctx.stroke();
 380     }
 381   }
 382
 383   if (this.options.drawXGrid) {
 384     var ticks = this.layout.xticks;
 385     ctx.save();
 386     ctx.strokeStyle = this.options.gridLineColor;
 387     ctx.lineWidth = this.options.axisLineWidth;
 388     for (var i=0; i<ticks.length; i++) {
 389       var x = this.area.x + ticks[i][0] * this.area.w;
 390       var y = this.area.y + this.area.h;
 391       ctx.beginPath();
 392       ctx.moveTo(x, y);
 393       ctx.lineTo(x, this.area.y);
 394       ctx.closePath();
 395       ctx.stroke();
 396     }
 397   }
 398
 399   // Do the ordinary rendering, as before
 400   this._renderLineChart();
 401   this._renderAxis();
 402   this._renderAnnotations();
 403 };
 404
 405
 406 DygraphCanvasRenderer.prototype._renderAxis = function() {
 407   if (!this.options.drawXAxis && !this.options.drawYAxis)
 408     return;
 409
 410   var context = this.element.getContext("2d");
 411
 412   var labelStyle = {
 413     "position": "absolute",
 414     "fontSize": this.options.axisLabelFontSize + "px",
 415     "zIndex": 10,
 416     "color": this.options.axisLabelColor,
 417     "width": this.options.axisLabelWidth + "px",
 418     "overflow": "hidden"
 419   };
 420   var makeDiv = function(txt) {
 421     var div = document.createElement("div");
 422     for (var name in labelStyle) {
 423       if (labelStyle.hasOwnProperty(name)) {
 424         div.style[name] = labelStyle[name];
 425       }
 426     }
 427     div.appendChild(document.createTextNode(txt));
 428     return div;
 429   };
 430
 431   // axis lines
 432   context.save();
 433   context.strokeStyle = this.options.axisLineColor;
 434   context.lineWidth = this.options.axisLineWidth;
 435
 436   if (this.options.drawYAxis) {
 437     if (this.layout.yticks && this.layout.yticks.length > 0) {
 438       for (var i = 0; i < this.layout.yticks.length; i++) {
 439         var tick = this.layout.yticks[i];
 440         if (typeof(tick) == "function") return;
 441         var x = this.area.x;
 442         var y = this.area.y + tick[0] * this.area.h;
 443         context.beginPath();
 444         context.moveTo(x, y);
 445         context.lineTo(x - this.options.axisTickSize, y);
 446         context.closePath();
 447         context.stroke();
 448
 449         var label = makeDiv(tick[1]);
 450         var top = (y - this.options.axisLabelFontSize / 2);
 451         if (top < 0) top = 0;
 452
 453         if (top + this.options.axisLabelFontSize + 3 > this.height) {
 454           label.style.bottom = "0px";
 455         } else {
 456           label.style.top = top + "px";
 457         }
 458         label.style.left = "0px";
 459         label.style.textAlign = "right";
 460         label.style.width = this.options.yAxisLabelWidth + "px";
 461         this.container.appendChild(label);
 462         this.ylabels.push(label);
 463       }
 464
 465       // The lowest tick on the y-axis often overlaps with the leftmost
 466       // tick on the x-axis. Shift the bottom tick up a little bit to
 467       // compensate if necessary.
 468       var bottomTick = this.ylabels[0];
 469       var fontSize = this.options.axisLabelFontSize;
 470       var bottom = parseInt(bottomTick.style.top) + fontSize;
 471       if (bottom > this.height - fontSize) {
 472         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 473             fontSize / 2) + "px";
 474       }
 475     }
 476
 477     context.beginPath();
 478     context.moveTo(this.area.x, this.area.y);
 479     context.lineTo(this.area.x, this.area.y + this.area.h);
 480     context.closePath();
 481     context.stroke();
 482   }
 483
 484   if (this.options.drawXAxis) {
 485     if (this.layout.xticks) {
 486       for (var i = 0; i < this.layout.xticks.length; i++) {
 487         var tick = this.layout.xticks[i];
 488         if (typeof(dataset) == "function") return;
 489
 490         var x = this.area.x + tick[0] * this.area.w;
 491         var y = this.area.y + this.area.h;
 492         context.beginPath();
 493         context.moveTo(x, y);
 494         context.lineTo(x, y + this.options.axisTickSize);
 495         context.closePath();
 496         context.stroke();
 497
 498         var label = makeDiv(tick[1]);
 499         label.style.textAlign = "center";
 500         label.style.bottom = "0px";
 501
 502         var left = (x - this.options.axisLabelWidth/2);
 503         if (left + this.options.axisLabelWidth > this.width) {
 504           left = this.width - this.options.xAxisLabelWidth;
 505           label.style.textAlign = "right";
 506         }
 507         if (left < 0) {
 508           left = 0;
 509           label.style.textAlign = "left";
 510         }
 511
 512         label.style.left = left + "px";
 513         label.style.width = this.options.xAxisLabelWidth + "px";
 514         this.container.appendChild(label);
 515         this.xlabels.push(label);
 516       }
 517     }
 518
 519     context.beginPath();
 520     context.moveTo(this.area.x, this.area.y + this.area.h);
 521     context.lineTo(this.area.x + this.area.w, this.area.y + this.area.h);
 522     context.closePath();
 523     context.stroke();
 524   }
 525
 526   context.restore();
 527 };
 528
 529
 530 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 531   var annotationStyle = {
 532     "position": "absolute",
 533     "fontSize": this.options.axisLabelFontSize + "px",
 534     "zIndex": 10,
 535     "overflow": "hidden"
 536   };
 537
 538   var bindEvt = function(eventName, classEventName, p, self) {
 539     return function(e) {
 540       var a = p.annotation;
 541       if (a.hasOwnProperty(eventName)) {
 542         a[eventName](a, p, self.dygraph_, e);
 543       } else if (self.dygraph_.attr_(classEventName)) {
 544         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 545       }
 546     };
 547   }
 548
 549   // Get a list of point with annotations.
 550   var points = this.layout.annotated_points;
 551   for (var i = 0; i < points.length; i++) {
 552     var p = points[i];
 553     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 554       continue;
 555     }
 556
 557     var a = p.annotation;
 558     var tick_height = 6;
 559     if (a.hasOwnProperty("tickHeight")) {
 560       tick_height = a.tickHeight;
 561     }
 562
 563     var div = document.createElement("div");
 564     for (var name in annotationStyle) {
 565       if (annotationStyle.hasOwnProperty(name)) {
 566         div.style[name] = annotationStyle[name];
 567       }
 568     }
 569     if (!a.hasOwnProperty('icon')) {
 570       div.className = "dygraphDefaultAnnotation";
 571     }
 572     if (a.hasOwnProperty('cssClass')) {
 573       div.className += " " + a.cssClass;
 574     }
 575
 576     var width = a.hasOwnProperty('width') ? a.width : 16;
 577     var height = a.hasOwnProperty('height') ? a.height : 16;
 578     if (a.hasOwnProperty('icon')) {
 579       var img = document.createElement("img");
 580       img.src = a.icon;
 581       img.width = width;
 582       img.height = height;
 583       div.appendChild(img);
 584     } else if (p.annotation.hasOwnProperty('shortText')) {
 585       div.appendChild(document.createTextNode(p.annotation.shortText));
 586     }
 587     div.style.left = (p.canvasx - width / 2) + "px";
 588     if (a.attachAtBottom) {
 589       div.style.top = (this.area.h - height - tick_height) + "px";
 590     } else {
 591       div.style.top = (p.canvasy - height - tick_height) + "px";
 592     }
 593     div.style.width = width + "px";
 594     div.style.height = height + "px";
 595     div.title = p.annotation.text;
 596     div.style.color = this.colors[p.name];
 597     div.style.borderColor = this.colors[p.name];
 598     a.div = div;
 599
 600     Dygraph.addEvent(div, 'click',
 601         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 602     Dygraph.addEvent(div, 'mouseover',
 603         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 604     Dygraph.addEvent(div, 'mouseout',
 605         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 606     Dygraph.addEvent(div, 'dblclick',
 607         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 608
 609     this.container.appendChild(div);
 610     this.annotations.push(div);
 611
 612     var ctx = this.element.getContext("2d");
 613     ctx.strokeStyle = this.colors[p.name];
 614     ctx.beginPath();
 615     if (!a.attachAtBottom) {
 616       ctx.moveTo(p.canvasx, p.canvasy);
 617       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 618     } else {
 619       ctx.moveTo(p.canvasx, this.area.h);
 620       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 621     }
 622     ctx.closePath();
 623     ctx.stroke();
 624   }
 625 };
 626
 627
 628 /**
 629  * Overrides the CanvasRenderer method to draw error bars
 630  */
 631 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 632   var context = this.element.getContext("2d");
 633   var colorCount = this.options.colorScheme.length;
 634   var colorScheme = this.options.colorScheme;
 635   var fillAlpha = this.options.fillAlpha;
 636   var errorBars = this.layout.options.errorBars;
 637   var fillGraph = this.layout.options.fillGraph;
 638   var stackedGraph = this.layout.options.stackedGraph;
 639   var stepPlot = this.layout.options.stepPlot;
 640
 641   var setNames = [];
 642   for (var name in this.layout.datasets) {
 643     if (this.layout.datasets.hasOwnProperty(name)) {
 644       setNames.push(name);
 645     }
 646   }
 647   var setCount = setNames.length;
 648
 649   this.colors = {}
 650   for (var i = 0; i < setCount; i++) {
 651     this.colors[setNames[i]] = colorScheme[i % colorCount];
 652   }
 653
 654   // Update Points
 655   // TODO(danvk): here
 656   for (var i = 0; i < this.layout.points.length; i++) {
 657     var point = this.layout.points[i];
 658     point.canvasx = this.area.w * point.x + this.area.x;
 659     point.canvasy = this.area.h * point.y + this.area.y;
 660   }
 661
 662   // create paths
 663   var isOK = function(x) { return x && !isNaN(x); };
 664
 665   var ctx = context;
 666   if (errorBars) {
 667     if (fillGraph) {
 668       this.dygraph_.warn("Can't use fillGraph option with error bars");
 669     }
 670
 671     for (var i = 0; i < setCount; i++) {
 672       var setName = setNames[i];
 673       var color = this.colors[setName];
 674
 675       // setup graphics context
 676       ctx.save();
 677       var prevX = NaN;
 678       var prevY = NaN;
 679       var prevYs = [-1, -1];
 680       var yscale = this.layout.yscale;
 681       // should be same color as the lines but only 15% opaque.
 682       var rgb = new RGBColor(color);
 683       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 684                             fillAlpha + ')';
 685       ctx.fillStyle = err_color;
 686       ctx.beginPath();
 687       for (var j = 0; j < this.layout.points.length; j++) {
 688         var point = this.layout.points[j];
 689         if (point.name == setName) {
 690           if (!isOK(point.y)) {
 691             prevX = NaN;
 692             continue;
 693           }
 694
 695           // TODO(danvk): here
 696           if (stepPlot) {
 697             var newYs = [ prevY - point.errorPlus * yscale,
 698                           prevY + point.errorMinus * yscale ];
 699             prevY = point.y;
 700           } else {
 701             var newYs = [ point.y - point.errorPlus * yscale,
 702                           point.y + point.errorMinus * yscale ];
 703           }
 704           newYs[0] = this.area.h * newYs[0] + this.area.y;
 705           newYs[1] = this.area.h * newYs[1] + this.area.y;
 706           if (!isNaN(prevX)) {
 707             if (stepPlot) {
 708               ctx.moveTo(prevX, newYs[0]);
 709             } else {
 710               ctx.moveTo(prevX, prevYs[0]);
 711             }
 712             ctx.lineTo(point.canvasx, newYs[0]);
 713             ctx.lineTo(point.canvasx, newYs[1]);
 714             if (stepPlot) {
 715               ctx.lineTo(prevX, newYs[1]);
 716             } else {
 717               ctx.lineTo(prevX, prevYs[1]);
 718             }
 719             ctx.closePath();
 720           }
 721           prevYs = newYs;
 722           prevX = point.canvasx;
 723         }
 724       }
 725       ctx.fill();
 726     }
 727   } else if (fillGraph) {
 728     var axisY = 1.0 + this.layout.minyval * this.layout.yscale;
 729     if (axisY < 0.0) axisY = 0.0;
 730     else if (axisY > 1.0) axisY = 1.0;
 731     axisY = this.area.h * axisY + this.area.y;
 732
 733     var baseline = []  // for stacked graphs: baseline for filling
 734
 735     // process sets in reverse order (needed for stacked graphs)
 736     for (var i = setCount - 1; i >= 0; i--) {
 737       var setName = setNames[i];
 738       var color = this.colors[setName];
 739
 740       // setup graphics context
 741       ctx.save();
 742       var prevX = NaN;
 743       var prevYs = [-1, -1];
 744       var yscale = this.layout.yscale;
 745       // should be same color as the lines but only 15% opaque.
 746       var rgb = new RGBColor(color);
 747       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 748                             fillAlpha + ')';
 749       ctx.fillStyle = err_color;
 750       ctx.beginPath();
 751       for (var j = 0; j < this.layout.points.length; j++) {
 752         var point = this.layout.points[j];
 753         if (point.name == setName) {
 754           if (!isOK(point.y)) {
 755             prevX = NaN;
 756             continue;
 757           }
 758           var newYs;
 759           if (stackedGraph) {
 760             lastY = baseline[point.canvasx];
 761             if (lastY === undefined) lastY = axisY;
 762             baseline[point.canvasx] = point.canvasy;
 763             newYs = [ point.canvasy, lastY ];
 764           } else {
 765             newYs = [ point.canvasy, axisY ];
 766           }
 767           if (!isNaN(prevX)) {
 768             ctx.moveTo(prevX, prevYs[0]);
 769             if (stepPlot) {
 770               ctx.lineTo(point.canvasx, prevYs[0]);
 771             } else {
 772               ctx.lineTo(point.canvasx, newYs[0]);
 773             }
 774             ctx.lineTo(point.canvasx, newYs[1]);
 775             ctx.lineTo(prevX, prevYs[1]);
 776             ctx.closePath();
 777           }
 778           prevYs = newYs;
 779           prevX = point.canvasx;
 780         }
 781       }
 782       ctx.fill();
 783     }
 784   }
 785
 786   for (var i = 0; i < setCount; i++) {
 787     var setName = setNames[i];
 788     var color = this.colors[setName];
 789     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 790
 791     // setup graphics context
 792     context.save();
 793     var point = this.layout.points[0];
 794     var pointSize = this.dygraph_.attr_("pointSize", setName);
 795     var prevX = null, prevY = null;
 796     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 797     var points = this.layout.points;
 798     for (var j = 0; j < points.length; j++) {
 799       var point = points[j];
 800       if (point.name == setName) {
 801         if (!isOK(point.canvasy)) {
 802           if (stepPlot && prevX != null) {
 803             // Draw a horizontal line to the start of the missing data
 804             ctx.beginPath();
 805             ctx.strokeStyle = color;
 806             ctx.lineWidth = this.options.strokeWidth;
 807             ctx.moveTo(prevX, prevY);
 808             ctx.lineTo(point.canvasx, prevY);
 809             ctx.stroke();
 810           }
 811           // this will make us move to the next point, not draw a line to it.
 812           prevX = prevY = null;
 813         } else {
 814           // A point is "isolated" if it is non-null but both the previous
 815           // and next points are null.
 816           var isIsolated = (!prevX && (j == points.length - 1 ||
 817                                        !isOK(points[j+1].canvasy)));
 818
 819           if (!prevX) {
 820             prevX = point.canvasx;
 821             prevY = point.canvasy;
 822           } else {
 823             // TODO(danvk): figure out why this conditional is necessary.
 824             if (strokeWidth) {
 825               ctx.beginPath();
 826               ctx.strokeStyle = color;
 827               ctx.lineWidth = strokeWidth;
 828               ctx.moveTo(prevX, prevY);
 829               if (stepPlot) {
 830                 ctx.lineTo(point.canvasx, prevY);
 831               }
 832               prevX = point.canvasx;
 833               prevY = point.canvasy;
 834               ctx.lineTo(prevX, prevY);
 835               ctx.stroke();
 836             }
 837           }
 838
 839           if (drawPoints || isIsolated) {
 840            ctx.beginPath();
 841            ctx.fillStyle = color;
 842            ctx.arc(point.canvasx, point.canvasy, pointSize,
 843                    0, 2 * Math.PI, false);
 844            ctx.fill();
 845           }
 846         }
 847       }
 848     }
 849   }
 850
 851   context.restore();
 852 };