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