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 };
  23
  24 DygraphLayout.prototype.attr_ = function(name) {
  25   return this.dygraph_.attr_(name);
  26 };
  27
  28 DygraphLayout.prototype.addDataset = function(setname, set_xy) {
  29   this.datasets[setname] = set_xy;
  30 };
  31
  32 // TODO(danvk): CONTRACT remove
  33 DygraphLayout.prototype.addAnnotation = function() {
  34   // Add an annotation to one series.
  35   this.annotations = [];
  36   for (var x = 10; x < 30; x += 2) {
  37     this.annotations.push( {
  38       series: 'sine wave',
  39       xval: this.attr_('xValueParser')("200610" + x),
  40       shortText: x,
  41       text: 'Stock Market Crash ' + x
  42     } );
  43   }
  44   this.annotations.push( {
  45     series: 'another line',
  46     xval: this.attr_('xValueParser')("20061013"),
  47     shortText: 'X',
  48     text: 'Another one'
  49   } );
  50 };
  51
  52 DygraphLayout.prototype.evaluate = function() {
  53   this._evaluateLimits();
  54   this._evaluateLineCharts();
  55   this._evaluateLineTicks();
  56   this._evaluateAnnotations();
  57 };
  58
  59 DygraphLayout.prototype._evaluateLimits = function() {
  60   this.minxval = this.maxxval = null;
  61   if (this.options.dateWindow) {
  62     this.minxval = this.options.dateWindow[0];
  63     this.maxxval = this.options.dateWindow[1];
  64   } else {
  65     for (var name in this.datasets) {
  66       if (!this.datasets.hasOwnProperty(name)) continue;
  67       var series = this.datasets[name];
  68       var x1 = series[0][0];
  69       if (!this.minxval || x1 < this.minxval) this.minxval = x1;
  70
  71       var x2 = series[series.length - 1][0];
  72       if (!this.maxxval || x2 > this.maxxval) this.maxxval = x2;
  73     }
  74   }
  75   this.xrange = this.maxxval - this.minxval;
  76   this.xscale = (this.xrange != 0 ? 1/this.xrange : 1.0);
  77
  78   this.minyval = this.options.yAxis[0];
  79   this.maxyval = this.options.yAxis[1];
  80   this.yrange = this.maxyval - this.minyval;
  81   this.yscale = (this.yrange != 0 ? 1/this.yrange : 1.0);
  82 };
  83
  84 DygraphLayout.prototype._evaluateLineCharts = function() {
  85   // add all the rects
  86   this.points = new Array();
  87   for (var setName in this.datasets) {
  88     if (!this.datasets.hasOwnProperty(setName)) continue;
  89
  90     var dataset = this.datasets[setName];
  91     for (var j = 0; j < dataset.length; j++) {
  92       var item = dataset[j];
  93       var point = {
  94         // TODO(danvk): here
  95         x: ((parseFloat(item[0]) - this.minxval) * this.xscale),
  96         y: 1.0 - ((parseFloat(item[1]) - this.minyval) * this.yscale),
  97         xval: parseFloat(item[0]),
  98         yval: parseFloat(item[1]),
  99         name: setName
 100       };
 101
 102       // limit the x, y values so they do not overdraw
 103       if (point.y <= 0.0) {
 104         point.y = 0.0;
 105       }
 106       if (point.y >= 1.0) {
 107         point.y = 1.0;
 108       }
 109       this.points.push(point);
 110     }
 111   }
 112 };
 113
 114 DygraphLayout.prototype._evaluateLineTicks = function() {
 115   this.xticks = new Array();
 116   for (var i = 0; i < this.options.xTicks.length; i++) {
 117     var tick = this.options.xTicks[i];
 118     var label = tick.label;
 119     var pos = this.xscale * (tick.v - this.minxval);
 120     if ((pos >= 0.0) && (pos <= 1.0)) {
 121       this.xticks.push([pos, label]);
 122     }
 123   }
 124
 125   this.yticks = new Array();
 126   for (var i = 0; i < this.options.yTicks.length; i++) {
 127     var tick = this.options.yTicks[i];
 128     var label = tick.label;
 129     var pos = 1.0 - (this.yscale * (tick.v - this.minyval));
 130     if ((pos >= 0.0) && (pos <= 1.0)) {
 131       this.yticks.push([pos, label]);
 132     }
 133   }
 134 };
 135
 136
 137 /**
 138  * Behaves the same way as PlotKit.Layout, but also copies the errors
 139  * @private
 140  */
 141 DygraphLayout.prototype.evaluateWithError = function() {
 142   this.evaluate();
 143   if (!this.options.errorBars) return;
 144
 145   // Copy over the error terms
 146   var i = 0; // index in this.points
 147   for (var setName in this.datasets) {
 148     if (!this.datasets.hasOwnProperty(setName)) continue;
 149     var j = 0;
 150     var dataset = this.datasets[setName];
 151     for (var j = 0; j < dataset.length; j++, i++) {
 152       var item = dataset[j];
 153       var xv = parseFloat(item[0]);
 154       var yv = parseFloat(item[1]);
 155
 156       if (xv == this.points[i].xval &&
 157           yv == this.points[i].yval) {
 158         this.points[i].errorMinus = parseFloat(item[2]);
 159         this.points[i].errorPlus = parseFloat(item[3]);
 160       }
 161     }
 162   }
 163 };
 164
 165 DygraphLayout.prototype._evaluateAnnotations = function() {
 166   // Add the annotations to the point to which they belong.
 167   // Make a map from (setName, xval) to annotation for quick lookups.
 168   var annotations = {};
 169   for (var i = 0; i < this.annotations.length; i++) {
 170     var a = this.annotations[i];
 171     annotations[a.xval + "," + a.series] = a;
 172   }
 173
 174   this.annotated_points = [];
 175   for (var i = 0; i < this.points.length; i++) {
 176     var p = this.points[i];
 177     var k = p.xval + "," + p.name;
 178     if (k in annotations) {
 179       p.annotation = annotations[k];
 180       this.annotated_points.push(p);
 181     }
 182   }
 183 };
 184
 185 /**
 186  * Convenience function to remove all the data sets from a graph
 187  */
 188 DygraphLayout.prototype.removeAllDatasets = function() {
 189   delete this.datasets;
 190   this.datasets = new Array();
 191 };
 192
 193 /**
 194  * Change the values of various layout options
 195  * @param {Object} new_options an associative array of new properties
 196  */
 197 DygraphLayout.prototype.updateOptions = function(new_options) {
 198   Dygraph.update(this.options, new_options ? new_options : {});
 199 };
 200
 201 // Subclass PlotKit.CanvasRenderer to add:
 202 // 1. X/Y grid overlay
 203 // 2. Ability to draw error bars (if required)
 204
 205 /**
 206  * Sets some PlotKit.CanvasRenderer options
 207  * @param {Object} element The canvas to attach to
 208  * @param {Layout} layout The DygraphLayout object for this graph.
 209  * @param {Object} options Options to pass on to CanvasRenderer
 210  */
 211 DygraphCanvasRenderer = function(dygraph, element, layout, options) {
 212   // TODO(danvk): remove options, just use dygraph.attr_.
 213   this.dygraph_ = dygraph;
 214
 215   // default options
 216   this.options = {
 217     "strokeWidth": 0.5,
 218     "drawXAxis": true,
 219     "drawYAxis": true,
 220     "axisLineColor": "black",
 221     "axisLineWidth": 0.5,
 222     "axisTickSize": 3,
 223     "axisLabelColor": "black",
 224     "axisLabelFont": "Arial",
 225     "axisLabelFontSize": 9,
 226     "axisLabelWidth": 50,
 227     "drawYGrid": true,
 228     "drawXGrid": true,
 229     "gridLineColor": "rgb(128,128,128)",
 230     "fillAlpha": 0.15,
 231     "underlayCallback": null
 232   };
 233   Dygraph.update(this.options, options);
 234
 235   this.layout = layout;
 236   this.element = element;
 237   this.container = this.element.parentNode;
 238
 239   this.height = this.element.height;
 240   this.width = this.element.width;
 241
 242   // --- check whether everything is ok before we return
 243   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
 244       throw "Canvas is not supported.";
 245
 246   // internal state
 247   this.xlabels = new Array();
 248   this.ylabels = new Array();
 249   this.annotations = new Array();
 250
 251   this.area = {
 252     x: this.options.yAxisLabelWidth + 2 * this.options.axisTickSize,
 253     y: 0
 254   };
 255   this.area.w = this.width - this.area.x - this.options.rightGap;
 256   this.area.h = this.height - this.options.axisLabelFontSize -
 257                 2 * this.options.axisTickSize;
 258
 259   this.container.style.position = "relative";
 260   this.container.style.width = this.width + "px";
 261 };
 262
 263 DygraphCanvasRenderer.prototype.clear = function() {
 264   if (this.isIE) {
 265     // VML takes a while to start up, so we just poll every this.IEDelay
 266     try {
 267       if (this.clearDelay) {
 268         this.clearDelay.cancel();
 269         this.clearDelay = null;
 270       }
 271       var context = this.element.getContext("2d");
 272     }
 273     catch (e) {
 274       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 275       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 276       this.clearDelay.addCallback(bind(this.clear, this));
 277       return;
 278     }
 279   }
 280
 281   var context = this.element.getContext("2d");
 282   context.clearRect(0, 0, this.width, this.height);
 283
 284   for (var i = 0; i < this.xlabels.length; i++) {
 285     var el = this.xlabels[i];
 286     el.parentNode.removeChild(el);
 287   }
 288   for (var i = 0; i < this.ylabels.length; i++) {
 289     var el = this.ylabels[i];
 290     el.parentNode.removeChild(el);
 291   }
 292   for (var i = 0; i < this.annotations.length; i++) {
 293     var el = this.annotations[i];
 294     el.parentNode.removeChild(el);
 295   }
 296   this.xlabels = new Array();
 297   this.ylabels = new Array();
 298   this.annotations = new Array();
 299 };
 300
 301
 302 DygraphCanvasRenderer.isSupported = function(canvasName) {
 303   var canvas = null;
 304   try {
 305     if (typeof(canvasName) == 'undefined' || canvasName == null)
 306       canvas = document.createElement("canvas");
 307     else
 308       canvas = canvasName;
 309     var context = canvas.getContext("2d");
 310   }
 311   catch (e) {
 312     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 313     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 314     if ((!ie) || (ie[1] < 6) || (opera))
 315       return false;
 316     return true;
 317   }
 318   return true;
 319 };
 320
 321 /**
 322  * Draw an X/Y grid on top of the existing plot
 323  */
 324 DygraphCanvasRenderer.prototype.render = function() {
 325   // Draw the new X/Y grid
 326   var ctx = this.element.getContext("2d");
 327
 328   if (this.options.underlayCallback) {
 329     this.options.underlayCallback(ctx, this.area, this.layout, this.dygraph_);
 330   }
 331
 332   if (this.options.drawYGrid) {
 333     var ticks = this.layout.yticks;
 334     ctx.save();
 335     ctx.strokeStyle = this.options.gridLineColor;
 336     ctx.lineWidth = this.options.axisLineWidth;
 337     for (var i = 0; i < ticks.length; i++) {
 338       var x = this.area.x;
 339       var y = this.area.y + ticks[i][0] * this.area.h;
 340       ctx.beginPath();
 341       ctx.moveTo(x, y);
 342       ctx.lineTo(x + this.area.w, y);
 343       ctx.closePath();
 344       ctx.stroke();
 345     }
 346   }
 347
 348   if (this.options.drawXGrid) {
 349     var ticks = this.layout.xticks;
 350     ctx.save();
 351     ctx.strokeStyle = this.options.gridLineColor;
 352     ctx.lineWidth = this.options.axisLineWidth;
 353     for (var i=0; i<ticks.length; i++) {
 354       var x = this.area.x + ticks[i][0] * this.area.w;
 355       var y = this.area.y + this.area.h;
 356       ctx.beginPath();
 357       ctx.moveTo(x, y);
 358       ctx.lineTo(x, this.area.y);
 359       ctx.closePath();
 360       ctx.stroke();
 361     }
 362   }
 363
 364   // Do the ordinary rendering, as before
 365   this._renderLineChart();
 366   this._renderAxis();
 367   this._renderAnnotations();
 368 };
 369
 370
 371 DygraphCanvasRenderer.prototype._renderAxis = function() {
 372   if (!this.options.drawXAxis && !this.options.drawYAxis)
 373     return;
 374
 375   var context = this.element.getContext("2d");
 376
 377   var labelStyle = {
 378     "position": "absolute",
 379     "fontSize": this.options.axisLabelFontSize + "px",
 380     "zIndex": 10,
 381     "color": this.options.axisLabelColor,
 382     "width": this.options.axisLabelWidth + "px",
 383     "overflow": "hidden"
 384   };
 385   var makeDiv = function(txt) {
 386     var div = document.createElement("div");
 387     for (var name in labelStyle) {
 388       if (labelStyle.hasOwnProperty(name)) {
 389         div.style[name] = labelStyle[name];
 390       }
 391     }
 392     div.appendChild(document.createTextNode(txt));
 393     return div;
 394   };
 395
 396   // axis lines
 397   context.save();
 398   context.strokeStyle = this.options.axisLineColor;
 399   context.lineWidth = this.options.axisLineWidth;
 400
 401   if (this.options.drawYAxis) {
 402     if (this.layout.yticks && this.layout.yticks.length > 0) {
 403       for (var i = 0; i < this.layout.yticks.length; i++) {
 404         var tick = this.layout.yticks[i];
 405         if (typeof(tick) == "function") return;
 406         var x = this.area.x;
 407         var y = this.area.y + tick[0] * this.area.h;
 408         context.beginPath();
 409         context.moveTo(x, y);
 410         context.lineTo(x - this.options.axisTickSize, y);
 411         context.closePath();
 412         context.stroke();
 413
 414         var label = makeDiv(tick[1]);
 415         var top = (y - this.options.axisLabelFontSize / 2);
 416         if (top < 0) top = 0;
 417
 418         if (top + this.options.axisLabelFontSize + 3 > this.height) {
 419           label.style.bottom = "0px";
 420         } else {
 421           label.style.top = top + "px";
 422         }
 423         label.style.left = "0px";
 424         label.style.textAlign = "right";
 425         label.style.width = this.options.yAxisLabelWidth + "px";
 426         this.container.appendChild(label);
 427         this.ylabels.push(label);
 428       }
 429
 430       // The lowest tick on the y-axis often overlaps with the leftmost
 431       // tick on the x-axis. Shift the bottom tick up a little bit to
 432       // compensate if necessary.
 433       var bottomTick = this.ylabels[0];
 434       var fontSize = this.options.axisLabelFontSize;
 435       var bottom = parseInt(bottomTick.style.top) + fontSize;
 436       if (bottom > this.height - fontSize) {
 437         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 438             fontSize / 2) + "px";
 439       }
 440     }
 441
 442     context.beginPath();
 443     context.moveTo(this.area.x, this.area.y);
 444     context.lineTo(this.area.x, this.area.y + this.area.h);
 445     context.closePath();
 446     context.stroke();
 447   }
 448
 449   if (this.options.drawXAxis) {
 450     if (this.layout.xticks) {
 451       for (var i = 0; i < this.layout.xticks.length; i++) {
 452         var tick = this.layout.xticks[i];
 453         if (typeof(dataset) == "function") return;
 454
 455         var x = this.area.x + tick[0] * this.area.w;
 456         var y = this.area.y + this.area.h;
 457         context.beginPath();
 458         context.moveTo(x, y);
 459         context.lineTo(x, y + this.options.axisTickSize);
 460         context.closePath();
 461         context.stroke();
 462
 463         var label = makeDiv(tick[1]);
 464         label.style.textAlign = "center";
 465         label.style.bottom = "0px";
 466
 467         var left = (x - this.options.axisLabelWidth/2);
 468         if (left + this.options.axisLabelWidth > this.width) {
 469           left = this.width - this.options.xAxisLabelWidth;
 470           label.style.textAlign = "right";
 471         }
 472         if (left < 0) {
 473           left = 0;
 474           label.style.textAlign = "left";
 475         }
 476
 477         label.style.left = left + "px";
 478         label.style.width = this.options.xAxisLabelWidth + "px";
 479         this.container.appendChild(label);
 480         this.xlabels.push(label);
 481       }
 482     }
 483
 484     context.beginPath();
 485     context.moveTo(this.area.x, this.area.y + this.area.h);
 486     context.lineTo(this.area.x + this.area.w, this.area.y + this.area.h);
 487     context.closePath();
 488     context.stroke();
 489   }
 490
 491   context.restore();
 492 };
 493
 494
 495 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 496   var annotationStyle = {
 497     "position": "absolute",
 498     "fontSize": this.options.axisLabelFontSize + "px",
 499     "zIndex": 10,
 500     "width": "20px",
 501     "overflow": "hidden",
 502     "border": "1px solid black",
 503     "background-color": "white",
 504     "text-align": "center"
 505   };
 506
 507   // Get a list of point with annotations.
 508   var points = this.layout.annotated_points;
 509   for (var i = 0; i < points.length; i++) {
 510     var p = points[i];
 511     var div = document.createElement("div");
 512     for (var name in annotationStyle) {
 513       if (annotationStyle.hasOwnProperty(name)) {
 514         div.style[name] = annotationStyle[name];
 515       }
 516     }
 517     div.appendChild(document.createTextNode(p.annotation.shortText));
 518     div.style.left = (p.canvasx - 10) + "px";
 519     div.style.top = p.canvasy + "px";
 520     div.title = p.annotation.text;
 521     div.style.color = this.colors[p.name];
 522     div.style.borderColor = this.colors[p.name];
 523     this.container.appendChild(div);
 524     this.annotations.push(div);
 525   }
 526 };
 527
 528
 529 /**
 530  * Overrides the CanvasRenderer method to draw error bars
 531  */
 532 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 533   var context = this.element.getContext("2d");
 534   var colorCount = this.options.colorScheme.length;
 535   var colorScheme = this.options.colorScheme;
 536   var fillAlpha = this.options.fillAlpha;
 537   var errorBars = this.layout.options.errorBars;
 538   var fillGraph = this.layout.options.fillGraph;
 539   var stackedGraph = this.layout.options.stackedGraph;
 540   var stepPlot = this.layout.options.stepPlot;
 541
 542   var setNames = [];
 543   for (var name in this.layout.datasets) {
 544     if (this.layout.datasets.hasOwnProperty(name)) {
 545       setNames.push(name);
 546     }
 547   }
 548   var setCount = setNames.length;
 549
 550   this.colors = {}
 551   for (var i = 0; i < setCount; i++) {
 552     this.colors[setNames[i]] = colorScheme[i % colorCount];
 553   }
 554
 555   // Update Points
 556   // TODO(danvk): here
 557   for (var i = 0; i < this.layout.points.length; i++) {
 558     var point = this.layout.points[i];
 559     point.canvasx = this.area.w * point.x + this.area.x;
 560     point.canvasy = this.area.h * point.y + this.area.y;
 561   }
 562
 563   // create paths
 564   var isOK = function(x) { return x && !isNaN(x); };
 565
 566   var ctx = context;
 567   if (errorBars) {
 568     if (fillGraph) {
 569       this.dygraph_.warn("Can't use fillGraph option with error bars");
 570     }
 571
 572     for (var i = 0; i < setCount; i++) {
 573       var setName = setNames[i];
 574       var color = this.colors[setName];
 575
 576       // setup graphics context
 577       ctx.save();
 578       var prevX = NaN;
 579       var prevY = NaN;
 580       var prevYs = [-1, -1];
 581       var yscale = this.layout.yscale;
 582       // should be same color as the lines but only 15% opaque.
 583       var rgb = new RGBColor(color);
 584       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 585                             fillAlpha + ')';
 586       ctx.fillStyle = err_color;
 587       ctx.beginPath();
 588       for (var j = 0; j < this.layout.points.length; j++) {
 589         var point = this.layout.points[j];
 590         if (point.name == setName) {
 591           if (!isOK(point.y)) {
 592             prevX = NaN;
 593             continue;
 594           }
 595
 596           // TODO(danvk): here
 597           if (stepPlot) {
 598             var newYs = [ prevY - point.errorPlus * yscale,
 599                           prevY + point.errorMinus * yscale ];
 600             prevY = point.y;
 601           } else {
 602             var newYs = [ point.y - point.errorPlus * yscale,
 603                           point.y + point.errorMinus * yscale ];
 604           }
 605           newYs[0] = this.area.h * newYs[0] + this.area.y;
 606           newYs[1] = this.area.h * newYs[1] + this.area.y;
 607           if (!isNaN(prevX)) {
 608             if (stepPlot) {
 609               ctx.moveTo(prevX, newYs[0]);
 610             } else {
 611               ctx.moveTo(prevX, prevYs[0]);
 612             }
 613             ctx.lineTo(point.canvasx, newYs[0]);
 614             ctx.lineTo(point.canvasx, newYs[1]);
 615             if (stepPlot) {
 616               ctx.lineTo(prevX, newYs[1]);
 617             } else {
 618               ctx.lineTo(prevX, prevYs[1]);
 619             }
 620             ctx.closePath();
 621           }
 622           prevYs = newYs;
 623           prevX = point.canvasx;
 624         }
 625       }
 626       ctx.fill();
 627     }
 628   } else if (fillGraph) {
 629     var axisY = 1.0 + this.layout.minyval * this.layout.yscale;
 630     if (axisY < 0.0) axisY = 0.0;
 631     else if (axisY > 1.0) axisY = 1.0;
 632     axisY = this.area.h * axisY + this.area.y;
 633
 634     var baseline = []  // for stacked graphs: baseline for filling
 635
 636     // process sets in reverse order (needed for stacked graphs)
 637     for (var i = setCount - 1; i >= 0; i--) {
 638       var setName = setNames[i];
 639       var color = this.colors[setName];
 640
 641       // setup graphics context
 642       ctx.save();
 643       var prevX = NaN;
 644       var prevYs = [-1, -1];
 645       var yscale = this.layout.yscale;
 646       // should be same color as the lines but only 15% opaque.
 647       var rgb = new RGBColor(color);
 648       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 649                             fillAlpha + ')';
 650       ctx.fillStyle = err_color;
 651       ctx.beginPath();
 652       for (var j = 0; j < this.layout.points.length; j++) {
 653         var point = this.layout.points[j];
 654         if (point.name == setName) {
 655           if (!isOK(point.y)) {
 656             prevX = NaN;
 657             continue;
 658           }
 659           var newYs;
 660           if (stackedGraph) {
 661             lastY = baseline[point.canvasx];
 662             if (lastY === undefined) lastY = axisY;
 663             baseline[point.canvasx] = point.canvasy;
 664             newYs = [ point.canvasy, lastY ];
 665           } else {
 666             newYs = [ point.canvasy, axisY ];
 667           }
 668           if (!isNaN(prevX)) {
 669             ctx.moveTo(prevX, prevYs[0]);
 670             if (stepPlot) {
 671               ctx.lineTo(point.canvasx, prevYs[0]);
 672             } else {
 673               ctx.lineTo(point.canvasx, newYs[0]);
 674             }
 675             ctx.lineTo(point.canvasx, newYs[1]);
 676             ctx.lineTo(prevX, prevYs[1]);
 677             ctx.closePath();
 678           }
 679           prevYs = newYs;
 680           prevX = point.canvasx;
 681         }
 682       }
 683       ctx.fill();
 684     }
 685   }
 686
 687   for (var i = 0; i < setCount; i++) {
 688     var setName = setNames[i];
 689     var color = this.colors[setName];
 690
 691     // setup graphics context
 692     context.save();
 693     var point = this.layout.points[0];
 694     var pointSize = this.dygraph_.attr_("pointSize");
 695     var prevX = null, prevY = null;
 696     var drawPoints = this.dygraph_.attr_("drawPoints");
 697     var points = this.layout.points;
 698     for (var j = 0; j < points.length; j++) {
 699       var point = points[j];
 700       if (point.name == setName) {
 701         if (!isOK(point.canvasy)) {
 702           // this will make us move to the next point, not draw a line to it.
 703           prevX = prevY = null;
 704         } else {
 705           // A point is "isolated" if it is non-null but both the previous
 706           // and next points are null.
 707           var isIsolated = (!prevX && (j == points.length - 1 ||
 708                                        !isOK(points[j+1].canvasy)));
 709
 710           if (!prevX) {
 711             prevX = point.canvasx;
 712             prevY = point.canvasy;
 713           } else {
 714             ctx.beginPath();
 715             ctx.strokeStyle = color;
 716             ctx.lineWidth = this.options.strokeWidth;
 717             ctx.moveTo(prevX, prevY);
 718             if (stepPlot) {
 719               ctx.lineTo(point.canvasx, prevY);
 720             }
 721             prevX = point.canvasx;
 722             prevY = point.canvasy;
 723             ctx.lineTo(prevX, prevY);
 724             ctx.stroke();
 725           }
 726
 727           if (drawPoints || isIsolated) {
 728            ctx.beginPath();
 729            ctx.fillStyle = color;
 730            ctx.arc(point.canvasx, point.canvasy, pointSize,
 731                    0, 2 * Math.PI, false);
 732            ctx.fill();
 733           }
 734         }
 735       }
 736     }
 737   }
 738
 739   context.restore();
 740 };