dygraph-canvas.js

   1 /**
   2  * @license
   3  * Copyright 2006 Dan Vanderkam (danvdk@gmail.com)
   4  * MIT-licensed (http://opensource.org/licenses/MIT)
   5  */
   6
   7 /**
   8  * @fileoverview Based on PlotKit.CanvasRenderer, but modified to meet the
   9  * needs of dygraphs.
  10  *
  11  * In particular, support for:
  12  * - grid overlays
  13  * - error bars
  14  * - dygraphs attribute system
  15  */
  16
  17 /**
  18  * The DygraphCanvasRenderer class does the actual rendering of the chart onto
  19  * a canvas. It's based on PlotKit.CanvasRenderer.
  20  * @param {Object} element The canvas to attach to
  21  * @param {Object} elementContext The 2d context of the canvas (injected so it
  22  * can be mocked for testing.)
  23  * @param {Layout} layout The DygraphLayout object for this graph.
  24  * @constructor
  25  */
  26 DygraphCanvasRenderer = function(dygraph, element, elementContext, layout) {
  27   this.dygraph_ = dygraph;
  28
  29   this.layout = layout;
  30   this.element = element;
  31   this.elementContext = elementContext;
  32   this.container = this.element.parentNode;
  33
  34   this.height = this.element.height;
  35   this.width = this.element.width;
  36
  37   // --- check whether everything is ok before we return
  38   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
  39       throw "Canvas is not supported.";
  40
  41   // internal state
  42   this.xlabels = new Array();
  43   this.ylabels = new Array();
  44   this.annotations = new Array();
  45   this.chartLabels = {};
  46
  47   this.area = this.computeArea_();
  48   this.container.style.position = "relative";
  49   this.container.style.width = this.width + "px";
  50
  51   // Set up a clipping area for the canvas (and the interaction canvas).
  52   // This ensures that we don't overdraw.
  53   var ctx = this.dygraph_.canvas_ctx_;
  54   ctx.beginPath();
  55   ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h);
  56   ctx.clip();
  57
  58   ctx = this.dygraph_.hidden_ctx_;
  59   ctx.beginPath();
  60   ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h);
  61   ctx.clip();
  62 };
  63
  64 DygraphCanvasRenderer.prototype.attr_ = function(x) {
  65   return this.dygraph_.attr_(x);
  66 };
  67
  68 // Compute the box which the chart should be drawn in. This is the canvas's
  69 // box, less space needed for axis and chart labels.
  70 // TODO(danvk): this belongs in DygraphLayout.
  71 DygraphCanvasRenderer.prototype.computeArea_ = function() {
  72   var area = {
  73     // TODO(danvk): per-axis setting.
  74     x: 0,
  75     y: 0
  76   };
  77   if (this.attr_('drawYAxis')) {
  78    area.x = this.attr_('yAxisLabelWidth') + 2 * this.attr_('axisTickSize');
  79   }
  80
  81   area.w = this.width - area.x - this.attr_('rightGap');
  82   area.h = this.height;
  83   if (this.attr_('drawXAxis')) {
  84     if (this.attr_('xAxisHeight')) {
  85       area.h -= this.attr_('xAxisHeight');
  86     } else {
  87       area.h -= this.attr_('axisLabelFontSize') + 2 * this.attr_('axisTickSize');
  88     }
  89   }
  90
  91   // Shrink the drawing area to accomodate additional y-axes.
  92   if (this.dygraph_.numAxes() == 2) {
  93     // TODO(danvk): per-axis setting.
  94     area.w -= (this.attr_('yAxisLabelWidth') + 2 * this.attr_('axisTickSize'));
  95   } else if (this.dygraph_.numAxes() > 2) {
  96     this.dygraph_.error("Only two y-axes are supported at this time. (Trying " +
  97                         "to use " + this.dygraph_.numAxes() + ")");
  98   }
  99
 100   // Add space for chart labels: title, xlabel and ylabel.
 101   if (this.attr_('title')) {
 102     area.h -= this.attr_('titleHeight');
 103     area.y += this.attr_('titleHeight');
 104   }
 105   if (this.attr_('xlabel')) {
 106     area.h -= this.attr_('xLabelHeight');
 107   }
 108   if (this.attr_('ylabel')) {
 109     // It would make sense to shift the chart here to make room for the y-axis
 110     // label, but the default yAxisLabelWidth is large enough that this results
 111     // in overly-padded charts. The y-axis label should fit fine. If it
 112     // doesn't, the yAxisLabelWidth option can be increased.
 113   }
 114
 115   return area;
 116 };
 117
 118 DygraphCanvasRenderer.prototype.clear = function() {
 119   if (this.isIE) {
 120     // VML takes a while to start up, so we just poll every this.IEDelay
 121     try {
 122       if (this.clearDelay) {
 123         this.clearDelay.cancel();
 124         this.clearDelay = null;
 125       }
 126       var context = this.elementContext;
 127     }
 128     catch (e) {
 129       // TODO(danvk): this is broken, since MochiKit.Async is gone.
 130       this.clearDelay = MochiKit.Async.wait(this.IEDelay);
 131       this.clearDelay.addCallback(bind(this.clear, this));
 132       return;
 133     }
 134   }
 135
 136   var context = this.elementContext;
 137   context.clearRect(0, 0, this.width, this.height);
 138
 139   for (var i = 0; i < this.xlabels.length; i++) {
 140     var el = this.xlabels[i];
 141     if (el.parentNode) el.parentNode.removeChild(el);
 142   }
 143   for (var i = 0; i < this.ylabels.length; i++) {
 144     var el = this.ylabels[i];
 145     if (el.parentNode) el.parentNode.removeChild(el);
 146   }
 147   for (var i = 0; i < this.annotations.length; i++) {
 148     var el = this.annotations[i];
 149     if (el.parentNode) el.parentNode.removeChild(el);
 150   }
 151   for (var k in this.chartLabels) {
 152     if (!this.chartLabels.hasOwnProperty(k)) continue;
 153     var el = this.chartLabels[k];
 154     if (el.parentNode) el.parentNode.removeChild(el);
 155   }
 156   this.xlabels = new Array();
 157   this.ylabels = new Array();
 158   this.annotations = new Array();
 159   this.chartLabels = {};
 160 };
 161
 162
 163 DygraphCanvasRenderer.isSupported = function(canvasName) {
 164   var canvas = null;
 165   try {
 166     if (typeof(canvasName) == 'undefined' || canvasName == null)
 167       canvas = document.createElement("canvas");
 168     else
 169       canvas = canvasName;
 170     var context = canvas.getContext("2d");
 171   }
 172   catch (e) {
 173     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 174     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 175     if ((!ie) || (ie[1] < 6) || (opera))
 176       return false;
 177     return true;
 178   }
 179   return true;
 180 };
 181
 182 /**
 183  * @param { [String] } colors Array of color strings. Should have one entry for
 184  * each series to be rendered.
 185  */
 186 DygraphCanvasRenderer.prototype.setColors = function(colors) {
 187   this.colorScheme_ = colors;
 188 };
 189
 190 /**
 191  * Draw an X/Y grid on top of the existing plot
 192  */
 193 DygraphCanvasRenderer.prototype.render = function() {
 194   // Draw the new X/Y grid. Lines appear crisper when pixels are rounded to
 195   // half-integers. This prevents them from drawing in two rows/cols.
 196   var ctx = this.elementContext;
 197   function halfUp(x){return Math.round(x)+0.5};
 198   function halfDown(y){return Math.round(y)-0.5};
 199
 200   if (this.attr_('underlayCallback')) {
 201     // NOTE: we pass the dygraph object to this callback twice to avoid breaking
 202     // users who expect a deprecated form of this callback.
 203     this.attr_('underlayCallback')(ctx, this.area, this.dygraph_, this.dygraph_);
 204   }
 205
 206   if (this.attr_('drawYGrid')) {
 207     var ticks = this.layout.yticks;
 208     ctx.save();
 209     ctx.strokeStyle = this.attr_('gridLineColor');
 210     ctx.lineWidth = this.attr_('gridLineWidth');
 211     for (var i = 0; i < ticks.length; i++) {
 212       // TODO(danvk): allow secondary axes to draw a grid, too.
 213       if (ticks[i][0] != 0) continue;
 214       var x = halfUp(this.area.x);
 215       var y = halfDown(this.area.y + ticks[i][1] * this.area.h);
 216       ctx.beginPath();
 217       ctx.moveTo(x, y);
 218       ctx.lineTo(x + this.area.w, y);
 219       ctx.closePath();
 220       ctx.stroke();
 221     }
 222   }
 223
 224   if (this.attr_('drawXGrid')) {
 225     var ticks = this.layout.xticks;
 226     ctx.save();
 227     ctx.strokeStyle = this.attr_('gridLineColor');
 228     ctx.lineWidth = this.attr_('gridLineWidth');
 229     for (var i=0; i<ticks.length; i++) {
 230       var x = halfUp(this.area.x + ticks[i][0] * this.area.w);
 231       var y = halfDown(this.area.y + this.area.h);
 232       ctx.beginPath();
 233       ctx.moveTo(x, y);
 234       ctx.lineTo(x, this.area.y);
 235       ctx.closePath();
 236       ctx.stroke();
 237     }
 238   }
 239
 240   // Do the ordinary rendering, as before
 241   this._renderLineChart();
 242   this._renderAxis();
 243   this._renderChartLabels();
 244   this._renderAnnotations();
 245 };
 246
 247
 248 DygraphCanvasRenderer.prototype._renderAxis = function() {
 249   if (!this.attr_('drawXAxis') && !this.attr_('drawYAxis')) return;
 250
 251   // Round pixels to half-integer boundaries for crisper drawing.
 252   function halfUp(x){return Math.round(x)+0.5};
 253   function halfDown(y){return Math.round(y)-0.5};
 254
 255   var context = this.elementContext;
 256
 257   var labelStyle = {
 258     position: "absolute",
 259     fontSize: this.attr_('axisLabelFontSize') + "px",
 260     zIndex: 10,
 261     color: this.attr_('axisLabelColor'),
 262     width: this.attr_('axisLabelWidth') + "px",
 263     // height: this.attr_('axisLabelFontSize') + 2 + "px",
 264     overflow: "hidden"
 265   };
 266   var makeDiv = function(txt, axis, prec_axis) {
 267     var div = document.createElement("div");
 268     for (var name in labelStyle) {
 269       if (labelStyle.hasOwnProperty(name)) {
 270         div.style[name] = labelStyle[name];
 271       }
 272     }
 273     var inner_div = document.createElement("div");
 274     inner_div.className = 'dygraph-axis-label' +
 275                           ' dygraph-axis-label-' + axis +
 276                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 277     inner_div.appendChild(document.createTextNode(txt));
 278     div.appendChild(inner_div);
 279     return div;
 280   };
 281
 282   // axis lines
 283   context.save();
 284   context.strokeStyle = this.attr_('axisLineColor');
 285   context.lineWidth = this.attr_('axisLineWidth');
 286
 287   if (this.attr_('drawYAxis')) {
 288     if (this.layout.yticks && this.layout.yticks.length > 0) {
 289       var num_axes = this.dygraph_.numAxes();
 290       for (var i = 0; i < this.layout.yticks.length; i++) {
 291         var tick = this.layout.yticks[i];
 292         if (typeof(tick) == "function") return;
 293         var x = this.area.x;
 294         var sgn = 1;
 295         var prec_axis = 'y1';
 296         if (tick[0] == 1) {  // right-side y-axis
 297           x = this.area.x + this.area.w;
 298           sgn = -1;
 299           prec_axis = 'y2';
 300         }
 301         var y = this.area.y + tick[1] * this.area.h;
 302         context.beginPath();
 303         context.moveTo(halfUp(x), halfDown(y));
 304         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 305         context.closePath();
 306         context.stroke();
 307
 308         var label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null);
 309         var top = (y - this.attr_('axisLabelFontSize') / 2);
 310         if (top < 0) top = 0;
 311
 312         if (top + this.attr_('axisLabelFontSize') + 3 > this.height) {
 313           label.style.bottom = "0px";
 314         } else {
 315           label.style.top = top + "px";
 316         }
 317         if (tick[0] == 0) {
 318           label.style.left = (this.area.x - this.attr_('yAxisLabelWidth') - this.attr_('axisTickSize')) + "px";
 319           label.style.textAlign = "right";
 320         } else if (tick[0] == 1) {
 321           label.style.left = (this.area.x + this.area.w +
 322                               this.attr_('axisTickSize')) + "px";
 323           label.style.textAlign = "left";
 324         }
 325         label.style.width = this.attr_('yAxisLabelWidth') + "px";
 326         this.container.appendChild(label);
 327         this.ylabels.push(label);
 328       }
 329
 330       // The lowest tick on the y-axis often overlaps with the leftmost
 331       // tick on the x-axis. Shift the bottom tick up a little bit to
 332       // compensate if necessary.
 333       var bottomTick = this.ylabels[0];
 334       var fontSize = this.attr_('axisLabelFontSize');
 335       var bottom = parseInt(bottomTick.style.top) + fontSize;
 336       if (bottom > this.height - fontSize) {
 337         bottomTick.style.top = (parseInt(bottomTick.style.top) -
 338             fontSize / 2) + "px";
 339       }
 340     }
 341
 342     // draw a vertical line on the left to separate the chart from the labels.
 343     context.beginPath();
 344     context.moveTo(halfUp(this.area.x), halfDown(this.area.y));
 345     context.lineTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 346     context.closePath();
 347     context.stroke();
 348
 349     // if there's a secondary y-axis, draw a vertical line for that, too.
 350     if (this.dygraph_.numAxes() == 2) {
 351       context.beginPath();
 352       context.moveTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y));
 353       context.lineTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 354       context.closePath();
 355       context.stroke();
 356     }
 357   }
 358
 359   if (this.attr_('drawXAxis')) {
 360     if (this.layout.xticks) {
 361       for (var i = 0; i < this.layout.xticks.length; i++) {
 362         var tick = this.layout.xticks[i];
 363         if (typeof(dataset) == "function") return;
 364
 365         var x = this.area.x + tick[0] * this.area.w;
 366         var y = this.area.y + this.area.h;
 367         context.beginPath();
 368         context.moveTo(halfUp(x), halfDown(y));
 369         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 370         context.closePath();
 371         context.stroke();
 372
 373         var label = makeDiv(tick[1], 'x');
 374         label.style.textAlign = "center";
 375         label.style.top = (y + this.attr_('axisTickSize')) + 'px';
 376
 377         var left = (x - this.attr_('axisLabelWidth')/2);
 378         if (left + this.attr_('axisLabelWidth') > this.width) {
 379           left = this.width - this.attr_('xAxisLabelWidth');
 380           label.style.textAlign = "right";
 381         }
 382         if (left < 0) {
 383           left = 0;
 384           label.style.textAlign = "left";
 385         }
 386
 387         label.style.left = left + "px";
 388         label.style.width = this.attr_('xAxisLabelWidth') + "px";
 389         this.container.appendChild(label);
 390         this.xlabels.push(label);
 391       }
 392     }
 393
 394     context.beginPath();
 395     context.moveTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 396     context.lineTo(halfUp(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 397     context.closePath();
 398     context.stroke();
 399   }
 400
 401   context.restore();
 402 };
 403
 404
 405 DygraphCanvasRenderer.prototype._renderChartLabels = function() {
 406   // Generate divs for the chart title, xlabel and ylabel.
 407   // Space for these divs has already been taken away from the charting area in
 408   // the DygraphCanvasRenderer constructor.
 409   if (this.attr_('title')) {
 410     var div = document.createElement("div");
 411     div.style.position = 'absolute';
 412     div.style.top = '0px';
 413     div.style.left = this.area.x + 'px';
 414     div.style.width = this.area.w + 'px';
 415     div.style.height = this.attr_('titleHeight') + 'px';
 416     div.style.textAlign = 'center';
 417     div.style.fontSize = (this.attr_('titleHeight') - 8) + 'px';
 418     div.style.fontWeight = 'bold';
 419     var class_div = document.createElement("div");
 420     class_div.className = 'dygraph-label dygraph-title';
 421     class_div.innerHTML = this.attr_('title');
 422     div.appendChild(class_div);
 423     this.container.appendChild(div);
 424     this.chartLabels.title = div;
 425   }
 426
 427   if (this.attr_('xlabel')) {
 428     var div = document.createElement("div");
 429     div.style.position = 'absolute';
 430     div.style.bottom = 0;  // TODO(danvk): this is lazy. Calculate style.top.
 431     div.style.left = this.area.x + 'px';
 432     div.style.width = this.area.w + 'px';
 433     div.style.height = this.attr_('xLabelHeight') + 'px';
 434     div.style.textAlign = 'center';
 435     div.style.fontSize = (this.attr_('xLabelHeight') - 2) + 'px';
 436
 437     var class_div = document.createElement("div");
 438     class_div.className = 'dygraph-label dygraph-xlabel';
 439     class_div.innerHTML = this.attr_('xlabel');
 440     div.appendChild(class_div);
 441     this.container.appendChild(div);
 442     this.chartLabels.xlabel = div;
 443   }
 444
 445   if (this.attr_('ylabel')) {
 446     var box = {
 447       left: 0,
 448       top: this.area.y,
 449       width: this.attr_('yLabelWidth'),
 450       height: this.area.h
 451     };
 452     // TODO(danvk): is this outer div actually necessary?
 453     var div = document.createElement("div");
 454     div.style.position = 'absolute';
 455     div.style.left = box.left;
 456     div.style.top = box.top + 'px';
 457     div.style.width = box.width + 'px';
 458     div.style.height = box.height + 'px';
 459     div.style.fontSize = (this.attr_('yLabelWidth') - 2) + 'px';
 460
 461     var inner_div = document.createElement("div");
 462     inner_div.style.position = 'absolute';
 463     inner_div.style.width = box.height + 'px';
 464     inner_div.style.height = box.width + 'px';
 465     inner_div.style.top = (box.height / 2 - box.width / 2) + 'px';
 466     inner_div.style.left = (box.width / 2 - box.height / 2) + 'px';
 467     inner_div.style.textAlign = 'center';
 468
 469     // CSS rotation is an HTML5 feature which is not standardized. Hence every
 470     // browser has its own name for the CSS style.
 471     inner_div.style.transform = 'rotate(-90deg)';        // HTML5
 472     inner_div.style.WebkitTransform = 'rotate(-90deg)';  // Safari/Chrome
 473     inner_div.style.MozTransform = 'rotate(-90deg)';     // Firefox
 474     inner_div.style.OTransform = 'rotate(-90deg)';       // Opera
 475     inner_div.style.msTransform = 'rotate(-90deg)';      // IE9
 476
 477     if (typeof(document.documentMode) !== 'undefined' &&
 478         document.documentMode < 9) {
 479       // We're dealing w/ an old version of IE, so we have to rotate the text
 480       // using a BasicImage transform. This uses a different origin of rotation
 481       // than HTML5 rotation (top left of div vs. its center).
 482       inner_div.style.filter =
 483        'progid:DXImageTransform.Microsoft.BasicImage(rotation=3)';
 484       inner_div.style.left = '0px';
 485       inner_div.style.top = '0px';
 486     }
 487
 488     var class_div = document.createElement("div");
 489     class_div.className = 'dygraph-label dygraph-ylabel';
 490     class_div.innerHTML = this.attr_('ylabel');
 491
 492     inner_div.appendChild(class_div);
 493     div.appendChild(inner_div);
 494     this.container.appendChild(div);
 495     this.chartLabels.ylabel = div;
 496   }
 497 };
 498
 499
 500 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 501   var annotationStyle = {
 502     "position": "absolute",
 503     "fontSize": this.attr_('axisLabelFontSize') + "px",
 504     "zIndex": 10,
 505     "overflow": "hidden"
 506   };
 507
 508   var bindEvt = function(eventName, classEventName, p, self) {
 509     return function(e) {
 510       var a = p.annotation;
 511       if (a.hasOwnProperty(eventName)) {
 512         a[eventName](a, p, self.dygraph_, e);
 513       } else if (self.dygraph_.attr_(classEventName)) {
 514         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 515       }
 516     };
 517   }
 518
 519   // Get a list of point with annotations.
 520   var points = this.layout.annotated_points;
 521   for (var i = 0; i < points.length; i++) {
 522     var p = points[i];
 523     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 524       continue;
 525     }
 526
 527     var a = p.annotation;
 528     var tick_height = 6;
 529     if (a.hasOwnProperty("tickHeight")) {
 530       tick_height = a.tickHeight;
 531     }
 532
 533     var div = document.createElement("div");
 534     for (var name in annotationStyle) {
 535       if (annotationStyle.hasOwnProperty(name)) {
 536         div.style[name] = annotationStyle[name];
 537       }
 538     }
 539     if (!a.hasOwnProperty('icon')) {
 540       div.className = "dygraphDefaultAnnotation";
 541     }
 542     if (a.hasOwnProperty('cssClass')) {
 543       div.className += " " + a.cssClass;
 544     }
 545
 546     var width = a.hasOwnProperty('width') ? a.width : 16;
 547     var height = a.hasOwnProperty('height') ? a.height : 16;
 548     if (a.hasOwnProperty('icon')) {
 549       var img = document.createElement("img");
 550       img.src = a.icon;
 551       img.width = width;
 552       img.height = height;
 553       div.appendChild(img);
 554     } else if (p.annotation.hasOwnProperty('shortText')) {
 555       div.appendChild(document.createTextNode(p.annotation.shortText));
 556     }
 557     div.style.left = (p.canvasx - width / 2) + "px";
 558     if (a.attachAtBottom) {
 559       div.style.top = (this.area.h - height - tick_height) + "px";
 560     } else {
 561       div.style.top = (p.canvasy - height - tick_height) + "px";
 562     }
 563     div.style.width = width + "px";
 564     div.style.height = height + "px";
 565     div.title = p.annotation.text;
 566     div.style.color = this.colors[p.name];
 567     div.style.borderColor = this.colors[p.name];
 568     a.div = div;
 569
 570     Dygraph.addEvent(div, 'click',
 571         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 572     Dygraph.addEvent(div, 'mouseover',
 573         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 574     Dygraph.addEvent(div, 'mouseout',
 575         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 576     Dygraph.addEvent(div, 'dblclick',
 577         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 578
 579     this.container.appendChild(div);
 580     this.annotations.push(div);
 581
 582     var ctx = this.elementContext;
 583     ctx.strokeStyle = this.colors[p.name];
 584     ctx.beginPath();
 585     if (!a.attachAtBottom) {
 586       ctx.moveTo(p.canvasx, p.canvasy);
 587       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 588     } else {
 589       ctx.moveTo(p.canvasx, this.area.h);
 590       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 591     }
 592     ctx.closePath();
 593     ctx.stroke();
 594   }
 595 };
 596
 597
 598 /**
 599  * Overrides the CanvasRenderer method to draw error bars
 600  */
 601 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 602   var isNullOrNaN = function(x) {
 603     return (x === null || isNaN(x));
 604   };
 605
 606   // TODO(danvk): use this.attr_ for many of these.
 607   var context = this.elementContext;
 608   var fillAlpha = this.attr_('fillAlpha');
 609   var errorBars = this.attr_("errorBars") || this.attr_("customBars");
 610   var fillGraph = this.attr_("fillGraph");
 611   var stackedGraph = this.attr_("stackedGraph");
 612   var stepPlot = this.attr_("stepPlot");
 613   var points = this.layout.points;
 614   var pointsLength = points.length;
 615
 616   var setNames = [];
 617   for (var name in this.layout.datasets) {
 618     if (this.layout.datasets.hasOwnProperty(name)) {
 619       setNames.push(name);
 620     }
 621   }
 622   var setCount = setNames.length;
 623
 624   // TODO(danvk): Move this mapping into Dygraph and get it out of here.
 625   this.colors = {}
 626   for (var i = 0; i < setCount; i++) {
 627     this.colors[setNames[i]] = this.colorScheme_[i % this.colorScheme_.length];
 628   }
 629
 630   // Update Points
 631   // TODO(danvk): here
 632   for (var i = pointsLength; i--;) {
 633     var point = points[i];
 634     point.canvasx = this.area.w * point.x + this.area.x;
 635     point.canvasy = this.area.h * point.y + this.area.y;
 636   }
 637
 638   // create paths
 639   var ctx = context;
 640   if (errorBars) {
 641     if (fillGraph) {
 642       this.dygraph_.warn("Can't use fillGraph option with error bars");
 643     }
 644
 645     for (var i = 0; i < setCount; i++) {
 646       var setName = setNames[i];
 647       var axis = this.dygraph_.axisPropertiesForSeries(setName);
 648       var color = this.colors[setName];
 649
 650       // setup graphics context
 651       ctx.save();
 652       var prevX = NaN;
 653       var prevY = NaN;
 654       var prevYs = [-1, -1];
 655       var yscale = axis.yscale;
 656       // should be same color as the lines but only 15% opaque.
 657       var rgb = new RGBColor(color);
 658       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 659                             fillAlpha + ')';
 660       ctx.fillStyle = err_color;
 661       ctx.beginPath();
 662       for (var j = 0; j < pointsLength; j++) {
 663         var point = points[j];
 664         if (point.name == setName) {
 665           if (!Dygraph.isOK(point.y)) {
 666             prevX = NaN;
 667             continue;
 668           }
 669
 670           // TODO(danvk): here
 671           if (stepPlot) {
 672             var newYs = [ point.y_bottom, point.y_top ];
 673             prevY = point.y;
 674           } else {
 675             var newYs = [ point.y_bottom, point.y_top ];
 676           }
 677           newYs[0] = this.area.h * newYs[0] + this.area.y;
 678           newYs[1] = this.area.h * newYs[1] + this.area.y;
 679           if (!isNaN(prevX)) {
 680             if (stepPlot) {
 681               ctx.moveTo(prevX, newYs[0]);
 682             } else {
 683               ctx.moveTo(prevX, prevYs[0]);
 684             }
 685             ctx.lineTo(point.canvasx, newYs[0]);
 686             ctx.lineTo(point.canvasx, newYs[1]);
 687             if (stepPlot) {
 688               ctx.lineTo(prevX, newYs[1]);
 689             } else {
 690               ctx.lineTo(prevX, prevYs[1]);
 691             }
 692             ctx.closePath();
 693           }
 694           prevYs = newYs;
 695           prevX = point.canvasx;
 696         }
 697       }
 698       ctx.fill();
 699     }
 700   } else if (fillGraph) {
 701     var baseline = []  // for stacked graphs: baseline for filling
 702
 703     // process sets in reverse order (needed for stacked graphs)
 704     for (var i = setCount - 1; i >= 0; i--) {
 705       var setName = setNames[i];
 706       var color = this.colors[setName];
 707       var axis = this.dygraph_.axisPropertiesForSeries(setName);
 708       var axisY = 1.0 + axis.minyval * axis.yscale;
 709       if (axisY < 0.0) axisY = 0.0;
 710       else if (axisY > 1.0) axisY = 1.0;
 711       axisY = this.area.h * axisY + this.area.y;
 712
 713       // setup graphics context
 714       ctx.save();
 715       var prevX = NaN;
 716       var prevYs = [-1, -1];
 717       var yscale = axis.yscale;
 718       // should be same color as the lines but only 15% opaque.
 719       var rgb = new RGBColor(color);
 720       var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 721                             fillAlpha + ')';
 722       ctx.fillStyle = err_color;
 723       ctx.beginPath();
 724       for (var j = 0; j < pointsLength; j++) {
 725         var point = points[j];
 726         if (point.name == setName) {
 727           if (!Dygraph.isOK(point.y)) {
 728             prevX = NaN;
 729             continue;
 730           }
 731           var newYs;
 732           if (stackedGraph) {
 733             lastY = baseline[point.canvasx];
 734             if (lastY === undefined) lastY = axisY;
 735             baseline[point.canvasx] = point.canvasy;
 736             newYs = [ point.canvasy, lastY ];
 737           } else {
 738             newYs = [ point.canvasy, axisY ];
 739           }
 740           if (!isNaN(prevX)) {
 741             ctx.moveTo(prevX, prevYs[0]);
 742             if (stepPlot) {
 743               ctx.lineTo(point.canvasx, prevYs[0]);
 744             } else {
 745               ctx.lineTo(point.canvasx, newYs[0]);
 746             }
 747             ctx.lineTo(point.canvasx, newYs[1]);
 748             ctx.lineTo(prevX, prevYs[1]);
 749             ctx.closePath();
 750           }
 751           prevYs = newYs;
 752           prevX = point.canvasx;
 753         }
 754       }
 755       ctx.fill();
 756     }
 757   }
 758
 759   // Drawing the lines.
 760   var firstIndexInSet = 0;
 761   var afterLastIndexInSet = 0;
 762   var setLength = 0;
 763   for (var i = 0; i < setCount; i += 1) {
 764     setLength = this.layout.setPointsLengths[i];
 765     afterLastIndexInSet += setLength;
 766     var setName = setNames[i];
 767     var color = this.colors[setName];
 768     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 769
 770     // setup graphics context
 771     context.save();
 772     var pointSize = this.dygraph_.attr_("pointSize", setName);
 773     var prevX = null, prevY = null;
 774     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 775     for (var j = firstIndexInSet; j < afterLastIndexInSet; j++) {
 776       var point = points[j];
 777       if (isNullOrNaN(point.canvasy)) {
 778         if (stepPlot && prevX != null) {
 779           // Draw a horizontal line to the start of the missing data
 780           ctx.beginPath();
 781           ctx.strokeStyle = color;
 782           ctx.lineWidth = this.attr_('strokeWidth');
 783           ctx.moveTo(prevX, prevY);
 784           ctx.lineTo(point.canvasx, prevY);
 785           ctx.stroke();
 786         }
 787         // this will make us move to the next point, not draw a line to it.
 788         prevX = prevY = null;
 789       } else {
 790         // A point is "isolated" if it is non-null but both the previous
 791         // and next points are null.
 792         var isIsolated = (!prevX && (j == points.length - 1 ||
 793                                      isNullOrNaN(points[j+1].canvasy)));
 794         if (prevX === null) {
 795           prevX = point.canvasx;
 796           prevY = point.canvasy;
 797         } else {
 798           // Skip over points that will be drawn in the same pixel.
 799           if (Math.round(prevX) == Math.round(point.canvasx) &&
 800               Math.round(prevY) == Math.round(point.canvasy)) {
 801             continue;
 802           }
 803           // TODO(antrob): skip over points that lie on a line that is already
 804           // going to be drawn. There is no need to have more than 2
 805           // consecutive points that are collinear.
 806           if (strokeWidth) {
 807             ctx.beginPath();
 808             ctx.strokeStyle = color;
 809             ctx.lineWidth = strokeWidth;
 810             ctx.moveTo(prevX, prevY);
 811             if (stepPlot) {
 812               ctx.lineTo(point.canvasx, prevY);
 813             }
 814             prevX = point.canvasx;
 815             prevY = point.canvasy;
 816             ctx.lineTo(prevX, prevY);
 817             ctx.stroke();
 818           }
 819         }
 820
 821         if (drawPoints || isIsolated) {
 822           ctx.beginPath();
 823           ctx.fillStyle = color;
 824           ctx.arc(point.canvasx, point.canvasy, pointSize,
 825                   0, 2 * Math.PI, false);
 826           ctx.fill();
 827         }
 828       }
 829     }
 830     firstIndexInSet = afterLastIndexInSet;
 831   }
 832
 833   context.restore();
 834 };