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
  27 /*jshint globalstrict: true */
  28 /*global Dygraph:false,RGBColor:false */
  29 "use strict";
  30
  31 var DygraphCanvasRenderer = function(dygraph, element, elementContext, layout) {
  32   this.dygraph_ = dygraph;
  33
  34   this.layout = layout;
  35   this.element = element;
  36   this.elementContext = elementContext;
  37   this.container = this.element.parentNode;
  38
  39   this.height = this.element.height;
  40   this.width = this.element.width;
  41
  42   // --- check whether everything is ok before we return
  43   if (!this.isIE && !(DygraphCanvasRenderer.isSupported(this.element)))
  44       throw "Canvas is not supported.";
  45
  46   // internal state
  47   this.xlabels = [];
  48   this.ylabels = [];
  49   this.annotations = [];
  50   this.chartLabels = {};
  51
  52   this.area = layout.getPlotArea();
  53   this.container.style.position = "relative";
  54   this.container.style.width = this.width + "px";
  55
  56   // Set up a clipping area for the canvas (and the interaction canvas).
  57   // This ensures that we don't overdraw.
  58   if (this.dygraph_.isUsingExcanvas_) {
  59     this._createIEClipArea();
  60   } else {
  61     // on Android 3 and 4, setting a clipping area on a canvas prevents it from
  62     // displaying anything.
  63     if (!Dygraph.isAndroid()) {
  64       var ctx = this.dygraph_.canvas_ctx_;
  65       ctx.beginPath();
  66       ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h);
  67       ctx.clip();
  68
  69       ctx = this.dygraph_.hidden_ctx_;
  70       ctx.beginPath();
  71       ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h);
  72       ctx.clip();
  73     }
  74   }
  75 };
  76
  77 DygraphCanvasRenderer.prototype.attr_ = function(x) {
  78   return this.dygraph_.attr_(x);
  79 };
  80
  81 DygraphCanvasRenderer.prototype.clear = function() {
  82   var context;
  83   if (this.isIE) {
  84     // VML takes a while to start up, so we just poll every this.IEDelay
  85     try {
  86       if (this.clearDelay) {
  87         this.clearDelay.cancel();
  88         this.clearDelay = null;
  89       }
  90       context = this.elementContext;
  91     }
  92     catch (e) {
  93       // TODO(danvk): this is broken, since MochiKit.Async is gone.
  94       // this.clearDelay = MochiKit.Async.wait(this.IEDelay);
  95       // this.clearDelay.addCallback(bind(this.clear, this));
  96       return;
  97     }
  98   }
  99
 100   context = this.elementContext;
 101   context.clearRect(0, 0, this.width, this.height);
 102
 103   function removeArray(ary) {
 104     for (var i = 0; i < ary.length; i++) {
 105       var el = ary[i];
 106       if (el.parentNode) el.parentNode.removeChild(el);
 107     }
 108   }
 109
 110   removeArray(this.xlabels);
 111   removeArray(this.ylabels);
 112   removeArray(this.annotations);
 113
 114   for (var k in this.chartLabels) {
 115     if (!this.chartLabels.hasOwnProperty(k)) continue;
 116     var el = this.chartLabels[k];
 117     if (el.parentNode) el.parentNode.removeChild(el);
 118   }
 119   this.xlabels = [];
 120   this.ylabels = [];
 121   this.annotations = [];
 122   this.chartLabels = {};
 123 };
 124
 125
 126 DygraphCanvasRenderer.isSupported = function(canvasName) {
 127   var canvas = null;
 128   try {
 129     if (typeof(canvasName) == 'undefined' || canvasName === null) {
 130       canvas = document.createElement("canvas");
 131     } else {
 132       canvas = canvasName;
 133     }
 134     canvas.getContext("2d");
 135   }
 136   catch (e) {
 137     var ie = navigator.appVersion.match(/MSIE (\d\.\d)/);
 138     var opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
 139     if ((!ie) || (ie[1] < 6) || (opera))
 140       return false;
 141     return true;
 142   }
 143   return true;
 144 };
 145
 146 /**
 147  * @param { [String] } colors Array of color strings. Should have one entry for
 148  * each series to be rendered.
 149  */
 150 DygraphCanvasRenderer.prototype.setColors = function(colors) {
 151   this.colorScheme_ = colors;
 152 };
 153
 154 /**
 155  * Draw an X/Y grid on top of the existing plot
 156  */
 157 DygraphCanvasRenderer.prototype.render = function() {
 158   // Draw the new X/Y grid. Lines appear crisper when pixels are rounded to
 159   // half-integers. This prevents them from drawing in two rows/cols.
 160   var ctx = this.elementContext;
 161   function halfUp(x)  { return Math.round(x) + 0.5; }
 162   function halfDown(y){ return Math.round(y) - 0.5; }
 163
 164   if (this.attr_('underlayCallback')) {
 165     // NOTE: we pass the dygraph object to this callback twice to avoid breaking
 166     // users who expect a deprecated form of this callback.
 167     this.attr_('underlayCallback')(ctx, this.area, this.dygraph_, this.dygraph_);
 168   }
 169
 170   var x, y, i, ticks;
 171   if (this.attr_('drawYGrid')) {
 172     ticks = this.layout.yticks;
 173     // TODO(konigsberg): I don't think these calls to save() have a corresponding restore().
 174     ctx.save();
 175     ctx.strokeStyle = this.attr_('gridLineColor');
 176     ctx.lineWidth = this.attr_('gridLineWidth');
 177     for (i = 0; i < ticks.length; i++) {
 178       // TODO(danvk): allow secondary axes to draw a grid, too.
 179       if (ticks[i][0] !== 0) continue;
 180       x = halfUp(this.area.x);
 181       y = halfDown(this.area.y + ticks[i][1] * this.area.h);
 182       ctx.beginPath();
 183       ctx.moveTo(x, y);
 184       ctx.lineTo(x + this.area.w, y);
 185       ctx.closePath();
 186       ctx.stroke();
 187     }
 188   }
 189
 190   if (this.attr_('drawXGrid')) {
 191     ticks = this.layout.xticks;
 192     ctx.save();
 193     ctx.strokeStyle = this.attr_('gridLineColor');
 194     ctx.lineWidth = this.attr_('gridLineWidth');
 195     for (i=0; i<ticks.length; i++) {
 196       x = halfUp(this.area.x + ticks[i][0] * this.area.w);
 197       y = halfDown(this.area.y + this.area.h);
 198       ctx.beginPath();
 199       ctx.moveTo(x, y);
 200       ctx.lineTo(x, this.area.y);
 201       ctx.closePath();
 202       ctx.stroke();
 203     }
 204   }
 205
 206   // Do the ordinary rendering, as before
 207   this._renderLineChart();
 208   this._renderAxis();
 209   this._renderChartLabels();
 210   this._renderAnnotations();
 211 };
 212
 213 DygraphCanvasRenderer.prototype._createIEClipArea = function() {
 214   var className = 'dygraph-clip-div';
 215   var graphDiv = this.dygraph_.graphDiv;
 216
 217   // Remove old clip divs.
 218   for (var i = graphDiv.childNodes.length-1; i >= 0; i--) {
 219     if (graphDiv.childNodes[i].className == className) {
 220       graphDiv.removeChild(graphDiv.childNodes[i]);
 221     }
 222   }
 223
 224   // Determine background color to give clip divs.
 225   var backgroundColor = document.bgColor;
 226   var element = this.dygraph_.graphDiv;
 227   while (element != document) {
 228     var bgcolor = element.currentStyle.backgroundColor;
 229     if (bgcolor && bgcolor != 'transparent') {
 230       backgroundColor = bgcolor;
 231       break;
 232     }
 233     element = element.parentNode;
 234   }
 235
 236   function createClipDiv(area) {
 237     if (area.w === 0 || area.h === 0) {
 238       return;
 239     }
 240     var elem = document.createElement('div');
 241     elem.className = className;
 242     elem.style.backgroundColor = backgroundColor;
 243     elem.style.position = 'absolute';
 244     elem.style.left = area.x + 'px';
 245     elem.style.top = area.y + 'px';
 246     elem.style.width = area.w + 'px';
 247     elem.style.height = area.h + 'px';
 248     graphDiv.appendChild(elem);
 249   }
 250
 251   var plotArea = this.area;
 252   // Left side
 253   createClipDiv({
 254     x:0, y:0,
 255     w:plotArea.x,
 256     h:this.height
 257   });
 258
 259   // Top
 260   createClipDiv({
 261     x: plotArea.x, y: 0,
 262     w: this.width - plotArea.x,
 263     h: plotArea.y
 264   });
 265
 266   // Right side
 267   createClipDiv({
 268     x: plotArea.x + plotArea.w, y: 0,
 269     w: this.width-plotArea.x - plotArea.w,
 270     h: this.height
 271   });
 272
 273   // Bottom
 274   createClipDiv({
 275     x: plotArea.x,
 276     y: plotArea.y + plotArea.h,
 277     w: this.width - plotArea.x,
 278     h: this.height - plotArea.h - plotArea.y
 279   });
 280 };
 281
 282 DygraphCanvasRenderer.prototype._renderAxis = function() {
 283   if (!this.attr_('drawXAxis') && !this.attr_('drawYAxis')) return;
 284
 285   // Round pixels to half-integer boundaries for crisper drawing.
 286   function halfUp(x)  { return Math.round(x) + 0.5; }
 287   function halfDown(y){ return Math.round(y) - 0.5; }
 288
 289   var context = this.elementContext;
 290
 291   var label, x, y, tick, i;
 292
 293   var labelStyle = {
 294     position: "absolute",
 295     fontSize: this.attr_('axisLabelFontSize') + "px",
 296     zIndex: 10,
 297     color: this.attr_('axisLabelColor'),
 298     width: this.attr_('axisLabelWidth') + "px",
 299     // height: this.attr_('axisLabelFontSize') + 2 + "px",
 300     lineHeight: "normal",  // Something other than "normal" line-height screws up label positioning.
 301     overflow: "hidden"
 302   };
 303   var makeDiv = function(txt, axis, prec_axis) {
 304     var div = document.createElement("div");
 305     for (var name in labelStyle) {
 306       if (labelStyle.hasOwnProperty(name)) {
 307         div.style[name] = labelStyle[name];
 308       }
 309     }
 310     var inner_div = document.createElement("div");
 311     inner_div.className = 'dygraph-axis-label' +
 312                           ' dygraph-axis-label-' + axis +
 313                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 314     inner_div.appendChild(document.createTextNode(txt));
 315     div.appendChild(inner_div);
 316     return div;
 317   };
 318
 319   // axis lines
 320   context.save();
 321   context.strokeStyle = this.attr_('axisLineColor');
 322   context.lineWidth = this.attr_('axisLineWidth');
 323
 324   if (this.attr_('drawYAxis')) {
 325     if (this.layout.yticks && this.layout.yticks.length > 0) {
 326       var num_axes = this.dygraph_.numAxes();
 327       for (i = 0; i < this.layout.yticks.length; i++) {
 328         tick = this.layout.yticks[i];
 329         if (typeof(tick) == "function") return;
 330         x = this.area.x;
 331         var sgn = 1;
 332         var prec_axis = 'y1';
 333         if (tick[0] == 1) {  // right-side y-axis
 334           x = this.area.x + this.area.w;
 335           sgn = -1;
 336           prec_axis = 'y2';
 337         }
 338         y = this.area.y + tick[1] * this.area.h;
 339
 340         /* Tick marks are currently clipped, so don't bother drawing them.
 341         context.beginPath();
 342         context.moveTo(halfUp(x), halfDown(y));
 343         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 344         context.closePath();
 345         context.stroke();
 346         */
 347
 348         label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null);
 349         var top = (y - this.attr_('axisLabelFontSize') / 2);
 350         if (top < 0) top = 0;
 351
 352         if (top + this.attr_('axisLabelFontSize') + 3 > this.height) {
 353           label.style.bottom = "0px";
 354         } else {
 355           label.style.top = top + "px";
 356         }
 357         if (tick[0] === 0) {
 358           label.style.left = (this.area.x - this.attr_('yAxisLabelWidth') - this.attr_('axisTickSize')) + "px";
 359           label.style.textAlign = "right";
 360         } else if (tick[0] == 1) {
 361           label.style.left = (this.area.x + this.area.w +
 362                               this.attr_('axisTickSize')) + "px";
 363           label.style.textAlign = "left";
 364         }
 365         label.style.width = this.attr_('yAxisLabelWidth') + "px";
 366         this.container.appendChild(label);
 367         this.ylabels.push(label);
 368       }
 369
 370       // The lowest tick on the y-axis often overlaps with the leftmost
 371       // tick on the x-axis. Shift the bottom tick up a little bit to
 372       // compensate if necessary.
 373       var bottomTick = this.ylabels[0];
 374       var fontSize = this.attr_('axisLabelFontSize');
 375       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 376       if (bottom > this.height - fontSize) {
 377         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 378             fontSize / 2) + "px";
 379       }
 380     }
 381
 382     // draw a vertical line on the left to separate the chart from the labels.
 383     context.beginPath();
 384     context.moveTo(halfUp(this.area.x), halfDown(this.area.y));
 385     context.lineTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 386     context.closePath();
 387     context.stroke();
 388
 389     // if there's a secondary y-axis, draw a vertical line for that, too.
 390     if (this.dygraph_.numAxes() == 2) {
 391       context.beginPath();
 392       context.moveTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y));
 393       context.lineTo(halfDown(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 394       context.closePath();
 395       context.stroke();
 396     }
 397   }
 398
 399   if (this.attr_('drawXAxis')) {
 400     if (this.layout.xticks) {
 401       for (i = 0; i < this.layout.xticks.length; i++) {
 402         tick = this.layout.xticks[i];
 403         x = this.area.x + tick[0] * this.area.w;
 404         y = this.area.y + this.area.h;
 405
 406         /* Tick marks are currently clipped, so don't bother drawing them.
 407         context.beginPath();
 408         context.moveTo(halfUp(x), halfDown(y));
 409         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 410         context.closePath();
 411         context.stroke();
 412         */
 413
 414         label = makeDiv(tick[1], 'x');
 415         label.style.textAlign = "center";
 416         label.style.top = (y + this.attr_('axisTickSize')) + 'px';
 417
 418         var left = (x - this.attr_('axisLabelWidth')/2);
 419         if (left + this.attr_('axisLabelWidth') > this.width) {
 420           left = this.width - this.attr_('xAxisLabelWidth');
 421           label.style.textAlign = "right";
 422         }
 423         if (left < 0) {
 424           left = 0;
 425           label.style.textAlign = "left";
 426         }
 427
 428         label.style.left = left + "px";
 429         label.style.width = this.attr_('xAxisLabelWidth') + "px";
 430         this.container.appendChild(label);
 431         this.xlabels.push(label);
 432       }
 433     }
 434
 435     context.beginPath();
 436     context.moveTo(halfUp(this.area.x), halfDown(this.area.y + this.area.h));
 437     context.lineTo(halfUp(this.area.x + this.area.w), halfDown(this.area.y + this.area.h));
 438     context.closePath();
 439     context.stroke();
 440   }
 441
 442   context.restore();
 443 };
 444
 445
 446 DygraphCanvasRenderer.prototype._renderChartLabels = function() {
 447   var div, class_div;
 448
 449   // Generate divs for the chart title, xlabel and ylabel.
 450   // Space for these divs has already been taken away from the charting area in
 451   // the DygraphCanvasRenderer constructor.
 452   if (this.attr_('title')) {
 453     div = document.createElement("div");
 454     div.style.position = 'absolute';
 455     div.style.top = '0px';
 456     div.style.left = this.area.x + 'px';
 457     div.style.width = this.area.w + 'px';
 458     div.style.height = this.attr_('titleHeight') + 'px';
 459     div.style.textAlign = 'center';
 460     div.style.fontSize = (this.attr_('titleHeight') - 8) + 'px';
 461     div.style.fontWeight = 'bold';
 462     class_div = document.createElement("div");
 463     class_div.className = 'dygraph-label dygraph-title';
 464     class_div.innerHTML = this.attr_('title');
 465     div.appendChild(class_div);
 466     this.container.appendChild(div);
 467     this.chartLabels.title = div;
 468   }
 469
 470   if (this.attr_('xlabel')) {
 471     div = document.createElement("div");
 472     div.style.position = 'absolute';
 473     div.style.bottom = 0;  // TODO(danvk): this is lazy. Calculate style.top.
 474     div.style.left = this.area.x + 'px';
 475     div.style.width = this.area.w + 'px';
 476     div.style.height = this.attr_('xLabelHeight') + 'px';
 477     div.style.textAlign = 'center';
 478     div.style.fontSize = (this.attr_('xLabelHeight') - 2) + 'px';
 479
 480     class_div = document.createElement("div");
 481     class_div.className = 'dygraph-label dygraph-xlabel';
 482     class_div.innerHTML = this.attr_('xlabel');
 483     div.appendChild(class_div);
 484     this.container.appendChild(div);
 485     this.chartLabels.xlabel = div;
 486   }
 487
 488   if (this.attr_('ylabel')) {
 489     var box = {
 490       left: 0,
 491       top: this.area.y,
 492       width: this.attr_('yLabelWidth'),
 493       height: this.area.h
 494     };
 495     // TODO(danvk): is this outer div actually necessary?
 496     div = document.createElement("div");
 497     div.style.position = 'absolute';
 498     div.style.left = box.left;
 499     div.style.top = box.top + 'px';
 500     div.style.width = box.width + 'px';
 501     div.style.height = box.height + 'px';
 502     div.style.fontSize = (this.attr_('yLabelWidth') - 2) + 'px';
 503
 504     var inner_div = document.createElement("div");
 505     inner_div.style.position = 'absolute';
 506     inner_div.style.width = box.height + 'px';
 507     inner_div.style.height = box.width + 'px';
 508     inner_div.style.top = (box.height / 2 - box.width / 2) + 'px';
 509     inner_div.style.left = (box.width / 2 - box.height / 2) + 'px';
 510     inner_div.style.textAlign = 'center';
 511
 512     // CSS rotation is an HTML5 feature which is not standardized. Hence every
 513     // browser has its own name for the CSS style.
 514     inner_div.style.transform = 'rotate(-90deg)';        // HTML5
 515     inner_div.style.WebkitTransform = 'rotate(-90deg)';  // Safari/Chrome
 516     inner_div.style.MozTransform = 'rotate(-90deg)';     // Firefox
 517     inner_div.style.OTransform = 'rotate(-90deg)';       // Opera
 518     inner_div.style.msTransform = 'rotate(-90deg)';      // IE9
 519
 520     if (typeof(document.documentMode) !== 'undefined' &&
 521         document.documentMode < 9) {
 522       // We're dealing w/ an old version of IE, so we have to rotate the text
 523       // using a BasicImage transform. This uses a different origin of rotation
 524       // than HTML5 rotation (top left of div vs. its center).
 525       inner_div.style.filter =
 526        'progid:DXImageTransform.Microsoft.BasicImage(rotation=3)';
 527       inner_div.style.left = '0px';
 528       inner_div.style.top = '0px';
 529     }
 530
 531     class_div = document.createElement("div");
 532     class_div.className = 'dygraph-label dygraph-ylabel';
 533     class_div.innerHTML = this.attr_('ylabel');
 534
 535     inner_div.appendChild(class_div);
 536     div.appendChild(inner_div);
 537     this.container.appendChild(div);
 538     this.chartLabels.ylabel = div;
 539   }
 540 };
 541
 542
 543 DygraphCanvasRenderer.prototype._renderAnnotations = function() {
 544   var annotationStyle = {
 545     "position": "absolute",
 546     "fontSize": this.attr_('axisLabelFontSize') + "px",
 547     "zIndex": 10,
 548     "overflow": "hidden"
 549   };
 550
 551   var bindEvt = function(eventName, classEventName, p, self) {
 552     return function(e) {
 553       var a = p.annotation;
 554       if (a.hasOwnProperty(eventName)) {
 555         a[eventName](a, p, self.dygraph_, e);
 556       } else if (self.dygraph_.attr_(classEventName)) {
 557         self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e );
 558       }
 559     };
 560   };
 561
 562   // Get a list of point with annotations.
 563   var points = this.layout.annotated_points;
 564   for (var i = 0; i < points.length; i++) {
 565     var p = points[i];
 566     if (p.canvasx < this.area.x || p.canvasx > this.area.x + this.area.w) {
 567       continue;
 568     }
 569
 570     var a = p.annotation;
 571     var tick_height = 6;
 572     if (a.hasOwnProperty("tickHeight")) {
 573       tick_height = a.tickHeight;
 574     }
 575
 576     var div = document.createElement("div");
 577     for (var name in annotationStyle) {
 578       if (annotationStyle.hasOwnProperty(name)) {
 579         div.style[name] = annotationStyle[name];
 580       }
 581     }
 582     if (!a.hasOwnProperty('icon')) {
 583       div.className = "dygraphDefaultAnnotation";
 584     }
 585     if (a.hasOwnProperty('cssClass')) {
 586       div.className += " " + a.cssClass;
 587     }
 588
 589     var width = a.hasOwnProperty('width') ? a.width : 16;
 590     var height = a.hasOwnProperty('height') ? a.height : 16;
 591     if (a.hasOwnProperty('icon')) {
 592       var img = document.createElement("img");
 593       img.src = a.icon;
 594       img.width = width;
 595       img.height = height;
 596       div.appendChild(img);
 597     } else if (p.annotation.hasOwnProperty('shortText')) {
 598       div.appendChild(document.createTextNode(p.annotation.shortText));
 599     }
 600     div.style.left = (p.canvasx - width / 2) + "px";
 601     if (a.attachAtBottom) {
 602       div.style.top = (this.area.h - height - tick_height) + "px";
 603     } else {
 604       div.style.top = (p.canvasy - height - tick_height) + "px";
 605     }
 606     div.style.width = width + "px";
 607     div.style.height = height + "px";
 608     div.title = p.annotation.text;
 609     div.style.color = this.colors[p.name];
 610     div.style.borderColor = this.colors[p.name];
 611     a.div = div;
 612
 613     Dygraph.addEvent(div, 'click',
 614         bindEvt('clickHandler', 'annotationClickHandler', p, this));
 615     Dygraph.addEvent(div, 'mouseover',
 616         bindEvt('mouseOverHandler', 'annotationMouseOverHandler', p, this));
 617     Dygraph.addEvent(div, 'mouseout',
 618         bindEvt('mouseOutHandler', 'annotationMouseOutHandler', p, this));
 619     Dygraph.addEvent(div, 'dblclick',
 620         bindEvt('dblClickHandler', 'annotationDblClickHandler', p, this));
 621
 622     this.container.appendChild(div);
 623     this.annotations.push(div);
 624
 625     var ctx = this.elementContext;
 626     ctx.strokeStyle = this.colors[p.name];
 627     ctx.beginPath();
 628     if (!a.attachAtBottom) {
 629       ctx.moveTo(p.canvasx, p.canvasy);
 630       ctx.lineTo(p.canvasx, p.canvasy - 2 - tick_height);
 631     } else {
 632       ctx.moveTo(p.canvasx, this.area.h);
 633       ctx.lineTo(p.canvasx, this.area.h - 2 - tick_height);
 634     }
 635     ctx.closePath();
 636     ctx.stroke();
 637   }
 638 };
 639
 640
 641 /**
 642  * Actually draw the lines chart, including error bars.
 643  * TODO(danvk): split this into several smaller functions.
 644  * @private
 645  */
 646 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 647   var isNullOrNaN = function(x) {
 648     return (x === null || isNaN(x));
 649   };
 650
 651   // TODO(danvk): use this.attr_ for many of these.
 652   var context = this.elementContext;
 653   var fillAlpha = this.attr_('fillAlpha');
 654   var errorBars = this.attr_("errorBars") || this.attr_("customBars");
 655   var fillGraph = this.attr_("fillGraph");
 656   var stackedGraph = this.attr_("stackedGraph");
 657   var stepPlot = this.attr_("stepPlot");
 658   var points = this.layout.points;
 659   var pointsLength = points.length;
 660   var point, i, j, prevX, prevY, prevYs, color, setName, newYs, err_color, rgb, yscale, axis;
 661
 662   var setNames = [];
 663   for (var name in this.layout.datasets) {
 664     if (this.layout.datasets.hasOwnProperty(name)) {
 665       setNames.push(name);
 666     }
 667   }
 668   var setCount = setNames.length;
 669
 670   // TODO(danvk): Move this mapping into Dygraph and get it out of here.
 671   this.colors = {};
 672   for (i = 0; i < setCount; i++) {
 673     this.colors[setNames[i]] = this.colorScheme_[i % this.colorScheme_.length];
 674   }
 675
 676   // Update Points
 677   // TODO(danvk): here
 678   for (i = pointsLength; i--;) {
 679     point = points[i];
 680     point.canvasx = this.area.w * point.x + this.area.x;
 681     point.canvasy = this.area.h * point.y + this.area.y;
 682   }
 683
 684   // create paths
 685   var ctx = context;
 686   if (errorBars) {
 687     if (fillGraph) {
 688       this.dygraph_.warn("Can't use fillGraph option with error bars");
 689     }
 690
 691     for (i = 0; i < setCount; i++) {
 692       setName = setNames[i];
 693       axis = this.dygraph_.axisPropertiesForSeries(setName);
 694       color = this.colors[setName];
 695
 696       // setup graphics context
 697       ctx.save();
 698       prevX = NaN;
 699       prevY = NaN;
 700       prevYs = [-1, -1];
 701       yscale = axis.yscale;
 702       // should be same color as the lines but only 15% opaque.
 703       rgb = new RGBColor(color);
 704       err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 705                             fillAlpha + ')';
 706       ctx.fillStyle = err_color;
 707       ctx.beginPath();
 708       for (j = 0; j < pointsLength; j++) {
 709         point = points[j];
 710         if (point.name == setName) {
 711           if (!Dygraph.isOK(point.y)) {
 712             prevX = NaN;
 713             continue;
 714           }
 715
 716           // TODO(danvk): here
 717           if (stepPlot) {
 718             newYs = [ point.y_bottom, point.y_top ];
 719             prevY = point.y;
 720           } else {
 721             newYs = [ point.y_bottom, point.y_top ];
 722           }
 723           newYs[0] = this.area.h * newYs[0] + this.area.y;
 724           newYs[1] = this.area.h * newYs[1] + this.area.y;
 725           if (!isNaN(prevX)) {
 726             if (stepPlot) {
 727               ctx.moveTo(prevX, newYs[0]);
 728             } else {
 729               ctx.moveTo(prevX, prevYs[0]);
 730             }
 731             ctx.lineTo(point.canvasx, newYs[0]);
 732             ctx.lineTo(point.canvasx, newYs[1]);
 733             if (stepPlot) {
 734               ctx.lineTo(prevX, newYs[1]);
 735             } else {
 736               ctx.lineTo(prevX, prevYs[1]);
 737             }
 738             ctx.closePath();
 739           }
 740           prevYs = newYs;
 741           prevX = point.canvasx;
 742         }
 743       }
 744       ctx.fill();
 745     }
 746   } else if (fillGraph) {
 747     var baseline = [];  // for stacked graphs: baseline for filling
 748
 749     // process sets in reverse order (needed for stacked graphs)
 750     for (i = setCount - 1; i >= 0; i--) {
 751       setName = setNames[i];
 752       color = this.colors[setName];
 753       axis = this.dygraph_.axisPropertiesForSeries(setName);
 754       var axisY = 1.0 + axis.minyval * axis.yscale;
 755       if (axisY < 0.0) axisY = 0.0;
 756       else if (axisY > 1.0) axisY = 1.0;
 757       axisY = this.area.h * axisY + this.area.y;
 758
 759       // setup graphics context
 760       ctx.save();
 761       prevX = NaN;
 762       prevYs = [-1, -1];
 763       yscale = axis.yscale;
 764       // should be same color as the lines but only 15% opaque.
 765       rgb = new RGBColor(color);
 766       err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' +
 767                             fillAlpha + ')';
 768       ctx.fillStyle = err_color;
 769       ctx.beginPath();
 770       for (j = 0; j < pointsLength; j++) {
 771         point = points[j];
 772         if (point.name == setName) {
 773           if (!Dygraph.isOK(point.y)) {
 774             prevX = NaN;
 775             continue;
 776           }
 777           if (stackedGraph) {
 778             var lastY = baseline[point.canvasx];
 779             if (lastY === undefined) lastY = axisY;
 780             baseline[point.canvasx] = point.canvasy;
 781             newYs = [ point.canvasy, lastY ];
 782           } else {
 783             newYs = [ point.canvasy, axisY ];
 784           }
 785           if (!isNaN(prevX)) {
 786             ctx.moveTo(prevX, prevYs[0]);
 787             if (stepPlot) {
 788               ctx.lineTo(point.canvasx, prevYs[0]);
 789             } else {
 790               ctx.lineTo(point.canvasx, newYs[0]);
 791             }
 792             ctx.lineTo(point.canvasx, newYs[1]);
 793             ctx.lineTo(prevX, prevYs[1]);
 794             ctx.closePath();
 795           }
 796           prevYs = newYs;
 797           prevX = point.canvasx;
 798         }
 799       }
 800       ctx.fill();
 801     }
 802   }
 803
 804   // Drawing the lines.
 805   var firstIndexInSet = 0;
 806   var afterLastIndexInSet = 0;
 807   var setLength = 0;
 808   for (i = 0; i < setCount; i += 1) {
 809     setLength = this.layout.setPointsLengths[i];
 810     afterLastIndexInSet += setLength;
 811     setName = setNames[i];
 812     color = this.colors[setName];
 813     var strokeWidth = this.dygraph_.attr_("strokeWidth", setName);
 814
 815     // setup graphics context
 816     context.save();
 817     var pointSize = this.dygraph_.attr_("pointSize", setName);
 818     prevX = null;
 819     prevY = null;
 820     var drawPoints = this.dygraph_.attr_("drawPoints", setName);
 821     for (j = firstIndexInSet; j < afterLastIndexInSet; j++) {
 822       point = points[j];
 823       if (isNullOrNaN(point.canvasy)) {
 824         if (stepPlot && prevX !== null) {
 825           // Draw a horizontal line to the start of the missing data
 826           ctx.beginPath();
 827           ctx.strokeStyle = color;
 828           ctx.lineWidth = this.attr_('strokeWidth');
 829           ctx.moveTo(prevX, prevY);
 830           ctx.lineTo(point.canvasx, prevY);
 831           ctx.stroke();
 832         }
 833         // this will make us move to the next point, not draw a line to it.
 834         prevX = prevY = null;
 835       } else {
 836         // A point is "isolated" if it is non-null but both the previous
 837         // and next points are null.
 838         var isIsolated = (!prevX && (j == points.length - 1 ||
 839                                      isNullOrNaN(points[j+1].canvasy)));
 840         if (prevX === null) {
 841           prevX = point.canvasx;
 842           prevY = point.canvasy;
 843         } else {
 844           // Skip over points that will be drawn in the same pixel.
 845           if (Math.round(prevX) == Math.round(point.canvasx) &&
 846               Math.round(prevY) == Math.round(point.canvasy)) {
 847             continue;
 848           }
 849           // TODO(antrob): skip over points that lie on a line that is already
 850           // going to be drawn. There is no need to have more than 2
 851           // consecutive points that are collinear.
 852           if (strokeWidth) {
 853             ctx.beginPath();
 854             ctx.strokeStyle = color;
 855             ctx.lineWidth = strokeWidth;
 856             ctx.moveTo(prevX, prevY);
 857             if (stepPlot) {
 858               ctx.lineTo(point.canvasx, prevY);
 859             }
 860             prevX = point.canvasx;
 861             prevY = point.canvasy;
 862             ctx.lineTo(prevX, prevY);
 863             ctx.stroke();
 864           }
 865         }
 866
 867         if (drawPoints || isIsolated) {
 868           ctx.beginPath();
 869           ctx.fillStyle = color;
 870           ctx.arc(point.canvasx, point.canvasy, pointSize,
 871                   0, 2 * Math.PI, false);
 872           ctx.fill();
 873         }
 874       }
 875     }
 876     firstIndexInSet = afterLastIndexInSet;
 877   }
 878
 879   context.restore();
 880 };