dygraph-range-selector.js

   1 // Copyright 2011 Paul Felix (paul.eric.felix@gmail.com)
   2 // All Rights Reserved.
   3
   4 /**
   5  * @fileoverview This file contains the DygraphRangeSelector class used to provide
   6  * a timeline range selector widget for dygraphs.
   7  */
   8
   9 "use strict";
  10
  11 /**
  12  * The DygraphRangeSelector class provides a timeline range selector widget.
  13  * @param {Dygraph} dygraph The dygraph object
  14  * @constructor
  15  */
  16 var DygraphRangeSelector = function(dygraph) {
  17   this.isIE_ = /MSIE/.test(navigator.userAgent) && !window.opera;
  18   this.isUsingExcanvas_ = dygraph.isUsingExcanvas_;
  19   this.dygraph_ = dygraph;
  20   this.createCanvases_();
  21   if (this.isUsingExcanvas_) {
  22     this.createIEPanOverlay_();
  23   }
  24   this.createZoomHandles_();
  25   this.initInteraction_();
  26 };
  27
  28 /**
  29  * Adds the range selector to the dygraph.
  30  * @param {Object} graphDiv The container div for the range selector.
  31  * @param {DygraphLayout} layout The DygraphLayout object for this graph.
  32  */
  33 DygraphRangeSelector.prototype.addToGraph = function(graphDiv, layout) {
  34   this.layout_ = layout;
  35   this.resize_();
  36   graphDiv.appendChild(this.bgcanvas_);
  37   graphDiv.appendChild(this.fgcanvas_);
  38   graphDiv.appendChild(this.leftZoomHandle_);
  39   graphDiv.appendChild(this.rightZoomHandle_);
  40 };
  41
  42 /**
  43  * Renders the static background portion of the range selector.
  44  */
  45 DygraphRangeSelector.prototype.renderStaticLayer = function() {
  46   this.resize_();
  47   this.drawStaticLayer_();
  48 };
  49
  50 /**
  51  * Renders the interactive foreground portion of the range selector.
  52  */
  53 DygraphRangeSelector.prototype.renderInteractiveLayer = function() {
  54   if (this.isChangingRange_) {
  55     return;
  56   }
  57   this.placeZoomHandles_();
  58   this.drawInteractiveLayer_();
  59 };
  60
  61 /**
  62  * @private
  63  * Resizes the range selector.
  64  */
  65 DygraphRangeSelector.prototype.resize_ = function() {
  66   function setElementRect(canvas, rect) {
  67     canvas.style.top = rect.y + 'px';
  68     canvas.style.left = rect.x + 'px';
  69     canvas.width = rect.w;
  70     canvas.height = rect.h;
  71     canvas.style.width = canvas.width + 'px';    // for IE
  72     canvas.style.height = canvas.height + 'px';  // for IE
  73   };
  74
  75   var plotArea = this.layout_.getPlotArea();
  76   var xAxisLabelHeight = this.attr_('axisLabelFontSize') + 2 * this.attr_('axisTickSize');
  77   this.canvasRect_ = {
  78     x: plotArea.x,
  79     y: plotArea.y + plotArea.h + xAxisLabelHeight + 4,
  80     w: plotArea.w,
  81     h: this.attr_('rangeSelectorHeight')
  82   };
  83
  84   setElementRect(this.bgcanvas_, this.canvasRect_);
  85   setElementRect(this.fgcanvas_, this.canvasRect_);
  86 };
  87
  88 DygraphRangeSelector.prototype.attr_ = function(name) {
  89   return this.dygraph_.attr_(name);
  90 };
  91
  92 /**
  93  * @private
  94  * Creates the background and foreground canvases.
  95  */
  96 DygraphRangeSelector.prototype.createCanvases_ = function() {
  97   this.bgcanvas_ = Dygraph.createCanvas();
  98   this.bgcanvas_.className = 'dygraph-rangesel-bgcanvas';
  99   this.bgcanvas_.style.position = 'absolute';
 100   this.bgcanvas_.style.zIndex = 9;
 101   this.bgcanvas_ctx_ = Dygraph.getContext(this.bgcanvas_);
 102
 103   this.fgcanvas_ = Dygraph.createCanvas();
 104   this.fgcanvas_.className = 'dygraph-rangesel-fgcanvas';
 105   this.fgcanvas_.style.position = 'absolute';
 106   this.fgcanvas_.style.zIndex = 9;
 107   this.fgcanvas_.style.cursor = 'default';
 108   this.fgcanvas_ctx_ = Dygraph.getContext(this.fgcanvas_);
 109 };
 110
 111 /**
 112  * @private
 113  * Creates overlay divs for IE/Excanvas so that mouse events are handled properly.
 114  */
 115 DygraphRangeSelector.prototype.createIEPanOverlay_ = function() {
 116   this.iePanOverlay_ = document.createElement("div");
 117   this.iePanOverlay_.style.position = 'absolute';
 118   this.iePanOverlay_.style.backgroundColor = 'white';
 119   this.iePanOverlay_.style.filter = 'alpha(opacity=0)';
 120   this.iePanOverlay_.style.display = 'none';
 121   this.iePanOverlay_.style.cursor = 'move';
 122   this.fgcanvas_.appendChild(this.iePanOverlay_);
 123 };
 124
 125 /**
 126  * @private
 127  * Creates the zoom handle elements.
 128  */
 129 DygraphRangeSelector.prototype.createZoomHandles_ = function() {
 130   var img = new Image();
 131   img.className = 'dygraph-rangesel-zoomhandle';
 132   img.style.position = 'absolute';
 133   img.style.zIndex = 10;
 134   img.style.visibility = 'hidden'; // Initially hidden so they don't show up in the wrong place.
 135   img.style.cursor = 'col-resize';
 136   if (/MSIE 7/.test(navigator.userAgent)) { // IE7 doesn't support embedded src data.
 137       img.width = 7;
 138       img.height = 14;
 139       img.style.backgroundColor = 'white';
 140       img.style.border = '1px solid #333333'; // Just show box in IE7.
 141   } else {
 142       img.width = 9;
 143       img.height = 16;
 144       img.src = 'data:image/png;base64,\
 145 iVBORw0KGgoAAAANSUhEUgAAAAkAAAAQCAYAAADESFVDAAAAAXNSR0IArs4c6QAAAAZiS0dEANAA\
 146 zwDP4Z7KegAAAAlwSFlzAAAOxAAADsQBlSsOGwAAAAd0SU1FB9sHGw0cMqdt1UwAAAAZdEVYdENv\
 147 bW1lbnQAQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAAaElEQVQoz+3SsRFAQBCF4Z9WJM8KCDVwownl\
 148 6YXsTmCUsyKGkZzcl7zkz3YLkypgAnreFmDEpHkIwVOMfpdi9CEEN2nGpFdwD03yEqDtOgCaun7s\
 149 qSTDH32I1pQA2Pb9sZecAxc5r3IAb21d6878xsAAAAAASUVORK5CYII=';
 150   }
 151
 152   this.leftZoomHandle_ = img;
 153   this.rightZoomHandle_ = img.cloneNode(false);
 154 };
 155
 156 /**
 157  * @private
 158  * Sets up the interaction for the range selector.
 159  */
 160 DygraphRangeSelector.prototype.initInteraction_ = function() {
 161   var self = this;
 162   var topElem = this.isIE_ ? document : window;
 163   var xLast = 0;
 164   var handle = null;
 165   var isZooming = false;
 166   var isPanning = false;
 167
 168   function toXDataWindow(zoomHandleStatus) {
 169     var xDataLimits = self.dygraph_.xAxisExtremes();
 170     var fact = (xDataLimits[1] - xDataLimits[0])/self.canvasRect_.w;
 171     var xDataMin = xDataLimits[0] + (zoomHandleStatus.leftHandlePos - self.canvasRect_.x)*fact;
 172     var xDataMax = xDataLimits[0] + (zoomHandleStatus.rightHandlePos - self.canvasRect_.x)*fact;
 173     return [xDataMin, xDataMax];
 174   };
 175
 176   function onZoomStart(e) {
 177     Dygraph.cancelEvent(e);
 178     isZooming = true;
 179     xLast = e.screenX;
 180     handle = e.target ? e.target : e.srcElement;
 181     Dygraph.addEvent(topElem, 'mousemove', onZoom);
 182     Dygraph.addEvent(topElem, 'mouseup', onZoomEnd);
 183     self.fgcanvas_.style.cursor = 'col-resize';
 184   };
 185
 186   function onZoom(e) {
 187     if (!isZooming) {
 188       return;
 189     }
 190     var delX = e.screenX - xLast;
 191     if (Math.abs(delX) < 4) {
 192       return;
 193     }
 194     xLast = e.screenX;
 195     var zoomHandleStatus = self.getZoomHandleStatus_();
 196     if (handle == self.leftZoomHandle_) {
 197       var newPos = zoomHandleStatus.leftHandlePos + delX;
 198       newPos = Math.min(newPos, zoomHandleStatus.rightHandlePos - handle.width - 3);
 199       newPos = Math.max(newPos, self.canvasRect_.x);
 200     } else {
 201       var newPos = zoomHandleStatus.rightHandlePos + delX;
 202       newPos = Math.min(newPos, self.canvasRect_.x + self.canvasRect_.w);
 203       newPos = Math.max(newPos, zoomHandleStatus.leftHandlePos + handle.width + 3);
 204     }
 205     var halfHandleWidth = handle.width/2;
 206     handle.style.left = (newPos - halfHandleWidth) + 'px';
 207     self.drawInteractiveLayer_();
 208
 209     // Zoom on the fly (if not using excanvas).
 210     if (!self.isUsingExcanvas_) {
 211       doZoom();
 212     }
 213   };
 214
 215   function onZoomEnd(e) {
 216     if (!isZooming) {
 217       return;
 218     }
 219     isZooming = false;
 220     Dygraph.removeEvent(topElem, 'mousemove', onZoom);
 221     Dygraph.removeEvent(topElem, 'mouseup', onZoomEnd);
 222     self.fgcanvas_.style.cursor = 'default';
 223
 224     // If using excanvas, Zoom now.
 225     if (self.isUsingExcanvas_) {
 226       doZoom();
 227     }
 228   };
 229
 230   function doZoom() {
 231     try {
 232       var zoomHandleStatus = self.getZoomHandleStatus_();
 233       self.isChangingRange_ = true;
 234       if (!zoomHandleStatus.isZoomed) {
 235         self.dygraph_.doUnzoom_();
 236       } else {
 237         var xDataWindow = toXDataWindow(zoomHandleStatus);
 238         self.dygraph_.doZoomXDates_(xDataWindow[0], xDataWindow[1]);
 239       }
 240     } finally {
 241       self.isChangingRange_ = false;
 242     }
 243   };
 244
 245   function isMouseInPanZone(e) {
 246     if (self.isUsingExcanvas_) {
 247         return e.srcElement == self.iePanOverlay_;
 248     } else {
 249       // Getting clientX directly from the event is not accurate enough :(
 250       var clientX = self.canvasRect_.x + (e.layerX != undefined ? e.layerX : e.offsetX);
 251       var zoomHandleStatus = self.getZoomHandleStatus_();
 252       return (clientX > zoomHandleStatus.leftHandlePos && clientX < zoomHandleStatus.rightHandlePos);
 253     }
 254   };
 255
 256   function onPanStart(e) {
 257     if (!isPanning && isMouseInPanZone(e) && self.getZoomHandleStatus_().isZoomed) {
 258       Dygraph.cancelEvent(e);
 259       isPanning = true;
 260       xLast = e.screenX;
 261       Dygraph.addEvent(topElem, 'mousemove', onPan);
 262       Dygraph.addEvent(topElem, 'mouseup', onPanEnd);
 263     }
 264   };
 265
 266   function onPan(e) {
 267     if (!isPanning) {
 268       return;
 269     }
 270     Dygraph.cancelEvent(e);
 271
 272     var delX = e.screenX - xLast;
 273     if (Math.abs(delX) < 4) {
 274       return;
 275     }
 276     xLast = e.screenX;
 277
 278     // Move range view
 279     var zoomHandleStatus = self.getZoomHandleStatus_();
 280     var leftHandlePos = zoomHandleStatus.leftHandlePos;
 281     var rightHandlePos = zoomHandleStatus.rightHandlePos;
 282     var rangeSize = rightHandlePos - leftHandlePos;
 283     if (leftHandlePos + delX <= self.canvasRect_.x) {
 284       leftHandlePos = self.canvasRect_.x;
 285       rightHandlePos = leftHandlePos + rangeSize;
 286     } else if (rightHandlePos + delX >= self.canvasRect_.x + self.canvasRect_.w) {
 287       rightHandlePos = self.canvasRect_.x + self.canvasRect_.w;
 288       leftHandlePos = rightHandlePos - rangeSize;
 289     } else {
 290       leftHandlePos += delX;
 291       rightHandlePos += delX;
 292     }
 293     var halfHandleWidth = self.leftZoomHandle_.width/2;
 294     self.leftZoomHandle_.style.left = (leftHandlePos - halfHandleWidth) + 'px';
 295     self.rightZoomHandle_.style.left = (rightHandlePos - halfHandleWidth) + 'px';
 296     self.drawInteractiveLayer_();
 297
 298     // Do pan on the fly (if not using excanvas).
 299     if (!self.isUsingExcanvas_) {
 300       doPan();
 301     }
 302   };
 303
 304   function onPanEnd(e) {
 305     if (!isPanning) {
 306       return;
 307     }
 308     isPanning = false;
 309     Dygraph.removeEvent(topElem, 'mousemove', onPan);
 310     Dygraph.removeEvent(topElem, 'mouseup', onPanEnd);
 311     // If using excanvas, do pan now.
 312     if (self.isUsingExcanvas_) {
 313       doPan();
 314     }
 315   };
 316
 317   function doPan() {
 318     try {
 319       self.isChangingRange_ = true;
 320       self.dygraph_.dateWindow_ = toXDataWindow(self.getZoomHandleStatus_());
 321       self.dygraph_.drawGraph_(false);
 322     } finally {
 323       self.isChangingRange_ = false;
 324     }
 325   };
 326
 327   function onCanvasMouseMove(e) {
 328     if (isZooming || isPanning) {
 329       return;
 330     }
 331     var cursor = isMouseInPanZone(e) ? 'move' : 'default';
 332     if (cursor != self.fgcanvas_.style.cursor) {
 333       self.fgcanvas_.style.cursor = cursor;
 334     }
 335   };
 336
 337   var interactionModel = {
 338     mousedown: function(event, g, context) {
 339       context.initializeMouseDown(event, g, context);
 340       Dygraph.startPan(event, g, context);
 341     },
 342     mousemove: function(event, g, context) {
 343       if (context.isPanning) {
 344         Dygraph.movePan(event, g, context);
 345       }
 346     },
 347     mouseup: function(event, g, context) {
 348       if (context.isPanning) {
 349         Dygraph.endPan(event, g, context);
 350       }
 351     }
 352   };
 353
 354   this.dygraph_.attrs_.interactionModel = interactionModel;
 355   this.dygraph_.attrs_.panEdgeFraction = .0001;
 356
 357   var dragStartEvent = window.opera ? 'mousedown' : 'dragstart';
 358   Dygraph.addEvent(this.leftZoomHandle_, dragStartEvent, onZoomStart);
 359   Dygraph.addEvent(this.rightZoomHandle_, dragStartEvent, onZoomStart);
 360
 361   if (this.isUsingExcanvas_) {
 362     Dygraph.addEvent(this.iePanOverlay_, 'mousedown', onPanStart);
 363   } else {
 364     Dygraph.addEvent(this.fgcanvas_, 'mousedown', onPanStart);
 365     Dygraph.addEvent(this.fgcanvas_, 'mousemove', onCanvasMouseMove);
 366   }
 367 };
 368
 369 /**
 370  * @private
 371  * Draws the static layer in the background canvas.
 372  */
 373 DygraphRangeSelector.prototype.drawStaticLayer_ = function() {
 374   var ctx = this.bgcanvas_ctx_;
 375   ctx.clearRect(0, 0, this.canvasRect_.w, this.canvasRect_.h);
 376   try {
 377     this.drawMiniPlot_();
 378   } catch(ex) {
 379   }
 380
 381   var margin = .5;
 382   this.bgcanvas_ctx_.lineWidth = 1;
 383   ctx.strokeStyle = 'gray';
 384   ctx.beginPath();
 385   ctx.moveTo(margin, margin);
 386   ctx.lineTo(margin, this.canvasRect_.h-margin);
 387   ctx.lineTo(this.canvasRect_.w-margin, this.canvasRect_.h-margin);
 388   ctx.lineTo(this.canvasRect_.w-margin, margin);
 389   ctx.stroke();
 390 };
 391
 392
 393 /**
 394  * @private
 395  * Draws the mini plot in the background canvas.
 396  */
 397 DygraphRangeSelector.prototype.drawMiniPlot_ = function() {
 398   var fillStyle = this.attr_('rangeSelectorPlotFillColor');
 399   var strokeStyle = this.attr_('rangeSelectorPlotStrokeColor');
 400   if (!fillStyle && !strokeStyle) {
 401     return;
 402   }
 403
 404   var combinedSeriesData = this.computeCombinedSeriesAndLimits_();
 405   var yRange = combinedSeriesData.yMax - combinedSeriesData.yMin;
 406
 407   // Draw the mini plot.
 408   var ctx = this.bgcanvas_ctx_;
 409   var margin = .5;
 410
 411   var xExtremes = this.dygraph_.xAxisExtremes();
 412   var xRange = Math.max(xExtremes[1] - xExtremes[0], 1.e-30);
 413   var xFact = (this.canvasRect_.w - margin)/xRange;
 414   var yFact = (this.canvasRect_.h - margin)/yRange;
 415   var canvasWidth = this.canvasRect_.w - margin;
 416   var canvasHeight = this.canvasRect_.h - margin;
 417
 418   ctx.beginPath();
 419   ctx.moveTo(margin, canvasHeight);
 420   for (var i = 0; i < combinedSeriesData.data.length; i++) {
 421     var dataPoint = combinedSeriesData.data[i];
 422     var x = (dataPoint[0] - xExtremes[0])*xFact;
 423     var y = canvasHeight - (dataPoint[1] - combinedSeriesData.yMin)*yFact;
 424     if (isFinite(x) && isFinite(y)) {
 425       ctx.lineTo(x, y);
 426     }
 427   }
 428   ctx.lineTo(canvasWidth, canvasHeight);
 429   ctx.closePath();
 430
 431   if (fillStyle) {
 432     var lingrad = this.bgcanvas_ctx_.createLinearGradient(0, 0, 0, canvasHeight);
 433     lingrad.addColorStop(0, 'white');
 434     lingrad.addColorStop(1, fillStyle);
 435     this.bgcanvas_ctx_.fillStyle = lingrad;
 436     ctx.fill();
 437   }
 438
 439   if (strokeStyle) {
 440     this.bgcanvas_ctx_.strokeStyle = strokeStyle;
 441     this.bgcanvas_ctx_.lineWidth = 1.5;
 442     ctx.stroke();
 443   }
 444 };
 445
 446 /**
 447  * @private
 448  * Computes and returns the combinded series data along with min/max for the mini plot.
 449  * @return {Object} An object containing combinded series array, ymin, ymax.
 450  */
 451 DygraphRangeSelector.prototype.computeCombinedSeriesAndLimits_ = function() {
 452   var data = this.dygraph_.rawData_;
 453   var logscale = this.attr_('logscale');
 454
 455   // Create a combined series (average of all series values).
 456   var combinedSeries = [];
 457   var sum;
 458   var count;
 459   var mutipleValues = typeof data[0][1] != 'number';
 460
 461   if (mutipleValues) {
 462     sum = [];
 463     count = [];
 464     for (var k = 0; k < data[0][1].length; k++) {
 465       sum.push(0);
 466       count.push(0);
 467     }
 468     mutipleValues = true;
 469   }
 470
 471   for (var i = 0; i < data.length; i++) {
 472     var dataPoint = data[i];
 473     var xVal = dataPoint[0];
 474     var yVal;
 475
 476     if (mutipleValues) {
 477       for (var k = 0; k < sum.length; k++) {
 478         sum[k] = count[k] = 0;
 479       }
 480     } else {
 481       sum = count = 0;
 482     }
 483
 484     for (var j = 1; j < dataPoint.length; j++) {
 485       if (this.dygraph_.visibility()[j-1]) {
 486         if (mutipleValues) {
 487           for (var k = 0; k < sum.length; k++) {
 488             var y = dataPoint[j][k];
 489             if (y == null || isNaN(y)) continue;
 490             sum[k] += y;
 491             count[k]++;
 492           }
 493         } else {
 494           var y = dataPoint[j];
 495           if (y == null || isNaN(y)) continue;
 496           sum += y;
 497           count++;
 498         }
 499       }
 500     }
 501
 502     if (mutipleValues) {
 503       for (var k = 0; k < sum.length; k++) {
 504         sum[k] /= count[k];
 505       }
 506       yVal = sum.slice(0);
 507     } else {
 508       yVal = sum/count;
 509     }
 510
 511     combinedSeries.push([xVal, yVal]);
 512   }
 513
 514   // Account for roll period, fractions.
 515   combinedSeries = this.dygraph_.rollingAverage(combinedSeries, this.dygraph_.rollPeriod_);
 516
 517   if (typeof combinedSeries[0][1] != 'number') {
 518     for (var i = 0; i < combinedSeries.length; i++) {
 519       var yVal = combinedSeries[i][1];
 520       combinedSeries[i][1] = yVal[0];
 521     }
 522   }
 523
 524   // Compute the y range.
 525   var yMin = Number.MAX_VALUE;
 526   var yMax = -Number.MAX_VALUE;
 527   for (var i = 0; i < combinedSeries.length; i++) {
 528     var yVal = combinedSeries[i][1];
 529     if (yVal != null && isFinite(yVal) && (!logscale || yVal > 0)) {
 530       yMin = Math.min(yMin, yVal);
 531       yMax = Math.max(yMax, yVal);
 532     }
 533   }
 534
 535   // Convert Y data to log scale if needed.
 536   // Also, expand the Y range to compress the mini plot a little.
 537   var extraPercent = .25;
 538   if (logscale) {
 539     yMax = Dygraph.log10(yMax);
 540     yMax += yMax*extraPercent;
 541     yMin = Dygraph.log10(yMin);
 542     for (var i = 0; i < combinedSeries.length; i++) {
 543       combinedSeries[i][1] = Dygraph.log10(combinedSeries[i][1]);
 544     }
 545   } else {
 546     var yExtra;
 547     yRange = yMax - yMin;
 548     if (yRange <= Number.MIN_VALUE) {
 549       yExtra = yMax*extraPercent;
 550     } else {
 551       yExtra = yRange*extraPercent;
 552     }
 553     yMax += yExtra;
 554     yMin -= yExtra;
 555   }
 556
 557   return {data: combinedSeries, yMin: yMin, yMax: yMax};
 558 };
 559
 560 /**
 561  * @private
 562  * Places the zoom handles in the proper position based on the current X data window.
 563  */
 564 DygraphRangeSelector.prototype.placeZoomHandles_ = function() {
 565   var xExtremes = this.dygraph_.xAxisExtremes();
 566   var xWindowLimits = this.dygraph_.xAxisRange();
 567   var xRange = xExtremes[1] - xExtremes[0];
 568   var leftPercent = Math.max(0, (xWindowLimits[0] - xExtremes[0])/xRange);
 569   var rightPercent = Math.max(0, (xExtremes[1] - xWindowLimits[1])/xRange);
 570   var leftCoord = this.canvasRect_.x + this.canvasRect_.w*leftPercent;
 571   var rightCoord = this.canvasRect_.x + this.canvasRect_.w*(1 - rightPercent);
 572   var handleTop = Math.max(this.canvasRect_.y, this.canvasRect_.y + (this.canvasRect_.h - this.leftZoomHandle_.height)/2);
 573   var halfHandleWidth = this.leftZoomHandle_.width/2;
 574   this.leftZoomHandle_.style.left = (leftCoord - halfHandleWidth) + 'px';
 575   this.leftZoomHandle_.style.top = handleTop + 'px';
 576   this.rightZoomHandle_.style.left = (rightCoord - halfHandleWidth) + 'px';
 577   this.rightZoomHandle_.style.top = this.leftZoomHandle_.style.top;
 578
 579   this.leftZoomHandle_.style.visibility = 'visible';
 580   this.rightZoomHandle_.style.visibility = 'visible';
 581 };
 582
 583 /**
 584  * @private
 585  * Draws the interactive layer in the foreground canvas.
 586  */
 587 DygraphRangeSelector.prototype.drawInteractiveLayer_ = function() {
 588   var ctx = this.fgcanvas_ctx_;
 589   ctx.clearRect(0, 0, this.canvasRect_.w, this.canvasRect_.h);
 590   var margin = 1;
 591   var width = this.canvasRect_.w - margin;
 592   var height = this.canvasRect_.h - margin;
 593   var zoomHandleStatus = this.getZoomHandleStatus_();
 594
 595   ctx.strokeStyle = 'black';
 596   if (!zoomHandleStatus.isZoomed) {
 597     ctx.beginPath();
 598     ctx.moveTo(margin, margin);
 599     ctx.lineTo(margin, height);
 600     ctx.lineTo(width, height);
 601     ctx.lineTo(width, margin);
 602     ctx.stroke();
 603     if (this.iePanOverlay_) {
 604       this.iePanOverlay_.style.display = 'none';
 605     }
 606   } else {
 607     leftHandleCanvasPos = Math.max(margin, zoomHandleStatus.leftHandlePos - this.canvasRect_.x);
 608     rightHandleCanvasPos = Math.min(width, zoomHandleStatus.rightHandlePos - this.canvasRect_.x);
 609
 610     ctx.fillStyle = 'rgba(240, 240, 240, 0.6)';
 611     ctx.fillRect(0, 0, leftHandleCanvasPos, this.canvasRect_.h);
 612     ctx.fillRect(rightHandleCanvasPos, 0, this.canvasRect_.w - rightHandleCanvasPos, this.canvasRect_.h);
 613
 614     ctx.beginPath();
 615     ctx.moveTo(margin, margin);
 616     ctx.lineTo(leftHandleCanvasPos, margin);
 617     ctx.lineTo(leftHandleCanvasPos, height);
 618     ctx.lineTo(rightHandleCanvasPos, height);
 619     ctx.lineTo(rightHandleCanvasPos, margin);
 620     ctx.lineTo(width, margin);
 621     ctx.stroke();
 622
 623     if (this.isUsingExcanvas_) {
 624       this.iePanOverlay_.style.width = (rightHandleCanvasPos - leftHandleCanvasPos) + 'px';
 625       this.iePanOverlay_.style.left = leftHandleCanvasPos + 'px';
 626       this.iePanOverlay_.style.height = height + 'px';
 627       this.iePanOverlay_.style.display = 'inline';
 628     }
 629   }
 630 };
 631
 632 /**
 633  * @private
 634  * Returns the current zoom handle position information.
 635  * @return {Object} The zoom handle status.
 636  */
 637 DygraphRangeSelector.prototype.getZoomHandleStatus_ = function() {
 638   var halfHandleWidth = this.leftZoomHandle_.width/2;
 639   var leftHandlePos = parseInt(this.leftZoomHandle_.style.left) + halfHandleWidth;
 640   var rightHandlePos = parseInt(this.rightZoomHandle_.style.left) + halfHandleWidth;
 641   return {
 642       leftHandlePos: leftHandlePos,
 643       rightHandlePos: rightHandlePos,
 644       isZoomed: (leftHandlePos - 1 > this.canvasRect_.x || rightHandlePos + 1 < this.canvasRect_.x+this.canvasRect_.w)
 645   };
 646 };