X-Git-Url: https://adrianiainlam.tk/git/?a=blobdiff_plain;f=dygraph-canvas.js;h=e2d304c8a22da3b6300ad50922223cc53934f38f;hb=758a629f806fa73483f730fb343013acd0ace078;hp=4f4a5472ee7b782807b6bc05617e0715cadbdcfa;hpb=48e614acf3084b9836803f8b014bf0e65f1ca119;p=dygraphs.git diff --git a/dygraph-canvas.js b/dygraph-canvas.js index 4f4a547..e2d304c 100644 --- a/dygraph-canvas.js +++ b/dygraph-canvas.js @@ -1,5 +1,8 @@ -// Copyright 2006 Dan Vanderkam (danvdk@gmail.com) -// All Rights Reserved. +/** + * @license + * Copyright 2006 Dan Vanderkam (danvdk@gmail.com) + * MIT-licensed (http://opensource.org/licenses/MIT) + */ /** * @fileoverview Based on PlotKit.CanvasRenderer, but modified to meet the @@ -20,7 +23,12 @@ * @param {Layout} layout The DygraphLayout object for this graph. * @constructor */ -DygraphCanvasRenderer = function(dygraph, element, elementContext, layout) { + +/*jshint globalstrict: true */ +/*global Dygraph:false,RGBColor:false */ +"use strict"; + +var DygraphCanvasRenderer = function(dygraph, element, elementContext, layout) { this.dygraph_ = dygraph; this.layout = layout; @@ -36,83 +44,42 @@ DygraphCanvasRenderer = function(dygraph, element, elementContext, layout) { throw "Canvas is not supported."; // internal state - this.xlabels = new Array(); - this.ylabels = new Array(); - this.annotations = new Array(); + this.xlabels = []; + this.ylabels = []; + this.annotations = []; this.chartLabels = {}; - this.area = this.computeArea_(); + this.area = layout.getPlotArea(); this.container.style.position = "relative"; this.container.style.width = this.width + "px"; // Set up a clipping area for the canvas (and the interaction canvas). // This ensures that we don't overdraw. - var ctx = this.dygraph_.canvas_ctx_; - ctx.beginPath(); - ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h); - ctx.clip(); - - ctx = this.dygraph_.hidden_ctx_; - ctx.beginPath(); - ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h); - ctx.clip(); -}; - -DygraphCanvasRenderer.prototype.attr_ = function(x) { - return this.dygraph_.attr_(x); -}; - -// Compute the box which the chart should be drawn in. This is the canvas's -// box, less space needed for axis and chart labels. -// TODO(danvk): this belongs in DygraphLayout. -DygraphCanvasRenderer.prototype.computeArea_ = function() { - var area = { - // TODO(danvk): per-axis setting. - x: 0, - y: 0 - }; - if (this.attr_('drawYAxis')) { - area.x = this.attr_('yAxisLabelWidth') + 2 * this.attr_('axisTickSize'); - } + if (this.dygraph_.isUsingExcanvas_) { + this._createIEClipArea(); + } else { + // on Android 3 and 4, setting a clipping area on a canvas prevents it from + // displaying anything. + if (!Dygraph.isAndroid()) { + var ctx = this.dygraph_.canvas_ctx_; + ctx.beginPath(); + ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h); + ctx.clip(); - area.w = this.width - area.x - this.attr_('rightGap'); - area.h = this.height; - if (this.attr_('drawXAxis')) { - if (this.attr_('xAxisHeight')) { - area.h -= this.attr_('xAxisHeight'); - } else { - area.h -= this.attr_('axisLabelFontSize') + 2 * this.attr_('axisTickSize'); + ctx = this.dygraph_.hidden_ctx_; + ctx.beginPath(); + ctx.rect(this.area.x, this.area.y, this.area.w, this.area.h); + ctx.clip(); } } +}; - // Shrink the drawing area to accomodate additional y-axes. - if (this.dygraph_.numAxes() == 2) { - // TODO(danvk): per-axis setting. - area.w -= (this.attr_('yAxisLabelWidth') + 2 * this.attr_('axisTickSize')); - } else if (this.dygraph_.numAxes() > 2) { - this.dygraph_.error("Only two y-axes are supported at this time. (Trying " + - "to use " + this.dygraph_.numAxes() + ")"); - } - - // Add space for chart labels: title, xlabel and ylabel. - if (this.attr_('title')) { - area.h -= this.attr_('titleHeight'); - area.y += this.attr_('titleHeight'); - } - if (this.attr_('xlabel')) { - area.h -= this.attr_('xLabelHeight'); - } - if (this.attr_('ylabel')) { - // It would make sense to shift the chart here to make room for the y-axis - // label, but the default yAxisLabelWidth is large enough that this results - // in overly-padded charts. The y-axis label should fit fine. If it - // doesn't, the yAxisLabelWidth option can be increased. - } - - return area; +DygraphCanvasRenderer.prototype.attr_ = function(x) { + return this.dygraph_.attr_(x); }; DygraphCanvasRenderer.prototype.clear = function() { + var context; if (this.isIE) { // VML takes a while to start up, so we just poll every this.IEDelay try { @@ -120,39 +87,38 @@ DygraphCanvasRenderer.prototype.clear = function() { this.clearDelay.cancel(); this.clearDelay = null; } - var context = this.elementContext; + context = this.elementContext; } catch (e) { // TODO(danvk): this is broken, since MochiKit.Async is gone. - this.clearDelay = MochiKit.Async.wait(this.IEDelay); - this.clearDelay.addCallback(bind(this.clear, this)); + // this.clearDelay = MochiKit.Async.wait(this.IEDelay); + // this.clearDelay.addCallback(bind(this.clear, this)); return; } } - var context = this.elementContext; + context = this.elementContext; context.clearRect(0, 0, this.width, this.height); - for (var i = 0; i < this.xlabels.length; i++) { - var el = this.xlabels[i]; - if (el.parentNode) el.parentNode.removeChild(el); - } - for (var i = 0; i < this.ylabels.length; i++) { - var el = this.ylabels[i]; - if (el.parentNode) el.parentNode.removeChild(el); - } - for (var i = 0; i < this.annotations.length; i++) { - var el = this.annotations[i]; - if (el.parentNode) el.parentNode.removeChild(el); + function removeArray(ary) { + for (var i = 0; i < ary.length; i++) { + var el = ary[i]; + if (el.parentNode) el.parentNode.removeChild(el); + } } + + removeArray(this.xlabels); + removeArray(this.ylabels); + removeArray(this.annotations); + for (var k in this.chartLabels) { if (!this.chartLabels.hasOwnProperty(k)) continue; var el = this.chartLabels[k]; if (el.parentNode) el.parentNode.removeChild(el); } - this.xlabels = new Array(); - this.ylabels = new Array(); - this.annotations = new Array(); + this.xlabels = []; + this.ylabels = []; + this.annotations = []; this.chartLabels = {}; }; @@ -160,11 +126,12 @@ DygraphCanvasRenderer.prototype.clear = function() { DygraphCanvasRenderer.isSupported = function(canvasName) { var canvas = null; try { - if (typeof(canvasName) == 'undefined' || canvasName == null) + if (typeof(canvasName) == 'undefined' || canvasName === null) { canvas = document.createElement("canvas"); - else + } else { canvas = canvasName; - var context = canvas.getContext("2d"); + } + canvas.getContext("2d"); } catch (e) { var ie = navigator.appVersion.match(/MSIE (\d\.\d)/); @@ -191,8 +158,8 @@ DygraphCanvasRenderer.prototype.render = function() { // Draw the new X/Y grid. Lines appear crisper when pixels are rounded to // half-integers. This prevents them from drawing in two rows/cols. var ctx = this.elementContext; - function halfUp(x){return Math.round(x)+0.5}; - function halfDown(y){return Math.round(y)-0.5}; + function halfUp(x) { return Math.round(x) + 0.5; } + function halfDown(y){ return Math.round(y) - 0.5; } if (this.attr_('underlayCallback')) { // NOTE: we pass the dygraph object to this callback twice to avoid breaking @@ -200,16 +167,18 @@ DygraphCanvasRenderer.prototype.render = function() { this.attr_('underlayCallback')(ctx, this.area, this.dygraph_, this.dygraph_); } + var x, y, i, ticks; if (this.attr_('drawYGrid')) { - var ticks = this.layout.yticks; + ticks = this.layout.yticks; + // TODO(konigsberg): I don't think these calls to save() have a corresponding restore(). ctx.save(); ctx.strokeStyle = this.attr_('gridLineColor'); ctx.lineWidth = this.attr_('gridLineWidth'); - for (var i = 0; i < ticks.length; i++) { + for (i = 0; i < ticks.length; i++) { // TODO(danvk): allow secondary axes to draw a grid, too. - if (ticks[i][0] != 0) continue; - var x = halfUp(this.area.x); - var y = halfDown(this.area.y + ticks[i][1] * this.area.h); + if (ticks[i][0] !== 0) continue; + x = halfUp(this.area.x); + y = halfDown(this.area.y + ticks[i][1] * this.area.h); ctx.beginPath(); ctx.moveTo(x, y); ctx.lineTo(x + this.area.w, y); @@ -219,13 +188,13 @@ DygraphCanvasRenderer.prototype.render = function() { } if (this.attr_('drawXGrid')) { - var ticks = this.layout.xticks; + ticks = this.layout.xticks; ctx.save(); ctx.strokeStyle = this.attr_('gridLineColor'); ctx.lineWidth = this.attr_('gridLineWidth'); - for (var i=0; i= 0; i--) { + if (graphDiv.childNodes[i].className == className) { + graphDiv.removeChild(graphDiv.childNodes[i]); + } + } + + // Determine background color to give clip divs. + var backgroundColor = document.bgColor; + var element = this.dygraph_.graphDiv; + while (element != document) { + var bgcolor = element.currentStyle.backgroundColor; + if (bgcolor && bgcolor != 'transparent') { + backgroundColor = bgcolor; + break; + } + element = element.parentNode; + } + + function createClipDiv(area) { + if (area.w === 0 || area.h === 0) { + return; + } + var elem = document.createElement('div'); + elem.className = className; + elem.style.backgroundColor = backgroundColor; + elem.style.position = 'absolute'; + elem.style.left = area.x + 'px'; + elem.style.top = area.y + 'px'; + elem.style.width = area.w + 'px'; + elem.style.height = area.h + 'px'; + graphDiv.appendChild(elem); + } + + var plotArea = this.area; + // Left side + createClipDiv({ + x:0, y:0, + w:plotArea.x, + h:this.height + }); + + // Top + createClipDiv({ + x: plotArea.x, y: 0, + w: this.width - plotArea.x, + h: plotArea.y + }); + + // Right side + createClipDiv({ + x: plotArea.x + plotArea.w, y: 0, + w: this.width-plotArea.x - plotArea.w, + h: this.height + }); + + // Bottom + createClipDiv({ + x: plotArea.x, + y: plotArea.y + plotArea.h, + w: this.width - plotArea.x, + h: this.height - plotArea.h - plotArea.y + }); +}; DygraphCanvasRenderer.prototype._renderAxis = function() { if (!this.attr_('drawXAxis') && !this.attr_('drawYAxis')) return; // Round pixels to half-integer boundaries for crisper drawing. - function halfUp(x){return Math.round(x)+0.5}; - function halfDown(y){return Math.round(y)-0.5}; + function halfUp(x) { return Math.round(x) + 0.5; } + function halfDown(y){ return Math.round(y) - 0.5; } var context = this.elementContext; + var label, x, y, tick, i; + var labelStyle = { position: "absolute", fontSize: this.attr_('axisLabelFontSize') + "px", @@ -258,6 +297,7 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { color: this.attr_('axisLabelColor'), width: this.attr_('axisLabelWidth') + "px", // height: this.attr_('axisLabelFontSize') + 2 + "px", + lineHeight: "normal", // Something other than "normal" line-height screws up label positioning. overflow: "hidden" }; var makeDiv = function(txt, axis, prec_axis) { @@ -284,10 +324,10 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { if (this.attr_('drawYAxis')) { if (this.layout.yticks && this.layout.yticks.length > 0) { var num_axes = this.dygraph_.numAxes(); - for (var i = 0; i < this.layout.yticks.length; i++) { - var tick = this.layout.yticks[i]; + for (i = 0; i < this.layout.yticks.length; i++) { + tick = this.layout.yticks[i]; if (typeof(tick) == "function") return; - var x = this.area.x; + x = this.area.x; var sgn = 1; var prec_axis = 'y1'; if (tick[0] == 1) { // right-side y-axis @@ -295,14 +335,17 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { sgn = -1; prec_axis = 'y2'; } - var y = this.area.y + tick[1] * this.area.h; + y = this.area.y + tick[1] * this.area.h; + + /* Tick marks are currently clipped, so don't bother drawing them. context.beginPath(); context.moveTo(halfUp(x), halfDown(y)); context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y)); context.closePath(); context.stroke(); + */ - var label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null); + label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null); var top = (y - this.attr_('axisLabelFontSize') / 2); if (top < 0) top = 0; @@ -311,7 +354,7 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { } else { label.style.top = top + "px"; } - if (tick[0] == 0) { + if (tick[0] === 0) { label.style.left = (this.area.x - this.attr_('yAxisLabelWidth') - this.attr_('axisTickSize')) + "px"; label.style.textAlign = "right"; } else if (tick[0] == 1) { @@ -329,9 +372,9 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { // compensate if necessary. var bottomTick = this.ylabels[0]; var fontSize = this.attr_('axisLabelFontSize'); - var bottom = parseInt(bottomTick.style.top) + fontSize; + var bottom = parseInt(bottomTick.style.top, 10) + fontSize; if (bottom > this.height - fontSize) { - bottomTick.style.top = (parseInt(bottomTick.style.top) - + bottomTick.style.top = (parseInt(bottomTick.style.top, 10) - fontSize / 2) + "px"; } } @@ -355,19 +398,20 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { if (this.attr_('drawXAxis')) { if (this.layout.xticks) { - for (var i = 0; i < this.layout.xticks.length; i++) { - var tick = this.layout.xticks[i]; - if (typeof(dataset) == "function") return; + for (i = 0; i < this.layout.xticks.length; i++) { + tick = this.layout.xticks[i]; + x = this.area.x + tick[0] * this.area.w; + y = this.area.y + this.area.h; - var x = this.area.x + tick[0] * this.area.w; - var y = this.area.y + this.area.h; + /* Tick marks are currently clipped, so don't bother drawing them. context.beginPath(); context.moveTo(halfUp(x), halfDown(y)); context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize'))); context.closePath(); context.stroke(); + */ - var label = makeDiv(tick[1], 'x'); + label = makeDiv(tick[1], 'x'); label.style.textAlign = "center"; label.style.top = (y + this.attr_('axisTickSize')) + 'px'; @@ -400,11 +444,13 @@ DygraphCanvasRenderer.prototype._renderAxis = function() { DygraphCanvasRenderer.prototype._renderChartLabels = function() { + var div, class_div; + // Generate divs for the chart title, xlabel and ylabel. // Space for these divs has already been taken away from the charting area in // the DygraphCanvasRenderer constructor. if (this.attr_('title')) { - var div = document.createElement("div"); + div = document.createElement("div"); div.style.position = 'absolute'; div.style.top = '0px'; div.style.left = this.area.x + 'px'; @@ -413,7 +459,7 @@ DygraphCanvasRenderer.prototype._renderChartLabels = function() { div.style.textAlign = 'center'; div.style.fontSize = (this.attr_('titleHeight') - 8) + 'px'; div.style.fontWeight = 'bold'; - var class_div = document.createElement("div"); + class_div = document.createElement("div"); class_div.className = 'dygraph-label dygraph-title'; class_div.innerHTML = this.attr_('title'); div.appendChild(class_div); @@ -422,7 +468,7 @@ DygraphCanvasRenderer.prototype._renderChartLabels = function() { } if (this.attr_('xlabel')) { - var div = document.createElement("div"); + div = document.createElement("div"); div.style.position = 'absolute'; div.style.bottom = 0; // TODO(danvk): this is lazy. Calculate style.top. div.style.left = this.area.x + 'px'; @@ -431,7 +477,7 @@ DygraphCanvasRenderer.prototype._renderChartLabels = function() { div.style.textAlign = 'center'; div.style.fontSize = (this.attr_('xLabelHeight') - 2) + 'px'; - var class_div = document.createElement("div"); + class_div = document.createElement("div"); class_div.className = 'dygraph-label dygraph-xlabel'; class_div.innerHTML = this.attr_('xlabel'); div.appendChild(class_div); @@ -447,7 +493,7 @@ DygraphCanvasRenderer.prototype._renderChartLabels = function() { height: this.area.h }; // TODO(danvk): is this outer div actually necessary? - var div = document.createElement("div"); + div = document.createElement("div"); div.style.position = 'absolute'; div.style.left = box.left; div.style.top = box.top + 'px'; @@ -482,7 +528,7 @@ DygraphCanvasRenderer.prototype._renderChartLabels = function() { inner_div.style.top = '0px'; } - var class_div = document.createElement("div"); + class_div = document.createElement("div"); class_div.className = 'dygraph-label dygraph-ylabel'; class_div.innerHTML = this.attr_('ylabel'); @@ -511,7 +557,7 @@ DygraphCanvasRenderer.prototype._renderAnnotations = function() { self.dygraph_.attr_(classEventName)(a, p, self.dygraph_,e ); } }; - } + }; // Get a list of point with annotations. var points = this.layout.annotated_points; @@ -593,13 +639,15 @@ DygraphCanvasRenderer.prototype._renderAnnotations = function() { /** - * Overrides the CanvasRenderer method to draw error bars + * Actually draw the lines chart, including error bars. + * TODO(danvk): split this into several smaller functions. + * @private */ DygraphCanvasRenderer.prototype._renderLineChart = function() { var isNullOrNaN = function(x) { return (x === null || isNaN(x)); }; - + // TODO(danvk): use this.attr_ for many of these. var context = this.elementContext; var fillAlpha = this.attr_('fillAlpha'); @@ -609,6 +657,7 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { var stepPlot = this.attr_("stepPlot"); var points = this.layout.points; var pointsLength = points.length; + var point, i, j, prevX, prevY, prevYs, color, setName, newYs, err_color, rgb, yscale, axis; var setNames = []; for (var name in this.layout.datasets) { @@ -619,15 +668,15 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { var setCount = setNames.length; // TODO(danvk): Move this mapping into Dygraph and get it out of here. - this.colors = {} - for (var i = 0; i < setCount; i++) { + this.colors = {}; + for (i = 0; i < setCount; i++) { this.colors[setNames[i]] = this.colorScheme_[i % this.colorScheme_.length]; } // Update Points // TODO(danvk): here - for (var i = pointsLength; i--;) { - var point = points[i]; + for (i = pointsLength; i--;) { + point = points[i]; point.canvasx = this.area.w * point.x + this.area.x; point.canvasy = this.area.h * point.y + this.area.y; } @@ -639,25 +688,25 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { this.dygraph_.warn("Can't use fillGraph option with error bars"); } - for (var i = 0; i < setCount; i++) { - var setName = setNames[i]; - var axis = this.dygraph_.axisPropertiesForSeries(setName); - var color = this.colors[setName]; + for (i = 0; i < setCount; i++) { + setName = setNames[i]; + axis = this.dygraph_.axisPropertiesForSeries(setName); + color = this.colors[setName]; // setup graphics context ctx.save(); - var prevX = NaN; - var prevY = NaN; - var prevYs = [-1, -1]; - var yscale = axis.yscale; + prevX = NaN; + prevY = NaN; + prevYs = [-1, -1]; + yscale = axis.yscale; // should be same color as the lines but only 15% opaque. - var rgb = new RGBColor(color); - var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' + + rgb = new RGBColor(color); + err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' + fillAlpha + ')'; ctx.fillStyle = err_color; ctx.beginPath(); - for (var j = 0; j < pointsLength; j++) { - var point = points[j]; + for (j = 0; j < pointsLength; j++) { + point = points[j]; if (point.name == setName) { if (!Dygraph.isOK(point.y)) { prevX = NaN; @@ -666,10 +715,10 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { // TODO(danvk): here if (stepPlot) { - var newYs = [ point.y_bottom, point.y_top ]; + newYs = [ point.y_bottom, point.y_top ]; prevY = point.y; } else { - var newYs = [ point.y_bottom, point.y_top ]; + newYs = [ point.y_bottom, point.y_top ]; } newYs[0] = this.area.h * newYs[0] + this.area.y; newYs[1] = this.area.h * newYs[1] + this.area.y; @@ -695,13 +744,13 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { ctx.fill(); } } else if (fillGraph) { - var baseline = [] // for stacked graphs: baseline for filling + var baseline = []; // for stacked graphs: baseline for filling // process sets in reverse order (needed for stacked graphs) - for (var i = setCount - 1; i >= 0; i--) { - var setName = setNames[i]; - var color = this.colors[setName]; - var axis = this.dygraph_.axisPropertiesForSeries(setName); + for (i = setCount - 1; i >= 0; i--) { + setName = setNames[i]; + color = this.colors[setName]; + axis = this.dygraph_.axisPropertiesForSeries(setName); var axisY = 1.0 + axis.minyval * axis.yscale; if (axisY < 0.0) axisY = 0.0; else if (axisY > 1.0) axisY = 1.0; @@ -709,25 +758,24 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { // setup graphics context ctx.save(); - var prevX = NaN; - var prevYs = [-1, -1]; - var yscale = axis.yscale; + prevX = NaN; + prevYs = [-1, -1]; + yscale = axis.yscale; // should be same color as the lines but only 15% opaque. - var rgb = new RGBColor(color); - var err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' + + rgb = new RGBColor(color); + err_color = 'rgba(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ',' + fillAlpha + ')'; ctx.fillStyle = err_color; ctx.beginPath(); - for (var j = 0; j < pointsLength; j++) { - var point = points[j]; + for (j = 0; j < pointsLength; j++) { + point = points[j]; if (point.name == setName) { if (!Dygraph.isOK(point.y)) { prevX = NaN; continue; } - var newYs; if (stackedGraph) { - lastY = baseline[point.canvasx]; + var lastY = baseline[point.canvasx]; if (lastY === undefined) lastY = axisY; baseline[point.canvasx] = point.canvasy; newYs = [ point.canvasy, lastY ]; @@ -757,22 +805,23 @@ DygraphCanvasRenderer.prototype._renderLineChart = function() { var firstIndexInSet = 0; var afterLastIndexInSet = 0; var setLength = 0; - for (var i = 0; i < setCount; i += 1) { + for (i = 0; i < setCount; i += 1) { setLength = this.layout.setPointsLengths[i]; afterLastIndexInSet += setLength; - var setName = setNames[i]; - var color = this.colors[setName]; + setName = setNames[i]; + color = this.colors[setName]; var strokeWidth = this.dygraph_.attr_("strokeWidth", setName); // setup graphics context context.save(); var pointSize = this.dygraph_.attr_("pointSize", setName); - var prevX = null, prevY = null; + prevX = null; + prevY = null; var drawPoints = this.dygraph_.attr_("drawPoints", setName); - for (var j = firstIndexInSet; j < afterLastIndexInSet; j++) { - var point = points[j]; + for (j = firstIndexInSet; j < afterLastIndexInSet; j++) { + point = points[j]; if (isNullOrNaN(point.canvasy)) { - if (stepPlot && prevX != null) { + if (stepPlot && prevX !== null) { // Draw a horizontal line to the start of the missing data ctx.beginPath(); ctx.strokeStyle = color;