plugins/axes.js

   1 /**
   2  * @license
   3  * Copyright 2012 Dan Vanderkam (danvdk@gmail.com)
   4  * MIT-licensed (http://opensource.org/licenses/MIT)
   5  */
   6
   7 /*global Dygraph:false */
   8
   9 Dygraph.Plugins.Axes = (function() {
  10
  11 "use strict";
  12
  13 /*
  14 Bits of jankiness:
  15 - Direct layout access
  16 - Direct area access
  17 - Should include calculation of ticks, not just the drawing.
  18
  19 Options left to make axis-friendly.
  20   ('axisTickSize')
  21   ('drawAxesAtZero')
  22   ('xAxisHeight')
  23
  24 These too. What is the difference between axisLablelWidth and {x,y}AxisLabelWidth?
  25   ('axisLabelWidth')
  26   ('xAxisLabelWidth')
  27   ('yAxisLabelWidth')
  28 */
  29
  30 /**
  31  * Draws the axes. This includes the labels on the x- and y-axes, as well
  32  * as the tick marks on the axes.
  33  * It does _not_ draw the grid lines which span the entire chart.
  34  */
  35 var axes = function() {
  36   this.xlabels_ = [];
  37   this.ylabels_ = [];
  38 };
  39
  40 axes.prototype.toString = function() {
  41   return "Axes Plugin";
  42 };
  43
  44 axes.prototype.activate = function(g) {
  45   return {
  46     layout: this.layout,
  47     clearChart: this.clearChart,
  48     willDrawChart: this.willDrawChart
  49   };
  50 };
  51
  52 axes.prototype.layout = function(e) {
  53   var g = e.dygraph;
  54
  55   if (g.getOptionForAxis('drawAxis', 'y')) {
  56     var w = g.getOption('yAxisLabelWidth') + 2 * g.getOption('axisTickSize');
  57     e.reserveSpaceLeft(w);
  58   }
  59
  60   if (g.getOptionForAxis('drawAxis', 'x')) {
  61     var h;
  62     // NOTE: I think this is probably broken now, since g.getOption() now
  63     // hits the dictionary. (That is, g.getOption('xAxisHeight') now always
  64     // has a value.)
  65     if (g.getOption('xAxisHeight')) {
  66       h = g.getOption('xAxisHeight');
  67     } else {
  68       h = g.getOptionForAxis('axisLabelFontSize', 'x') + 2 * g.getOption('axisTickSize');
  69     }
  70     e.reserveSpaceBottom(h);
  71   }
  72
  73   if (g.numAxes() == 2) {
  74     // TODO(danvk): introduce a 'drawAxis' per-axis property.
  75     if (g.getOptionForAxis('drawAxis', 'y')) {
  76       // TODO(danvk): per-axis setting.
  77       var w = g.getOption('yAxisLabelWidth') + 2 * g.getOption('axisTickSize');
  78       e.reserveSpaceRight(w);
  79     }
  80   } else if (g.numAxes() > 2) {
  81     g.error("Only two y-axes are supported at this time. (Trying " +
  82             "to use " + g.numAxes() + ")");
  83   }
  84 };
  85
  86 axes.prototype.detachLabels = function() {
  87   function removeArray(ary) {
  88     for (var i = 0; i < ary.length; i++) {
  89       var el = ary[i];
  90       if (el.parentNode) el.parentNode.removeChild(el);
  91     }
  92   }
  93
  94   removeArray(this.xlabels_);
  95   removeArray(this.ylabels_);
  96   this.xlabels_ = [];
  97   this.ylabels_ = [];
  98 };
  99
 100 axes.prototype.clearChart = function(e) {
 101   this.detachLabels();
 102 };
 103
 104 axes.prototype.willDrawChart = function(e) {
 105   var g = e.dygraph;
 106
 107   if (!g.getOptionForAxis('drawAxis', 'x') && !g.getOptionForAxis('drawAxis', 'y')) return;
 108
 109   // Round pixels to half-integer boundaries for crisper drawing.
 110   function halfUp(x)  { return Math.round(x) + 0.5; }
 111   function halfDown(y){ return Math.round(y) - 0.5; }
 112
 113   var context = e.drawingContext;
 114   var containerDiv = e.canvas.parentNode;
 115   var canvasWidth = e.canvas.width;
 116   var canvasHeight = e.canvas.height;
 117
 118   var label, x, y, tick, i;
 119
 120   var makeLabelStyle = function(axis) {
 121     return {
 122       position: "absolute",
 123       fontSize: g.getOptionForAxis('axisLabelFontSize', axis) + "px",
 124       zIndex: 10,
 125       color: g.getOptionForAxis('axisLabelColor', axis),
 126       width: g.getOption('axisLabelWidth') + "px",
 127       // height: g.getOptionForAxis('axisLabelFontSize', 'x') + 2 + "px",
 128       lineHeight: "normal",  // Something other than "normal" line-height screws up label positioning.
 129       overflow: "hidden"
 130     };
 131   };
 132
 133   var labelStyles = {
 134     x : makeLabelStyle('x'),
 135     y : makeLabelStyle('y'),
 136     y2 : makeLabelStyle('y2')
 137   };
 138
 139   var makeDiv = function(txt, axis, prec_axis) {
 140     /*
 141      * This seems to be called with the following three sets of axis/prec_axis:
 142      * x: undefined
 143      * y: y1
 144      * y: y2
 145      */
 146     var div = document.createElement("div");
 147     var labelStyle = labelStyles[prec_axis == 'y2' ? 'y2' : axis];
 148     for (var name in labelStyle) {
 149       if (labelStyle.hasOwnProperty(name)) {
 150         div.style[name] = labelStyle[name];
 151       }
 152     }
 153     var inner_div = document.createElement("div");
 154     inner_div.className = 'dygraph-axis-label' +
 155                           ' dygraph-axis-label-' + axis +
 156                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 157     inner_div.innerHTML = txt;
 158     div.appendChild(inner_div);
 159     return div;
 160   };
 161
 162   // axis lines
 163   context.save();
 164
 165   var layout = g.layout_;
 166   var area = e.dygraph.plotter_.area;
 167
 168   if (g.getOptionForAxis('drawAxis', 'y')) {
 169     if (layout.yticks && layout.yticks.length > 0) {
 170       var num_axes = g.numAxes();
 171       for (i = 0; i < layout.yticks.length; i++) {
 172         tick = layout.yticks[i];
 173         if (typeof(tick) == "function") return;
 174         x = area.x;
 175         var sgn = 1;
 176         var prec_axis = 'y1';
 177         if (tick[0] == 1) {  // right-side y-axis
 178           x = area.x + area.w;
 179           sgn = -1;
 180           prec_axis = 'y2';
 181         }
 182         var fontSize = g.getOptionForAxis('axisLabelFontSize', prec_axis);
 183         y = area.y + tick[1] * area.h;
 184
 185         /* Tick marks are currently clipped, so don't bother drawing them.
 186         context.beginPath();
 187         context.moveTo(halfUp(x), halfDown(y));
 188         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 189         context.closePath();
 190         context.stroke();
 191         */
 192
 193         label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null);
 194         var top = (y - fontSize / 2);
 195         if (top < 0) top = 0;
 196
 197         if (top + fontSize + 3 > canvasHeight) {
 198           label.style.bottom = "0px";
 199         } else {
 200           label.style.top = top + "px";
 201         }
 202         if (tick[0] === 0) {
 203           label.style.left = (area.x - g.getOption('yAxisLabelWidth') - g.getOption('axisTickSize')) + "px";
 204           label.style.textAlign = "right";
 205         } else if (tick[0] == 1) {
 206           label.style.left = (area.x + area.w +
 207                               g.getOption('axisTickSize')) + "px";
 208           label.style.textAlign = "left";
 209         }
 210         label.style.width = g.getOption('yAxisLabelWidth') + "px";
 211         containerDiv.appendChild(label);
 212         this.ylabels_.push(label);
 213       }
 214
 215       // The lowest tick on the y-axis often overlaps with the leftmost
 216       // tick on the x-axis. Shift the bottom tick up a little bit to
 217       // compensate if necessary.
 218       var bottomTick = this.ylabels_[0];
 219       // Interested in the y2 axis also?
 220       var fontSize = g.getOptionForAxis('axisLabelFontSize', "y");
 221       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 222       if (bottom > canvasHeight - fontSize) {
 223         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 224             fontSize / 2) + "px";
 225       }
 226     }
 227
 228     // draw a vertical line on the left to separate the chart from the labels.
 229     var axisX;
 230     if (g.getOption('drawAxesAtZero')) {
 231       var r = g.toPercentXCoord(0);
 232       if (r > 1 || r < 0 || isNaN(r)) r = 0;
 233       axisX = halfUp(area.x + r * area.w);
 234     } else {
 235       axisX = halfUp(area.x);
 236     }
 237
 238     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y');
 239     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y');
 240
 241     context.beginPath();
 242     context.moveTo(axisX, halfDown(area.y));
 243     context.lineTo(axisX, halfDown(area.y + area.h));
 244     context.closePath();
 245     context.stroke();
 246
 247     // if there's a secondary y-axis, draw a vertical line for that, too.
 248     if (g.numAxes() == 2) {
 249       context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y2');
 250       context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y2');
 251       context.beginPath();
 252       context.moveTo(halfDown(area.x + area.w), halfDown(area.y));
 253       context.lineTo(halfDown(area.x + area.w), halfDown(area.y + area.h));
 254       context.closePath();
 255       context.stroke();
 256     }
 257   }
 258
 259   if (g.getOptionForAxis('drawAxis', 'x')) {
 260     if (layout.xticks) {
 261       for (i = 0; i < layout.xticks.length; i++) {
 262         tick = layout.xticks[i];
 263         x = area.x + tick[0] * area.w;
 264         y = area.y + area.h;
 265
 266         /* Tick marks are currently clipped, so don't bother drawing them.
 267         context.beginPath();
 268         context.moveTo(halfUp(x), halfDown(y));
 269         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 270         context.closePath();
 271         context.stroke();
 272         */
 273
 274         label = makeDiv(tick[1], 'x');
 275         label.style.textAlign = "center";
 276         label.style.top = (y + g.getOption('axisTickSize')) + 'px';
 277
 278         var left = (x - g.getOption('axisLabelWidth')/2);
 279         if (left + g.getOption('axisLabelWidth') > canvasWidth) {
 280           left = canvasWidth - g.getOption('xAxisLabelWidth');
 281           label.style.textAlign = "right";
 282         }
 283         if (left < 0) {
 284           left = 0;
 285           label.style.textAlign = "left";
 286         }
 287
 288         label.style.left = left + "px";
 289         label.style.width = g.getOption('xAxisLabelWidth') + "px";
 290         containerDiv.appendChild(label);
 291         this.xlabels_.push(label);
 292       }
 293     }
 294
 295     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'x');
 296     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'x');
 297     context.beginPath();
 298     var axisY;
 299     if (g.getOption('drawAxesAtZero')) {
 300       var r = g.toPercentYCoord(0, 0);
 301       if (r > 1 || r < 0) r = 1;
 302       axisY = halfDown(area.y + r * area.h);
 303     } else {
 304       axisY = halfDown(area.y + area.h);
 305     }
 306     context.moveTo(halfUp(area.x), axisY);
 307     context.lineTo(halfUp(area.x + area.w), axisY);
 308     context.closePath();
 309     context.stroke();
 310   }
 311
 312   context.restore();
 313 };
 314
 315 return axes;
 316 })();