src/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   ('drawAxesAtZero')
  21   ('xAxisHeight')
  22 */
  23
  24 /**
  25  * Draws the axes. This includes the labels on the x- and y-axes, as well
  26  * as the tick marks on the axes.
  27  * It does _not_ draw the grid lines which span the entire chart.
  28  */
  29 var axes = function() {
  30   this.xlabels_ = [];
  31   this.ylabels_ = [];
  32 };
  33
  34 axes.prototype.toString = function() {
  35   return 'Axes Plugin';
  36 };
  37
  38 axes.prototype.activate = function(g) {
  39   return {
  40     layout: this.layout,
  41     clearChart: this.clearChart,
  42     willDrawChart: this.willDrawChart
  43   };
  44 };
  45
  46 axes.prototype.layout = function(e) {
  47   var g = e.dygraph;
  48
  49   if (g.getOptionForAxis('drawAxis', 'y')) {
  50     var w = g.getOptionForAxis('axisLabelWidth', 'y') + 2 * g.getOptionForAxis('axisTickSize', 'y');
  51     e.reserveSpaceLeft(w);
  52   }
  53
  54   if (g.getOptionForAxis('drawAxis', 'x')) {
  55     var h;
  56     // NOTE: I think this is probably broken now, since g.getOption() now
  57     // hits the dictionary. (That is, g.getOption('xAxisHeight') now always
  58     // has a value.)
  59     if (g.getOption('xAxisHeight')) {
  60       h = g.getOption('xAxisHeight');
  61     } else {
  62       h = g.getOptionForAxis('axisLabelFontSize', 'x') + 2 * g.getOptionForAxis('axisTickSize', 'x');
  63     }
  64     e.reserveSpaceBottom(h);
  65   }
  66
  67   if (g.numAxes() == 2) {
  68     if (g.getOptionForAxis('drawAxis', 'y2')) {
  69       var w = g.getOptionForAxis('axisLabelWidth', 'y2') + 2 * g.getOptionForAxis('axisTickSize', 'y2');
  70       e.reserveSpaceRight(w);
  71     }
  72   } else if (g.numAxes() > 2) {
  73     g.error('Only two y-axes are supported at this time. (Trying ' +
  74             'to use ' + g.numAxes() + ')');
  75   }
  76 };
  77
  78 axes.prototype.detachLabels = function() {
  79   function removeArray(ary) {
  80     for (var i = 0; i < ary.length; i++) {
  81       var el = ary[i];
  82       if (el.parentNode) el.parentNode.removeChild(el);
  83     }
  84   }
  85
  86   removeArray(this.xlabels_);
  87   removeArray(this.ylabels_);
  88   this.xlabels_ = [];
  89   this.ylabels_ = [];
  90 };
  91
  92 axes.prototype.clearChart = function(e) {
  93   this.detachLabels();
  94 };
  95
  96 axes.prototype.willDrawChart = function(e) {
  97   var g = e.dygraph;
  98
  99   if (!g.getOptionForAxis('drawAxis', 'x') &&
 100       !g.getOptionForAxis('drawAxis', 'y') &&
 101       !g.getOptionForAxis('drawAxis', 'y2')) {
 102     return;
 103   }
 104
 105   // Round pixels to half-integer boundaries for crisper drawing.
 106   function halfUp(x)  { return Math.round(x) + 0.5; }
 107   function halfDown(y){ return Math.round(y) - 0.5; }
 108
 109   var context = e.drawingContext;
 110   var containerDiv = e.canvas.parentNode;
 111   var canvasWidth = g.width_;  // e.canvas.width is affected by pixel ratio.
 112   var canvasHeight = g.height_;
 113
 114   var label, x, y, tick, i;
 115
 116   var makeLabelStyle = function(axis) {
 117     return {
 118       position: 'absolute',
 119       fontSize: g.getOptionForAxis('axisLabelFontSize', axis) + 'px',
 120       zIndex: 10,
 121       color: g.getOptionForAxis('axisLabelColor', axis),
 122       width: g.getOptionForAxis('axisLabelWidth', axis) + 'px',
 123       // height: g.getOptionForAxis('axisLabelFontSize', 'x') + 2 + "px",
 124       lineHeight: 'normal',  // Something other than "normal" line-height screws up label positioning.
 125       overflow: 'hidden'
 126     };
 127   };
 128
 129   var labelStyles = {
 130     x : makeLabelStyle('x'),
 131     y : makeLabelStyle('y'),
 132     y2 : makeLabelStyle('y2')
 133   };
 134
 135   var makeDiv = function(txt, axis, prec_axis) {
 136     /*
 137      * This seems to be called with the following three sets of axis/prec_axis:
 138      * x: undefined
 139      * y: y1
 140      * y: y2
 141      */
 142     var div = document.createElement('div');
 143     var labelStyle = labelStyles[prec_axis == 'y2' ? 'y2' : axis];
 144     for (var name in labelStyle) {
 145       if (labelStyle.hasOwnProperty(name)) {
 146         div.style[name] = labelStyle[name];
 147       }
 148     }
 149     var inner_div = document.createElement('div');
 150     inner_div.className = 'dygraph-axis-label' +
 151                           ' dygraph-axis-label-' + axis +
 152                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 153     inner_div.innerHTML = txt;
 154     div.appendChild(inner_div);
 155     return div;
 156   };
 157
 158   // axis lines
 159   context.save();
 160
 161   var layout = g.layout_;
 162   var area = e.dygraph.plotter_.area;
 163
 164   // Helper for repeated axis-option accesses.
 165   var makeOptionGetter = function(axis) {
 166     return function(option) {
 167       return g.getOptionForAxis(option, axis);
 168     };
 169   };
 170
 171   if (g.getOptionForAxis('drawAxis', 'y')) {
 172     if (layout.yticks && layout.yticks.length > 0) {
 173       var num_axes = g.numAxes();
 174       var getOptions = [makeOptionGetter('y'), makeOptionGetter('y2')];
 175       for (i = 0; i < layout.yticks.length; i++) {
 176         tick = layout.yticks[i];
 177         if (typeof(tick) == 'function') return;  // <-- when would this happen?
 178         x = area.x;
 179         var sgn = 1;
 180         var prec_axis = 'y1';
 181         var getAxisOption = getOptions[0];
 182         if (tick[0] == 1) {  // right-side y-axis
 183           x = area.x + area.w;
 184           sgn = -1;
 185           prec_axis = 'y2';
 186           getAxisOption = getOptions[1];
 187         }
 188         var fontSize = getAxisOption('axisLabelFontSize');
 189         y = area.y + tick[1] * area.h;
 190
 191         /* Tick marks are currently clipped, so don't bother drawing them.
 192         context.beginPath();
 193         context.moveTo(halfUp(x), halfDown(y));
 194         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 195         context.closePath();
 196         context.stroke();
 197         */
 198
 199         label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null);
 200         var top = (y - fontSize / 2);
 201         if (top < 0) top = 0;
 202
 203         if (top + fontSize + 3 > canvasHeight) {
 204           label.style.bottom = '0';
 205         } else {
 206           label.style.top = top + 'px';
 207         }
 208         if (tick[0] === 0) {
 209           label.style.left = (area.x - getAxisOption('axisLabelWidth') - getAxisOption('axisTickSize')) + 'px';
 210           label.style.textAlign = 'right';
 211         } else if (tick[0] == 1) {
 212           label.style.left = (area.x + area.w +
 213                               getAxisOption('axisTickSize')) + 'px';
 214           label.style.textAlign = 'left';
 215         }
 216         label.style.width = getAxisOption('axisLabelWidth') + 'px';
 217         containerDiv.appendChild(label);
 218         this.ylabels_.push(label);
 219       }
 220
 221       // The lowest tick on the y-axis often overlaps with the leftmost
 222       // tick on the x-axis. Shift the bottom tick up a little bit to
 223       // compensate if necessary.
 224       var bottomTick = this.ylabels_[0];
 225       // Interested in the y2 axis also?
 226       var fontSize = g.getOptionForAxis('axisLabelFontSize', 'y');
 227       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 228       if (bottom > canvasHeight - fontSize) {
 229         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 230             fontSize / 2) + 'px';
 231       }
 232     }
 233
 234     // draw a vertical line on the left to separate the chart from the labels.
 235     var axisX;
 236     if (g.getOption('drawAxesAtZero')) {
 237       var r = g.toPercentXCoord(0);
 238       if (r > 1 || r < 0 || isNaN(r)) r = 0;
 239       axisX = halfUp(area.x + r * area.w);
 240     } else {
 241       axisX = halfUp(area.x);
 242     }
 243
 244     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y');
 245     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y');
 246
 247     context.beginPath();
 248     context.moveTo(axisX, halfDown(area.y));
 249     context.lineTo(axisX, halfDown(area.y + area.h));
 250     context.closePath();
 251     context.stroke();
 252
 253     // if there's a secondary y-axis, draw a vertical line for that, too.
 254     if (g.numAxes() == 2) {
 255       context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y2');
 256       context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y2');
 257       context.beginPath();
 258       context.moveTo(halfDown(area.x + area.w), halfDown(area.y));
 259       context.lineTo(halfDown(area.x + area.w), halfDown(area.y + area.h));
 260       context.closePath();
 261       context.stroke();
 262     }
 263   }
 264
 265   if (g.getOptionForAxis('drawAxis', 'x')) {
 266     if (layout.xticks) {
 267       var getAxisOption = makeOptionGetter('x');
 268       for (i = 0; i < layout.xticks.length; i++) {
 269         tick = layout.xticks[i];
 270         x = area.x + tick[0] * area.w;
 271         y = area.y + area.h;
 272
 273         /* Tick marks are currently clipped, so don't bother drawing them.
 274         context.beginPath();
 275         context.moveTo(halfUp(x), halfDown(y));
 276         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 277         context.closePath();
 278         context.stroke();
 279         */
 280
 281         label = makeDiv(tick[1], 'x');
 282         label.style.textAlign = 'center';
 283         label.style.top = (y + getAxisOption('axisTickSize')) + 'px';
 284
 285         var left = (x - getAxisOption('axisLabelWidth')/2);
 286         if (left + getAxisOption('axisLabelWidth') > canvasWidth) {
 287           left = canvasWidth - getAxisOption('axisLabelWidth');
 288           label.style.textAlign = 'right';
 289         }
 290         if (left < 0) {
 291           left = 0;
 292           label.style.textAlign = 'left';
 293         }
 294
 295         label.style.left = left + 'px';
 296         label.style.width = getAxisOption('axisLabelWidth') + 'px';
 297         containerDiv.appendChild(label);
 298         this.xlabels_.push(label);
 299       }
 300     }
 301
 302     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'x');
 303     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'x');
 304     context.beginPath();
 305     var axisY;
 306     if (g.getOption('drawAxesAtZero')) {
 307       var r = g.toPercentYCoord(0, 0);
 308       if (r > 1 || r < 0) r = 1;
 309       axisY = halfDown(area.y + r * area.h);
 310     } else {
 311       axisY = halfDown(area.y + area.h);
 312     }
 313     context.moveTo(halfUp(area.x), axisY);
 314     context.lineTo(halfUp(area.x + area.w), axisY);
 315     context.closePath();
 316     context.stroke();
 317   }
 318
 319   context.restore();
 320 };
 321
 322 return axes;
 323 })();