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 'use strict';
  10
  11 /*
  12 Bits of jankiness:
  13 - Direct layout access
  14 - Direct area access
  15 - Should include calculation of ticks, not just the drawing.
  16
  17 Options left to make axis-friendly.
  18   ('drawAxesAtZero')
  19   ('xAxisHeight')
  20 */
  21
  22 /**
  23  * Draws the axes. This includes the labels on the x- and y-axes, as well
  24  * as the tick marks on the axes.
  25  * It does _not_ draw the grid lines which span the entire chart.
  26  */
  27 var axes = function() {
  28   this.xlabels_ = [];
  29   this.ylabels_ = [];
  30 };
  31
  32 axes.prototype.toString = function() {
  33   return 'Axes Plugin';
  34 };
  35
  36 axes.prototype.activate = function(g) {
  37   return {
  38     layout: this.layout,
  39     clearChart: this.clearChart,
  40     willDrawChart: this.willDrawChart
  41   };
  42 };
  43
  44 axes.prototype.layout = function(e) {
  45   var g = e.dygraph;
  46
  47   if (g.getOptionForAxis('drawAxis', 'y')) {
  48     var w = g.getOptionForAxis('axisLabelWidth', 'y') + 2 * g.getOptionForAxis('axisTickSize', 'y');
  49     e.reserveSpaceLeft(w);
  50   }
  51
  52   if (g.getOptionForAxis('drawAxis', 'x')) {
  53     var h;
  54     // NOTE: I think this is probably broken now, since g.getOption() now
  55     // hits the dictionary. (That is, g.getOption('xAxisHeight') now always
  56     // has a value.)
  57     if (g.getOption('xAxisHeight')) {
  58       h = g.getOption('xAxisHeight');
  59     } else {
  60       h = g.getOptionForAxis('axisLabelFontSize', 'x') + 2 * g.getOptionForAxis('axisTickSize', 'x');
  61     }
  62     e.reserveSpaceBottom(h);
  63   }
  64
  65   if (g.numAxes() == 2) {
  66     if (g.getOptionForAxis('drawAxis', 'y2')) {
  67       var w = g.getOptionForAxis('axisLabelWidth', 'y2') + 2 * g.getOptionForAxis('axisTickSize', 'y2');
  68       e.reserveSpaceRight(w);
  69     }
  70   } else if (g.numAxes() > 2) {
  71     g.error('Only two y-axes are supported at this time. (Trying ' +
  72             'to use ' + g.numAxes() + ')');
  73   }
  74 };
  75
  76 axes.prototype.detachLabels = function() {
  77   function removeArray(ary) {
  78     for (var i = 0; i < ary.length; i++) {
  79       var el = ary[i];
  80       if (el.parentNode) el.parentNode.removeChild(el);
  81     }
  82   }
  83
  84   removeArray(this.xlabels_);
  85   removeArray(this.ylabels_);
  86   this.xlabels_ = [];
  87   this.ylabels_ = [];
  88 };
  89
  90 axes.prototype.clearChart = function(e) {
  91   this.detachLabels();
  92 };
  93
  94 axes.prototype.willDrawChart = function(e) {
  95   var g = e.dygraph;
  96
  97   if (!g.getOptionForAxis('drawAxis', 'x') &&
  98       !g.getOptionForAxis('drawAxis', 'y') &&
  99       !g.getOptionForAxis('drawAxis', 'y2')) {
 100     return;
 101   }
 102
 103   // Round pixels to half-integer boundaries for crisper drawing.
 104   function halfUp(x)  { return Math.round(x) + 0.5; }
 105   function halfDown(y){ return Math.round(y) - 0.5; }
 106
 107   var context = e.drawingContext;
 108   var containerDiv = e.canvas.parentNode;
 109   var canvasWidth = g.width_;  // e.canvas.width is affected by pixel ratio.
 110   var canvasHeight = g.height_;
 111
 112   var label, x, y, tick, i;
 113
 114   var makeLabelStyle = function(axis) {
 115     return {
 116       position: 'absolute',
 117       fontSize: g.getOptionForAxis('axisLabelFontSize', axis) + 'px',
 118       zIndex: 10,
 119       color: g.getOptionForAxis('axisLabelColor', axis),
 120       width: g.getOptionForAxis('axisLabelWidth', axis) + 'px',
 121       // height: g.getOptionForAxis('axisLabelFontSize', 'x') + 2 + "px",
 122       lineHeight: 'normal',  // Something other than "normal" line-height screws up label positioning.
 123       overflow: 'hidden'
 124     };
 125   };
 126
 127   var labelStyles = {
 128     x : makeLabelStyle('x'),
 129     y : makeLabelStyle('y'),
 130     y2 : makeLabelStyle('y2')
 131   };
 132
 133   var makeDiv = function(txt, axis, prec_axis) {
 134     /*
 135      * This seems to be called with the following three sets of axis/prec_axis:
 136      * x: undefined
 137      * y: y1
 138      * y: y2
 139      */
 140     var div = document.createElement('div');
 141     var labelStyle = labelStyles[prec_axis == 'y2' ? 'y2' : axis];
 142     for (var name in labelStyle) {
 143       if (labelStyle.hasOwnProperty(name)) {
 144         div.style[name] = labelStyle[name];
 145       }
 146     }
 147     var inner_div = document.createElement('div');
 148     inner_div.className = 'dygraph-axis-label' +
 149                           ' dygraph-axis-label-' + axis +
 150                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 151     inner_div.innerHTML = txt;
 152     div.appendChild(inner_div);
 153     return div;
 154   };
 155
 156   // axis lines
 157   context.save();
 158
 159   var layout = g.layout_;
 160   var area = e.dygraph.plotter_.area;
 161
 162   // Helper for repeated axis-option accesses.
 163   var makeOptionGetter = function(axis) {
 164     return function(option) {
 165       return g.getOptionForAxis(option, axis);
 166     };
 167   };
 168
 169   if (g.getOptionForAxis('drawAxis', 'y')) {
 170     if (layout.yticks && layout.yticks.length > 0) {
 171       var num_axes = g.numAxes();
 172       var getOptions = [makeOptionGetter('y'), makeOptionGetter('y2')];
 173       for (var tick of layout.yticks) {
 174         if (tick.label === undefined) continue;  // this tick only has a grid line.
 175         x = area.x;
 176         var sgn = 1;
 177         var prec_axis = 'y1';
 178         var getAxisOption = getOptions[0];
 179         if (tick.axis == 1) {  // right-side y-axis
 180           x = area.x + area.w;
 181           sgn = -1;
 182           prec_axis = 'y2';
 183           getAxisOption = getOptions[1];
 184         }
 185         var fontSize = getAxisOption('axisLabelFontSize');
 186         y = area.y + tick.pos * area.h;
 187
 188         /* Tick marks are currently clipped, so don't bother drawing them.
 189         context.beginPath();
 190         context.moveTo(halfUp(x), halfDown(y));
 191         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 192         context.closePath();
 193         context.stroke();
 194         */
 195
 196         label = makeDiv(tick.label, 'y', num_axes == 2 ? prec_axis : null);
 197         var top = (y - fontSize / 2);
 198         if (top < 0) top = 0;
 199
 200         if (top + fontSize + 3 > canvasHeight) {
 201           label.style.bottom = '0';
 202         } else {
 203           label.style.top = top + 'px';
 204         }
 205         if (tick.axis === 0) {
 206           label.style.left = (area.x - getAxisOption('axisLabelWidth') - getAxisOption('axisTickSize')) + 'px';
 207           label.style.textAlign = 'right';
 208         } else if (tick.axis == 1) {
 209           label.style.left = (area.x + area.w +
 210                               getAxisOption('axisTickSize')) + 'px';
 211           label.style.textAlign = 'left';
 212         }
 213         label.style.width = getAxisOption('axisLabelWidth') + 'px';
 214         containerDiv.appendChild(label);
 215         this.ylabels_.push(label);
 216       }
 217
 218       // The lowest tick on the y-axis often overlaps with the leftmost
 219       // tick on the x-axis. Shift the bottom tick up a little bit to
 220       // compensate if necessary.
 221       var bottomTick = this.ylabels_[0];
 222       // Interested in the y2 axis also?
 223       var fontSize = g.getOptionForAxis('axisLabelFontSize', 'y');
 224       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 225       if (bottom > canvasHeight - fontSize) {
 226         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 227             fontSize / 2) + 'px';
 228       }
 229     }
 230
 231     // draw a vertical line on the left to separate the chart from the labels.
 232     var axisX;
 233     if (g.getOption('drawAxesAtZero')) {
 234       var r = g.toPercentXCoord(0);
 235       if (r > 1 || r < 0 || isNaN(r)) r = 0;
 236       axisX = halfUp(area.x + r * area.w);
 237     } else {
 238       axisX = halfUp(area.x);
 239     }
 240
 241     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y');
 242     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y');
 243
 244     context.beginPath();
 245     context.moveTo(axisX, halfDown(area.y));
 246     context.lineTo(axisX, halfDown(area.y + area.h));
 247     context.closePath();
 248     context.stroke();
 249
 250     // if there's a secondary y-axis, draw a vertical line for that, too.
 251     if (g.numAxes() == 2) {
 252       context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y2');
 253       context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y2');
 254       context.beginPath();
 255       context.moveTo(halfDown(area.x + area.w), halfDown(area.y));
 256       context.lineTo(halfDown(area.x + area.w), halfDown(area.y + area.h));
 257       context.closePath();
 258       context.stroke();
 259     }
 260   }
 261
 262   if (g.getOptionForAxis('drawAxis', 'x')) {
 263     if (layout.xticks) {
 264       var getAxisOption = makeOptionGetter('x');
 265       for (var tick of layout.xticks) {
 266         if (tick.label === undefined) continue;  // this tick only has a grid line.
 267         x = area.x + tick.pos * area.w;
 268         y = area.y + area.h;
 269
 270         /* Tick marks are currently clipped, so don't bother drawing them.
 271         context.beginPath();
 272         context.moveTo(halfUp(x), halfDown(y));
 273         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 274         context.closePath();
 275         context.stroke();
 276         */
 277
 278         label = makeDiv(tick.label, 'x');
 279         label.style.textAlign = 'center';
 280         label.style.top = (y + getAxisOption('axisTickSize')) + 'px';
 281
 282         var left = (x - getAxisOption('axisLabelWidth')/2);
 283         if (left + getAxisOption('axisLabelWidth') > canvasWidth) {
 284           left = canvasWidth - getAxisOption('axisLabelWidth');
 285           label.style.textAlign = 'right';
 286         }
 287         if (left < 0) {
 288           left = 0;
 289           label.style.textAlign = 'left';
 290         }
 291
 292         label.style.left = left + 'px';
 293         label.style.width = getAxisOption('axisLabelWidth') + 'px';
 294         containerDiv.appendChild(label);
 295         this.xlabels_.push(label);
 296       }
 297     }
 298
 299     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'x');
 300     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'x');
 301     context.beginPath();
 302     var axisY;
 303     if (g.getOption('drawAxesAtZero')) {
 304       var r = g.toPercentYCoord(0, 0);
 305       if (r > 1 || r < 0) r = 1;
 306       axisY = halfDown(area.y + r * area.h);
 307     } else {
 308       axisY = halfDown(area.y + area.h);
 309     }
 310     context.moveTo(halfUp(area.x), axisY);
 311     context.lineTo(halfUp(area.x + area.w), axisY);
 312     context.closePath();
 313     context.stroke();
 314   }
 315
 316   context.restore();
 317 };
 318
 319 export default axes;