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 import * as utils from '../dygraph-utils';
  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       width: g.getOptionForAxis('axisLabelWidth', axis) + 'px',
 121     };
 122   };
 123
 124   var labelStyles = {
 125     x: makeLabelStyle('x'),
 126     y: makeLabelStyle('y'),
 127     y2: makeLabelStyle('y2')
 128   };
 129
 130   var makeDiv = function(txt, axis, prec_axis) {
 131     /*
 132      * This seems to be called with the following three sets of axis/prec_axis:
 133      * x: undefined
 134      * y: y1
 135      * y: y2
 136      */
 137     var div = document.createElement('div');
 138     var labelStyle = labelStyles[prec_axis == 'y2' ? 'y2' : axis];
 139     utils.update(div.style, labelStyle);
 140     // TODO: combine outer & inner divs
 141     var inner_div = document.createElement('div');
 142     inner_div.className = 'dygraph-axis-label' +
 143                           ' dygraph-axis-label-' + axis +
 144                           (prec_axis ? ' dygraph-axis-label-' + prec_axis : '');
 145     inner_div.innerHTML = txt;
 146     div.appendChild(inner_div);
 147     return div;
 148   };
 149
 150   // axis lines
 151   context.save();
 152
 153   var layout = g.layout_;
 154   var area = e.dygraph.plotter_.area;
 155
 156   // Helper for repeated axis-option accesses.
 157   var makeOptionGetter = function(axis) {
 158     return function(option) {
 159       return g.getOptionForAxis(option, axis);
 160     };
 161   };
 162
 163   if (g.getOptionForAxis('drawAxis', 'y')) {
 164     if (layout.yticks && layout.yticks.length > 0) {
 165       var num_axes = g.numAxes();
 166       var getOptions = [makeOptionGetter('y'), makeOptionGetter('y2')];
 167       for (var tick of layout.yticks) {
 168         if (tick.label === undefined) continue;  // this tick only has a grid line.
 169         x = area.x;
 170         var sgn = 1;
 171         var prec_axis = 'y1';
 172         var getAxisOption = getOptions[0];
 173         if (tick.axis == 1) {  // right-side y-axis
 174           x = area.x + area.w;
 175           sgn = -1;
 176           prec_axis = 'y2';
 177           getAxisOption = getOptions[1];
 178         }
 179         var fontSize = getAxisOption('axisLabelFontSize');
 180         y = area.y + tick.pos * area.h;
 181
 182         /* Tick marks are currently clipped, so don't bother drawing them.
 183         context.beginPath();
 184         context.moveTo(halfUp(x), halfDown(y));
 185         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 186         context.closePath();
 187         context.stroke();
 188         */
 189
 190         label = makeDiv(tick.label, 'y', num_axes == 2 ? prec_axis : null);
 191         var top = (y - fontSize / 2);
 192         if (top < 0) top = 0;
 193
 194         if (top + fontSize + 3 > canvasHeight) {
 195           label.style.bottom = '0';
 196         } else {
 197           label.style.top = top + 'px';
 198         }
 199         // TODO: replace these with css classes?
 200         if (tick.axis === 0) {
 201           label.style.left = (area.x - getAxisOption('axisLabelWidth') - getAxisOption('axisTickSize')) + 'px';
 202           label.style.textAlign = 'right';
 203         } else if (tick.axis == 1) {
 204           label.style.left = (area.x + area.w +
 205                               getAxisOption('axisTickSize')) + 'px';
 206           label.style.textAlign = 'left';
 207         }
 208         label.style.width = getAxisOption('axisLabelWidth') + 'px';
 209         containerDiv.appendChild(label);
 210         this.ylabels_.push(label);
 211       }
 212
 213       // The lowest tick on the y-axis often overlaps with the leftmost
 214       // tick on the x-axis. Shift the bottom tick up a little bit to
 215       // compensate if necessary.
 216       var bottomTick = this.ylabels_[0];
 217       // Interested in the y2 axis also?
 218       var fontSize = g.getOptionForAxis('axisLabelFontSize', 'y');
 219       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 220       if (bottom > canvasHeight - fontSize) {
 221         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 222             fontSize / 2) + 'px';
 223       }
 224     }
 225
 226     // draw a vertical line on the left to separate the chart from the labels.
 227     var axisX;
 228     if (g.getOption('drawAxesAtZero')) {
 229       var r = g.toPercentXCoord(0);
 230       if (r > 1 || r < 0 || isNaN(r)) r = 0;
 231       axisX = halfUp(area.x + r * area.w);
 232     } else {
 233       axisX = halfUp(area.x);
 234     }
 235
 236     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y');
 237     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y');
 238
 239     context.beginPath();
 240     context.moveTo(axisX, halfDown(area.y));
 241     context.lineTo(axisX, halfDown(area.y + area.h));
 242     context.closePath();
 243     context.stroke();
 244
 245     // if there's a secondary y-axis, draw a vertical line for that, too.
 246     if (g.numAxes() == 2) {
 247       context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y2');
 248       context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y2');
 249       context.beginPath();
 250       context.moveTo(halfDown(area.x + area.w), halfDown(area.y));
 251       context.lineTo(halfDown(area.x + area.w), halfDown(area.y + area.h));
 252       context.closePath();
 253       context.stroke();
 254     }
 255   }
 256
 257   if (g.getOptionForAxis('drawAxis', 'x')) {
 258     if (layout.xticks) {
 259       var getAxisOption = makeOptionGetter('x');
 260       for (var tick of layout.xticks) {
 261         if (tick.label === undefined) continue;  // this tick only has a grid line.
 262         x = area.x + tick.pos * area.w;
 263         y = area.y + area.h;
 264
 265         /* Tick marks are currently clipped, so don't bother drawing them.
 266         context.beginPath();
 267         context.moveTo(halfUp(x), halfDown(y));
 268         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 269         context.closePath();
 270         context.stroke();
 271         */
 272
 273         label = makeDiv(tick.label, 'x');
 274         label.style.textAlign = 'center';
 275         label.style.top = (y + getAxisOption('axisTickSize')) + 'px';
 276
 277         var left = (x - getAxisOption('axisLabelWidth')/2);
 278         if (left + getAxisOption('axisLabelWidth') > canvasWidth) {
 279           left = canvasWidth - getAxisOption('axisLabelWidth');
 280           label.style.textAlign = 'right';
 281         }
 282         if (left < 0) {
 283           left = 0;
 284           label.style.textAlign = 'left';
 285         }
 286
 287         label.style.left = left + 'px';
 288         label.style.width = getAxisOption('axisLabelWidth') + 'px';
 289         containerDiv.appendChild(label);
 290         this.xlabels_.push(label);
 291       }
 292     }
 293
 294     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'x');
 295     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'x');
 296     context.beginPath();
 297     var axisY;
 298     if (g.getOption('drawAxesAtZero')) {
 299       var r = g.toPercentYCoord(0, 0);
 300       if (r > 1 || r < 0) r = 1;
 301       axisY = halfDown(area.y + r * area.h);
 302     } else {
 303       axisY = halfDown(area.y + area.h);
 304     }
 305     context.moveTo(halfUp(area.x), axisY);
 306     context.lineTo(halfUp(area.x + area.w), axisY);
 307     context.closePath();
 308     context.stroke();
 309   }
 310
 311   context.restore();
 312 };
 313
 314 export default axes;