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.getOption('drawYAxis')) {
  56     var w = g.getOption('yAxisLabelWidth') + 2 * g.getOption('axisTickSize');
  57     e.reserveSpaceLeft(w);
  58   }
  59
  60   if (g.getOption('drawXAxis')) {
  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): per-axis setting.
  75     var w = g.getOption('yAxisLabelWidth') + 2 * g.getOption('axisTickSize');
  76     e.reserveSpaceRight(w);
  77   } else if (g.numAxes() > 2) {
  78     g.error("Only two y-axes are supported at this time. (Trying " +
  79             "to use " + g.numAxes() + ")");
  80   }
  81 };
  82
  83 axes.prototype.detachLabels = function() {
  84   function removeArray(ary) {
  85     for (var i = 0; i < ary.length; i++) {
  86       var el = ary[i];
  87       if (el.parentNode) el.parentNode.removeChild(el);
  88     }
  89   }
  90
  91   removeArray(this.xlabels_);
  92   removeArray(this.ylabels_);
  93   this.xlabels_ = [];
  94   this.ylabels_ = [];
  95 };
  96
  97 axes.prototype.clearChart = function(e) {
  98   this.detachLabels();
  99 };
 100
 101 axes.prototype.willDrawChart = function(e) {
 102   var g = e.dygraph;
 103   if (!g.getOption('drawXAxis') && !g.getOption('drawYAxis')) return;
 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 = e.canvas.width;
 112   var canvasHeight = e.canvas.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.getOption('axisLabelWidth') + "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   if (g.getOption('drawYAxis')) {
 165     if (layout.yticks && layout.yticks.length > 0) {
 166       var num_axes = g.numAxes();
 167       for (i = 0; i < layout.yticks.length; i++) {
 168         tick = layout.yticks[i];
 169         if (typeof(tick) == "function") return;
 170         x = area.x;
 171         var sgn = 1;
 172         var prec_axis = 'y1';
 173         if (tick[0] == 1) {  // right-side y-axis
 174           x = area.x + area.w;
 175           sgn = -1;
 176           prec_axis = 'y2';
 177         }
 178         var fontSize = g.getOptionForAxis('axisLabelFontSize', prec_axis);
 179         y = area.y + tick[1] * area.h;
 180
 181         /* Tick marks are currently clipped, so don't bother drawing them.
 182         context.beginPath();
 183         context.moveTo(halfUp(x), halfDown(y));
 184         context.lineTo(halfUp(x - sgn * this.attr_('axisTickSize')), halfDown(y));
 185         context.closePath();
 186         context.stroke();
 187         */
 188
 189         label = makeDiv(tick[2], 'y', num_axes == 2 ? prec_axis : null);
 190         var top = (y - fontSize / 2);
 191         if (top < 0) top = 0;
 192
 193         if (top + fontSize + 3 > canvasHeight) {
 194           label.style.bottom = "0px";
 195         } else {
 196           label.style.top = top + "px";
 197         }
 198         if (tick[0] === 0) {
 199           label.style.left = (area.x - g.getOption('yAxisLabelWidth') - g.getOption('axisTickSize')) + "px";
 200           label.style.textAlign = "right";
 201         } else if (tick[0] == 1) {
 202           label.style.left = (area.x + area.w +
 203                               g.getOption('axisTickSize')) + "px";
 204           label.style.textAlign = "left";
 205         }
 206         label.style.width = g.getOption('yAxisLabelWidth') + "px";
 207         containerDiv.appendChild(label);
 208         this.ylabels_.push(label);
 209       }
 210
 211       // The lowest tick on the y-axis often overlaps with the leftmost
 212       // tick on the x-axis. Shift the bottom tick up a little bit to
 213       // compensate if necessary.
 214       var bottomTick = this.ylabels_[0];
 215       // Interested in the y2 axis also?
 216       var fontSize = g.getOptionForAxis('axisLabelFontSize', "y");
 217       var bottom = parseInt(bottomTick.style.top, 10) + fontSize;
 218       if (bottom > canvasHeight - fontSize) {
 219         bottomTick.style.top = (parseInt(bottomTick.style.top, 10) -
 220             fontSize / 2) + "px";
 221       }
 222     }
 223
 224     // draw a vertical line on the left to separate the chart from the labels.
 225     var axisX;
 226     if (g.getOption('drawAxesAtZero')) {
 227       var r = g.toPercentXCoord(0);
 228       if (r > 1 || r < 0) r = 0;
 229       axisX = halfUp(area.x + r * area.w);
 230     } else {
 231       axisX = halfUp(area.x);
 232     }
 233
 234     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y');
 235     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y');
 236
 237     context.beginPath();
 238     context.moveTo(axisX, halfDown(area.y));
 239     context.lineTo(axisX, halfDown(area.y + area.h));
 240     context.closePath();
 241     context.stroke();
 242
 243     // if there's a secondary y-axis, draw a vertical line for that, too.
 244     if (g.numAxes() == 2) {
 245       context.strokeStyle = g.getOptionForAxis('axisLineColor', 'y2');
 246       context.lineWidth = g.getOptionForAxis('axisLineWidth', 'y2');
 247       context.beginPath();
 248       context.moveTo(halfDown(area.x + area.w), halfDown(area.y));
 249       context.lineTo(halfDown(area.x + area.w), halfDown(area.y + area.h));
 250       context.closePath();
 251       context.stroke();
 252     }
 253   }
 254
 255   if (g.getOption('drawXAxis')) {
 256     if (layout.xticks) {
 257       for (i = 0; i < layout.xticks.length; i++) {
 258         tick = layout.xticks[i];
 259         x = area.x + tick[0] * area.w;
 260         y = area.y + area.h;
 261
 262         /* Tick marks are currently clipped, so don't bother drawing them.
 263         context.beginPath();
 264         context.moveTo(halfUp(x), halfDown(y));
 265         context.lineTo(halfUp(x), halfDown(y + this.attr_('axisTickSize')));
 266         context.closePath();
 267         context.stroke();
 268         */
 269
 270         label = makeDiv(tick[1], 'x');
 271         label.style.textAlign = "center";
 272         label.style.top = (y + g.getOption('axisTickSize')) + 'px';
 273
 274         var left = (x - g.getOption('axisLabelWidth')/2);
 275         if (left + g.getOption('axisLabelWidth') > canvasWidth) {
 276           left = canvasWidth - g.getOption('xAxisLabelWidth');
 277           label.style.textAlign = "right";
 278         }
 279         if (left < 0) {
 280           left = 0;
 281           label.style.textAlign = "left";
 282         }
 283
 284         label.style.left = left + "px";
 285         label.style.width = g.getOption('xAxisLabelWidth') + "px";
 286         containerDiv.appendChild(label);
 287         this.xlabels_.push(label);
 288       }
 289     }
 290
 291     context.strokeStyle = g.getOptionForAxis('axisLineColor', 'x');
 292     context.lineWidth = g.getOptionForAxis('axisLineWidth', 'x');
 293     context.beginPath();
 294     var axisY;
 295     if (g.getOption('drawAxesAtZero')) {
 296       var r = g.toPercentYCoord(0, 0);
 297       if (r > 1 || r < 0) r = 1;
 298       axisY = halfDown(area.y + r * area.h);
 299     } else {
 300       axisY = halfDown(area.y + area.h);
 301     }
 302     context.moveTo(halfUp(area.x), axisY);
 303     context.lineTo(halfUp(area.x + area.w), axisY);
 304     context.closePath();
 305     context.stroke();
 306   }
 307
 308   context.restore();
 309 };
 310
 311 return axes;
 312 })();