plugins/legend.js

   1 /**
   2  * @license
   3  * Copyright 2012 Dan Vanderkam (danvdk@gmail.com)
   4  * MIT-licensed (http://opensource.org/licenses/MIT)
   5  */
   6 /*global Dygraph:false */
   7
   8 Dygraph.Plugins.Legend = (function() {
   9 /*
  10 Current bits of jankiness:
  11 - Uses two private APIs:
  12     1. Dygraph.optionsViewForAxis_
  13     2. dygraph.plotter_.area
  14 - Registers for a "predraw" event, which should be renamed.
  15 - I call calculateEmWidthInDiv more often than needed.
  16 */
  17
  18 /*global Dygraph:false */
  19 "use strict";
  20
  21
  22 /**
  23  * Creates the legend, which appears when the user hovers over the chart.
  24  * The legend can be either a user-specified or generated div.
  25  *
  26  * @constructor
  27  */
  28 var legend = function() {
  29   this.legend_div_ = null;
  30   this.is_generated_div_ = false;  // do we own this div, or was it user-specified?
  31 };
  32
  33 legend.prototype.toString = function() {
  34   return "Legend Plugin";
  35 };
  36
  37 // (defined below)
  38 var generateLegendDashHTML;
  39
  40 /**
  41  * This is called during the dygraph constructor, after options have been set
  42  * but before the data is available.
  43  *
  44  * Proper tasks to do here include:
  45  * - Reading your own options
  46  * - DOM manipulation
  47  * - Registering event listeners
  48  *
  49  * @param {Dygraph} g Graph instance.
  50  * @return {object.<string, function(ev)>} Mapping of event names to callbacks.
  51  */
  52 legend.prototype.activate = function(g) {
  53   var div;
  54   var divWidth = g.getOption('labelsDivWidth');
  55
  56   var userLabelsDiv = g.getOption('labelsDiv');
  57   if (userLabelsDiv && null !== userLabelsDiv) {
  58     if (typeof(userLabelsDiv) == "string" || userLabelsDiv instanceof String) {
  59       div = document.getElementById(userLabelsDiv);
  60     } else {
  61       div = userLabelsDiv;
  62     }
  63   } else {
  64     // Default legend styles. These can be overridden in CSS by adding
  65     // "!important" after your rule, e.g. "left: 30px !important;"
  66     var messagestyle = {
  67       "position": "absolute",
  68       "fontSize": "14px",
  69       "zIndex": 10,
  70       "width": divWidth + "px",
  71       "top": "0px",
  72       "left": (g.size().width - divWidth - 2) + "px",
  73       "background": "white",
  74       "lineHeight": "normal",
  75       "textAlign": "left",
  76       "overflow": "hidden"};
  77
  78     // TODO(danvk): get rid of labelsDivStyles? CSS is better.
  79     Dygraph.update(messagestyle, g.getOption('labelsDivStyles'));
  80     div = document.createElement("div");
  81     div.className = "dygraph-legend";
  82     for (var name in messagestyle) {
  83       if (!messagestyle.hasOwnProperty(name)) continue;
  84
  85       try {
  86         div.style[name] = messagestyle[name];
  87       } catch (e) {
  88         console.warn("You are using unsupported css properties for your " +
  89             "browser in labelsDivStyles");
  90       }
  91     }
  92
  93     // TODO(danvk): come up with a cleaner way to expose this.
  94     g.graphDiv.appendChild(div);
  95     this.is_generated_div_ = true;
  96   }
  97
  98   this.legend_div_ = div;
  99   this.one_em_width_ = 10;  // just a guess, will be updated.
 100
 101   return {
 102     select: this.select,
 103     deselect: this.deselect,
 104     // TODO(danvk): rethink the name "predraw" before we commit to it in any API.
 105     predraw: this.predraw,
 106     didDrawChart: this.didDrawChart
 107   };
 108 };
 109
 110 // Needed for dashed lines.
 111 var calculateEmWidthInDiv = function(div) {
 112   var sizeSpan = document.createElement('span');
 113   sizeSpan.setAttribute('style', 'margin: 0; padding: 0 0 0 1em; border: 0;');
 114   div.appendChild(sizeSpan);
 115   var oneEmWidth=sizeSpan.offsetWidth;
 116   div.removeChild(sizeSpan);
 117   return oneEmWidth;
 118 };
 119
 120 var escapeHTML = function(str) {
 121   return str.replace(/&/g, "&amp;").replace(/"/g, "&quot;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
 122 };
 123
 124 legend.prototype.select = function(e) {
 125   var xValue = e.selectedX;
 126   var points = e.selectedPoints;
 127
 128   var html = legend.generateLegendHTML(e.dygraph, xValue, points, this.one_em_width_);
 129   this.legend_div_.innerHTML = html;
 130 };
 131
 132 legend.prototype.deselect = function(e) {
 133   // Have to do this every time, since styles might have changed.
 134   var oneEmWidth = calculateEmWidthInDiv(this.legend_div_);
 135   this.one_em_width_ = oneEmWidth;
 136
 137   var html = legend.generateLegendHTML(e.dygraph, undefined, undefined, oneEmWidth);
 138   this.legend_div_.innerHTML = html;
 139 };
 140
 141 legend.prototype.didDrawChart = function(e) {
 142   this.deselect(e);
 143 };
 144
 145 // Right edge should be flush with the right edge of the charting area (which
 146 // may not be the same as the right edge of the div, if we have two y-axes.
 147 // TODO(danvk): is any of this really necessary? Could just set "right" in "activate".
 148 /**
 149  * Position the labels div so that:
 150  * - its right edge is flush with the right edge of the charting area
 151  * - its top edge is flush with the top edge of the charting area
 152  * @private
 153  */
 154 legend.prototype.predraw = function(e) {
 155   // Don't touch a user-specified labelsDiv.
 156   if (!this.is_generated_div_) return;
 157
 158   // TODO(danvk): only use real APIs for this.
 159   e.dygraph.graphDiv.appendChild(this.legend_div_);
 160   var area = e.dygraph.plotter_.area;
 161   var labelsDivWidth = e.dygraph.getOption("labelsDivWidth");
 162   this.legend_div_.style.left = area.x + area.w - labelsDivWidth - 1 + "px";
 163   this.legend_div_.style.top = area.y + "px";
 164   this.legend_div_.style.width = labelsDivWidth + "px";
 165 };
 166
 167 /**
 168  * Called when dygraph.destroy() is called.
 169  * You should null out any references and detach any DOM elements.
 170  */
 171 legend.prototype.destroy = function() {
 172   this.legend_div_ = null;
 173 };
 174
 175 /**
 176  * @private
 177  * Generates HTML for the legend which is displayed when hovering over the
 178  * chart. If no selected points are specified, a default legend is returned
 179  * (this may just be the empty string).
 180  * @param { Number } [x] The x-value of the selected points.
 181  * @param { [Object] } [sel_points] List of selected points for the given
 182  * x-value. Should have properties like 'name', 'yval' and 'canvasy'.
 183  * @param { Number } [oneEmWidth] The pixel width for 1em in the legend. Only
 184  * relevant when displaying a legend with no selection (i.e. {legend:
 185  * 'always'}) and with dashed lines.
 186  */
 187 legend.generateLegendHTML = function(g, x, sel_points, oneEmWidth) {
 188   // TODO(danvk): deprecate this option in place of {legend: 'never'}
 189   if (g.getOption('showLabelsOnHighlight') !== true) return '';
 190
 191   // If no points are selected, we display a default legend. Traditionally,
 192   // this has been blank. But a better default would be a conventional legend,
 193   // which provides essential information for a non-interactive chart.
 194   var html, sepLines, i, dash, strokePattern;
 195   var labels = g.getLabels();
 196
 197   if (typeof(x) === 'undefined') {
 198     if (g.getOption('legend') != 'always') {
 199       return '';
 200     }
 201
 202     sepLines = g.getOption('labelsSeparateLines');
 203     html = '';
 204     for (i = 1; i < labels.length; i++) {
 205       var series = g.getPropertiesForSeries(labels[i]);
 206       if (!series.visible) continue;
 207
 208       if (html !== '') html += (sepLines ? '<br/>' : ' ');
 209       strokePattern = g.getOption("strokePattern", labels[i]);
 210       dash = generateLegendDashHTML(strokePattern, series.color, oneEmWidth);
 211       html += "<span style='font-weight: bold; color: " + series.color + ";'>" +
 212           dash + " " + escapeHTML(labels[i]) + "</span>";
 213     }
 214     return html;
 215   }
 216
 217   // TODO(danvk): remove this use of a private API
 218   var xOptView = g.optionsViewForAxis_('x');
 219   var xvf = xOptView('valueFormatter');
 220   html = xvf(x, xOptView, labels[0], g);
 221   if (html !== '') {
 222     html += ':';
 223   }
 224
 225   var yOptViews = [];
 226   var num_axes = g.numAxes();
 227   for (i = 0; i < num_axes; i++) {
 228     // TODO(danvk): remove this use of a private API
 229     yOptViews[i] = g.optionsViewForAxis_('y' + (i ? 1 + i : ''));
 230   }
 231   var showZeros = g.getOption("labelsShowZeroValues");
 232   sepLines = g.getOption("labelsSeparateLines");
 233   var highlightSeries = g.getHighlightSeries();
 234   for (i = 0; i < sel_points.length; i++) {
 235     var pt = sel_points[i];
 236     if (pt.yval === 0 && !showZeros) continue;
 237     if (!Dygraph.isOK(pt.canvasy)) continue;
 238     if (sepLines) html += "<br/>";
 239
 240     var series = g.getPropertiesForSeries(pt.name);
 241     var yOptView = yOptViews[series.axis - 1];
 242     var fmtFunc = yOptView('valueFormatter');
 243     var yval = fmtFunc(pt.yval, yOptView, pt.name, g);
 244
 245     var cls = (pt.name == highlightSeries) ? " class='highlight'" : "";
 246
 247     // TODO(danvk): use a template string here and make it an attribute.
 248     html += "<span" + cls + ">" + " <b><span style='color: " + series.color + ";'>" +
 249         escapeHTML(pt.name) + "</span></b>:&#160;" + yval + "</span>";
 250   }
 251   return html;
 252 };
 253
 254
 255 /**
 256  * Generates html for the "dash" displayed on the legend when using "legend: always".
 257  * In particular, this works for dashed lines with any stroke pattern. It will
 258  * try to scale the pattern to fit in 1em width. Or if small enough repeat the
 259  * pattern for 1em width.
 260  *
 261  * @param strokePattern The pattern
 262  * @param color The color of the series.
 263  * @param oneEmWidth The width in pixels of 1em in the legend.
 264  * @private
 265  */
 266 generateLegendDashHTML = function(strokePattern, color, oneEmWidth) {
 267   // IE 7,8 fail at these divs, so they get boring legend, have not tested 9.
 268   var isIE = (/MSIE/.test(navigator.userAgent) && !window.opera);
 269   if (isIE) return "&mdash;";
 270
 271   // Easy, common case: a solid line
 272   if (!strokePattern || strokePattern.length <= 1) {
 273     return "<div style=\"display: inline-block; position: relative; " +
 274     "bottom: .5ex; padding-left: 1em; height: 1px; " +
 275     "border-bottom: 2px solid " + color + ";\"></div>";
 276   }
 277
 278   var i, j, paddingLeft, marginRight;
 279   var strokePixelLength = 0, segmentLoop = 0;
 280   var normalizedPattern = [];
 281   var loop;
 282
 283   // Compute the length of the pixels including the first segment twice,
 284   // since we repeat it.
 285   for (i = 0; i <= strokePattern.length; i++) {
 286     strokePixelLength += strokePattern[i%strokePattern.length];
 287   }
 288
 289   // See if we can loop the pattern by itself at least twice.
 290   loop = Math.floor(oneEmWidth/(strokePixelLength-strokePattern[0]));
 291   if (loop > 1) {
 292     // This pattern fits at least two times, no scaling just convert to em;
 293     for (i = 0; i < strokePattern.length; i++) {
 294       normalizedPattern[i] = strokePattern[i]/oneEmWidth;
 295     }
 296     // Since we are repeating the pattern, we don't worry about repeating the
 297     // first segment in one draw.
 298     segmentLoop = normalizedPattern.length;
 299   } else {
 300     // If the pattern doesn't fit in the legend we scale it to fit.
 301     loop = 1;
 302     for (i = 0; i < strokePattern.length; i++) {
 303       normalizedPattern[i] = strokePattern[i]/strokePixelLength;
 304     }
 305     // For the scaled patterns we do redraw the first segment.
 306     segmentLoop = normalizedPattern.length+1;
 307   }
 308
 309   // Now make the pattern.
 310   var dash = "";
 311   for (j = 0; j < loop; j++) {
 312     for (i = 0; i < segmentLoop; i+=2) {
 313       // The padding is the drawn segment.
 314       paddingLeft = normalizedPattern[i%normalizedPattern.length];
 315       if (i < strokePattern.length) {
 316         // The margin is the space segment.
 317         marginRight = normalizedPattern[(i+1)%normalizedPattern.length];
 318       } else {
 319         // The repeated first segment has no right margin.
 320         marginRight = 0;
 321       }
 322       dash += "<div style=\"display: inline-block; position: relative; " +
 323         "bottom: .5ex; margin-right: " + marginRight + "em; padding-left: " +
 324         paddingLeft + "em; height: 1px; border-bottom: 2px solid " + color +
 325         ";\"></div>";
 326     }
 327   }
 328   return dash;
 329 };
 330
 331
 332 return legend;
 333 })();