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
  11 Current bits of jankiness:
  12 - Uses two private APIs:
  13     1. Dygraph.optionsViewForAxis_
  14     2. dygraph.plotter_.area
  15 - Registers for a "predraw" event, which should be renamed.
  16 - I call calculateEmWidthInDiv more often than needed.
  17
  18 */
  19
  20 /*jshint globalstrict: true */
  21 /*global Dygraph:false */
  22 "use strict";
  23
  24
  25 /**
  26  * Creates the legend, which appears when the user hovers over the chart.
  27  * The legend can be either a user-specified or generated div.
  28  *
  29  * @constructor
  30  */
  31 var legend = function() {
  32   this.legend_div_ = null;
  33   this.is_generated_div_ = false;  // do we own this div, or was it user-specified?
  34 };
  35
  36 legend.prototype.toString = function() {
  37   return "Legend Plugin";
  38 };
  39
  40 // (defined below)
  41 var generateLegendDashHTML;
  42
  43 /**
  44  * This is called during the dygraph constructor, after options have been set
  45  * but before the data is available.
  46  *
  47  * Proper tasks to do here include:
  48  * - Reading your own options
  49  * - DOM manipulation
  50  * - Registering event listeners
  51  *
  52  * @param {Dygraph} g Graph instance.
  53  * @return {object.<string, function(ev)>} Mapping of event names to callbacks.
  54  */
  55 legend.prototype.activate = function(g) {
  56   var div;
  57   var divWidth = g.getOption('labelsDivWidth');
  58
  59   var userLabelsDiv = g.getOption('labelsDiv');
  60   if (userLabelsDiv && null !== userLabelsDiv) {
  61     if (typeof(userLabelsDiv) == "string" || userLabelsDiv instanceof String) {
  62       div = document.getElementById(userLabelsDiv);
  63     } else {
  64       div = userLabelsDiv;
  65     }
  66   } else {
  67     // Default legend styles. These can be overridden in CSS by adding
  68     // "!important" after your rule, e.g. "left: 30px !important;"
  69     var messagestyle = {
  70       "position": "absolute",
  71       "fontSize": "14px",
  72       "zIndex": 10,
  73       "width": divWidth + "px",
  74       "top": "0px",
  75       "left": (g.size().width - divWidth - 2) + "px",
  76       "background": "white",
  77       "lineHeight": "normal",
  78       "textAlign": "left",
  79       "overflow": "hidden"};
  80
  81     // TODO(danvk): get rid of labelsDivStyles? CSS is better.
  82     Dygraph.update(messagestyle, g.getOption('labelsDivStyles'));
  83     div = document.createElement("div");
  84     div.className = "dygraph-legend";
  85     for (var name in messagestyle) {
  86       if (!messagestyle.hasOwnProperty(name)) continue;
  87
  88       try {
  89         div.style[name] = messagestyle[name];
  90       } catch (e) {
  91         console.warn("You are using unsupported css properties for your " +
  92             "browser in labelsDivStyles");
  93       }
  94     }
  95
  96     // TODO(danvk): come up with a cleaner way to expose this.
  97     g.graphDiv.appendChild(div);
  98     this.is_generated_div_ = true;
  99   }
 100
 101   this.legend_div_ = div;
 102   this.one_em_width_ = 10;  // just a guess, will be updated.
 103
 104   return {
 105     select: this.select,
 106     deselect: this.deselect,
 107     // TODO(danvk): rethink the name "predraw" before we commit to it in any API.
 108     predraw: this.predraw,
 109     didDrawChart: this.didDrawChart
 110   };
 111 };
 112
 113 // Needed for dashed lines.
 114 var calculateEmWidthInDiv = function(div) {
 115   var sizeSpan = document.createElement('span');
 116   sizeSpan.setAttribute('style', 'margin: 0; padding: 0 0 0 1em; border: 0;');
 117   div.appendChild(sizeSpan);
 118   var oneEmWidth=sizeSpan.offsetWidth;
 119   div.removeChild(sizeSpan);
 120   return oneEmWidth;
 121 };
 122
 123 var escapeHTML = function(str) {
 124   return str.replace(/&/g, "&amp;").replace(/"/g, "&quot;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
 125 };
 126
 127 legend.prototype.select = function(e) {
 128   var xValue = e.selectedX;
 129   var points = e.selectedPoints;
 130
 131   var html = legend.generateLegendHTML(e.dygraph, xValue, points, this.one_em_width_);
 132   this.legend_div_.innerHTML = html;
 133 };
 134
 135 legend.prototype.deselect = function(e) {
 136   // Have to do this every time, since styles might have changed.
 137   var oneEmWidth = calculateEmWidthInDiv(this.legend_div_);
 138   this.one_em_width_ = oneEmWidth;
 139
 140   var html = legend.generateLegendHTML(e.dygraph, undefined, undefined, oneEmWidth);
 141   this.legend_div_.innerHTML = html;
 142 };
 143
 144 legend.prototype.didDrawChart = function(e) {
 145   this.deselect(e);
 146 };
 147
 148 // Right edge should be flush with the right edge of the charting area (which
 149 // may not be the same as the right edge of the div, if we have two y-axes.
 150 // TODO(danvk): is any of this really necessary? Could just set "right" in "activate".
 151 /**
 152  * Position the labels div so that:
 153  * - its right edge is flush with the right edge of the charting area
 154  * - its top edge is flush with the top edge of the charting area
 155  * @private
 156  */
 157 legend.prototype.predraw = function(e) {
 158   // Don't touch a user-specified labelsDiv.
 159   if (!this.is_generated_div_) return;
 160
 161   // TODO(danvk): only use real APIs for this.
 162   e.dygraph.graphDiv.appendChild(this.legend_div_);
 163   var area = e.dygraph.plotter_.area;
 164   var labelsDivWidth = e.dygraph.getOption("labelsDivWidth");
 165   this.legend_div_.style.left = area.x + area.w - labelsDivWidth - 1 + "px";
 166   this.legend_div_.style.top = area.y + "px";
 167   this.legend_div_.style.width = labelsDivWidth + "px";
 168 };
 169
 170 /**
 171  * Called when dygraph.destroy() is called.
 172  * You should null out any references and detach any DOM elements.
 173  */
 174 legend.prototype.destroy = function() {
 175   this.legend_div_ = null;
 176 };
 177
 178 /**
 179  * @private
 180  * Generates HTML for the legend which is displayed when hovering over the
 181  * chart. If no selected points are specified, a default legend is returned
 182  * (this may just be the empty string).
 183  * @param { Number } [x] The x-value of the selected points.
 184  * @param { [Object] } [sel_points] List of selected points for the given
 185  * x-value. Should have properties like 'name', 'yval' and 'canvasy'.
 186  * @param { Number } [oneEmWidth] The pixel width for 1em in the legend. Only
 187  * relevant when displaying a legend with no selection (i.e. {legend:
 188  * 'always'}) and with dashed lines.
 189  */
 190 legend.generateLegendHTML = function(g, x, sel_points, oneEmWidth) {
 191   // TODO(danvk): deprecate this option in place of {legend: 'never'}
 192   if (g.getOption('showLabelsOnHighlight') !== true) return '';
 193
 194   // If no points are selected, we display a default legend. Traditionally,
 195   // this has been blank. But a better default would be a conventional legend,
 196   // which provides essential information for a non-interactive chart.
 197   var html, sepLines, i, dash, strokePattern;
 198   var labels = g.getLabels();
 199
 200   if (typeof(x) === 'undefined') {
 201     if (g.getOption('legend') != 'always') {
 202       return '';
 203     }
 204
 205     sepLines = g.getOption('labelsSeparateLines');
 206     html = '';
 207     for (i = 1; i < labels.length; i++) {
 208       var series = g.getPropertiesForSeries(labels[i]);
 209       if (!series.visible) continue;
 210
 211       if (html !== '') html += (sepLines ? '<br/>' : ' ');
 212       strokePattern = g.getOption("strokePattern", labels[i]);
 213       dash = generateLegendDashHTML(strokePattern, series.color, oneEmWidth);
 214       html += "<span style='font-weight: bold; color: " + series.color + ";'>" +
 215           dash + " " + escapeHTML(labels[i]) + "</span>";
 216     }
 217     return html;
 218   }
 219
 220   // TODO(danvk): remove this use of a private API
 221   var xOptView = g.optionsViewForAxis_('x');
 222   var xvf = xOptView('valueFormatter');
 223   html = xvf(x, xOptView, labels[0], g);
 224   if (html !== '') {
 225     html += ':';
 226   }
 227
 228   var yOptViews = [];
 229   var num_axes = g.numAxes();
 230   for (i = 0; i < num_axes; i++) {
 231     // TODO(danvk): remove this use of a private API
 232     yOptViews[i] = g.optionsViewForAxis_('y' + (i ? 1 + i : ''));
 233   }
 234   var showZeros = g.getOption("labelsShowZeroValues");
 235   sepLines = g.getOption("labelsSeparateLines");
 236   var highlightSeries = g.getHighlightSeries();
 237   for (i = 0; i < sel_points.length; i++) {
 238     var pt = sel_points[i];
 239     if (pt.yval === 0 && !showZeros) continue;
 240     if (!Dygraph.isOK(pt.canvasy)) continue;
 241     if (sepLines) html += "<br/>";
 242
 243     var series = g.getPropertiesForSeries(pt.name);
 244     var yOptView = yOptViews[series.axis - 1];
 245     var fmtFunc = yOptView('valueFormatter');
 246     var yval = fmtFunc(pt.yval, yOptView, pt.name, g);
 247
 248     var cls = (pt.name == highlightSeries) ? " class='highlight'" : "";
 249
 250     // TODO(danvk): use a template string here and make it an attribute.
 251     html += "<span" + cls + ">" + " <b><span style='color: " + series.color + ";'>" +
 252         escapeHTML(pt.name) + "</span></b>:&#160;" + yval + "</span>";
 253   }
 254   return html;
 255 };
 256
 257
 258 /**
 259  * Generates html for the "dash" displayed on the legend when using "legend: always".
 260  * In particular, this works for dashed lines with any stroke pattern. It will
 261  * try to scale the pattern to fit in 1em width. Or if small enough repeat the
 262  * pattern for 1em width.
 263  *
 264  * @param strokePattern The pattern
 265  * @param color The color of the series.
 266  * @param oneEmWidth The width in pixels of 1em in the legend.
 267  * @private
 268  */
 269 generateLegendDashHTML = function(strokePattern, color, oneEmWidth) {
 270   // IE 7,8 fail at these divs, so they get boring legend, have not tested 9.
 271   var isIE = (/MSIE/.test(navigator.userAgent) && !window.opera);
 272   if (isIE) return "&mdash;";
 273
 274   // Easy, common case: a solid line
 275   if (!strokePattern || strokePattern.length <= 1) {
 276     return "<div style=\"display: inline-block; position: relative; " +
 277     "bottom: .5ex; padding-left: 1em; height: 1px; " +
 278     "border-bottom: 2px solid " + color + ";\"></div>";
 279   }
 280
 281   var i, j, paddingLeft, marginRight;
 282   var strokePixelLength = 0, segmentLoop = 0;
 283   var normalizedPattern = [];
 284   var loop;
 285
 286   // Compute the length of the pixels including the first segment twice,
 287   // since we repeat it.
 288   for (i = 0; i <= strokePattern.length; i++) {
 289     strokePixelLength += strokePattern[i%strokePattern.length];
 290   }
 291
 292   // See if we can loop the pattern by itself at least twice.
 293   loop = Math.floor(oneEmWidth/(strokePixelLength-strokePattern[0]));
 294   if (loop > 1) {
 295     // This pattern fits at least two times, no scaling just convert to em;
 296     for (i = 0; i < strokePattern.length; i++) {
 297       normalizedPattern[i] = strokePattern[i]/oneEmWidth;
 298     }
 299     // Since we are repeating the pattern, we don't worry about repeating the
 300     // first segment in one draw.
 301     segmentLoop = normalizedPattern.length;
 302   } else {
 303     // If the pattern doesn't fit in the legend we scale it to fit.
 304     loop = 1;
 305     for (i = 0; i < strokePattern.length; i++) {
 306       normalizedPattern[i] = strokePattern[i]/strokePixelLength;
 307     }
 308     // For the scaled patterns we do redraw the first segment.
 309     segmentLoop = normalizedPattern.length+1;
 310   }
 311
 312   // Now make the pattern.
 313   var dash = "";
 314   for (j = 0; j < loop; j++) {
 315     for (i = 0; i < segmentLoop; i+=2) {
 316       // The padding is the drawn segment.
 317       paddingLeft = normalizedPattern[i%normalizedPattern.length];
 318       if (i < strokePattern.length) {
 319         // The margin is the space segment.
 320         marginRight = normalizedPattern[(i+1)%normalizedPattern.length];
 321       } else {
 322         // The repeated first segment has no right margin.
 323         marginRight = 0;
 324       }
 325       dash += "<div style=\"display: inline-block; position: relative; " +
 326         "bottom: .5ex; margin-right: " + marginRight + "em; padding-left: " +
 327         paddingLeft + "em; height: 1px; border-bottom: 2px solid " + color +
 328         ";\"></div>";
 329     }
 330   }
 331   return dash;
 332 };
 333
 334
 335 return legend;
 336 })();