plugins/legend.js

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