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