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   var row = e.selectedRow;
 128
 129   var legendMode = e.dygraph.getOption('legend');
 130   if (legendMode === 'never') {
 131     this.legend_div_.style.display = 'none';
 132     return;
 133   }
 134
 135   if (legendMode === 'follow') {
 136     // create floating legend div
 137     var area = e.dygraph.plotter_.area;
 138     var labelsDivWidth = e.dygraph.getOption('labelsDivWidth');
 139     var yAxisLabelWidth = e.dygraph.getOptionForAxis('axisLabelWidth', 'y');
 140     // determine floating [left, top] coordinates of the legend div
 141     // within the plotter_ area
 142     // offset 20 px to the right and down from the first selection point
 143     // 20 px is guess based on mouse cursor size
 144     var leftLegend = points[0].x * area.w + 20;
 145     var topLegend  = points[0].y * area.h - 20;
 146
 147     // if legend floats to end of the window area, it flips to the other
 148     // side of the selection point
 149     if ((leftLegend + labelsDivWidth + 1) > (window.scrollX + window.innerWidth)) {
 150       leftLegend = leftLegend - 2 * 20 - labelsDivWidth - (yAxisLabelWidth - area.x);
 151     }
 152
 153     e.dygraph.graphDiv.appendChild(this.legend_div_);
 154     this.legend_div_.style.left = yAxisLabelWidth + leftLegend + "px";
 155     this.legend_div_.style.top = topLegend + "px";
 156   }
 157
 158   var html = legend.generateLegendHTML(e.dygraph, xValue, points, this.one_em_width_, row);
 159   this.legend_div_.innerHTML = html;
 160   this.legend_div_.style.display = '';
 161 };
 162
 163 legend.prototype.deselect = function(e) {
 164   var legendMode = e.dygraph.getOption('legend');
 165   if (legendMode !== 'always') {
 166     this.legend_div_.style.display = "none";
 167   }
 168
 169   // Have to do this every time, since styles might have changed.
 170   var oneEmWidth = calculateEmWidthInDiv(this.legend_div_);
 171   this.one_em_width_ = oneEmWidth;
 172
 173   var html = legend.generateLegendHTML(e.dygraph, undefined, undefined, oneEmWidth, null);
 174   this.legend_div_.innerHTML = html;
 175 };
 176
 177 legend.prototype.didDrawChart = function(e) {
 178   this.deselect(e);
 179 };
 180
 181 // Right edge should be flush with the right edge of the charting area (which
 182 // may not be the same as the right edge of the div, if we have two y-axes.
 183 // TODO(danvk): is any of this really necessary? Could just set "right" in "activate".
 184 /**
 185  * Position the labels div so that:
 186  * - its right edge is flush with the right edge of the charting area
 187  * - its top edge is flush with the top edge of the charting area
 188  * @private
 189  */
 190 legend.prototype.predraw = function(e) {
 191   // Don't touch a user-specified labelsDiv.
 192   if (!this.is_generated_div_) return;
 193
 194   // TODO(danvk): only use real APIs for this.
 195   e.dygraph.graphDiv.appendChild(this.legend_div_);
 196   var area = e.dygraph.plotter_.area;
 197   var labelsDivWidth = e.dygraph.getOption("labelsDivWidth");
 198   this.legend_div_.style.left = area.x + area.w - labelsDivWidth - 1 + "px";
 199   this.legend_div_.style.top = area.y + "px";
 200   this.legend_div_.style.width = labelsDivWidth + "px";
 201 };
 202
 203 /**
 204  * Called when dygraph.destroy() is called.
 205  * You should null out any references and detach any DOM elements.
 206  */
 207 legend.prototype.destroy = function() {
 208   this.legend_div_ = null;
 209 };
 210
 211 /**
 212  * @private
 213  * Generates HTML for the legend which is displayed when hovering over the
 214  * chart. If no selected points are specified, a default legend is returned
 215  * (this may just be the empty string).
 216  * @param {number} x The x-value of the selected points.
 217  * @param {Object} sel_points List of selected points for the given
 218  *   x-value. Should have properties like 'name', 'yval' and 'canvasy'.
 219  * @param {number} oneEmWidth The pixel width for 1em in the legend. Only
 220  *   relevant when displaying a legend with no selection (i.e. {legend:
 221  *   'always'}) and with dashed lines.
 222  * @param {number} row The selected row index.
 223  */
 224 legend.generateLegendHTML = function(g, x, sel_points, oneEmWidth, row) {
 225   // TODO(danvk): deprecate this option in place of {legend: 'never'}
 226   if (g.getOption('showLabelsOnHighlight') !== true) return '';
 227
 228   // If no points are selected, we display a default legend. Traditionally,
 229   // this has been blank. But a better default would be a conventional legend,
 230   // which provides essential information for a non-interactive chart.
 231   var html, sepLines, i, dash, strokePattern;
 232   var labels = g.getLabels();
 233
 234   if (typeof(x) === 'undefined') {
 235     if (g.getOption('legend') != 'always') {
 236       return '';
 237     }
 238
 239     sepLines = g.getOption('labelsSeparateLines');
 240     html = '';
 241     for (i = 1; i < labels.length; i++) {
 242       var series = g.getPropertiesForSeries(labels[i]);
 243       if (!series.visible) continue;
 244
 245       if (html !== '') html += (sepLines ? '<br/>' : ' ');
 246       strokePattern = g.getOption("strokePattern", labels[i]);
 247       dash = generateLegendDashHTML(strokePattern, series.color, oneEmWidth);
 248       html += "<span style='font-weight: bold; color: " + series.color + ";'>" +
 249           dash + " " + escapeHTML(labels[i]) + "</span>";
 250     }
 251     return html;
 252   }
 253
 254   // TODO(danvk): remove this use of a private API
 255   var xOptView = g.optionsViewForAxis_('x');
 256   var xvf = xOptView('valueFormatter');
 257   html = xvf.call(g, x, xOptView, labels[0], g, row, 0);
 258   if (html !== '') {
 259     html += ':';
 260   }
 261
 262   var yOptViews = [];
 263   var num_axes = g.numAxes();
 264   for (i = 0; i < num_axes; i++) {
 265     // TODO(danvk): remove this use of a private API
 266     yOptViews[i] = g.optionsViewForAxis_('y' + (i ? 1 + i : ''));
 267   }
 268   var showZeros = g.getOption("labelsShowZeroValues");
 269   sepLines = g.getOption("labelsSeparateLines");
 270   var highlightSeries = g.getHighlightSeries();
 271   for (i = 0; i < sel_points.length; i++) {
 272     var pt = sel_points[i];
 273     if (pt.yval === 0 && !showZeros) continue;
 274     if (!Dygraph.isOK(pt.canvasy)) continue;
 275     if (sepLines) html += "<br/>";
 276
 277     var series = g.getPropertiesForSeries(pt.name);
 278     var yOptView = yOptViews[series.axis - 1];
 279     var fmtFunc = yOptView('valueFormatter');
 280     var yval = fmtFunc.call(g, pt.yval, yOptView, pt.name, g, row, labels.indexOf(pt.name));
 281
 282     var cls = (pt.name == highlightSeries) ? " class='highlight'" : "";
 283
 284     // TODO(danvk): use a template string here and make it an attribute.
 285     html += "<span" + cls + ">" + " <b><span style='color: " + series.color + ";'>" +
 286         escapeHTML(pt.name) + "</span></b>:&#160;" + yval + "</span>";
 287   }
 288   return html;
 289 };
 290
 291
 292 /**
 293  * Generates html for the "dash" displayed on the legend when using "legend: always".
 294  * In particular, this works for dashed lines with any stroke pattern. It will
 295  * try to scale the pattern to fit in 1em width. Or if small enough repeat the
 296  * pattern for 1em width.
 297  *
 298  * @param strokePattern The pattern
 299  * @param color The color of the series.
 300  * @param oneEmWidth The width in pixels of 1em in the legend.
 301  * @private
 302  */
 303 generateLegendDashHTML = function(strokePattern, color, oneEmWidth) {
 304   // Easy, common case: a solid line
 305   if (!strokePattern || strokePattern.length <= 1) {
 306     return "<div style=\"display: inline-block; position: relative; " +
 307     "bottom: .5ex; padding-left: 1em; height: 1px; " +
 308     "border-bottom: 2px solid " + color + ";\"></div>";
 309   }
 310
 311   var i, j, paddingLeft, marginRight;
 312   var strokePixelLength = 0, segmentLoop = 0;
 313   var normalizedPattern = [];
 314   var loop;
 315
 316   // Compute the length of the pixels including the first segment twice,
 317   // since we repeat it.
 318   for (i = 0; i <= strokePattern.length; i++) {
 319     strokePixelLength += strokePattern[i%strokePattern.length];
 320   }
 321
 322   // See if we can loop the pattern by itself at least twice.
 323   loop = Math.floor(oneEmWidth/(strokePixelLength-strokePattern[0]));
 324   if (loop > 1) {
 325     // This pattern fits at least two times, no scaling just convert to em;
 326     for (i = 0; i < strokePattern.length; i++) {
 327       normalizedPattern[i] = strokePattern[i]/oneEmWidth;
 328     }
 329     // Since we are repeating the pattern, we don't worry about repeating the
 330     // first segment in one draw.
 331     segmentLoop = normalizedPattern.length;
 332   } else {
 333     // If the pattern doesn't fit in the legend we scale it to fit.
 334     loop = 1;
 335     for (i = 0; i < strokePattern.length; i++) {
 336       normalizedPattern[i] = strokePattern[i]/strokePixelLength;
 337     }
 338     // For the scaled patterns we do redraw the first segment.
 339     segmentLoop = normalizedPattern.length+1;
 340   }
 341
 342   // Now make the pattern.
 343   var dash = "";
 344   for (j = 0; j < loop; j++) {
 345     for (i = 0; i < segmentLoop; i+=2) {
 346       // The padding is the drawn segment.
 347       paddingLeft = normalizedPattern[i%normalizedPattern.length];
 348       if (i < strokePattern.length) {
 349         // The margin is the space segment.
 350         marginRight = normalizedPattern[(i+1)%normalizedPattern.length];
 351       } else {
 352         // The repeated first segment has no right margin.
 353         marginRight = 0;
 354       }
 355       dash += "<div style=\"display: inline-block; position: relative; " +
 356         "bottom: .5ex; margin-right: " + marginRight + "em; padding-left: " +
 357         paddingLeft + "em; height: 1px; border-bottom: 2px solid " + color +
 358         ";\"></div>";
 359     }
 360   }
 361   return dash;
 362 };
 363
 364
 365 return legend;
 366 })();