chrome/browser/resources/chromeos/chromevox/common/math_semantic_util.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * @fileoverview Utility functions for semantic tree computations.
   7  */
   8
   9 goog.provide('cvox.SemanticUtil');
  10
  11
  12 /**
  13  * @constructor
  14  */
  15 cvox.SemanticUtil = function() { };
  16
  17
  18 /**
  19  * Merges keys of objects into an array.
  20  * @param {...Object<string>} objects Optional objects.
  21  * @return {Array<string>} Array of all keys of the objects.
  22  */
  23 cvox.SemanticUtil.objectsToKeys = function(objects) {
  24   objects = Array.prototype.slice.call(arguments, 0);
  25   var keys = [];
  26   return keys.concat.apply(keys, objects.map(Object.keys));
  27 };
  28
  29
  30 /**
  31  * Merges values of objects into an array.
  32  * @param {...Object<string>} objects Optional objects.
  33  * @return {Array<string>} Array of all values of the objects.
  34  */
  35 cvox.SemanticUtil.objectsToValues = function(objects) {
  36   objects = Array.prototype.slice.call(arguments, 0);
  37   var result = [];
  38   var collectValues = function(obj) {
  39     for (var key in obj) {
  40       result.push(obj[key]);
  41     }
  42   };
  43   objects.forEach(collectValues);
  44   return result;
  45 };
  46
  47
  48 /**
  49  * Transforms a unicode character into numeric representation. Returns null if
  50  * the input string is not a valid unicode character.
  51  * @param {string} unicode Character.
  52  * @return {?number} The decimal representation if it exists.
  53  */
  54 cvox.SemanticUtil.unicodeToNumber = function(unicode) {
  55   if (!unicode || unicode.length > 2) {
  56     return null;
  57   }
  58   // Treating surrogate pairs.
  59   if (unicode.length == 2) {
  60     var hi = unicode.charCodeAt(0);
  61     var low = unicode.charCodeAt(1);
  62     if (0xD800 <= hi && hi <= 0xDBFF && !isNaN(low)) {
  63       return ((hi - 0xD800) * 0x400) + (low - 0xDC00) + 0x10000;
  64     }
  65     return null;
  66   }
  67   return unicode.charCodeAt(0);
  68 };
  69
  70
  71 /**
  72  * Transforms a numberic representation of a unicode character into its
  73  * corresponding string.
  74  * @param {number} number Unicode point.
  75  * @return {string} The string representation.
  76  */
  77 cvox.SemanticUtil.numberToUnicode = function(number) {
  78   if (number >= 0x10000) {
  79     var hi = (number - 0x10000) / 0x0400 + 0xD800;
  80     var lo = (number - 0x10000) % 0x0400 + 0xDC00;
  81     return String.fromCharCode(hi, lo);
  82   }
  83   return String.fromCharCode(number);
  84 };
  85
  86
  87 /**
  88  * Returns the tagname of an element node in upper case.
  89  * @param {Element} node The node.
  90  * @return {string} The node's tagname.
  91  */
  92 cvox.SemanticUtil.tagName = function(node) {
  93   return node.tagName.toUpperCase();
  94 };
  95
  96
  97 /**
  98  * List of MathML Tags that are to be ignored.
  99  * @type {Array<string>}
 100  * @const
 101  */
 102 cvox.SemanticUtil.IGNORETAGS = [
 103   'MERROR', 'MPHANTOM', 'MSPACE', 'MACTION', 'MALIGNGROUP', 'MALIGNMARK',
 104   'MACTION'
 105 ];
 106
 107
 108 /**
 109  * List of MathML Tags to be ignore if they have no children.
 110  * @type {Array<string>}
 111  * @const
 112  */
 113 cvox.SemanticUtil.EMPTYTAGS = ['MATH', 'MROW', 'MPADDED', 'MSTYLE'];
 114
 115
 116 /**
 117  * Removes elements from a list of MathML nodes that are either to be ignored or
 118  * ignored if they have empty children.
 119  * Observe that this is currently not recursive, i.e. will not take care of
 120  * pathological cases, where content is hidden in incorrectly used tags!
 121  * @param {Array<Element>} nodes The node list to be cleaned.
 122  * @return {Array<Element>} The cleansed list.
 123  */
 124 cvox.SemanticUtil.purgeNodes = function(nodes) {
 125   var nodeArray = [];
 126   for (var i = 0, node; node = nodes[i]; i++) {
 127     var tagName = cvox.SemanticUtil.tagName(node);
 128     if (cvox.SemanticUtil.IGNORETAGS.indexOf(tagName) != -1) continue;
 129     if (cvox.SemanticUtil.EMPTYTAGS.indexOf(tagName) != -1 &&
 130         node.childNodes.length == 0)
 131     continue;
 132     nodeArray.push(node);
 133   }
 134   return nodeArray;
 135 };