chrome/browser/resources/chromeos/chromevox/walkers/abstract_selection_walker.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 An abstract class for walking at the sub-element level.
   7  * For example, walking at the sentence, word, or character level.
   8  * This class is an adapter around TraverseContent which exposes the interface
   9  * required by walkers. Subclasses must override the this.grain attribute
  10  * on initialization.
  11  */
  12
  13
  14 goog.provide('cvox.AbstractSelectionWalker');
  15
  16 goog.require('cvox.AbstractWalker');
  17 goog.require('cvox.BareObjectWalker');
  18 goog.require('cvox.DescriptionUtil');
  19 goog.require('cvox.DomUtil');
  20 goog.require('cvox.Spannable');
  21 goog.require('cvox.TraverseContent');
  22
  23 /**
  24  * @constructor
  25  * @extends {cvox.AbstractWalker}
  26  */
  27 cvox.AbstractSelectionWalker = function() {
  28   cvox.AbstractWalker.call(this);
  29   this.objWalker_ = new cvox.BareObjectWalker();
  30   this.tc_ = cvox.TraverseContent.getInstance();
  31   this.grain /** @protected */ = ''; // child must override
  32 };
  33 goog.inherits(cvox.AbstractSelectionWalker, cvox.AbstractWalker);
  34
  35 /**
  36  * @override
  37  */
  38 cvox.AbstractSelectionWalker.prototype.next = function(sel) {
  39   var r = sel.isReversed();
  40   this.tc_.syncToCursorSelection(sel.clone().setReversed(false));
  41   var ret = r ? this.tc_.prevElement(this.grain) :
  42       this.tc_.nextElement(this.grain);
  43   if (ret == null) {
  44     // Unfortunately, we can't trust TraverseContent; fall back to ObjectWalker.
  45     return this.objWalker_.next(sel);
  46   }
  47   var retSel = this.tc_.getCurrentCursorSelection().setReversed(r);
  48   var objSel = this.objWalker_.next(sel);
  49   objSel = objSel ? objSel.setReversed(r) : null;
  50
  51   // ObjectWalker wins when there's a discrepancy between it and
  52   // TraverseContent. The only exception is with an end cursor on a text node.
  53   // In all other cases, this makes sure we visit the same selections as
  54   // object walker.
  55   if (objSel &&
  56       (retSel.end.node.constructor.name != 'Text' ||
  57           objSel.end.node.constructor.name != 'Text') &&
  58       !cvox.DomUtil.isDescendantOfNode(retSel.end.node, sel.end.node) &&
  59       !cvox.DomUtil.isDescendantOfNode(retSel.end.node, objSel.end.node)) {
  60     return objSel;
  61   }
  62   return retSel;
  63 };
  64
  65 /**
  66  * @override
  67  */
  68 cvox.AbstractSelectionWalker.prototype.sync = function(sel) {
  69   var r = sel.isReversed();
  70   var newSel = null;
  71   if (sel.start.equals(sel.end) && sel.start.node.constructor.name != 'Text') {
  72     var node = sel.start.node;
  73
  74     // Find the deepest visible node; written specifically here because we want
  75     // to move across siblings if necessary and take the deepest node which can
  76     // be BODY.
  77     while (node &&
  78         cvox.DomUtil.directedFirstChild(node, r) &&
  79         !cvox.TraverseUtil.treatAsLeafNode(node)) {
  80       var child = cvox.DomUtil.directedFirstChild(node, r);
  81
  82       // Find the first visible child.
  83       while (child) {
  84         if (cvox.DomUtil.isVisible(child,
  85             {checkAncestors: false, checkDescendants: false})) {
  86           node = child;
  87           break;
  88         } else {
  89           child = cvox.DomUtil.directedNextSibling(child, r);
  90         }
  91       }
  92
  93       // node has no visible children; it's therefore the deepest visible node.
  94       if (!child) {
  95         break;
  96       }
  97     }
  98     newSel = cvox.CursorSelection.fromNode(node);
  99   } else {
 100     newSel = sel.clone();
 101     if (r) {
 102       newSel.start = newSel.end;
 103     } else {
 104       newSel.end = newSel.start;
 105     }
 106   }
 107
 108   // This.next places us at the correct initial position (except below).
 109   newSel = this.next(newSel.setReversed(false));
 110
 111   // ObjectWalker wins when there's a discrepancy between it and
 112   // TraverseContent. The only exception is with an end cursor on a text node.
 113   // In all other cases, this makes sure we visit the same selections as
 114   // object walker.
 115   var objSel = this.objWalker_.sync(sel);
 116   objSel = objSel ? objSel.setReversed(r) : null;
 117
 118   if (!newSel) {
 119     return objSel;
 120   }
 121
 122   newSel.setReversed(r);
 123
 124   if (objSel &&
 125       (newSel.end.node.constructor.name != 'Text' ||
 126           objSel.end.node.constructor.name != 'Text') &&
 127       !cvox.DomUtil.isDescendantOfNode(newSel.end.node, sel.end.node) &&
 128       !cvox.DomUtil.isDescendantOfNode(newSel.end.node, objSel.end.node)) {
 129     return objSel;
 130   }
 131   return newSel;
 132 };
 133
 134 /**
 135  * @override
 136  */
 137 cvox.AbstractSelectionWalker.prototype.getDescription = function(prevSel, sel) {
 138   var description = cvox.DescriptionUtil.getDescriptionFromAncestors(
 139       cvox.DomUtil.getUniqueAncestors(prevSel.end.node, sel.start.node),
 140       true,
 141       cvox.ChromeVox.verbosity);
 142   description.text = sel.getText() || description.text;
 143   return [description];
 144 };
 145
 146 /**
 147  * @override
 148  */
 149 cvox.AbstractSelectionWalker.prototype.getBraille = function(prevSel, sel) {
 150   var node = sel.absStart().node;
 151   var text = cvox.TraverseUtil.getNodeText(node);
 152   var spannable = new cvox.Spannable(text);
 153   spannable.setSpan(node, 0, text.length);
 154   return new cvox.NavBraille({
 155     text: spannable,
 156     startIndex: sel.absStart().index,
 157     endIndex: sel.absEnd().index
 158   });
 159 };