chrome/browser/resources/chromeos/chromevox/walkers/abstract_node_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 A base class for walkers that have a concept of lowest-level
   7  * node. Base classes must override the stopNodeDescent method to define
   8  * what a lowest-level node is. Then this walker will use those nodes as the
   9  * set of valid CursorSelections.
  10  */
  11
  12
  13 goog.provide('cvox.AbstractNodeWalker');
  14
  15 goog.require('cvox.AbstractWalker');
  16 goog.require('cvox.CursorSelection');
  17 goog.require('cvox.DomUtil');
  18
  19 /**
  20  * @constructor
  21  * @extends {cvox.AbstractWalker}
  22  */
  23 cvox.AbstractNodeWalker = function() {
  24   goog.base(this);
  25
  26   /**
  27    * To keep track of and break infinite loops when trying to call next on
  28    * a body that does not DomUtil.hasContent().
  29    * @type {boolean}
  30    * @private
  31    */
  32   this.wasBegin_ = false;
  33 };
  34 goog.inherits(cvox.AbstractNodeWalker, cvox.AbstractWalker);
  35
  36 /**
  37  * @override
  38  */
  39 cvox.AbstractNodeWalker.prototype.next = function(sel) {
  40   var r = sel.isReversed();
  41   var node = sel.end.node || document.body;
  42
  43   do {
  44     node = cvox.DomUtil.directedNextLeafLikeNode(node, r,
  45         goog.bind(this.stopNodeDescent, this));
  46     if (!node) {
  47       return null;
  48     }
  49     // and repeat all of the above until we have a node that is not empty
  50   } while (node && !cvox.DomUtil.hasContent(node));
  51
  52   return cvox.CursorSelection.fromNode(node).setReversed(r);
  53 };
  54
  55 /**
  56  * @override
  57  */
  58 cvox.AbstractNodeWalker.prototype.sync = function(sel) {
  59   var ret = this.privateSync_(sel);
  60   this.wasBegin_ = false;
  61   return ret;
  62 };
  63
  64
  65 /**
  66  * Private version of sync to ensure that when a body has no content, we
  67  * don't do an infinite loop trying to find an empty node.
  68  * @param {!cvox.CursorSelection} sel The selection.
  69  * @return {cvox.CursorSelection} The synced selection.
  70  * @private
  71  */
  72 cvox.AbstractNodeWalker.prototype.privateSync_ = function(sel) {
  73   var r = sel.isReversed();
  74
  75   if (sel.equals(cvox.CursorSelection.fromBody())) {
  76     if (this.wasBegin_) {
  77       // if body is empty, we return just the body selection
  78       return cvox.CursorSelection.fromBody().setReversed(r);
  79     }
  80     this.wasBegin_ = true;
  81   }
  82
  83   var node = sel.start.node;
  84
  85   while (node != document.body && node.parentNode &&
  86       this.stopNodeDescent(node.parentNode)) {
  87     node = node.parentNode;
  88   }
  89
  90   while (!this.stopNodeDescent(node)) {
  91     node = cvox.DomUtil.directedFirstChild(node, r);
  92   }
  93
  94   var n = cvox.CursorSelection.fromNode(node);
  95   if (!cvox.DomUtil.hasContent(node)) {
  96     n = this.next(/** @type {!cvox.CursorSelection} */
  97         (cvox.CursorSelection.fromNode(node)).setReversed(r));
  98   }
  99   if (n) {
 100     return n.setReversed(r);
 101   }
 102   return this.begin({reversed: r});
 103 };
 104
 105 /**
 106  * Returns true if this is "a leaf node" or lower. That is,
 107  * it is at the lowest valid level or lower for this granularity.
 108  * RESTRICTION: true for a node => true for all child nodes
 109  * RESTRICTION: true if node has no children
 110  * @param {!Node} node The node to check.
 111  * @return {boolean} true if this is at the "leaf node" level or lower
 112  * for this granularity.
 113  * @protected
 114  */
 115 cvox.AbstractNodeWalker.prototype.stopNodeDescent = goog.abstractMethod;