Adding ChromeVox as a component extensions (enabled only for ChromeOS, for no...

chrome/browser/resources/access_chromevox/chromevox/injected/user_commands.js

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+goog.provide('cvox.ChromeVoxUserCommands');
+
+goog.require('cvox.AbstractEarcons');
+goog.require('cvox.ChromeVox');
+goog.require('cvox.ChromeVoxSearch');
+goog.require('cvox.ExtensionBridge');
+goog.require('cvox.SelectionUtil');
+
+/**
+ * @fileoverview High level commands that the user can invoke using hotkeys.
+ */
+cvox.ChromeVoxUserCommands = function() { };
+
+/**
+ * @type {number}
+ */
+cvox.ChromeVoxUserCommands.silenceLevel = 0;
+
+/**
+ * @type {Object}
+ */
+cvox.ChromeVoxUserCommands.commands = {};
+
+/**
+ * Stops speech.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['stopSpeech'] = function() {
+  cvox.ChromeVox.tts.stop();
+  return false;
+};
+
+/**
+ * Moves forward and speaks the result.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['forward'] = function() {
+  cvox.ChromeVoxUserCommands.silenceEventWatchers_();
+  cvox.ChromeVox.navigationManager.next();
+  cvox.ChromeVoxUserCommands.finishNavCommand('');
+  return false;
+};
+
+/**
+ * Moves backward and speaks the result.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['backward'] = function() {
+  cvox.ChromeVoxUserCommands.silenceEventWatchers_();
+  cvox.ChromeVox.navigationManager.previous();
+  cvox.ChromeVoxUserCommands.finishNavCommand('');
+  return false;
+};
+
+/**
+ * Moves up to a different navigation strategy and speaks a summary of the
+ * current position.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousGranularity'] = function() {
+  cvox.ChromeVox.navigationManager.up();
+  var strategy = cvox.ChromeVox.navigationManager.getStrategy();
+  if (strategy == 'SELECTION') {
+    strategy = cvox.ChromeVox.navigationManager.getGranularity();
+  }
+  cvox.ChromeVoxUserCommands.finishNavCommand(strategy + ' ');
+  return false;
+};
+
+/**
+ * Moves down to a different navigation strategy and speaks a summary of the
+ * current position.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextGranularity'] = function() {
+  cvox.ChromeVox.navigationManager.down();
+  var strategy = cvox.ChromeVox.navigationManager.getStrategy();
+  if (strategy == 'SELECTION') {
+    strategy = cvox.ChromeVox.navigationManager.getGranularity();
+  }
+  cvox.ChromeVoxUserCommands.finishNavCommand(strategy + ' ');
+  return false;
+};
+
+/**
+ * This is a NOP command. It is needed in case we would like
+ * to swallow certain keys via mapping them to a NOP operation.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nop'] = function() {
+  /* do nothing */
+  return false;
+};
+
+/**
+ * Perform all of the actions that should happen at the end of any
+ * navigation operation: update the lens, play earcons, and speak the
+ * description of the object that was navigated to.
+ *
+ * @param {string} messagePrefixStr The string to be prepended to what
+ * is spoken to the user.
+ */
+cvox.ChromeVoxUserCommands.finishNavCommand = function(messagePrefixStr) {
+  cvox.ChromeVox.lens.updateText();
+  var message = cvox.ChromeVox.navigationManager.getCurrentDescription();
+  // Remove all whitespace from the beginning and end, and collapse all
+  // inner strings of whitespace to a single space.
+  message = message.replace(/\s+/g, ' ').replace(/^\s+|\s+$/g, '');
+  setTimeout(function() {
+    cvox.ChromeVox.navigationManager.setFocus();
+  }, 0);
+  cvox.SelectionUtil.scrollToSelection(window.getSelection());
+  cvox.ChromeVox.tts.speak(messagePrefixStr + message, 0, null);
+  cvox.ChromeVoxUserCommands.playEarcons();
+};
+
+/**
+ * Play earcons for the object that was most recently navigated to.
+ */
+cvox.ChromeVoxUserCommands.playEarcons = function() {
+  var ancestors = cvox.ChromeVox.navigationManager.getChangedAncestors();
+  var earcons = [];
+  for (var i = 0; i < ancestors.length; i++) {
+    var node = ancestors[i];
+    switch (node.tagName) {
+      case 'BUTTON':
+        earcons.push(cvox.AbstractEarcons.BUTTON);
+        break;
+      case 'A':
+        earcons.push(cvox.AbstractEarcons.LINK);
+        break;
+      case 'LI':
+        earcons.push(cvox.AbstractEarcons.LIST_ITEM);
+        break;
+      case 'SELECT':
+        earcons.push(cvox.AbstractEarcons.LISTBOX);
+        break;
+      case 'TEXTAREA':
+        earcons.push(cvox.AbstractEarcons.EDITABLE_TEXT);
+        break;
+      case 'INPUT':
+        switch (node.type) {
+          case 'submit':
+          case 'reset':
+            earcons.push(cvox.AbstractEarcons.BUTTON);
+            break;
+          case 'checkbox':
+          case 'radio':
+            if (node.value) {
+              earcons.push(cvox.AbstractEarcons.CHECK_ON);
+            } else {
+              earcons.push(cvox.AbstractEarcons.CHECK_OFF);
+            }
+            break;
+          default:
+            if (cvox.DomUtil.isInputTypeText(node)) {
+              // 'text', 'password', etc.
+              earcons.push(cvox.AbstractEarcons.EDITABLE_TEXT);
+            }
+            break;
+        }
+    }
+  }
+
+  for (var j = 0; j < earcons.length; j++) {
+    cvox.ChromeVox.earcons.playEarcon(earcons[j]);
+  }
+};
+
+/**
+ * Find the next occurrence of an item defined by the given predicate.
+ * @param {function(Array.<Node>)} predicate A function taking a node as a
+ *     parameter and returning true if it's what to search for.
+ * @param {string} errorStr A string to speak if the item couldn't be found.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.findNextAndSpeak_ = function(predicate,
+    errorStr) {
+  cvox.ChromeVoxUserCommands.silenceEventWatchers_();
+  if (!cvox.ChromeVox.navigationManager.findNext(predicate)) {
+    cvox.ChromeVox.tts.speak(errorStr, 0, null);
+    return;
+  }
+  cvox.ChromeVoxUserCommands.finishNavCommand('');
+};
+
+/**
+ * Find the next occurrence of an item defined by the given predicate.
+ * @param {function(Array.<Node>)} predicate A function taking a node as a
+ *     parameter and returning true if it's what to search for.
+ * @param {string} errorStr A string to speak if the item couldn't be found.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.findPreviousAndSpeak_ = function(predicate,
+    errorStr) {
+  cvox.ChromeVoxUserCommands.silenceEventWatchers_();
+  if (!cvox.ChromeVox.navigationManager.findPrevious(predicate)) {
+    cvox.ChromeVox.tts.speak(errorStr, 0, null);
+    return;
+  }
+  cvox.ChromeVoxUserCommands.finishNavCommand('');
+};
+
+/**
+ * @param {Array} arr Array of nodes.
+ * @param {string} tagName The name of the tag.
+ * @return {boolean} True if obj is in the array.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.containsTagName_ = function(arr, tagName) {
+  var i = arr.length;
+  while (i--) {
+    if (arr[i].tagName == tagName) {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Temporarily silence event watchers, then automatically un-silence them
+ * after a short delay. This prevents us from speaking that something has
+ * focused when the focusing was a result of a ChromeVox action.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.silenceEventWatchers_ = function() {
+  cvox.ChromeVoxUserCommands.silenceLevel += 1;
+  setTimeout(function() {
+    cvox.ChromeVoxUserCommands.silenceLevel -= 1;
+  }, 100);
+};
+
+/**
+ * Handles TAB navigation by putting focus at the user's position.
+ * This function will create dummy nodes if there is nothing that
+ * is focusable at the current position.
+ *
+ * @return {boolean} Always return true since we rely on the default action.
+ */
+cvox.ChromeVoxUserCommands.commands['handleTab'] = function() {
+  // Clean up after any previous runs
+  var previousDummySpan = document.getElementById('ChromeVoxTabDummySpan');
+  if (previousDummySpan) {
+    previousDummySpan.parentNode.removeChild(previousDummySpan);
+  }
+
+  // Hide the search widget if it is shown.
+  cvox.ChromeVoxSearch.hide();
+
+  var tagName = 'A';
+  // If the user is already focused on a link or control,
+  // nothing more needs to be done.
+  if ((document.activeElement.tagName == tagName) ||
+      cvox.DomUtil.isControl(document.activeElement)) {
+    return true;
+  }
+
+  // Try to find something reasonable to focus on in the current selection.
+  var sel = window.getSelection();
+  if (sel == null || sel.anchorNode == null || sel.focusNode == null) {
+    return true;
+  }
+  if (sel.anchorNode.tagName &&
+      ((sel.anchorNode.tagName == tagName) ||
+      cvox.DomUtil.isControl(sel.anchorNode))) {
+    sel.anchorNode.focus();
+    return true;
+  }
+  if (sel.focusNode.tagName &&
+      ((sel.focusNode.tagName == tagName) ||
+      cvox.DomUtil.isControl(sel.focusNode))) {
+    sel.focusNode.focus();
+    return true;
+  }
+  if (sel.anchorNode.parentNode.tagName &&
+      ((sel.anchorNode.parentNode.tagName == tagName) ||
+      cvox.DomUtil.isControl(sel.anchorNode.parentNode))) {
+    sel.anchorNode.parentNode.focus();
+    return true;
+  }
+  if (sel.focusNode.parentNode.tagName &&
+      ((sel.focusNode.parentNode.tagName == tagName) ||
+      cvox.DomUtil.isControl(sel.focusNode))) {
+    sel.focusNode.parentNode.focus();
+    return true;
+  }
+
+  // Create a dummy span immediately before the current position and focus
+  // on it so that the default tab action will start off as close to the
+  // user's current position as possible.
+  var span = document.createElement('span');
+  span.id = 'ChromeVoxTabDummySpan';
+  sel.anchorNode.parentNode.insertBefore(span, sel.anchorNode);
+  span.tabIndex = -1;
+  span.focus();
+  return true;
+};
+
+/**
+ * Toggles between searching and browsing.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['toggleSearchWidget'] = function() {
+  if (cvox.ChromeVoxSearch.isActive()) {
+    cvox.ChromeVoxSearch.hide();
+    cvox.ChromeVox.tts.speak('Browse', 0, null);
+  } else {
+    cvox.ChromeVoxSearch.show();
+    cvox.ChromeVox.tts.speak('Search', 0, null);
+  }
+  return false;
+};
+
+/**
+ * Cycles through the Text-To-Speech Engines.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextTtsEngine'] = function() {
+  cvox.ChromeVox.tts.nextEngine();
+  return false;
+};
+
+/**
+ * Decreases the tts rate.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['decreaseTtsRate'] = function() {
+  cvox.ChromeVox.tts.decreaseProperty('Rate');
+  return false;
+};
+
+/**
+ * Increases the tts rate.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['increaseTtsRate'] = function() {
+  cvox.ChromeVox.tts.increaseProperty('Rate');
+  return false;
+};
+
+/**
+ * Decreases the tts pitch.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['decreaseTtsPitch'] = function() {
+  cvox.ChromeVox.tts.decreaseProperty('Pitch');
+  return false;
+};
+
+/**
+ * Increases the tts pitch.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['increaseTtsPitch'] = function() {
+  cvox.ChromeVox.tts.increaseProperty('Pitch');
+  return false;
+};
+
+/**
+ * Decreases the tts volume.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['decreaseTtsVolume'] = function() {
+  cvox.ChromeVox.tts.decreaseProperty('Volume');
+  return false;
+};
+
+/**
+ * Increases the tts volume.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['increaseTtsVolume'] = function() {
+  cvox.ChromeVox.tts.increaseProperty('Volume');
+  return false;
+};
+
+/**
+ * Shows the bookmark manager
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['showBookmarkManager'] = function() {
+  cvox.ExtensionBridge.send({
+      'target': 'BookmarkManager',
+      'action': 'open'});
+  return false;
+};
+
+/**
+ * Debug function - useful for quickly trying out some behavior
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['debug'] = function() {
+  alert('ok');
+  return false;
+};
+
+//
+// Jump commands - jump to the next / previous node of a certain category
+//
+
+/**
+ * Next checkbox.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextCheckbox'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.checkboxPredicate_,
+      'No next checkbox.');
+  return false;
+};
+
+/**
+ * Previous checkbox.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousCheckbox'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.checkboxPredicate_,
+      'No previous checkbox.');
+  return false;
+};
+
+/**
+ * Next radio button.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextRadio'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.radioPredicate_,
+      'No next radio button.');
+  return false;
+};
+
+/**
+ * Previous radio button.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousRadio'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.radioPredicate_,
+      'No previous radio button.');
+  return false;
+};
+
+/**
+ * Next slider.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextSlider'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.sliderPredicate_,
+      'No next slider.');
+  return false;
+};
+
+/**
+ * Previous slider.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousSlider'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.sliderPredicate_,
+      'No previous slider.');
+  return false;
+};
+
+/**
+ * Next graphic.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextGraphic'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.graphicPredicate_,
+      'No next graphic.');
+  return false;
+};
+
+/**
+ * Previous graphic.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousGraphic'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.graphicPredicate_,
+      'No previous graphic.');
+  return false;
+};
+
+/**
+ * Next button.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextButton'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.buttonPredicate_,
+      'No next button.');
+  return false;
+};
+
+/**
+ * Previous button.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousButton'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.buttonPredicate_,
+      'No previous button.');
+  return false;
+};
+
+/**
+ * Next combo box.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextComboBox'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.comboBoxPredicate_,
+      'No next combo box.');
+  return false;
+};
+
+/**
+ * Previous combo box.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousComboBox'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.comboBoxPredicate_,
+      'No previous combo box.');
+  return false;
+};
+
+/**
+ * Next editable text field.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextEditText'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.editTextPredicate_,
+      'No next editable text field.');
+  return false;
+};
+
+/**
+ * Previous editable text field.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousEditText'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.editTextPredicate_,
+      'No previous editable text field.');
+  return false;
+};
+
+/**
+ * Next heading.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.headingPredicate_,
+      'No next heading.');
+  return false;
+};
+
+/**
+ * Previous heading.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.headingPredicate_,
+      'No previous heading.');
+  return false;
+};
+
+/**
+ * Next heading level 1.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading1'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading1Predicate_,
+      'No next level 1 heading.');
+  return false;
+};
+
+/**
+ * Previous heading level 1.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading1'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading1Predicate_,
+      'No previous level 1 heading.');
+  return false;
+};
+
+/**
+ * Next heading level 2.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading2'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading2Predicate_,
+      'No next level 2 heading.');
+  return false;
+};
+
+/**
+ * Previous heading level 2.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading2'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading2Predicate_,
+      'No previous level 2 heading.');
+  return false;
+};
+
+/**
+ * Next heading level 3.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading3'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading3Predicate_,
+      'No next level 3 heading.');
+  return false;
+};
+
+/**
+ * Previous heading level 3.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading3'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading3Predicate_,
+      'No previous level 3 heading.');
+  return false;
+};
+
+/**
+ * Next heading level 4.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading4'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading4Predicate_,
+      'No next level 4 heading.');
+  return false;
+};
+
+/**
+ * Previous heading level 4.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading4'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading4Predicate_,
+      'No previous level 4 heading.');
+  return false;
+};
+
+/**
+ * Next heading level 5.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading5'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading5Predicate_,
+      'No next level 5 heading.');
+  return false;
+};
+
+/**
+ * Previous heading level 5.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading5'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading5Predicate_,
+      'No previous level 5 heading.');
+  return false;
+};
+
+/**
+ * Next heading level 6.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextHeading6'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading6Predicate_,
+      'No next level 6 heading.');
+  return false;
+};
+
+/**
+ * Previous heading level 6.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousHeading6'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.heading6Predicate_,
+      'No previous level 6 heading.');
+  return false;
+};
+
+/**
+ * Next not-link.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextNotLink'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.notLinkPredicate_,
+      'No next item that isn\'t a link.');
+  return false;
+};
+
+/**
+ * Previous not-link.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousNotLink'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.notLinkPredicate_,
+      'No previous item that isn\'t a link.');
+  return false;
+};
+
+/**
+ * Next link.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextLink'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.linkPredicate_,
+      'No next link.');
+  return false;
+};
+
+/**
+ * Previous link.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousLink'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.linkPredicate_,
+      'No previous link.');
+  return false;
+};
+
+/**
+ * Next table.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextTable'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.tablePredicate_,
+      'No next table.');
+  return false;
+};
+
+/**
+ * Previous table.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousTable'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.tablePredicate_,
+      'No previous table.');
+  return false;
+};
+
+/**
+ * Next list.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextList'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.listPredicate_,
+      'No next list.');
+  return false;
+};
+
+/**
+ * Previous list.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousList'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.listPredicate_,
+      'No previous list.');
+  return false;
+};
+
+/**
+ * Next list item.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextListItem'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.listItemPredicate_,
+      'No next list item.');
+  return false;
+};
+
+/**
+ * Previous list item.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousListItem'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.listItemPredicate_,
+      'No previous list item.');
+  return false;
+};
+
+/**
+ * Next blockquote.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextBlockquote'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.blockquotePredicate_,
+      'No next blockquote.');
+  return false;
+};
+
+/**
+ * Previous blockquote.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousBlockquote'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.blockquotePredicate_,
+      'No previous blockquote.');
+  return false;
+};
+
+/**
+ * Next form field.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['nextFormField'] = function() {
+  cvox.ChromeVoxUserCommands.findNextAndSpeak_(
+      cvox.ChromeVoxUserCommands.formFieldPredicate_,
+      'No next form field.');
+  return false;
+};
+
+/**
+ * Previous form field.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['previousFormField'] = function() {
+  cvox.ChromeVoxUserCommands.findPreviousAndSpeak_(
+      cvox.ChromeVoxUserCommands.formFieldPredicate_,
+      'No previous form field.');
+  return false;
+};
+
+/**
+ * Attempts to do something reasonable given the current item that the user is
+ * on.
+ * For example, if the user is on a chunk of text that contains a link, navigate
+ * to that link. If there are multiple links in that chunk, bring up a menu to
+ * let the user choose which link they meant to click on.
+ *
+ * @return {boolean} Always return false since we want to prevent the default
+ * action.
+ */
+cvox.ChromeVoxUserCommands.commands['actOnCurrentItem'] = function() {
+  var actionTaken = cvox.ChromeVox.navigationManager.actOnCurrentItem();
+  if (!actionTaken) {
+    cvox.ChromeVox.tts.speak('No actions available.', 0, null);
+  }
+  return false;
+};
+
+
+//
+// Predicates - functions that take an array of ancestor nodes that have
+// changed and returns true if a certain category has been found. Used for
+// implementing functions like nextCheckbox / prevCheckbox, and so on.
+//
+
+/**
+ * Checkbox.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a checkbox.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.checkboxPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'checkbox') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT' && nodes[i].type == 'checkbox') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Radio button.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a radio button.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.radioPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'radio') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT' && nodes[i].type == 'radio') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Slider.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a slider.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.sliderPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'slider') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT' && nodes[i].type == 'range') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Graphic.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a graphic.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.graphicPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].tagName == 'IMG') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT' && nodes[i].type == 'img') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Button.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a button.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.buttonPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'button') {
+      return true;
+    }
+    if (nodes[i].tagName == 'BUTTON') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT' && nodes[i].type == 'submit') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT' && nodes[i].type == 'reset') {
+      return true;
+    }
+  }
+};
+
+/**
+ * Combo box.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a combo box.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.comboBoxPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'combobox') {
+      return true;
+    }
+    if (nodes[i].tagName == 'SELECT') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Editable text field.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains an editable text field.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.editTextPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'textbox') {
+      return true;
+    }
+    if (nodes[i].tagName == 'TEXTAREA') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT') {
+      return cvox.DomUtil.isInputTypeText(nodes[i]);
+    }
+  }
+  return false;
+};
+
+/**
+ * Heading.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.headingPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'heading') {
+      return true;
+    }
+    switch (nodes[i].tagName) {
+      case 'H1':
+      case 'H2':
+      case 'H3':
+      case 'H4':
+      case 'H5':
+      case 'H6':
+        return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Heading level 1.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading level 1.
+ * TODO: handle ARIA headings with ARIA heading levels?
+ * @private
+ */
+cvox.ChromeVoxUserCommands.heading1Predicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'H1');
+};
+
+/**
+ * Heading level 2.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading level 2.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.heading2Predicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'H2');
+};
+
+/**
+ * Heading level 3.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading level 3.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.heading3Predicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'H3');
+};
+
+/**
+ * Heading level 4.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading level 4.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.heading4Predicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'H4');
+};
+
+/**
+ * Heading level 5.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading level 5.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.heading5Predicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'H5');
+};
+
+/**
+ * Heading level 6.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a heading level 6.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.heading6Predicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'H6');
+};
+
+/**
+ * Not-link.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if none of the items in the array is a link.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.notLinkPredicate_ = function(nodes) {
+  return !cvox.ChromeVoxUserCommands.linkPredicate_(nodes);
+};
+
+/**
+ * Link.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a link.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.linkPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'link') {
+      return true;
+    }
+    if (nodes[i].tagName == 'A') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * Table.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a table.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.tablePredicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'TABLE');
+};
+
+/**
+ * List.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a list.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.listPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].tagName == 'UL') {
+      return true;
+    }
+    if (nodes[i].tagName == 'OL') {
+      return true;
+    }
+  }
+  return false;
+};
+
+/**
+ * List item.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a list item.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.listItemPredicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'TABLE');
+};
+
+/**
+ * Blockquote.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains a blockquote.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.blockquotePredicate_ = function(nodes) {
+  return cvox.ChromeVoxUserCommands.containsTagName_(nodes, 'BLOCKQUOTE');
+};
+
+/**
+ * Form field.
+ * @param {Array.<Node>} nodes An array of nodes to check.
+ * @return {boolean} True if the array contains any type of form field.
+ * @private
+ */
+cvox.ChromeVoxUserCommands.formFieldPredicate_ = function(nodes) {
+  for (var i = 0; i < nodes.length; i++) {
+    if (nodes[i].role == 'button') {
+      return true;
+    }
+    if (nodes[i].role == 'checkbox') {
+      return true;
+    }
+    if (nodes[i].role == 'combobox') {
+      return true;
+    }
+    if (nodes[i].role == 'radio') {
+      return true;
+    }
+    if (nodes[i].role == 'slider') {
+      return true;
+    }
+    if (nodes[i].role == 'spinbutton') {
+      return true;
+    }
+    if (nodes[i].role == 'textbox') {
+      return true;
+    }
+    if (nodes[i].tagName == 'INPUT') {
+      return true;
+    }
+    if (nodes[i].tagName == 'SELECT') {
+      return true;
+    }
+    if (nodes[i].tagName == 'BUTTON') {
+      return true;
+    }
+  }
+  return false;
+};