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// Copyright 2012 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview A plugin to enable the First Strong Bidi algorithm.  The First
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 * Strong algorithm as a heuristic used to automatically set paragraph direction
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 * depending on its content.
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 *
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 * In the documentation below, a 'paragraph' is the local element which we
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 * evaluate as a whole for purposes of determining directionality. It may be a
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 * block-level element (e.g. <div>) or a whole list (e.g. <ul>).
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 *
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 * This implementation is based on, but is not identical to, the original
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 * First Strong algorithm defined in Unicode
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 * @see http://www.unicode.org/reports/tr9/
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 * The central difference from the original First Strong algorithm is that this
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 * implementation decides the paragraph direction based on the first strong
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 * character that is <em>typed</em> into the paragraph, regardless of its
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 * location in the paragraph, as opposed to the original algorithm where it is
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 * the first character in the paragraph <em>by location</em>, regardless of
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 * whether other strong characters already appear in the paragraph, further its
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 * start.
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 *
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 * <em>Please note</em> that this plugin does not perform the direction change
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 * itself. Rather, it fires editor commands upon the key up event when a
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 * direction change needs to be performed; {@code goog.editor.Command.DIR_RTL}
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 * or {@code goog.editor.Command.DIR_RTL}.
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 *
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 */
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goog.provide('goog.editor.plugins.FirstStrong');
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goog.require('goog.dom.NodeType');
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goog.require('goog.dom.TagIterator');
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goog.require('goog.dom.TagName');
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goog.require('goog.editor.Command');
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goog.require('goog.editor.Field');
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goog.require('goog.editor.Plugin');
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goog.require('goog.editor.node');
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goog.require('goog.editor.range');
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goog.require('goog.i18n.bidi');
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goog.require('goog.i18n.uChar');
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goog.require('goog.iter');
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goog.require('goog.userAgent');
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/**
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 * First Strong plugin.
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 * @constructor
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 * @extends {goog.editor.Plugin}
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 * @final
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 */
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goog.editor.plugins.FirstStrong = function() {
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  goog.editor.plugins.FirstStrong.base(this, 'constructor');
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  /**
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   * Indicates whether or not the cursor is in a paragraph we have not yet
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   * finished evaluating for directionality. This is set to true whenever the
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   * cursor is moved, and set to false after seeing a strong character in the
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   * paragraph the cursor is currently in.
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   *
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   * @type {boolean}
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   * @private
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   */
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  this.isNewBlock_ = true;
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  /**
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   * Indicates whether or not the current paragraph the cursor is in should be
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   * set to Right-To-Left directionality.
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   *
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   * @type {boolean}
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   * @private
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   */
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  this.switchToRtl_ = false;
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  /**
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   * Indicates whether or not the current paragraph the cursor is in should be
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   * set to Left-To-Right directionality.
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   *
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   * @type {boolean}
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   * @private
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   */
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  this.switchToLtr_ = false;
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};
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goog.inherits(goog.editor.plugins.FirstStrong, goog.editor.Plugin);
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/** @override */
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goog.editor.plugins.FirstStrong.prototype.getTrogClassId = function() {
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  return 'FirstStrong';
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};
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/** @override */
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goog.editor.plugins.FirstStrong.prototype.queryCommandValue = function(
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    command) {
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  return false;
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};
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/** @override */
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goog.editor.plugins.FirstStrong.prototype.handleSelectionChange = function(
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    e, node) {
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  this.isNewBlock_ = true;
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  return false;
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};
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/**
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 * The name of the attribute which records the input text.
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 *
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 * @type {string}
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 * @const
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 */
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goog.editor.plugins.FirstStrong.INPUT_ATTRIBUTE = 'fs-input';
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/** @override */
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goog.editor.plugins.FirstStrong.prototype.handleKeyPress = function(e) {
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  if (goog.editor.Field.SELECTION_CHANGE_KEYCODES[e.keyCode]) {
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    // Key triggered selection change event (e.g. on ENTER) is throttled and a
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    // later LTR/RTL strong keypress may come before it. Need to capture it.
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    this.isNewBlock_ = true;
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    return false;  // A selection-changing key is not LTR/RTL strong.
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  }
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  if (!this.isNewBlock_) {
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    return false;  // We've already determined this paragraph's direction.
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  }
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  // Ignore non-character key press events.
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  if (e.ctrlKey || e.metaKey) {
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    return false;
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  }
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  var newInput = goog.i18n.uChar.fromCharCode(e.charCode);
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  // IME's may return 0 for the charCode, which is a legitimate, non-Strong
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  // charCode, or they may return an illegal charCode (for which newInput will
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  // be false).
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  if (!newInput || !e.charCode) {
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    var browserEvent = e.getBrowserEvent();
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    if (browserEvent) {
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      if (goog.userAgent.IE && browserEvent['getAttribute']) {
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        newInput = browserEvent['getAttribute'](
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            goog.editor.plugins.FirstStrong.INPUT_ATTRIBUTE);
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      } else {
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        newInput =
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            browserEvent[goog.editor.plugins.FirstStrong.INPUT_ATTRIBUTE];
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      }
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    }
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  }
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  if (!newInput) {
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    return false;  // Unrecognized key.
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  }
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  var isLtr = goog.i18n.bidi.isLtrChar(newInput);
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  var isRtl = !isLtr && goog.i18n.bidi.isRtlChar(newInput);
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  if (!isLtr && !isRtl) {
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    return false;  // This character cannot change anything (it is not Strong).
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  }
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  // This character is Strongly LTR or Strongly RTL. We might switch direction
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  // on it now, but in any case we do not need to check any more characters in
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  // this paragraph after it.
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  this.isNewBlock_ = false;
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  // Are there no Strong characters already in the paragraph?
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  if (this.isNeutralBlock_()) {
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    this.switchToRtl_ = isRtl;
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    this.switchToLtr_ = isLtr;
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  }
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  return false;
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};
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/**
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 * Calls the flip directionality commands.  This is done here so things go into
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 * the redo-undo stack at the expected order; fist enter the input, then flip
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 * directionality.
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 * @override
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 */
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goog.editor.plugins.FirstStrong.prototype.handleKeyUp = function(e) {
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  if (this.switchToRtl_) {
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    var field = this.getFieldObject();
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    field.dispatchChange(true);
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    field.execCommand(goog.editor.Command.DIR_RTL);
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    this.switchToRtl_ = false;
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  } else if (this.switchToLtr_) {
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    var field = this.getFieldObject();
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    field.dispatchChange(true);
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    field.execCommand(goog.editor.Command.DIR_LTR);
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    this.switchToLtr_ = false;
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  }
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  return false;
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};
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/**
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 * @return {Element} The lowest Block element ancestor of the node where the
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 *     next character will be placed.
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 * @private
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 */
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goog.editor.plugins.FirstStrong.prototype.getBlockAncestor_ = function() {
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  var start = this.getFieldObject().getRange().getStartNode();
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  // Go up in the DOM until we reach a Block element.
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  while (!goog.editor.plugins.FirstStrong.isBlock_(start)) {
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    start = start.parentNode;
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  }
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  return /** @type {Element} */ (start);
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};
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/**
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 * @return {boolean} Whether the paragraph where the next character will be
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 *     entered contains only non-Strong characters.
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 * @private
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 */
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goog.editor.plugins.FirstStrong.prototype.isNeutralBlock_ = function() {
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  var root = this.getBlockAncestor_();
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  // The exact node with the cursor location. Simply calling getStartNode() on
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  // the range only returns the containing block node.
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  var cursor =
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      goog.editor.range.getDeepEndPoint(this.getFieldObject().getRange(), false)
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          .node;
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  // In FireFox the BR tag also represents a change in paragraph if not inside a
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  // list. So we need special handling to only look at the sub-block between
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  // BR elements.
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  var blockFunction = (goog.userAgent.GECKO && !this.isList_(root)) ?
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      goog.editor.plugins.FirstStrong.isGeckoBlock_ :
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      goog.editor.plugins.FirstStrong.isBlock_;
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  var paragraph = this.getTextAround_(root, cursor, blockFunction);
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  // Not using {@code goog.i18n.bidi.isNeutralText} as it contains additional,
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  // unwanted checks to the content.
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  return !goog.i18n.bidi.hasAnyLtr(paragraph) &&
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      !goog.i18n.bidi.hasAnyRtl(paragraph);
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};
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/**
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 * Checks if an element is a list element ('UL' or 'OL').
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 *
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 * @param {Element} element The element to test.
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 * @return {boolean} Whether the element is a list element ('UL' or 'OL').
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 * @private
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 */
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goog.editor.plugins.FirstStrong.prototype.isList_ = function(element) {
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  if (!element) {
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    return false;
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  }
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  var tagName = element.tagName;
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  return tagName == goog.dom.TagName.UL || tagName == goog.dom.TagName.OL;
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};
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/**
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 * Returns the text within the local paragraph around the cursor.
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 * Notice that for GECKO a BR represents a pargraph change despite not being a
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 * block element.
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 *
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 * @param {Element} root The first block element ancestor of the node the cursor
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 *     is in.
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 * @param {Node} cursorLocation Node where the cursor currently is, marking the
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 *     paragraph whose text we will return.
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 * @param {function(Node): boolean} isParagraphBoundary The function to
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 *     determine if a node represents the start or end of the paragraph.
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 * @return {string} the text in the paragraph around the cursor location.
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 * @private
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 */
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goog.editor.plugins.FirstStrong.prototype.getTextAround_ = function(
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    root, cursorLocation, isParagraphBoundary) {
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  // The buffer where we're collecting the text.
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  var buffer = [];
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  // Have we reached the cursor yet, or are we still before it?
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  var pastCursorLocation = false;
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  if (root && cursorLocation) {
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    goog.iter.some(new goog.dom.TagIterator(root), function(node) {
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      if (node == cursorLocation) {
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        pastCursorLocation = true;
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      } else if (isParagraphBoundary(node)) {
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        if (pastCursorLocation) {
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          // This is the end of the paragraph containing the cursor. We're done.
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          return true;
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        } else {
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          // All we collected so far does not count; it was in a previous
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          // paragraph that did not contain the cursor.
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          buffer = [];
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        }
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      }
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      if (node.nodeType == goog.dom.NodeType.TEXT) {
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        buffer.push(node.nodeValue);
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      }
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      return false;  // Keep going.
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    });
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  }
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  return buffer.join('');
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};
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/**
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 * @param {Node} node Node to check.
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 * @return {boolean} Does the given node represent a Block element? Notice we do
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 *     not consider list items as Block elements in the algorithm.
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 * @private
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 */
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goog.editor.plugins.FirstStrong.isBlock_ = function(node) {
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  return !!node && goog.editor.node.isBlockTag(node) &&
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      /** @type {!Element} */ (node).tagName != goog.dom.TagName.LI;
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};
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/**
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 * @param {Node} node Node to check.
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 * @return {boolean} Does the given node represent a Block element from the
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 *     point of view of FireFox? Notice we do not consider list items as Block
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 *     elements in the algorithm.
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 * @private
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 */
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goog.editor.plugins.FirstStrong.isGeckoBlock_ = function(node) {
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  return !!node &&
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      (/** @type {!Element} */ (node).tagName == goog.dom.TagName.BR ||
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       goog.editor.plugins.FirstStrong.isBlock_(node));
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};
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