text: // This file is part of Moodle - http://moodle.org/
  //
  // Moodle is free software: you can redistribute it and/or modify
  // it under the terms of the GNU General Public License as published by
  // the Free Software Foundation, either version 3 of the License, or
  // (at your option) any later version.
  //
  // Moodle is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  // GNU General Public License for more details.
  //
  // You should have received a copy of the GNU General Public License
  // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  
  /**
   * @module moodle-editor_atto-plugin
   * @submodule buttons
   */
  
  /**
   * Button functions for an Atto Plugin.
   *
   * See {{#crossLink "M.editor_atto.EditorPlugin"}}{{/crossLink}} for details.
   *
   * @namespace M.editor_atto
   * @class EditorPluginButtons
   */
  
  var MENUTEMPLATE = '' +
          '<button class="{{buttonClass}} atto_hasmenu" ' +
              'id="{{id}}" ' +
              'tabindex="-1" ' +
              'title="{{title}}" ' +
              'type="button" ' +
              'aria-haspopup="true" ' +
              'aria-controls="{{id}}_menu">' +
              '<span class="editor_atto_menu_icon"></span>' +
              '<span class="editor_atto_menu_expand"></span>' +
          '</button>';
  
  var DISABLED = 'disabled',
      HIGHLIGHT = 'highlight',
      LOGNAME = 'moodle-editor_atto-editor-plugin',
      CSS = {
          EDITORWRAPPER: '.editor_atto_content',
          MENUICON: '.editor_atto_menu_icon',
          MENUEXPAND: '.editor_atto_menu_expand'
      };
  
  function EditorPluginButtons() {}
  
  EditorPluginButtons.ATTRS = {
  };
  
  EditorPluginButtons.prototype = {
      /**
       * All of the buttons that belong to this plugin instance.
       *
       * Buttons are stored by button name.
       *
       * @property buttons
       * @type object
       */
      buttons: null,
  
      /**
       * A list of each of the button names.
       *
       * @property buttonNames
       * @type array
       */
      buttonNames: null,
  
      /**
       * A read-only view of the current state for each button. Mappings are stored by name.
       *
       * Possible states are:
       * <ul>
       * <li>{{#crossLink "M.editor_atto.EditorPluginButtons/ENABLED:property"}}{{/crossLink}}; and</li>
       * <li>{{#crossLink "M.editor_atto.EditorPluginButtons/DISABLED:property"}}{{/crossLink}}.</li>
       * </ul>
       *
       * @property buttonStates
       * @type object
       */
      buttonStates: null,
  
      /**
       * The menus belonging to this plugin instance.
       *
       * @property menus
       * @type object
       */
      menus: null,
  
      /**
       * The state for a disabled button.
       *
       * @property DISABLED
       * @type Number
       * @static
       * @value 0
       */
      DISABLED: 0,
  
      /**
       * The state for an enabled button.
       *
       * @property ENABLED
       * @type Number
       * @static
       * @value 1
       */
      ENABLED: 1,
  
      /**
       * The list of Event Handlers for buttons.
       *
       * @property _buttonHandlers
       * @protected
       * @type array
       */
      _buttonHandlers: null,
  
      /**
       * Hide handlers which are cancelled when the menu is hidden.
       *
       * @property _menuHideHandlers
       * @protected
       * @type array
       */
      _menuHideHandlers: null,
  
      /**
       * A textual description of the primary keyboard shortcut for this
       * plugin.
       *
       * This will be null if no keyboard shortcut has been registered.
       *
       * @property _primaryKeyboardShortcut
       * @protected
       * @type String
       * @default null
       */
      _primaryKeyboardShortcut: null,
  
      /**
       * An list of objects returned by Y.soon().
       *
       * The keys will be the buttonName of the button, and the value the Y.soon() object.
       *
       * @property _highlightQueue
       * @protected
       * @type Object
       * @default null
       */
      _highlightQueue: null,
  
      /**
       * Add a button for this plugin to the toolbar.
       *
       * @method addButton
       * @param {object} config The configuration for this button
       * @param {string} [config.iconurl] The URL for the icon. If not specified, then the icon and component will be used instead.
       * @param {string} [config.icon] The icon identifier.
       * @param {string} [config.iconComponent='core'] The icon component.
       * @param {string} [config.keys] The shortcut key that can call this plugin from the keyboard.
       * @param {string} [config.keyDescription] An optional description for the keyboard shortcuts.
       * If not specified, this is automatically generated based on config.keys.
       * If multiple key bindings are supplied to config.keys, then only the first is used.
       * If set to false, then no description is added to the title.
       * @param {string} [config.tags] The tags that trigger this button to be highlighted.
       * @param {boolean} [config.tagMatchRequiresAll=true] Working in combination with the tags parameter, when true
       * every tag of the selection has to match. When false, only one match is needed. Only set this to false when
       * necessary as it is much less efficient.
       * See {{#crossLink "M.editor_atto.EditorSelection/selectionFilterMatches:method"}}{{/crossLink}} for more information.
       * @param {string} [config.title=this.name] The string identifier in the plugin's language file.
       * @param {string} [config.buttonName=this.name] The name of the button. This is used in the buttons object, and if
       * specified, in the class for the button.
       * @param {function} config.callback A callback function to call when the button is clicked.
       * @param {object} [config.callbackArgs] Any arguments to pass to the callback.
       * @param {boolean} [config.inlineFormat] Delay callback for text input if selection is collapsed.
       * @return {Node} The Node representing the newly created button.
       */
      addButton: function(config) {
          var group = this.get('group'),
              pluginname = this.name,
              buttonClass = 'atto_' + pluginname + '_button',
              button,
              host = this.get('host');
  
          if (config.exec) {
              buttonClass = buttonClass + '_' + config.exec;
          }
  
          if (!config.buttonName) {
              // Set a default button name - this is used as an identifier in the button object.
              config.buttonName = config.exec || pluginname;
          } else {
              buttonClass = buttonClass + '_' + config.buttonName;
          }
          config.buttonClass = buttonClass;
  
          // Normalize icon configuration.
          config = this._normalizeIcon(config);
  
          if (!config.title) {
              config.title = 'pluginname';
          }
          var title = M.util.get_string(config.title, 'atto_' + pluginname);
  
          // Create the actual button.
          button = Y.Node.create('<button type="button" class="' + buttonClass + '"' +
                  'tabindex="-1"></button>');
          button.setAttribute('title', title);
          window.require(['core/templates'], function(Templates) {
              Templates.renderPix(config.icon, config.iconComponent, title).then(function(iconhtml) {
                  button.append(iconhtml);
              });
          });
  
          // Append it to the group.
          group.append(button);
  
          var currentfocus = this.toolbar.getAttribute('aria-activedescendant');
          if (!currentfocus) {
              // Initially set the first button in the toolbar to be the default on keyboard focus.
              button.setAttribute('tabindex', '0');
              this.toolbar.setAttribute('aria-activedescendant', button.generateID());
              this.get('host')._tabFocus = button;
          }
  
          // Normalize the callback parameters.
          config = this._normalizeCallback(config);
  
          // Add the standard click handler to the button.
          this._buttonHandlers.push(
              this.toolbar.delegate('click', config.callback, '.' + buttonClass, this)
          );
  
          // Handle button click via shortcut key.
          if (config.keys) {
              if (typeof config.keyDescription !== 'undefined') {
                  // A keyboard shortcut description was specified - use it.
                  this._primaryKeyboardShortcut[buttonClass] = config.keyDescription;
              }
              this._addKeyboardListener(config.callback, config.keys, buttonClass);
  
              if (this._primaryKeyboardShortcut[buttonClass]) {
                  // If we have a valid keyboard shortcut description, then set it with the title.
                  button.setAttribute('title', M.util.get_string('plugin_title_shortcut', 'editor_atto', {
                          title: title,
                          shortcut: this._primaryKeyboardShortcut[buttonClass]
                      }));
              }
          }
  
          // Handle highlighting of the button.
          if (config.tags) {
              var tagMatchRequiresAll = true;
              if (typeof config.tagMatchRequiresAll === 'boolean') {
                  tagMatchRequiresAll = config.tagMatchRequiresAll;
              }
              this._buttonHandlers.push(
                  host.on(['atto:selectionchanged', 'change'], function(e) {
                      if (typeof this._highlightQueue[config.buttonName] !== 'undefined') {
                          this._highlightQueue[config.buttonName].cancel();
                      }
                      // Async the highlighting.
                      this._highlightQueue[config.buttonName] = Y.soon(Y.bind(function(e) {
                          if (host.selectionFilterMatches(config.tags, e.selectedNodes, tagMatchRequiresAll)) {
                              this.highlightButtons(config.buttonName);
                          } else {
                              this.unHighlightButtons(config.buttonName);
                          }
                      }, this, e));
                  }, this)
              );
          }
  
          // Add the button reference to the buttons array for later reference.
          this.buttonNames.push(config.buttonName);
          this.buttons[config.buttonName] = button;
          this.buttonStates[config.buttonName] = this.ENABLED;
          return button;
      },
  
      /**
       * Add a basic button which ties into the execCommand.
       *
       * See {{#crossLink "M.editor_atto.EditorPluginButtons/addButton:method"}}addButton{{/crossLink}}
       * for full details of the optional parameters.
       *
       * @method addBasicButton
       * @param {object} config The button configuration
       * @param {string} config.exec The execCommand to call on the document.
       * @param {string} [config.iconurl] The URL for the icon. If not specified, then the icon and component will be used instead.
       * @param {string} [config.icon] The icon identifier.
       * @param {string} [config.iconComponent='core'] The icon component.
       * @param {string} [config.keys] The shortcut key that can call this plugin from the keyboard.
       * @param {string} [config.tags] The tags that trigger this button to be highlighted.
       * @param {boolean} [config.tagMatchRequiresAll=false] Working in combination with the tags parameter, highlight
       * this button when any match is good enough.
       *
       * See {{#crossLink "M.editor_atto.EditorSelection/selectionFilterMatches:method"}}{{/crossLink}} for more information.
       * @param {string} [config.title=this.name] The string identifier in the plugin's language file.
       * @param {string} [config.buttonName=this.name] The name of the button. This is used in the buttons object, and if
       * specified, in the class for the button.
       * @return {Node} The Node representing the newly created button.
       */
      addBasicButton: function(config) {
          if (!config.exec) {
              Y.log('No exec command specified. Cannot proceed.',
                      'warn', 'moodle-editor_atto-plugin');
              return null;
          }
  
          // The default icon - true for most core plugins.
          if (!config.icon) {
              config.icon = 'e/' + config.exec;
          }
  
          // The default callback.
          config.callback = function() {
              document.execCommand(config.exec, false, null);
  
              // And mark the text area as updated.
              this.markUpdated();
          };
  
          // Return the newly created button.
          return this.addButton(config);
      },
  
      /**
       * Add a menu for this plugin to the editor toolbar.
       *
       * @method addToolbarMenu
       * @param {object} config The configuration for this button
       * @param {string} [config.iconurl] The URL for the icon. If not specified, then the icon and component will be used instead.
       * @param {string} [config.icon] The icon identifier.
       * @param {string} [config.iconComponent='core'] The icon component.
       * @param {string} [config.title=this.name] The string identifier in the plugin's language file.
       * @param {string} [config.buttonName=this.name] The name of the button. This is used in the buttons object, and if
       * specified, in the class for the button.
       * @param {function} config.callback A callback function to call when the button is clicked.
       * @param {object} [config.callbackArgs] Any arguments to pass to the callback.
       * @param {boolean} [config.inlineFormat] Delay callback for text input if selection is collapsed.
       * @param {array} config.entries List of menu entries with the string (entry.text) and the handlers (entry.handler).
       * @param {number} [config.overlayWidth=14] The width of the menu. This will be suffixed with the 'em' unit.
       * @param {string} [config.menuColor] menu icon background color
       * @return {Node} The Node representing the newly created button.
       */
      addToolbarMenu: function(config) {
          var group = this.get('group'),
              pluginname = this.name,
              buttonClass = 'atto_' + pluginname + '_button',
              button,
              currentFocus;
  
          if (!config.buttonName) {
              // Set a default button name - this is used as an identifier in the button object.
              config.buttonName = pluginname;
          } else {
              buttonClass = buttonClass + '_' + config.buttonName;
          }
          config.buttonClass = buttonClass;
  
          // Normalize icon configuration.
          config = this._normalizeIcon(config);
  
          if (!config.title) {
              config.title = 'pluginname';
          }
          var title = M.util.get_string(config.title, 'atto_' + pluginname);
  
          if (!config.menuColor) {
              config.menuColor = 'transparent';
          }
  
          // Create the actual button.
          var id = 'atto_' + pluginname + '_menubutton_' + Y.stamp(this);
          var template = Y.Handlebars.compile(MENUTEMPLATE);
          button = Y.Node.create(template({
              buttonClass: buttonClass,
              config: config,
              title: title,
              id: id
          }));
  
          // Add this button id to the config. It will be used in the menu later.
          config.buttonId = id;
  
          window.require(['core/templates'], function(Templates) {
              Templates.renderPix(config.icon, config.iconComponent, title).then(function(iconhtml) {
                  button.one(CSS.MENUICON).append(iconhtml);
              });
              Templates.renderPix('t/expanded', 'core', '').then(function(iconhtml) {
                  button.one(CSS.MENUEXPAND).append(iconhtml);
              });
          });
  
          // Append it to the group.
          group.append(button);
  
          currentFocus = this.toolbar.getAttribute('aria-activedescendant');
          if (!currentFocus) {
              // Initially set the first button in the toolbar to be the default on keyboard focus.
              button.setAttribute('tabindex', '0');
              this.toolbar.setAttribute('aria-activedescendant', button.generateID());
          }
  
          // Add the standard click handler to the menu.
          this._buttonHandlers.push(
              this.toolbar.delegate('click', this._showToolbarMenu, '.' + buttonClass, this, config),
              this.toolbar.delegate('key', this._showToolbarMenuAndFocus, '40, 32, enter', '.' + buttonClass, this, config)
          );
  
          // Add the button reference to the buttons array for later reference.
          this.buttonNames.push(config.buttonName);
          this.buttons[config.buttonName] = button;
          this.buttonStates[config.buttonName] = this.ENABLED;
  
          return button;
      },
  
      /**
       * Display a toolbar menu.
       *
       * @method _showToolbarMenu
       * @param {EventFacade} e
       * @param {object} config The configuration for the whole toolbar.
       * @param {Number} [config.overlayWidth=14] The width of the menu
       * @private
       */
      _showToolbarMenu: function(e, config) {
          // Prevent default primarily to prevent arrow press changes.
          e.preventDefault();
  
          if (!this.isEnabled()) {
              // Exit early if the plugin is disabled.
              return;
          }
  
          var menuButton = e.currentTarget.ancestor('button', true);
          if (menuButton.hasAttribute(DISABLED)) {
              // Exit early if the clicked button was disabled.
              return;
          }
  
          var menuDialogue;
  
          if (!this.menus[config.buttonClass]) {
              if (!config.overlayWidth) {
                  config.overlayWidth = '14';
              }
  
              if (!config.innerOverlayWidth) {
                  config.innerOverlayWidth = parseInt(config.overlayWidth, 10) - 2 + 'em';
              }
              config.overlayWidth = parseInt(config.overlayWidth, 10) + 'em';
  
              this.menus[config.buttonClass] = new Y.M.editor_atto.Menu(config);
  
              this.menus[config.buttonClass].get('contentBox').delegate('click',
                      this._chooseMenuItem, '.atto_menuentry a', this, config);
          }
  
          // Clear the focusAfterHide for any other menus which may be open.
          Y.Array.each(this.get('host').openMenus, function(menu) {
              menu.set('focusAfterHide', null);
          });
  
          // Ensure that we focus on this button next time.
          var creatorButton = this.buttons[config.buttonName];
          creatorButton.focus();
          this.get('host')._setTabFocus(creatorButton);
  
          // Get a reference to the menu dialogue.
          menuDialogue = this.menus[config.buttonClass];
  
          // Focus on the button by default after hiding this menu.
          menuDialogue.set('focusAfterHide', creatorButton);
  
          // Display the menu.
          menuDialogue.show();
  
          // Indicate that the menu is expanded.
          menuButton.setAttribute("aria-expanded", true);
  
          // Position it next to the button which opened it.
          menuDialogue.align(this.buttons[config.buttonName], [Y.WidgetPositionAlign.TL, Y.WidgetPositionAlign.BL]);
  
          this.get('host').openMenus = [menuDialogue];
      },
  
      /**
       * Display a toolbar menu and focus upon the first item.
       *
       * @method _showToolbarMenuAndFocus
       * @param {EventFacade} e
       * @param {object} config The configuration for the whole toolbar.
       * @param {Number} [config.overlayWidth=14] The width of the menu
       * @private
       */
      _showToolbarMenuAndFocus: function(e, config) {
          this._showToolbarMenu(e, config);
  
          // Focus on the first element in the menu.
          this.menus[config.buttonClass].get('boundingBox').one('a').focus();
      },
  
      /**
       * Select a menu item and call the appropriate callbacks.
       *
       * @method _chooseMenuItem
       * @param {EventFacade} e
       * @param {object} config
       * @param {M.core.dialogue} menuDialogue The Dialogue to hide.
       * @private
       */
      _chooseMenuItem: function(e, config, menuDialogue) {
          // Get the index from the clicked anchor.
          var index = e.target.ancestor('a', true).getData('index'),
  
              // And the normalized callback configuration.
              buttonConfig = this._normalizeCallback(config.items[index], config.globalItemConfig);
  
              menuDialogue = this.menus[config.buttonClass];
  
          // Prevent the dialogue to be closed because of some browser weirdness.
          menuDialogue.set('preventHideMenu', true);
  
          // Call the callback for this button.
          buttonConfig.callback(e, buttonConfig._callback, buttonConfig.callbackArgs);
  
          // Cancel the hide menu prevention.
          menuDialogue.set('preventHideMenu', false);
  
          // Set the focus after hide so that focus is returned to the editor and changes are made correctly.
          menuDialogue.set('focusAfterHide', this.get('host').editor);
          menuDialogue.hide(e);
      },
  
      /**
       * Normalize and sanitize the configuration variables relating to callbacks.
       *
       * @method _normalizeCallback
       * @param {object} config
       * @param {function} config.callback A callback function to call when the button is clicked.
       * @param {object} [config.callbackArgs] Any arguments to pass to the callback.
       * @param {boolean} [config.inlineFormat] Delay callback for text input if selection is collapsed.
       * @param {object} [inheritFrom] A parent configuration that this configuration may inherit from.
       * @return {object} The normalized configuration
       * @private
       */
      _normalizeCallback: function(config, inheritFrom) {
          if (config._callbackNormalized) {
              // Return early if the callback has already been normalized.
              return config;
          }
  
          if (!inheritFrom) {
              // Create an empty inheritFrom to make life easier below.
              inheritFrom = {};
          }
  
  
          // First we wrap the callback in function to handle formating of text inserted into collapsed selection.
          config.inlineFormat = config.inlineFormat || inheritFrom.inlineFormat;
          config._inlineCallback = config.callback || inheritFrom.callback;
          config._callback = config.callback || inheritFrom.callback;
          if (config.inlineFormat && typeof config._inlineCallback === 'function') {
              config._callback = function(e, args) {
                  this.get('host').applyFormat(e, config._inlineCallback, this, args);
              };
          }
          // We wrap the callback in function to prevent the default action, check whether the editor is
          // active and focus it, and then mark the field as updated.
          config.callback = Y.rbind(this._callbackWrapper, this, config._callback, config.callbackArgs);
  
          config._callbackNormalized = true;
  
          return config;
      },
  
      /**
       * Normalize and sanitize the configuration variables relating to icons.
       *
       * @method _normalizeIcon
       * @param {object} config
       * @param {string} [config.iconurl] The URL for the icon. If not specified, then the icon and component will be used instead.
       * @param {string} [config.icon] The icon identifier.
       * @param {string} [config.iconComponent='core'] The icon component.
       * @return {object} The normalized configuration
       * @private
       */
      _normalizeIcon: function(config) {
          if (!config.iconurl) {
              // The default icon component.
              if (!config.iconComponent || config.iconComponent == 'moodle') {
                  config.iconComponent = 'core';
              }
              config.iconurl = M.util.image_url(config.icon, config.iconComponent);
          }
  
          return config;
      },
  
      /**
       * A wrapper in which to run the callbacks.
       *
       * This handles common functionality such as:
       * <ul>
       *  <li>preventing the default action; and</li>
       *  <li>focusing the editor if relevant.</li>
       * </ul>
       *
       * @method _callbackWrapper
       * @param {EventFacade} e
       * @param {Function} callback The function to call which makes the relevant changes.
       * @param {Array} [callbackArgs] The arguments passed to this callback.
       * @return {Mixed} The value returned by the callback.
       * @private
       */
      _callbackWrapper: function(e, callback, callbackArgs) {
          e.preventDefault();
  
          if (!this.isEnabled()) {
              // Exit early if the plugin is disabled.
              return;
          }
  
          var creatorButton = e.currentTarget.ancestor('button', true);
  
          if (creatorButton && creatorButton.hasAttribute(DISABLED)) {
              // Exit early if the clicked button was disabled.
              return;
          }
  
          if (!(YUI.Env.UA.android || this.get('host').isActive())) {
              // We must not focus for Android here, even if the editor is not active because the keyboard auto-completion
              // changes the cursor position.
              // If we save that change, then when we restore the change later we get put in the wrong place.
              // Android is fine to save the selection without the editor being in focus.
              this.get('host').focus();
          }
  
          // Save the selection.
          this.get('host').saveSelection();
  
          // Ensure that we focus on this button next time.
          if (creatorButton) {
              this.get('host')._setTabFocus(creatorButton);
          }
  
          // Build the arguments list, but remove the callback we're calling.
          var args = [e, callbackArgs];
  
          // Restore selection before making changes.
          this.get('host').restoreSelection();
  
          // Actually call the callback now.
          return callback.apply(this, args);
      },
  
      /**
       * Add a keyboard listener to call the callback.
       *
       * The keyConfig will take either an array of keyConfigurations, in
       * which case _addKeyboardListener is called multiple times; an object
       * containing an optional eventtype, optional container, and a set of
       * keyCodes, or just a string containing the keyCodes. When keyConfig is
       * not an object, it is wrapped around a function that ensures that
       * only the expected key modifiers were used. For instance, it checks
       * that space+ctrl is not triggered when the user presses ctrl+shift+space.
       * When using an object, the developer should check that manually.
       *
       * @method _addKeyboardListener
       * @param {function} callback
       * @param {array|object|string} keyConfig
       * @param {string} [keyConfig.eventtype=key] The type of event
       * @param {string} [keyConfig.container=.editor_atto_content] The containing element.
       * @param {string} keyConfig.keyCodes The keycodes to user for the event.
       * @private
       *
       */
      _addKeyboardListener: function(callback, keyConfig, buttonName) {
          var eventtype = 'key',
              container = CSS.EDITORWRAPPER,
              keys,
              handler,
              modifier;
  
          if (Y.Lang.isArray(keyConfig)) {
              // If an Array was specified, call the add function for each element.
              Y.Array.each(keyConfig, function(config) {
                  this._addKeyboardListener(callback, config);
              }, this);
  
              return this;
  
          } else if (typeof keyConfig === "object") {
              if (keyConfig.eventtype) {
                  eventtype = keyConfig.eventtype;
              }
  
              if (keyConfig.container) {
                  container = keyConfig.container;
              }
  
              // Must be specified.
              keys = keyConfig.keyCodes;
              handler = callback;
  
          } else {
              modifier = this._getDefaultMetaKey();
              keys = this._getKeyEvent() + keyConfig + '+' + modifier;
              if (typeof this._primaryKeyboardShortcut[buttonName] === 'undefined') {
                  this._primaryKeyboardShortcut[buttonName] = this._getDefaultMetaKeyDescription(keyConfig);
              }
  
              // Wrap the callback into a handler to check if it uses the specified modifiers, not more.
              handler = Y.bind(function(modifiers, e) {
                  if (this._eventUsesExactKeyModifiers(modifiers, e)) {
                      callback.apply(this, [e]);
                  }
              }, this, [modifier]);
          }
  
          this._buttonHandlers.push(
              this.editor.delegate(
                  eventtype,
                  handler,
                  keys,
                  container,
                  this
              )
          );
  
          Y.log('Atto shortcut registered: ' + keys + ' now triggers for ' + buttonName,
                  'debug', LOGNAME);
      },
  
      /**
       * Checks if a key event was strictly defined for the modifiers passed.
       *
       * @method _eventUsesExactKeyModifiers
       * @param  {Array} modifiers List of key modifiers to check for (alt, ctrl, meta or shift).
       * @param  {EventFacade} e The event facade.
       * @return {Boolean} True if the event was stricly using the modifiers specified.
       */
      _eventUsesExactKeyModifiers: function(modifiers, e) {
          var exactMatch = true,
              hasKey;
  
          if (e.type !== 'key') {
              return false;
          }
  
          hasKey = Y.Array.indexOf(modifiers, 'alt') > -1;
          exactMatch = exactMatch && ((e.altKey && hasKey) || (!e.altKey && !hasKey));
          hasKey = Y.Array.indexOf(modifiers, 'ctrl') > -1;
          exactMatch = exactMatch && ((e.ctrlKey && hasKey) || (!e.ctrlKey && !hasKey));
          hasKey = Y.Array.indexOf(modifiers, 'meta') > -1;
          exactMatch = exactMatch && ((e.metaKey && hasKey) || (!e.metaKey && !hasKey));
          hasKey = Y.Array.indexOf(modifiers, 'shift') > -1;
          exactMatch = exactMatch && ((e.shiftKey && hasKey) || (!e.shiftKey && !hasKey));
  
          return exactMatch;
      },
  
      /**
       * Determine if this plugin is enabled, based upon the state of it's buttons.
       *
       * @method isEnabled
       * @return {boolean}
       */
      isEnabled: function() {
          // The first instance of an undisabled button will make this return true.
          var found = Y.Object.some(this.buttonStates, function(button) {
              return (button === this.ENABLED);
          }, this);
  
          return found;
      },
  
      /**
       * Enable one button, or all buttons relating to this Plugin.
       *
       * If no button is specified, all buttons are disabled.
       *
       * @method disableButtons
       * @param {String} [button] The name of a specific plugin to enable.
       * @chainable
       */
      disableButtons: function(button) {
          return this._setButtonState(false, button);
      },
  
      /**
       * Enable one button, or all buttons relating to this Plugin.
       *
       * If no button is specified, all buttons are enabled.
       *
       * @method enableButtons
       * @param {String} [button] The name of a specific plugin to enable.
       * @chainable
       */
      enableButtons: function(button) {
          return this._setButtonState(true, button);
      },
  
      /**
       * Set the button state for one button, or all buttons associated with this plugin.
       *
       * @method _setButtonState
       * @param {Boolean} enable Whether to enable this button.
       * @param {String} [button] The name of a specific plugin to set state for.
       * @chainable
       * @private
       */
      _setButtonState: function(enable, button) {
          var attributeChange = 'setAttribute';
          if (enable) {
              attributeChange = 'removeAttribute';
          }
          if (button) {
              if (this.buttons[button]) {
                  this.buttons[button][attributeChange](DISABLED, DISABLED);
                  this.buttonStates[button] = enable ? this.ENABLED : this.DISABLED;
              }
          } else {
              Y.Array.each(this.buttonNames, function(button) {
                  this.buttons[button][attributeChange](DISABLED, DISABLED);
                  this.buttonStates[button] = enable ? this.ENABLED : this.DISABLED;
              }, this);
          }
  
          this.get('host').checkTabFocus();
          return this;
      },
  
      /**
       * Highlight a button, or buttons in the toolbar.
       *
       * If no button is specified, all buttons are highlighted.
       *
       * @method highlightButtons
       * @param {string} [button] If a plugin has multiple buttons, the specific button to highlight.
       * @chainable
       */
      highlightButtons: function(button) {
          return this._changeButtonHighlight(true, button);
      },
  
      /**
       * Un-highlight a button, or buttons in the toolbar.
       *
       * If no button is specified, all buttons are un-highlighted.
       *
       * @method unHighlightButtons
       * @param {string} [button] If a plugin has multiple buttons, the specific button to highlight.
       * @chainable
       */
      unHighlightButtons: function(button) {
          return this._changeButtonHighlight(false, button);
      },
  
      /**
       * Highlight a button, or buttons in the toolbar.
       *
       * @method _changeButtonHighlight
       * @param {boolean} highlight true
       * @param {string} [button] If a plugin has multiple buttons, the specific button to highlight.
       * @protected
       * @chainable
       */
      _changeButtonHighlight: function(highlight, button) {
          var method = 'addClass';
  
          if (!highlight) {
              method = 'removeClass';
          }
          if (button) {
              if (this.buttons[button]) {
                  this.buttons[button][method](HIGHLIGHT);
                  this._buttonHighlightToggled(button, highlight);
              }
          } else {
              Y.Object.each(this.buttons, function(button) {
                  button[method](HIGHLIGHT);
                  this._buttonHighlightToggled(button, highlight);
              }, this);
          }
  
          return this;
      },
  
      /**
       * Fires a custom event that notifies listeners that a button's highlight has been toggled.
       *
       * @param {String} buttonName The button name.
       * @param {Boolean} highlight True when the button was highlighted. False, otherwise.
       * @private
       */
      _buttonHighlightToggled: function(buttonName, highlight) {
          var toggledButton = this.buttons[buttonName];
          if (toggledButton) {
              // Fire an event that the button highlight was toggled.
              require(['editor_atto/events'], function(attoEvents) {
                  attoEvents.notifyButtonHighlightToggled(toggledButton.getDOMNode(), buttonName, highlight);
              });
          }
      },
  
      /**
       * Get the default meta key to use with keyboard events.
       *
       * On a Mac, this will be the 'meta' key for Command; otherwise it will
       * be the Control key.
       *
       * @method _getDefaultMetaKey
       * @return {string}
       * @private
       */
      _getDefaultMetaKey: function() {
          if (Y.UA.os === 'macintosh') {
              return 'meta';
          } else {
              return 'ctrl';
          }
      },
  
      /**
       * Get the user-visible description of the meta key to use with keyboard events.
       *
       * On a Mac, this will be 'Command' ; otherwise it will be 'Control'.
       *
       * @method _getDefaultMetaKeyDescription
       * @return {string}
       * @private
       */
      _getDefaultMetaKeyDescription: function(keyCode) {
          if (Y.UA.os === 'macintosh') {
              return M.util.get_string('editor_command_keycode', 'editor_atto', String.fromCharCode(keyCode).toLowerCase());
          } else {
              return M.util.get_string('editor_control_keycode', 'editor_atto', String.fromCharCode(keyCode).toLowerCase());
          }
      },
  
      /**
       * Get the standard key event to use for keyboard events.
       *
       * @method _getKeyEvent
       * @return {string}
       * @private
       */
      _getKeyEvent: function() {
          return 'down:';
      }
  };
  
  Y.Base.mix(Y.M.editor_atto.EditorPlugin, [EditorPluginButtons]);
  