michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: 'use strict';
michael@0: 
michael@0: const Ci = Components.interfaces;
michael@0: const Cu = Components.utils;
michael@0: 
michael@0: const TEXT_NODE = 3;
michael@0: 
michael@0: Cu.import('resource://gre/modules/XPCOMUtils.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'Services',
michael@0:   'resource://gre/modules/Services.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'Utils',
michael@0:   'resource://gre/modules/accessibility/Utils.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'Logger',
michael@0:   'resource://gre/modules/accessibility/Utils.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'Presentation',
michael@0:   'resource://gre/modules/accessibility/Presentation.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'TraversalRules',
michael@0:   'resource://gre/modules/accessibility/TraversalRules.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'Roles',
michael@0:   'resource://gre/modules/accessibility/Constants.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'Events',
michael@0:   'resource://gre/modules/accessibility/Constants.jsm');
michael@0: XPCOMUtils.defineLazyModuleGetter(this, 'States',
michael@0:   'resource://gre/modules/accessibility/Constants.jsm');
michael@0: 
michael@0: this.EXPORTED_SYMBOLS = ['EventManager'];
michael@0: 
michael@0: this.EventManager = function EventManager(aContentScope) {
michael@0:   this.contentScope = aContentScope;
michael@0:   this.addEventListener = this.contentScope.addEventListener.bind(
michael@0:     this.contentScope);
michael@0:   this.removeEventListener = this.contentScope.removeEventListener.bind(
michael@0:     this.contentScope);
michael@0:   this.sendMsgFunc = this.contentScope.sendAsyncMessage.bind(
michael@0:     this.contentScope);
michael@0:   this.webProgress = this.contentScope.docShell.
michael@0:     QueryInterface(Ci.nsIInterfaceRequestor).
michael@0:     getInterface(Ci.nsIWebProgress);
michael@0: };
michael@0: 
michael@0: this.EventManager.prototype = {
michael@0:   editState: {},
michael@0: 
michael@0:   start: function start() {
michael@0:     try {
michael@0:       if (!this._started) {
michael@0:         Logger.debug('EventManager.start');
michael@0: 
michael@0:         this._started = true;
michael@0: 
michael@0:         AccessibilityEventObserver.addListener(this);
michael@0: 
michael@0:         this.webProgress.addProgressListener(this,
michael@0:           (Ci.nsIWebProgress.NOTIFY_STATE_ALL |
michael@0:            Ci.nsIWebProgress.NOTIFY_LOCATION));
michael@0:         this.addEventListener('wheel', this, true);
michael@0:         this.addEventListener('scroll', this, true);
michael@0:         this.addEventListener('resize', this, true);
michael@0:       }
michael@0:       this.present(Presentation.tabStateChanged(null, 'newtab'));
michael@0: 
michael@0:     } catch (x) {
michael@0:       Logger.logException(x, 'Failed to start EventManager');
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   // XXX: Stop is not called when the tab is closed (|TabClose| event is too
michael@0:   // late). It is only called when the AccessFu is disabled explicitly.
michael@0:   stop: function stop() {
michael@0:     if (!this._started) {
michael@0:       return;
michael@0:     }
michael@0:     Logger.debug('EventManager.stop');
michael@0:     AccessibilityEventObserver.removeListener(this);
michael@0:     try {
michael@0:       this.webProgress.removeProgressListener(this);
michael@0:       this.removeEventListener('wheel', this, true);
michael@0:       this.removeEventListener('scroll', this, true);
michael@0:       this.removeEventListener('resize', this, true);
michael@0:     } catch (x) {
michael@0:       // contentScope is dead.
michael@0:     } finally {
michael@0:       this._started = false;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   handleEvent: function handleEvent(aEvent) {
michael@0:     Logger.debug(() => {
michael@0:       return ['DOMEvent', aEvent.type];
michael@0:     });
michael@0: 
michael@0:     try {
michael@0:       switch (aEvent.type) {
michael@0:       case 'wheel':
michael@0:       {
michael@0:         let attempts = 0;
michael@0:         let delta = aEvent.deltaX || aEvent.deltaY;
michael@0:         this.contentScope.contentControl.autoMove(
michael@0:          null,
michael@0:          { moveMethod: delta > 0 ? 'moveNext' : 'movePrevious',
michael@0:            onScreenOnly: true, noOpIfOnScreen: true, delay: 500 });
michael@0:         break;
michael@0:       }
michael@0:       case 'scroll':
michael@0:       case 'resize':
michael@0:       {
michael@0:         // the target could be an element, document or window
michael@0:         let window = null;
michael@0:         if (aEvent.target instanceof Ci.nsIDOMWindow)
michael@0:           window = aEvent.target;
michael@0:         else if (aEvent.target instanceof Ci.nsIDOMDocument)
michael@0:           window = aEvent.target.defaultView;
michael@0:         else if (aEvent.target instanceof Ci.nsIDOMElement)
michael@0:           window = aEvent.target.ownerDocument.defaultView;
michael@0:         this.present(Presentation.viewportChanged(window));
michael@0:         break;
michael@0:       }
michael@0:       }
michael@0:     } catch (x) {
michael@0:       Logger.logException(x, 'Error handling DOM event');
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   handleAccEvent: function handleAccEvent(aEvent) {
michael@0:     Logger.debug(() => {
michael@0:       return ['A11yEvent', Logger.eventToString(aEvent),
michael@0:               Logger.accessibleToString(aEvent.accessible)];
michael@0:     });
michael@0: 
michael@0:     // Don't bother with non-content events in firefox.
michael@0:     if (Utils.MozBuildApp == 'browser' &&
michael@0:         aEvent.eventType != Events.VIRTUALCURSOR_CHANGED &&
michael@0:         // XXX Bug 442005 results in DocAccessible::getDocType returning
michael@0:         // NS_ERROR_FAILURE. Checking for aEvent.accessibleDocument.docType ==
michael@0:         // 'window' does not currently work.
michael@0:         (aEvent.accessibleDocument.DOMDocument.doctype &&
michael@0:          aEvent.accessibleDocument.DOMDocument.doctype.name === 'window')) {
michael@0:       return;
michael@0:     }
michael@0: 
michael@0:     switch (aEvent.eventType) {
michael@0:       case Events.VIRTUALCURSOR_CHANGED:
michael@0:       {
michael@0:         let pivot = aEvent.accessible.
michael@0:           QueryInterface(Ci.nsIAccessibleDocument).virtualCursor;
michael@0:         let position = pivot.position;
michael@0:         if (position && position.role == Roles.INTERNAL_FRAME)
michael@0:           break;
michael@0:         let event = aEvent.
michael@0:           QueryInterface(Ci.nsIAccessibleVirtualCursorChangeEvent);
michael@0:         let reason = event.reason;
michael@0:         let oldAccessible = event.oldAccessible;
michael@0: 
michael@0:         if (this.editState.editing) {
michael@0:           aEvent.accessibleDocument.takeFocus();
michael@0:         }
michael@0:         this.present(
michael@0:           Presentation.pivotChanged(position, oldAccessible, reason,
michael@0:                                     pivot.startOffset, pivot.endOffset));
michael@0: 
michael@0:         break;
michael@0:       }
michael@0:       case Events.STATE_CHANGE:
michael@0:       {
michael@0:         let event = aEvent.QueryInterface(Ci.nsIAccessibleStateChangeEvent);
michael@0:         let state = Utils.getState(event);
michael@0:         if (state.contains(States.CHECKED)) {
michael@0:           this.present(
michael@0:             Presentation.
michael@0:               actionInvoked(aEvent.accessible,
michael@0:                             event.isEnabled ? 'check' : 'uncheck'));
michael@0:         } else if (state.contains(States.SELECTED)) {
michael@0:           this.present(
michael@0:             Presentation.
michael@0:               actionInvoked(aEvent.accessible,
michael@0:                             event.isEnabled ? 'select' : 'unselect'));
michael@0:         }
michael@0:         break;
michael@0:       }
michael@0:       case Events.SCROLLING_START:
michael@0:       {
michael@0:         this.contentScope.contentControl.autoMove(aEvent.accessible);
michael@0:         break;
michael@0:       }
michael@0:       case Events.TEXT_CARET_MOVED:
michael@0:       {
michael@0:         let acc = aEvent.accessible;
michael@0:         let characterCount = acc.
michael@0:           QueryInterface(Ci.nsIAccessibleText).characterCount;
michael@0:         let caretOffset = aEvent.
michael@0:           QueryInterface(Ci.nsIAccessibleCaretMoveEvent).caretOffset;
michael@0: 
michael@0:         // Update editing state, both for presenter and other things
michael@0:         let state = Utils.getState(acc);
michael@0:         let editState = {
michael@0:           editing: state.contains(States.EDITABLE),
michael@0:           multiline: state.contains(States.MULTI_LINE),
michael@0:           atStart: caretOffset == 0,
michael@0:           atEnd: caretOffset == characterCount
michael@0:         };
michael@0: 
michael@0:         // Not interesting
michael@0:         if (!editState.editing && editState.editing == this.editState.editing)
michael@0:           break;
michael@0: 
michael@0:         if (editState.editing != this.editState.editing)
michael@0:           this.present(Presentation.editingModeChanged(editState.editing));
michael@0: 
michael@0:         if (editState.editing != this.editState.editing ||
michael@0:             editState.multiline != this.editState.multiline ||
michael@0:             editState.atEnd != this.editState.atEnd ||
michael@0:             editState.atStart != this.editState.atStart)
michael@0:           this.sendMsgFunc("AccessFu:Input", editState);
michael@0: 
michael@0:         this.present(Presentation.textSelectionChanged(acc.getText(0,-1),
michael@0:                      caretOffset, caretOffset, 0, 0, aEvent.isFromUserInput));
michael@0: 
michael@0:         this.editState = editState;
michael@0:         break;
michael@0:       }
michael@0:       case Events.SHOW:
michael@0:       {
michael@0:         let {liveRegion, isPolite} = this._handleLiveRegion(aEvent,
michael@0:           ['additions', 'all']);
michael@0:         // Only handle show if it is a relevant live region.
michael@0:         if (!liveRegion) {
michael@0:           break;
michael@0:         }
michael@0:         // Show for text is handled by the EVENT_TEXT_INSERTED handler.
michael@0:         if (aEvent.accessible.role === Roles.TEXT_LEAF) {
michael@0:           break;
michael@0:         }
michael@0:         this._dequeueLiveEvent(Events.HIDE, liveRegion);
michael@0:         this.present(Presentation.liveRegion(liveRegion, isPolite, false));
michael@0:         break;
michael@0:       }
michael@0:       case Events.HIDE:
michael@0:       {
michael@0:         let evt = aEvent.QueryInterface(Ci.nsIAccessibleHideEvent);
michael@0:         let {liveRegion, isPolite} = this._handleLiveRegion(
michael@0:           evt, ['removals', 'all']);
michael@0:         if (liveRegion) {
michael@0:           // Hide for text is handled by the EVENT_TEXT_REMOVED handler.
michael@0:           if (aEvent.accessible.role === Roles.TEXT_LEAF) {
michael@0:             break;
michael@0:           }
michael@0:           this._queueLiveEvent(Events.HIDE, liveRegion, isPolite);
michael@0:         } else {
michael@0:           let vc = Utils.getVirtualCursor(this.contentScope.content.document);
michael@0:           if (vc.position &&
michael@0:             (Utils.getState(vc.position).contains(States.DEFUNCT) ||
michael@0:               Utils.isInSubtree(vc.position, aEvent.accessible))) {
michael@0:             this.contentScope.contentControl.autoMove(
michael@0:               evt.targetPrevSibling || evt.targetParent,
michael@0:               { moveToFocused: true, delay: 500 });
michael@0:           }
michael@0:         }
michael@0:         break;
michael@0:       }
michael@0:       case Events.TEXT_INSERTED:
michael@0:       case Events.TEXT_REMOVED:
michael@0:       {
michael@0:         let {liveRegion, isPolite} = this._handleLiveRegion(aEvent,
michael@0:           ['text', 'all']);
michael@0:         if (aEvent.isFromUserInput || liveRegion) {
michael@0:           // Handle all text mutations coming from the user or if they happen
michael@0:           // on a live region.
michael@0:           this._handleText(aEvent, liveRegion, isPolite);
michael@0:         }
michael@0:         break;
michael@0:       }
michael@0:       case Events.FOCUS:
michael@0:       {
michael@0:         // Put vc where the focus is at
michael@0:         let acc = aEvent.accessible;
michael@0:         let doc = aEvent.accessibleDocument;
michael@0:         if (acc.role != Roles.DOCUMENT && doc.role != Roles.CHROME_WINDOW) {
michael@0:          this.contentScope.contentControl.autoMove(acc);
michael@0:        }
michael@0:        break;
michael@0:       }
michael@0:       case Events.DOCUMENT_LOAD_COMPLETE:
michael@0:       {
michael@0:         if (aEvent.accessible === aEvent.accessibleDocument) {
michael@0:           break;
michael@0:         }
michael@0:         this.contentScope.contentControl.autoMove(
michael@0:           aEvent.accessible, { delay: 500 });
michael@0:         break;
michael@0:       }
michael@0:       case Events.VALUE_CHANGE:
michael@0:       {
michael@0:         let position = this.contentScope.contentControl.vc.position;
michael@0:         let target = aEvent.accessible;
michael@0:         if (position === target ||
michael@0:             Utils.getEmbeddedControl(position) === target) {
michael@0:           this.present(Presentation.valueChanged(target));
michael@0:         }
michael@0:       }
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _handleText: function _handleText(aEvent, aLiveRegion, aIsPolite) {
michael@0:     let event = aEvent.QueryInterface(Ci.nsIAccessibleTextChangeEvent);
michael@0:     let isInserted = event.isInserted;
michael@0:     let txtIface = aEvent.accessible.QueryInterface(Ci.nsIAccessibleText);
michael@0: 
michael@0:     let text = '';
michael@0:     try {
michael@0:       text = txtIface.getText(0, Ci.nsIAccessibleText.TEXT_OFFSET_END_OF_TEXT);
michael@0:     } catch (x) {
michael@0:       // XXX we might have gotten an exception with of a
michael@0:       // zero-length text. If we did, ignore it (bug #749810).
michael@0:       if (txtIface.characterCount) {
michael@0:         throw x;
michael@0:       }
michael@0:     }
michael@0:     // If there are embedded objects in the text, ignore them.
michael@0:     // Assuming changes to the descendants would already be handled by the
michael@0:     // show/hide event.
michael@0:     let modifiedText = event.modifiedText.replace(/\uFFFC/g, '').trim();
michael@0:     if (!modifiedText) {
michael@0:       return;
michael@0:     }
michael@0:     if (aLiveRegion) {
michael@0:       if (aEvent.eventType === Events.TEXT_REMOVED) {
michael@0:         this._queueLiveEvent(Events.TEXT_REMOVED, aLiveRegion, aIsPolite,
michael@0:           modifiedText);
michael@0:       } else {
michael@0:         this._dequeueLiveEvent(Events.TEXT_REMOVED, aLiveRegion);
michael@0:         this.present(Presentation.liveRegion(aLiveRegion, aIsPolite, false,
michael@0:           modifiedText));
michael@0:       }
michael@0:     } else {
michael@0:       this.present(Presentation.textChanged(isInserted, event.start,
michael@0:         event.length, text, modifiedText));
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _handleLiveRegion: function _handleLiveRegion(aEvent, aRelevant) {
michael@0:     if (aEvent.isFromUserInput) {
michael@0:       return {};
michael@0:     }
michael@0:     let parseLiveAttrs = function parseLiveAttrs(aAccessible) {
michael@0:       let attrs = Utils.getAttributes(aAccessible);
michael@0:       if (attrs['container-live']) {
michael@0:         return {
michael@0:           live: attrs['container-live'],
michael@0:           relevant: attrs['container-relevant'] || 'additions text',
michael@0:           busy: attrs['container-busy'],
michael@0:           atomic: attrs['container-atomic'],
michael@0:           memberOf: attrs['member-of']
michael@0:         };
michael@0:       }
michael@0:       return null;
michael@0:     };
michael@0:     // XXX live attributes are not set for hidden accessibles yet. Need to
michael@0:     // climb up the tree to check for them.
michael@0:     let getLiveAttributes = function getLiveAttributes(aEvent) {
michael@0:       let liveAttrs = parseLiveAttrs(aEvent.accessible);
michael@0:       if (liveAttrs) {
michael@0:         return liveAttrs;
michael@0:       }
michael@0:       let parent = aEvent.targetParent;
michael@0:       while (parent) {
michael@0:         liveAttrs = parseLiveAttrs(parent);
michael@0:         if (liveAttrs) {
michael@0:           return liveAttrs;
michael@0:         }
michael@0:         parent = parent.parent
michael@0:       }
michael@0:       return {};
michael@0:     };
michael@0:     let {live, relevant, busy, atomic, memberOf} = getLiveAttributes(aEvent);
michael@0:     // If container-live is not present or is set to |off| ignore the event.
michael@0:     if (!live || live === 'off') {
michael@0:       return {};
michael@0:     }
michael@0:     // XXX: support busy and atomic.
michael@0: 
michael@0:     // Determine if the type of the mutation is relevant. Default is additions
michael@0:     // and text.
michael@0:     let isRelevant = Utils.matchAttributeValue(relevant, aRelevant);
michael@0:     if (!isRelevant) {
michael@0:       return {};
michael@0:     }
michael@0:     return {
michael@0:       liveRegion: aEvent.accessible,
michael@0:       isPolite: live === 'polite'
michael@0:     };
michael@0:   },
michael@0: 
michael@0:   _dequeueLiveEvent: function _dequeueLiveEvent(aEventType, aLiveRegion) {
michael@0:     let domNode = aLiveRegion.DOMNode;
michael@0:     if (this._liveEventQueue && this._liveEventQueue.has(domNode)) {
michael@0:       let queue = this._liveEventQueue.get(domNode);
michael@0:       let nextEvent = queue[0];
michael@0:       if (nextEvent.eventType === aEventType) {
michael@0:         Utils.win.clearTimeout(nextEvent.timeoutID);
michael@0:         queue.shift();
michael@0:         if (queue.length === 0) {
michael@0:           this._liveEventQueue.delete(domNode)
michael@0:         }
michael@0:       }
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   _queueLiveEvent: function _queueLiveEvent(aEventType, aLiveRegion, aIsPolite, aModifiedText) {
michael@0:     if (!this._liveEventQueue) {
michael@0:       this._liveEventQueue = new WeakMap();
michael@0:     }
michael@0:     let eventHandler = {
michael@0:       eventType: aEventType,
michael@0:       timeoutID: Utils.win.setTimeout(this.present.bind(this),
michael@0:         20, // Wait for a possible EVENT_SHOW or EVENT_TEXT_INSERTED event.
michael@0:         Presentation.liveRegion(aLiveRegion, aIsPolite, true, aModifiedText))
michael@0:     };
michael@0: 
michael@0:     let domNode = aLiveRegion.DOMNode;
michael@0:     if (this._liveEventQueue.has(domNode)) {
michael@0:       this._liveEventQueue.get(domNode).push(eventHandler);
michael@0:     } else {
michael@0:       this._liveEventQueue.set(domNode, [eventHandler]);
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   present: function present(aPresentationData) {
michael@0:     this.sendMsgFunc("AccessFu:Present", aPresentationData);
michael@0:   },
michael@0: 
michael@0:   onStateChange: function onStateChange(aWebProgress, aRequest, aStateFlags, aStatus) {
michael@0:     let tabstate = '';
michael@0: 
michael@0:     let loadingState = Ci.nsIWebProgressListener.STATE_TRANSFERRING |
michael@0:       Ci.nsIWebProgressListener.STATE_IS_DOCUMENT;
michael@0:     let loadedState = Ci.nsIWebProgressListener.STATE_STOP |
michael@0:       Ci.nsIWebProgressListener.STATE_IS_NETWORK;
michael@0: 
michael@0:     if ((aStateFlags & loadingState) == loadingState) {
michael@0:       tabstate = 'loading';
michael@0:     } else if ((aStateFlags & loadedState) == loadedState &&
michael@0:                !aWebProgress.isLoadingDocument) {
michael@0:       tabstate = 'loaded';
michael@0:     }
michael@0: 
michael@0:     if (tabstate) {
michael@0:       let docAcc = Utils.AccRetrieval.getAccessibleFor(aWebProgress.DOMWindow.document);
michael@0:       this.present(Presentation.tabStateChanged(docAcc, tabstate));
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   onProgressChange: function onProgressChange() {},
michael@0: 
michael@0:   onLocationChange: function onLocationChange(aWebProgress, aRequest, aLocation, aFlags) {
michael@0:     let docAcc = Utils.AccRetrieval.getAccessibleFor(aWebProgress.DOMWindow.document);
michael@0:     this.present(Presentation.tabStateChanged(docAcc, 'newdoc'));
michael@0:   },
michael@0: 
michael@0:   onStatusChange: function onStatusChange() {},
michael@0: 
michael@0:   onSecurityChange: function onSecurityChange() {},
michael@0: 
michael@0:   QueryInterface: XPCOMUtils.generateQI([Ci.nsIWebProgressListener,
michael@0:                                          Ci.nsISupportsWeakReference,
michael@0:                                          Ci.nsISupports,
michael@0:                                          Ci.nsIObserver])
michael@0: };
michael@0: 
michael@0: const AccessibilityEventObserver = {
michael@0: 
michael@0:   /**
michael@0:    * A WeakMap containing [content, EventManager] pairs.
michael@0:    */
michael@0:   eventManagers: new WeakMap(),
michael@0: 
michael@0:   /**
michael@0:    * A total number of registered eventManagers.
michael@0:    */
michael@0:   listenerCount: 0,
michael@0: 
michael@0:   /**
michael@0:    * An indicator of an active 'accessible-event' observer.
michael@0:    */
michael@0:   started: false,
michael@0: 
michael@0:   /**
michael@0:    * Start an AccessibilityEventObserver.
michael@0:    */
michael@0:   start: function start() {
michael@0:     if (this.started || this.listenerCount === 0) {
michael@0:       return;
michael@0:     }
michael@0:     Services.obs.addObserver(this, 'accessible-event', false);
michael@0:     this.started = true;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Stop an AccessibilityEventObserver.
michael@0:    */
michael@0:   stop: function stop() {
michael@0:     if (!this.started) {
michael@0:       return;
michael@0:     }
michael@0:     Services.obs.removeObserver(this, 'accessible-event');
michael@0:     // Clean up all registered event managers.
michael@0:     this.eventManagers.clear();
michael@0:     this.listenerCount = 0;
michael@0:     this.started = false;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Register an EventManager and start listening to the
michael@0:    * 'accessible-event' messages.
michael@0:    *
michael@0:    * @param aEventManager EventManager
michael@0:    *        An EventManager object that was loaded into the specific content.
michael@0:    */
michael@0:   addListener: function addListener(aEventManager) {
michael@0:     let content = aEventManager.contentScope.content;
michael@0:     if (!this.eventManagers.has(content)) {
michael@0:       this.listenerCount++;
michael@0:     }
michael@0:     this.eventManagers.set(content, aEventManager);
michael@0:     // Since at least one EventManager was registered, start listening.
michael@0:     Logger.debug('AccessibilityEventObserver.addListener. Total:',
michael@0:       this.listenerCount);
michael@0:     this.start();
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Unregister an EventManager and, optionally, stop listening to the
michael@0:    * 'accessible-event' messages.
michael@0:    *
michael@0:    * @param aEventManager EventManager
michael@0:    *        An EventManager object that was stopped in the specific content.
michael@0:    */
michael@0:   removeListener: function removeListener(aEventManager) {
michael@0:     let content = aEventManager.contentScope.content;
michael@0:     if (!this.eventManagers.delete(content)) {
michael@0:       return;
michael@0:     }
michael@0:     this.listenerCount--;
michael@0:     Logger.debug('AccessibilityEventObserver.removeListener. Total:',
michael@0:       this.listenerCount);
michael@0:     if (this.listenerCount === 0) {
michael@0:       // If there are no EventManagers registered at the moment, stop listening
michael@0:       // to the 'accessible-event' messages.
michael@0:       this.stop();
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Lookup an EventManager for a specific content. If the EventManager is not
michael@0:    * found, walk up the hierarchy of parent windows.
michael@0:    * @param content Window
michael@0:    *        A content Window used to lookup the corresponding EventManager.
michael@0:    */
michael@0:   getListener: function getListener(content) {
michael@0:     let eventManager = this.eventManagers.get(content);
michael@0:     if (eventManager) {
michael@0:       return eventManager;
michael@0:     }
michael@0:     let parent = content.parent;
michael@0:     if (parent === content) {
michael@0:       // There is no parent or the parent is of a different type.
michael@0:       return null;
michael@0:     }
michael@0:     return this.getListener(parent);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handle the 'accessible-event' message.
michael@0:    */
michael@0:   observe: function observe(aSubject, aTopic, aData) {
michael@0:     if (aTopic !== 'accessible-event') {
michael@0:       return;
michael@0:     }
michael@0:     let event = aSubject.QueryInterface(Ci.nsIAccessibleEvent);
michael@0:     if (!event.accessibleDocument) {
michael@0:       Logger.warning(
michael@0:         'AccessibilityEventObserver.observe: no accessible document:',
michael@0:         Logger.eventToString(event), "accessible:",
michael@0:         Logger.accessibleToString(event.accessible));
michael@0:       return;
michael@0:     }
michael@0:     let content = event.accessibleDocument.window;
michael@0:     // Match the content window to its EventManager.
michael@0:     let eventManager = this.getListener(content);
michael@0:     if (!eventManager || !eventManager._started) {
michael@0:       if (Utils.MozBuildApp === 'browser' &&
michael@0:           !(content instanceof Ci.nsIDOMChromeWindow)) {
michael@0:         Logger.warning(
michael@0:           'AccessibilityEventObserver.observe: ignored event:',
michael@0:           Logger.eventToString(event), "accessible:",
michael@0:           Logger.accessibleToString(event.accessible), "document:",
michael@0:           Logger.accessibleToString(event.accessibleDocument));
michael@0:       }
michael@0:       return;
michael@0:     }
michael@0:     try {
michael@0:       eventManager.handleAccEvent(event);
michael@0:     } catch (x) {
michael@0:       Logger.logException(x, 'Error handing accessible event');
michael@0:     } finally {
michael@0:       return;
michael@0:     }
michael@0:   }
michael@0: };