gecko-dev/accessible/jsat/EventManager.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

'use strict';

const Ci = Components.interfaces;
const Cu = Components.utils;

const TEXT_NODE = 3;

Cu.import('resource://gre/modules/XPCOMUtils.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'Services',
  'resource://gre/modules/Services.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'Utils',
  'resource://gre/modules/accessibility/Utils.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'Logger',
  'resource://gre/modules/accessibility/Utils.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'Presentation',
  'resource://gre/modules/accessibility/Presentation.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'TraversalRules',
  'resource://gre/modules/accessibility/TraversalRules.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'Roles',
  'resource://gre/modules/accessibility/Constants.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'Events',
  'resource://gre/modules/accessibility/Constants.jsm');
XPCOMUtils.defineLazyModuleGetter(this, 'States',
  'resource://gre/modules/accessibility/Constants.jsm');

this.EXPORTED_SYMBOLS = ['EventManager'];

this.EventManager = function EventManager(aContentScope) {
  this.contentScope = aContentScope;
  this.addEventListener = this.contentScope.addEventListener.bind(
    this.contentScope);
  this.removeEventListener = this.contentScope.removeEventListener.bind(
    this.contentScope);
  this.sendMsgFunc = this.contentScope.sendAsyncMessage.bind(
    this.contentScope);
  this.webProgress = this.contentScope.docShell.
    QueryInterface(Ci.nsIInterfaceRequestor).
    getInterface(Ci.nsIWebProgress);
};

this.EventManager.prototype = {
  editState: {},

  start: function start() {
    try {
      if (!this._started) {
        Logger.debug('EventManager.start');

        this._started = true;

        AccessibilityEventObserver.addListener(this);

        this.webProgress.addProgressListener(this,
          (Ci.nsIWebProgress.NOTIFY_STATE_ALL |
           Ci.nsIWebProgress.NOTIFY_LOCATION));
        this.addEventListener('wheel', this, true);
        this.addEventListener('scroll', this, true);
        this.addEventListener('resize', this, true);
      }
      this.present(Presentation.tabStateChanged(null, 'newtab'));

    } catch (x) {
      Logger.logException(x, 'Failed to start EventManager');
    }
  },

  // XXX: Stop is not called when the tab is closed (|TabClose| event is too
  // late). It is only called when the AccessFu is disabled explicitly.
  stop: function stop() {
    if (!this._started) {
      return;
    }
    Logger.debug('EventManager.stop');
    AccessibilityEventObserver.removeListener(this);
    try {
      this.webProgress.removeProgressListener(this);
      this.removeEventListener('wheel', this, true);
      this.removeEventListener('scroll', this, true);
      this.removeEventListener('resize', this, true);
    } catch (x) {
      // contentScope is dead.
    } finally {
      this._started = false;
    }
  },

  handleEvent: function handleEvent(aEvent) {
    Logger.debug(() => {
      return ['DOMEvent', aEvent.type];
    });

    try {
      switch (aEvent.type) {
      case 'wheel':
      {
        let attempts = 0;
        let delta = aEvent.deltaX || aEvent.deltaY;
        this.contentScope.contentControl.autoMove(
         null,
         { moveMethod: delta > 0 ? 'moveNext' : 'movePrevious',
           onScreenOnly: true, noOpIfOnScreen: true, delay: 500 });
        break;
      }
      case 'scroll':
      case 'resize':
      {
        // the target could be an element, document or window
        let window = null;
        if (aEvent.target instanceof Ci.nsIDOMWindow)
          window = aEvent.target;
        else if (aEvent.target instanceof Ci.nsIDOMDocument)
          window = aEvent.target.defaultView;
        else if (aEvent.target instanceof Ci.nsIDOMElement)
          window = aEvent.target.ownerDocument.defaultView;
        this.present(Presentation.viewportChanged(window));
        break;
      }
      }
    } catch (x) {
      Logger.logException(x, 'Error handling DOM event');
    }
  },

  handleAccEvent: function handleAccEvent(aEvent) {
    Logger.debug(() => {
      return ['A11yEvent', Logger.eventToString(aEvent),
              Logger.accessibleToString(aEvent.accessible)];
    });

    // Don't bother with non-content events in firefox.
    if (Utils.MozBuildApp == 'browser' &&
        aEvent.eventType != Events.VIRTUALCURSOR_CHANGED &&
        // XXX Bug 442005 results in DocAccessible::getDocType returning
        // NS_ERROR_FAILURE. Checking for aEvent.accessibleDocument.docType ==
        // 'window' does not currently work.
        (aEvent.accessibleDocument.DOMDocument.doctype &&
         aEvent.accessibleDocument.DOMDocument.doctype.name === 'window')) {
      return;
    }

    switch (aEvent.eventType) {
      case Events.VIRTUALCURSOR_CHANGED:
      {
        let pivot = aEvent.accessible.
          QueryInterface(Ci.nsIAccessibleDocument).virtualCursor;
        let position = pivot.position;
        if (position && position.role == Roles.INTERNAL_FRAME)
          break;
        let event = aEvent.
          QueryInterface(Ci.nsIAccessibleVirtualCursorChangeEvent);
        let reason = event.reason;
        let oldAccessible = event.oldAccessible;

        if (this.editState.editing) {
          aEvent.accessibleDocument.takeFocus();
        }
        this.present(
          Presentation.pivotChanged(position, oldAccessible, reason,
                                    pivot.startOffset, pivot.endOffset));

        break;
      }
      case Events.STATE_CHANGE:
      {
        let event = aEvent.QueryInterface(Ci.nsIAccessibleStateChangeEvent);
        let state = Utils.getState(event);
        if (state.contains(States.CHECKED)) {
          this.present(
            Presentation.
              actionInvoked(aEvent.accessible,
                            event.isEnabled ? 'check' : 'uncheck'));
        } else if (state.contains(States.SELECTED)) {
          this.present(
            Presentation.
              actionInvoked(aEvent.accessible,
                            event.isEnabled ? 'select' : 'unselect'));
        }
        break;
      }
      case Events.SCROLLING_START:
      {
        this.contentScope.contentControl.autoMove(aEvent.accessible);
        break;
      }
      case Events.TEXT_CARET_MOVED:
      {
        let acc = aEvent.accessible;
        let characterCount = acc.
          QueryInterface(Ci.nsIAccessibleText).characterCount;
        let caretOffset = aEvent.
          QueryInterface(Ci.nsIAccessibleCaretMoveEvent).caretOffset;

        // Update editing state, both for presenter and other things
        let state = Utils.getState(acc);
        let editState = {
          editing: state.contains(States.EDITABLE),
          multiline: state.contains(States.MULTI_LINE),
          atStart: caretOffset == 0,
          atEnd: caretOffset == characterCount
        };

        // Not interesting
        if (!editState.editing && editState.editing == this.editState.editing)
          break;

        if (editState.editing != this.editState.editing)
          this.present(Presentation.editingModeChanged(editState.editing));

        if (editState.editing != this.editState.editing ||
            editState.multiline != this.editState.multiline ||
            editState.atEnd != this.editState.atEnd ||
            editState.atStart != this.editState.atStart)
          this.sendMsgFunc("AccessFu:Input", editState);

        this.present(Presentation.textSelectionChanged(acc.getText(0,-1),
                     caretOffset, caretOffset, 0, 0, aEvent.isFromUserInput));

        this.editState = editState;
        break;
      }
      case Events.SHOW:
      {
        let {liveRegion, isPolite} = this._handleLiveRegion(aEvent,
          ['additions', 'all']);
        // Only handle show if it is a relevant live region.
        if (!liveRegion) {
          break;
        }
        // Show for text is handled by the EVENT_TEXT_INSERTED handler.
        if (aEvent.accessible.role === Roles.TEXT_LEAF) {
          break;
        }
        this._dequeueLiveEvent(Events.HIDE, liveRegion);
        this.present(Presentation.liveRegion(liveRegion, isPolite, false));
        break;
      }
      case Events.HIDE:
      {
        let evt = aEvent.QueryInterface(Ci.nsIAccessibleHideEvent);
        let {liveRegion, isPolite} = this._handleLiveRegion(
          evt, ['removals', 'all']);
        if (liveRegion) {
          // Hide for text is handled by the EVENT_TEXT_REMOVED handler.
          if (aEvent.accessible.role === Roles.TEXT_LEAF) {
            break;
          }
          this._queueLiveEvent(Events.HIDE, liveRegion, isPolite);
        } else {
          let vc = Utils.getVirtualCursor(this.contentScope.content.document);
          if (vc.position &&
            (Utils.getState(vc.position).contains(States.DEFUNCT) ||
              Utils.isInSubtree(vc.position, aEvent.accessible))) {
            this.contentScope.contentControl.autoMove(
              evt.targetPrevSibling || evt.targetParent,
              { moveToFocused: true, delay: 500 });
          }
        }
        break;
      }
      case Events.TEXT_INSERTED:
      case Events.TEXT_REMOVED:
      {
        let {liveRegion, isPolite} = this._handleLiveRegion(aEvent,
          ['text', 'all']);
        if (aEvent.isFromUserInput || liveRegion) {
          // Handle all text mutations coming from the user or if they happen
          // on a live region.
          this._handleText(aEvent, liveRegion, isPolite);
        }
        break;
      }
      case Events.FOCUS:
      {
        // Put vc where the focus is at
        let acc = aEvent.accessible;
        let doc = aEvent.accessibleDocument;
        if (acc.role != Roles.DOCUMENT && doc.role != Roles.CHROME_WINDOW) {
         this.contentScope.contentControl.autoMove(acc);
       }
       break;
      }
      case Events.DOCUMENT_LOAD_COMPLETE:
      {
        this.contentScope.contentControl.autoMove(
          aEvent.accessible, { delay: 500 });
        break;
      }
      case Events.VALUE_CHANGE:
      {
        let position = this.contentScope.contentControl.vc.position;
        let target = aEvent.accessible;
        if (position === target ||
            Utils.getEmbeddedControl(position) === target) {
          this.present(Presentation.valueChanged(target));
        }
      }
    }
  },

  _handleText: function _handleText(aEvent, aLiveRegion, aIsPolite) {
    let event = aEvent.QueryInterface(Ci.nsIAccessibleTextChangeEvent);
    let isInserted = event.isInserted;
    let txtIface = aEvent.accessible.QueryInterface(Ci.nsIAccessibleText);

    let text = '';
    try {
      text = txtIface.getText(0, Ci.nsIAccessibleText.TEXT_OFFSET_END_OF_TEXT);
    } catch (x) {
      // XXX we might have gotten an exception with of a
      // zero-length text. If we did, ignore it (bug #749810).
      if (txtIface.characterCount) {
        throw x;
      }
    }
    // If there are embedded objects in the text, ignore them.
    // Assuming changes to the descendants would already be handled by the
    // show/hide event.
    let modifiedText = event.modifiedText.replace(/\uFFFC/g, '').trim();
    if (!modifiedText) {
      return;
    }
    if (aLiveRegion) {
      if (aEvent.eventType === Events.TEXT_REMOVED) {
        this._queueLiveEvent(Events.TEXT_REMOVED, aLiveRegion, aIsPolite,
          modifiedText);
      } else {
        this._dequeueLiveEvent(Events.TEXT_REMOVED, aLiveRegion);
        this.present(Presentation.liveRegion(aLiveRegion, aIsPolite, false,
          modifiedText));
      }
    } else {
      this.present(Presentation.textChanged(isInserted, event.start,
        event.length, text, modifiedText));
    }
  },

  _handleLiveRegion: function _handleLiveRegion(aEvent, aRelevant) {
    if (aEvent.isFromUserInput) {
      return {};
    }
    let parseLiveAttrs = function parseLiveAttrs(aAccessible) {
      let attrs = Utils.getAttributes(aAccessible);
      if (attrs['container-live']) {
        return {
          live: attrs['container-live'],
          relevant: attrs['container-relevant'] || 'additions text',
          busy: attrs['container-busy'],
          atomic: attrs['container-atomic'],
          memberOf: attrs['member-of']
        };
      }
      return null;
    };
    // XXX live attributes are not set for hidden accessibles yet. Need to
    // climb up the tree to check for them.
    let getLiveAttributes = function getLiveAttributes(aEvent) {
      let liveAttrs = parseLiveAttrs(aEvent.accessible);
      if (liveAttrs) {
        return liveAttrs;
      }
      let parent = aEvent.targetParent;
      while (parent) {
        liveAttrs = parseLiveAttrs(parent);
        if (liveAttrs) {
          return liveAttrs;
        }
        parent = parent.parent
      }
      return {};
    };
    let {live, relevant, busy, atomic, memberOf} = getLiveAttributes(aEvent);
    // If container-live is not present or is set to |off| ignore the event.
    if (!live || live === 'off') {
      return {};
    }
    // XXX: support busy and atomic.

    // Determine if the type of the mutation is relevant. Default is additions
    // and text.
    let isRelevant = Utils.matchAttributeValue(relevant, aRelevant);
    if (!isRelevant) {
      return {};
    }
    return {
      liveRegion: aEvent.accessible,
      isPolite: live === 'polite'
    };
  },

  _dequeueLiveEvent: function _dequeueLiveEvent(aEventType, aLiveRegion) {
    let domNode = aLiveRegion.DOMNode;
    if (this._liveEventQueue && this._liveEventQueue.has(domNode)) {
      let queue = this._liveEventQueue.get(domNode);
      let nextEvent = queue[0];
      if (nextEvent.eventType === aEventType) {
        Utils.win.clearTimeout(nextEvent.timeoutID);
        queue.shift();
        if (queue.length === 0) {
          this._liveEventQueue.delete(domNode)
        }
      }
    }
  },

  _queueLiveEvent: function _queueLiveEvent(aEventType, aLiveRegion, aIsPolite, aModifiedText) {
    if (!this._liveEventQueue) {
      this._liveEventQueue = new WeakMap();
    }
    let eventHandler = {
      eventType: aEventType,
      timeoutID: Utils.win.setTimeout(this.present.bind(this),
        20, // Wait for a possible EVENT_SHOW or EVENT_TEXT_INSERTED event.
        Presentation.liveRegion(aLiveRegion, aIsPolite, true, aModifiedText))
    };

    let domNode = aLiveRegion.DOMNode;
    if (this._liveEventQueue.has(domNode)) {
      this._liveEventQueue.get(domNode).push(eventHandler);
    } else {
      this._liveEventQueue.set(domNode, [eventHandler]);
    }
  },

  present: function present(aPresentationData) {
    this.sendMsgFunc("AccessFu:Present", aPresentationData);
  },

  onStateChange: function onStateChange(aWebProgress, aRequest, aStateFlags, aStatus) {
    let tabstate = '';

    let loadingState = Ci.nsIWebProgressListener.STATE_TRANSFERRING |
      Ci.nsIWebProgressListener.STATE_IS_DOCUMENT;
    let loadedState = Ci.nsIWebProgressListener.STATE_STOP |
      Ci.nsIWebProgressListener.STATE_IS_NETWORK;

    if ((aStateFlags & loadingState) == loadingState) {
      tabstate = 'loading';
    } else if ((aStateFlags & loadedState) == loadedState &&
               !aWebProgress.isLoadingDocument) {
      tabstate = 'loaded';
    }

    if (tabstate) {
      let docAcc = Utils.AccRetrieval.getAccessibleFor(aWebProgress.DOMWindow.document);
      this.present(Presentation.tabStateChanged(docAcc, tabstate));
    }
  },

  onProgressChange: function onProgressChange() {},

  onLocationChange: function onLocationChange(aWebProgress, aRequest, aLocation, aFlags) {
    let docAcc = Utils.AccRetrieval.getAccessibleFor(aWebProgress.DOMWindow.document);
    this.present(Presentation.tabStateChanged(docAcc, 'newdoc'));
  },

  onStatusChange: function onStatusChange() {},

  onSecurityChange: function onSecurityChange() {},

  QueryInterface: XPCOMUtils.generateQI([Ci.nsIWebProgressListener,
                                         Ci.nsISupportsWeakReference,
                                         Ci.nsISupports,
                                         Ci.nsIObserver])
};

const AccessibilityEventObserver = {

  /**
   * A WeakMap containing [content, EventManager] pairs.
   */
  eventManagers: new WeakMap(),

  /**
   * A total number of registered eventManagers.
   */
  listenerCount: 0,

  /**
   * An indicator of an active 'accessible-event' observer.
   */
  started: false,

  /**
   * Start an AccessibilityEventObserver.
   */
  start: function start() {
    if (this.started || this.listenerCount === 0) {
      return;
    }
    Services.obs.addObserver(this, 'accessible-event', false);
    this.started = true;
  },

  /**
   * Stop an AccessibilityEventObserver.
   */
  stop: function stop() {
    if (!this.started) {
      return;
    }
    Services.obs.removeObserver(this, 'accessible-event');
    // Clean up all registered event managers.
    this.eventManagers.clear();
    this.listenerCount = 0;
    this.started = false;
  },

  /**
   * Register an EventManager and start listening to the
   * 'accessible-event' messages.
   *
   * @param aEventManager EventManager
   *        An EventManager object that was loaded into the specific content.
   */
  addListener: function addListener(aEventManager) {
    let content = aEventManager.contentScope.content;
    if (!this.eventManagers.has(content)) {
      this.listenerCount++;
    }
    this.eventManagers.set(content, aEventManager);
    // Since at least one EventManager was registered, start listening.
    Logger.debug('AccessibilityEventObserver.addListener. Total:',
      this.listenerCount);
    this.start();
  },

  /**
   * Unregister an EventManager and, optionally, stop listening to the
   * 'accessible-event' messages.
   *
   * @param aEventManager EventManager
   *        An EventManager object that was stopped in the specific content.
   */
  removeListener: function removeListener(aEventManager) {
    let content = aEventManager.contentScope.content;
    if (!this.eventManagers.delete(content)) {
      return;
    }
    this.listenerCount--;
    Logger.debug('AccessibilityEventObserver.removeListener. Total:',
      this.listenerCount);
    if (this.listenerCount === 0) {
      // If there are no EventManagers registered at the moment, stop listening
      // to the 'accessible-event' messages.
      this.stop();
    }
  },

  /**
   * Lookup an EventManager for a specific content. If the EventManager is not
   * found, walk up the hierarchy of parent windows.
   * @param content Window
   *        A content Window used to lookup the corresponding EventManager.
   */
  getListener: function getListener(content) {
    let eventManager = this.eventManagers.get(content);
    if (eventManager) {
      return eventManager;
    }
    let parent = content.parent;
    if (parent === content) {
      // There is no parent or the parent is of a different type.
      return null;
    }
    return this.getListener(parent);
  },

  /**
   * Handle the 'accessible-event' message.
   */
  observe: function observe(aSubject, aTopic, aData) {
    if (aTopic !== 'accessible-event') {
      return;
    }
    let event = aSubject.QueryInterface(Ci.nsIAccessibleEvent);
    if (!event.accessibleDocument) {
      Logger.warning(
        'AccessibilityEventObserver.observe: no accessible document:',
        Logger.eventToString(event), "accessible:",
        Logger.accessibleToString(event.accessible));
      return;
    }
    let content = event.accessibleDocument.window;
    // Match the content window to its EventManager.
    let eventManager = this.getListener(content);
    if (!eventManager || !eventManager._started) {
      if (Utils.MozBuildApp === 'browser' &&
          !(content instanceof Ci.nsIDOMChromeWindow)) {
        Logger.warning(
          'AccessibilityEventObserver.observe: ignored event:',
          Logger.eventToString(event), "accessible:",
          Logger.accessibleToString(event.accessible), "document:",
          Logger.accessibleToString(event.accessibleDocument));
      }
      return;
    }
    try {
      eventManager.handleAccEvent(event);
    } catch (x) {
      Logger.logException(x, 'Error handing accessible event');
    } finally {
      return;
    }
  }
};