gecko/accessible/src/jsat/AccessFu.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 Cc = Components.classes;
const Ci = Components.interfaces;
const Cu = Components.utils;
const Cr = Components.results;

this.EXPORTED_SYMBOLS = ['AccessFu'];

Cu.import('resource://gre/modules/Services.jsm');

Cu.import('resource://gre/modules/accessibility/Utils.jsm');

const ACCESSFU_DISABLE = 0;
const ACCESSFU_ENABLE = 1;
const ACCESSFU_AUTO = 2;

const SCREENREADER_SETTING = 'accessibility.screenreader';

this.AccessFu = {
  /**
   * Initialize chrome-layer accessibility functionality.
   * If accessibility is enabled on the platform, then a special accessibility
   * mode is started.
   */
  attach: function attach(aWindow) {
    Utils.init(aWindow);

    try {
      let bridgeCc = Cc['@mozilla.org/android/bridge;1'];
      bridgeCc.getService(Ci.nsIAndroidBridge).handleGeckoMessage(
          JSON.stringify({ type: 'Accessibility:Ready' }));
      Services.obs.addObserver(this, 'Accessibility:Settings', false);
    } catch (x) {
      // Not on Android
      if (aWindow.navigator.mozSettings) {
        let lock = aWindow.navigator.mozSettings.createLock();
        let req = lock.get(SCREENREADER_SETTING);
        req.addEventListener('success', () => {
          this._systemPref = req.result[SCREENREADER_SETTING];
          this._enableOrDisable();
        });
        aWindow.navigator.mozSettings.addObserver(
          SCREENREADER_SETTING, this.handleEvent.bind(this));
      }
    }

    this._activatePref = new PrefCache(
      'accessibility.accessfu.activate', this._enableOrDisable.bind(this));

    this._enableOrDisable();
  },

  /**
   * Shut down chrome-layer accessibility functionality from the outside.
   */
  detach: function detach() {
    // Avoid disabling twice.
    if (this._enabled) {
      this._disable();
    }
    if (Utils.MozBuildApp === 'mobile/android') {
      Services.obs.removeObserver(this, 'Accessibility:Settings');
    } else if (Utils.win.navigator.mozSettings) {
      Utils.win.navigator.mozSettings.removeObserver(
        SCREENREADER_SETTING, this.handleEvent.bind(this));
    }
    delete this._activatePref;
    Utils.uninit();
  },

  /**
   * Start AccessFu mode, this primarily means controlling the virtual cursor
   * with arrow keys.
   */
  _enable: function _enable() {
    if (this._enabled)
      return;
    this._enabled = true;

    Cu.import('resource://gre/modules/accessibility/Utils.jsm');
    Cu.import('resource://gre/modules/accessibility/TouchAdapter.jsm');
    Cu.import('resource://gre/modules/accessibility/Presentation.jsm');

    Logger.info('Enabled');

    for each (let mm in Utils.AllMessageManagers) {
      this._addMessageListeners(mm);
      this._loadFrameScript(mm);
    }

    // Add stylesheet
    let stylesheetURL = 'chrome://global/content/accessibility/AccessFu.css';
    let stylesheet = Utils.win.document.createProcessingInstruction(
      'xml-stylesheet', 'href="' + stylesheetURL + '" type="text/css"');
    Utils.win.document.insertBefore(stylesheet, Utils.win.document.firstChild);
    this.stylesheet = Cu.getWeakReference(stylesheet);


    // Populate quicknav modes
    this._quicknavModesPref =
      new PrefCache(
        'accessibility.accessfu.quicknav_modes',
        (aName, aValue) => {
          this.Input.quickNavMode.updateModes(aValue);
        }, true);

    // Check for output notification
    this._notifyOutputPref =
      new PrefCache('accessibility.accessfu.notify_output');


    this.Input.start();
    Output.start();
    TouchAdapter.start();

    Services.obs.addObserver(this, 'remote-browser-shown', false);
    Services.obs.addObserver(this, 'inprocess-browser-shown', false);
    Services.obs.addObserver(this, 'Accessibility:NextObject', false);
    Services.obs.addObserver(this, 'Accessibility:PreviousObject', false);
    Services.obs.addObserver(this, 'Accessibility:Focus', false);
    Services.obs.addObserver(this, 'Accessibility:ActivateObject', false);
    Services.obs.addObserver(this, 'Accessibility:LongPress', false);
    Services.obs.addObserver(this, 'Accessibility:MoveByGranularity', false);
    Utils.win.addEventListener('TabOpen', this);
    Utils.win.addEventListener('TabClose', this);
    Utils.win.addEventListener('TabSelect', this);

    if (this.readyCallback) {
      this.readyCallback();
      delete this.readyCallback;
    }
  },

  /**
   * Disable AccessFu and return to default interaction mode.
   */
  _disable: function _disable() {
    if (!this._enabled)
      return;

    this._enabled = false;

    Logger.info('Disabled');

    Utils.win.document.removeChild(this.stylesheet.get());

    for each (let mm in Utils.AllMessageManagers) {
      mm.sendAsyncMessage('AccessFu:Stop');
      this._removeMessageListeners(mm);
    }

    this.Input.stop();
    Output.stop();
    TouchAdapter.stop();

    Utils.win.removeEventListener('TabOpen', this);
    Utils.win.removeEventListener('TabClose', this);
    Utils.win.removeEventListener('TabSelect', this);

    Services.obs.removeObserver(this, 'remote-browser-shown');
    Services.obs.removeObserver(this, 'inprocess-browser-shown');
    Services.obs.removeObserver(this, 'Accessibility:NextObject');
    Services.obs.removeObserver(this, 'Accessibility:PreviousObject');
    Services.obs.removeObserver(this, 'Accessibility:Focus');
    Services.obs.removeObserver(this, 'Accessibility:ActivateObject');
    Services.obs.removeObserver(this, 'Accessibility:LongPress');
    Services.obs.removeObserver(this, 'Accessibility:MoveByGranularity');

    delete this._quicknavModesPref;
    delete this._notifyOutputPref;

    if (this.doneCallback) {
      this.doneCallback();
      delete this.doneCallback;
    }
  },

  _enableOrDisable: function _enableOrDisable() {
    try {
      if (!this._activatePref) {
        return;
      }
      let activatePref = this._activatePref.value;
      if (activatePref == ACCESSFU_ENABLE ||
          this._systemPref && activatePref == ACCESSFU_AUTO)
        this._enable();
      else
        this._disable();
    } catch (x) {
      dump('Error ' + x.message + ' ' + x.fileName + ':' + x.lineNumber);
    }
  },

  receiveMessage: function receiveMessage(aMessage) {
    Logger.debug(() => {
      return ['Recieved', aMessage.name, JSON.stringify(aMessage.json)];
    });

    switch (aMessage.name) {
      case 'AccessFu:Ready':
        let mm = Utils.getMessageManager(aMessage.target);
        if (this._enabled) {
          mm.sendAsyncMessage('AccessFu:Start',
                              {method: 'start', buildApp: Utils.MozBuildApp});
        }
        break;
      case 'AccessFu:Present':
        this._output(aMessage.json, aMessage.target);
        break;
      case 'AccessFu:Input':
        this.Input.setEditState(aMessage.json);
        break;
      case 'AccessFu:ActivateContextMenu':
        this.Input.activateContextMenu(aMessage.json);
        break;
      case 'AccessFu:DoScroll':
        this.Input.doScroll(aMessage.json);
        break;
    }
  },

  _output: function _output(aPresentationData, aBrowser) {
    for each (let presenter in aPresentationData) {
      if (!presenter)
        continue;

      try {
        Output[presenter.type](presenter.details, aBrowser);
      } catch (x) {
        Logger.logException(x);
      }
    }

    if (this._notifyOutputPref.value) {
      Services.obs.notifyObservers(null, 'accessfu-output',
                                   JSON.stringify(aPresentationData));
    }
  },

  _loadFrameScript: function _loadFrameScript(aMessageManager) {
    if (this._processedMessageManagers.indexOf(aMessageManager) < 0) {
      aMessageManager.loadFrameScript(
        'chrome://global/content/accessibility/content-script.js', true);
      this._processedMessageManagers.push(aMessageManager);
    } else if (this._enabled) {
      // If the content-script is already loaded and AccessFu is enabled,
      // send an AccessFu:Start message.
      aMessageManager.sendAsyncMessage('AccessFu:Start',
        {method: 'start', buildApp: Utils.MozBuildApp});
    }
  },

  _addMessageListeners: function _addMessageListeners(aMessageManager) {
    aMessageManager.addMessageListener('AccessFu:Present', this);
    aMessageManager.addMessageListener('AccessFu:Input', this);
    aMessageManager.addMessageListener('AccessFu:Ready', this);
    aMessageManager.addMessageListener('AccessFu:ActivateContextMenu', this);
    aMessageManager.addMessageListener('AccessFu:DoScroll', this);
  },

  _removeMessageListeners: function _removeMessageListeners(aMessageManager) {
    aMessageManager.removeMessageListener('AccessFu:Present', this);
    aMessageManager.removeMessageListener('AccessFu:Input', this);
    aMessageManager.removeMessageListener('AccessFu:Ready', this);
    aMessageManager.removeMessageListener('AccessFu:ActivateContextMenu', this);
    aMessageManager.removeMessageListener('AccessFu:DoScroll', this);
  },

  _handleMessageManager: function _handleMessageManager(aMessageManager) {
    if (this._enabled) {
      this._addMessageListeners(aMessageManager);
    }
    this._loadFrameScript(aMessageManager);
  },

  observe: function observe(aSubject, aTopic, aData) {
    switch (aTopic) {
      case 'Accessibility:Settings':
        this._systemPref = JSON.parse(aData).enabled;
        this._enableOrDisable();
        break;
      case 'Accessibility:NextObject':
        this.Input.moveCursor('moveNext', 'Simple', 'gesture');
        break;
      case 'Accessibility:PreviousObject':
        this.Input.moveCursor('movePrevious', 'Simple', 'gesture');
        break;
      case 'Accessibility:ActivateObject':
        this.Input.activateCurrent(JSON.parse(aData));
        break;
      case 'Accessibility:LongPress':
        this.Input.sendContextMenuMessage();
        break;
      case 'Accessibility:Focus':
        this._focused = JSON.parse(aData);
        if (this._focused) {
          this.showCurrent(true);
        }
        break;
      case 'Accessibility:MoveByGranularity':
        this.Input.moveByGranularity(JSON.parse(aData));
        break;
      case 'remote-browser-shown':
      case 'inprocess-browser-shown':
      {
        // Ignore notifications that aren't from a BrowserOrApp
        let frameLoader = aSubject.QueryInterface(Ci.nsIFrameLoader);
        if (!frameLoader.ownerIsBrowserOrAppFrame) {
          return;
        }
        this._handleMessageManager(frameLoader.messageManager);
        break;
      }
    }
  },

  handleEvent: function handleEvent(aEvent) {
    switch (aEvent.type) {
      case 'TabOpen':
      {
        let mm = Utils.getMessageManager(aEvent.target);
        this._handleMessageManager(mm);
        break;
      }
      case 'TabClose':
      {
        let mm = Utils.getMessageManager(aEvent.target);
        let mmIndex = this._processedMessageManagers.indexOf(mm);
        if (mmIndex > -1) {
          this._removeMessageListeners(mm);
          this._processedMessageManagers.splice(mmIndex, 1);
        }
        break;
      }
      case 'TabSelect':
      {
        if (this._focused) {
          // We delay this for half a second so the awesomebar could close,
          // and we could use the current coordinates for the content item.
          // XXX TODO figure out how to avoid magic wait here.
          Utils.win.setTimeout(
            function () {
              this.showCurrent(false);
            }.bind(this), 500);
        }
        break;
      }
      default:
      {
        // A settings change, it does not have an event type
        if (aEvent.settingName == SCREENREADER_SETTING) {
          this._systemPref = aEvent.settingValue;
          this._enableOrDisable();
        }
        break;
      }
    }
  },

  showCurrent: function showCurrent(aMove) {
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    mm.sendAsyncMessage('AccessFu:ShowCurrent', { move: aMove });
  },

  announce: function announce(aAnnouncement) {
    this._output(Presentation.announce(aAnnouncement),
                 Utils.CurrentBrowser);
  },

  // So we don't enable/disable twice
  _enabled: false,

  // Layerview is focused
  _focused: false,

  // Keep track of message managers tha already have a 'content-script.js'
  // injected.
  _processedMessageManagers: [],

  /**
   * Adjusts the given bounds relative to the given browser. Converts from screen
   * or device pixels to either device or CSS pixels.
   * @param {Rect} aJsonBounds the bounds to adjust
   * @param {browser} aBrowser the browser we want the bounds relative to
   * @param {bool} aToCSSPixels whether to convert to CSS pixels (as opposed to
   *               device pixels)
   * @param {bool} aFromDevicePixels whether to convert from device pixels (as
   *               opposed to screen pixels)
   */
  adjustContentBounds: function(aJsonBounds, aBrowser, aToCSSPixels, aFromDevicePixels) {
    let bounds = new Rect(aJsonBounds.left, aJsonBounds.top,
                          aJsonBounds.right - aJsonBounds.left,
                          aJsonBounds.bottom - aJsonBounds.top);
    let win = Utils.win;
    let dpr = win.devicePixelRatio;
    let vp = Utils.getViewport(win);
    let offset = { left: -win.mozInnerScreenX, top: -win.mozInnerScreenY };

    if (!aBrowser.contentWindow) {
      // OOP browser, add offset of browser.
      // The offset of the browser element in relation to its parent window.
      let clientRect = aBrowser.getBoundingClientRect();
      let win = aBrowser.ownerDocument.defaultView;
      offset.left += clientRect.left + win.mozInnerScreenX;
      offset.top += clientRect.top + win.mozInnerScreenY;
    }

    // Here we scale from screen pixels to layout device pixels by dividing by
    // the resolution (caused by pinch-zooming). The resolution is the viewport
    // zoom divided by the devicePixelRatio. If there's no viewport, then we're
    // on a platform without pinch-zooming and we can just ignore this.
    if (!aFromDevicePixels && vp) {
      bounds = bounds.scale(vp.zoom / dpr, vp.zoom / dpr);
    }

    // Add the offset; the offset is in CSS pixels, so multiply the
    // devicePixelRatio back in before adding to preserve unit consistency.
    bounds = bounds.translate(offset.left * dpr, offset.top * dpr);

    // If we want to get to CSS pixels from device pixels, this needs to be
    // further divided by the devicePixelRatio due to widget scaling.
    if (aToCSSPixels) {
      bounds = bounds.scale(1 / dpr, 1 / dpr);
    }

    return bounds.expandToIntegers();
  }
};

var Output = {
  brailleState: {
    startOffset: 0,
    endOffset: 0,
    text: '',
    selectionStart: 0,
    selectionEnd: 0,

    init: function init(aOutput) {
      if (aOutput && 'output' in aOutput) {
        this.startOffset = aOutput.startOffset;
        this.endOffset = aOutput.endOffset;
        // We need to append a space at the end so that the routing key corresponding
        // to the end of the output (i.e. the space) can be hit to move the caret there.
        this.text = aOutput.output + ' ';
        this.selectionStart = typeof aOutput.selectionStart === 'number' ?
                              aOutput.selectionStart : this.selectionStart;
        this.selectionEnd = typeof aOutput.selectionEnd === 'number' ?
                            aOutput.selectionEnd : this.selectionEnd;

        return { text: this.text,
                 selectionStart: this.selectionStart,
                 selectionEnd: this.selectionEnd };
      }

      return null;
    },

    adjustText: function adjustText(aText) {
      let newBraille = [];
      let braille = {};

      let prefix = this.text.substring(0, this.startOffset).trim();
      if (prefix) {
        prefix += ' ';
        newBraille.push(prefix);
      }

      newBraille.push(aText);

      let suffix = this.text.substring(this.endOffset).trim();
      if (suffix) {
        suffix = ' ' + suffix;
        newBraille.push(suffix);
      }

      this.startOffset = braille.startOffset = prefix.length;
      this.text = braille.text = newBraille.join('') + ' ';
      this.endOffset = braille.endOffset = braille.text.length - suffix.length;
      braille.selectionStart = this.selectionStart;
      braille.selectionEnd = this.selectionEnd;

      return braille;
    },

    adjustSelection: function adjustSelection(aSelection) {
      let braille = {};

      braille.startOffset = this.startOffset;
      braille.endOffset = this.endOffset;
      braille.text = this.text;
      this.selectionStart = braille.selectionStart = aSelection.selectionStart + this.startOffset;
      this.selectionEnd = braille.selectionEnd = aSelection.selectionEnd + this.startOffset;

      return braille;
    }
  },

  speechHelper: {
    EARCONS: ['virtual_cursor_move.ogg',
              'virtual_cursor_key.ogg',
              'clicked.ogg'],

    earconBuffers: {},

    inited: false,

    webspeechEnabled: false,

    deferredOutputs: [],

    init: function init() {
      let window = Utils.win;
      this.webspeechEnabled = !!window.speechSynthesis;

      let settingsToGet = 2;
      let settingsCallback = (aName, aSetting) => {
        if (--settingsToGet > 0) {
          return;
        }

        this.inited = true;

        for (let actions of this.deferredOutputs) {
          this.output(actions);
        }
      };

      this._volumeSetting = new SettingCache(
        'accessibility.screenreader-volume', settingsCallback,
        { defaultValue: 1, callbackNow: true, callbackOnce: true });
      this._rateSetting = new SettingCache(
        'accessibility.screenreader-rate', settingsCallback,
        { defaultValue: 0, callbackNow: true, callbackOnce: true });

      for (let earcon of this.EARCONS) {
        let earconName = /(^.*)\..*$/.exec(earcon)[1];
        this.earconBuffers[earconName] = new WeakMap();
        this.earconBuffers[earconName].set(
          window, new window.Audio('chrome://global/content/accessibility/' + earcon));
      }
    },

    uninit: function uninit() {
      if (this.inited) {
        delete this._volumeSetting;
        delete this._rateSetting;
      }
      this.inited = false;
    },

    output: function output(aActions) {
      if (!this.inited) {
        this.deferredOutputs.push(aActions);
        return;
      }

      for (let action of aActions) {
        let window = Utils.win;
        Logger.debug('tts.' + action.method, '"' + action.data + '"',
                     JSON.stringify(action.options));

        if (!action.options.enqueue && this.webspeechEnabled) {
          window.speechSynthesis.cancel();
        }

        if (action.method === 'speak' && this.webspeechEnabled) {
          let utterance = new window.SpeechSynthesisUtterance(action.data);
          let requestedRate = this._rateSetting.value;
          utterance.volume = this._volumeSetting.value;
          utterance.rate = requestedRate >= 0 ?
            requestedRate + 1 : 1 / (Math.abs(requestedRate) + 1);
          window.speechSynthesis.speak(utterance);
        } else if (action.method === 'playEarcon') {
          let audioBufferWeakMap = this.earconBuffers[action.data];
          if (audioBufferWeakMap) {
            let node = audioBufferWeakMap.get(window).cloneNode(false);
            node.volume = this._volumeSetting.value;
            node.play();
          }
        }
      }
    }
  },

  start: function start() {
    Cu.import('resource://gre/modules/Geometry.jsm');
    this.speechHelper.init();
  },

  stop: function stop() {
    if (this.highlightBox) {
      Utils.win.document.documentElement.removeChild(this.highlightBox.get());
      delete this.highlightBox;
    }

    if (this.announceBox) {
      Utils.win.document.documentElement.removeChild(this.announceBox.get());
      delete this.announceBox;
    }

    this.speechHelper.uninit();
  },

  Speech: function Speech(aDetails, aBrowser) {
    this.speechHelper.output(aDetails.actions);
  },

  Visual: function Visual(aDetails, aBrowser) {
    switch (aDetails.method) {
      case 'showBounds':
      {
        let highlightBox = null;
        if (!this.highlightBox) {
          // Add highlight box
          highlightBox = Utils.win.document.
            createElementNS('http://www.w3.org/1999/xhtml', 'div');
          Utils.win.document.documentElement.appendChild(highlightBox);
          highlightBox.id = 'virtual-cursor-box';

          // Add highlight inset for inner shadow
          let inset = Utils.win.document.
            createElementNS('http://www.w3.org/1999/xhtml', 'div');
          inset.id = 'virtual-cursor-inset';

          highlightBox.appendChild(inset);
          this.highlightBox = Cu.getWeakReference(highlightBox);
        } else {
          highlightBox = this.highlightBox.get();
        }

        let padding = aDetails.padding;
        let r = AccessFu.adjustContentBounds(aDetails.bounds, aBrowser, true);

        // First hide it to avoid flickering when changing the style.
        highlightBox.style.display = 'none';
        highlightBox.style.top = (r.top - padding) + 'px';
        highlightBox.style.left = (r.left - padding) + 'px';
        highlightBox.style.width = (r.width + padding*2) + 'px';
        highlightBox.style.height = (r.height + padding*2) + 'px';
        highlightBox.style.display = 'block';

        break;
      }
      case 'hideBounds':
      {
        let highlightBox = this.highlightBox ? this.highlightBox.get() : null;
        if (highlightBox)
          highlightBox.style.display = 'none';
        break;
      }
      case 'showAnnouncement':
      {
        let announceBox = this.announceBox ? this.announceBox.get() : null;
        if (!announceBox) {
          announceBox = Utils.win.document.
            createElementNS('http://www.w3.org/1999/xhtml', 'div');
          announceBox.id = 'announce-box';
          Utils.win.document.documentElement.appendChild(announceBox);
          this.announceBox = Cu.getWeakReference(announceBox);
        }

        announceBox.innerHTML = '<div>' + aDetails.text + '</div>';
        announceBox.classList.add('showing');

        if (this._announceHideTimeout)
          Utils.win.clearTimeout(this._announceHideTimeout);

        if (aDetails.duration > 0)
          this._announceHideTimeout = Utils.win.setTimeout(
            function () {
              announceBox.classList.remove('showing');
              this._announceHideTimeout = 0;
            }.bind(this), aDetails.duration);
        break;
      }
      case 'hideAnnouncement':
      {
        let announceBox = this.announceBox ? this.announceBox.get() : null;
        if (announceBox)
          announceBox.classList.remove('showing');
        break;
      }
    }
  },

  Android: function Android(aDetails, aBrowser) {
    const ANDROID_VIEW_TEXT_CHANGED = 0x10;
    const ANDROID_VIEW_TEXT_SELECTION_CHANGED = 0x2000;

    if (!this._bridge)
      this._bridge = Cc['@mozilla.org/android/bridge;1'].getService(Ci.nsIAndroidBridge);

    for each (let androidEvent in aDetails) {
      androidEvent.type = 'Accessibility:Event';
      if (androidEvent.bounds)
        androidEvent.bounds = AccessFu.adjustContentBounds(androidEvent.bounds, aBrowser);

      switch(androidEvent.eventType) {
        case ANDROID_VIEW_TEXT_CHANGED:
          androidEvent.brailleOutput = this.brailleState.adjustText(androidEvent.text);
          break;
        case ANDROID_VIEW_TEXT_SELECTION_CHANGED:
          androidEvent.brailleOutput = this.brailleState.adjustSelection(androidEvent.brailleOutput);
          break;
        default:
          androidEvent.brailleOutput = this.brailleState.init(androidEvent.brailleOutput);
          break;
      }
      this._bridge.handleGeckoMessage(JSON.stringify(androidEvent));
    }
  },

  Haptic: function Haptic(aDetails, aBrowser) {
    Utils.win.navigator.vibrate(aDetails.pattern);
  },

  Braille: function Braille(aDetails, aBrowser) {
    Logger.debug('Braille output: ' + aDetails.text);
  }
};

var Input = {
  editState: {},

  start: function start() {
    // XXX: This is too disruptive on desktop for now.
    // Might need to add special modifiers.
    if (Utils.MozBuildApp != 'browser') {
      Utils.win.document.addEventListener('keypress', this, true);
    }
    Utils.win.addEventListener('mozAccessFuGesture', this, true);
  },

  stop: function stop() {
    if (Utils.MozBuildApp != 'browser') {
      Utils.win.document.removeEventListener('keypress', this, true);
    }
    Utils.win.removeEventListener('mozAccessFuGesture', this, true);
  },

  handleEvent: function Input_handleEvent(aEvent) {
    try {
      switch (aEvent.type) {
      case 'keypress':
        this._handleKeypress(aEvent);
        break;
      case 'mozAccessFuGesture':
        this._handleGesture(aEvent.detail);
        break;
      }
    } catch (x) {
      Logger.logException(x);
    }
  },

  _handleGesture: function _handleGesture(aGesture) {
    let gestureName = aGesture.type + aGesture.touches.length;
    Logger.debug('Gesture', aGesture.type,
                 '(fingers: ' + aGesture.touches.length + ')');

    switch (gestureName) {
      case 'dwell1':
      case 'explore1':
        this.moveToPoint('Simple', aGesture.x, aGesture.y);
        break;
      case 'doubletap1':
        this.activateCurrent();
        break;
      case 'doubletaphold1':
        this.sendContextMenuMessage();
        break;
      case 'swiperight1':
        this.moveCursor('moveNext', 'Simple', 'gestures');
        break;
      case 'swipeleft1':
        this.moveCursor('movePrevious', 'Simple', 'gesture');
        break;
      case 'swipeup1':
        this.contextAction('backward');
        break;
      case 'swipedown1':
        this.contextAction('forward');
        break;
      case 'exploreend1':
      case 'dwellend1':
        this.activateCurrent(null, true);
        break;
      case 'swiperight2':
        this.sendScrollMessage(-1, true);
        break;
      case 'swipedown2':
        this.sendScrollMessage(-1);
        break;
      case 'swipeleft2':
        this.sendScrollMessage(1, true);
        break;
      case 'swipeup2':
        this.sendScrollMessage(1);
        break;
      case 'explore2':
        Utils.CurrentBrowser.contentWindow.scrollBy(
          -aGesture.deltaX, -aGesture.deltaY);
        break;
      case 'swiperight3':
        this.moveCursor('moveNext', this.quickNavMode.current, 'gesture');
        break;
      case 'swipeleft3':
        this.moveCursor('movePrevious', this.quickNavMode.current, 'gesture');
        break;
      case 'swipedown3':
        this.quickNavMode.next();
        AccessFu.announce('quicknav_' + this.quickNavMode.current);
        break;
      case 'swipeup3':
        this.quickNavMode.previous();
        AccessFu.announce('quicknav_' + this.quickNavMode.current);
        break;
    }
  },

  _handleKeypress: function _handleKeypress(aEvent) {
    let target = aEvent.target;

    // Ignore keys with modifiers so the content could take advantage of them.
    if (aEvent.ctrlKey || aEvent.altKey || aEvent.metaKey)
      return;

    switch (aEvent.keyCode) {
      case 0:
        // an alphanumeric key was pressed, handle it separately.
        // If it was pressed with either alt or ctrl, just pass through.
        // If it was pressed with meta, pass the key on without the meta.
        if (this.editState.editing)
          return;

        let key = String.fromCharCode(aEvent.charCode);
        try {
          let [methodName, rule] = this.keyMap[key];
          this.moveCursor(methodName, rule, 'keyboard');
        } catch (x) {
          return;
        }
        break;
      case aEvent.DOM_VK_RIGHT:
        if (this.editState.editing) {
          if (!this.editState.atEnd)
            // Don't move forward if caret is not at end of entry.
            // XXX: Fix for rtl
            return;
          else
            target.blur();
        }
        this.moveCursor(aEvent.shiftKey ? 'moveLast' : 'moveNext', 'Simple', 'keyboard');
        break;
      case aEvent.DOM_VK_LEFT:
        if (this.editState.editing) {
          if (!this.editState.atStart)
            // Don't move backward if caret is not at start of entry.
            // XXX: Fix for rtl
            return;
          else
            target.blur();
        }
        this.moveCursor(aEvent.shiftKey ? 'moveFirst' : 'movePrevious', 'Simple', 'keyboard');
        break;
      case aEvent.DOM_VK_UP:
        if (this.editState.multiline) {
          if (!this.editState.atStart)
            // Don't blur content if caret is not at start of text area.
            return;
          else
            target.blur();
        }

        if (Utils.MozBuildApp == 'mobile/android')
          // Return focus to native Android browser chrome.
          Cc['@mozilla.org/android/bridge;1'].
            getService(Ci.nsIAndroidBridge).handleGeckoMessage(
              JSON.stringify({ type: 'ToggleChrome:Focus' }));
        break;
      case aEvent.DOM_VK_RETURN:
        if (this.editState.editing)
          return;
        this.activateCurrent();
        break;
    default:
      return;
    }

    aEvent.preventDefault();
    aEvent.stopPropagation();
  },

  moveToPoint: function moveToPoint(aRule, aX, aY) {
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    mm.sendAsyncMessage('AccessFu:MoveToPoint', {rule: aRule,
                                                 x: aX, y: aY,
                                                 origin: 'top'});
  },

  moveCursor: function moveCursor(aAction, aRule, aInputType) {
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    mm.sendAsyncMessage('AccessFu:MoveCursor',
                        {action: aAction, rule: aRule,
                         origin: 'top', inputType: aInputType});
  },

  contextAction: function contextAction(aDirection) {
    // XXX: For now, the only supported context action is adjusting a range.
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    mm.sendAsyncMessage('AccessFu:AdjustRange', {direction: aDirection});
  },

  moveByGranularity: function moveByGranularity(aDetails) {
    const MOVEMENT_GRANULARITY_PARAGRAPH = 8;

    if (!this.editState.editing) {
      if (aDetails.granularity === MOVEMENT_GRANULARITY_PARAGRAPH) {
        this.moveCursor('move' + aDetails.direction, 'Paragraph', 'gesture');
        return;
      }
    } else {
      aDetails.atStart = this.editState.atStart;
      aDetails.atEnd = this.editState.atEnd;
    }

    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    let type = this.editState.editing ? 'AccessFu:MoveCaret' :
                                        'AccessFu:MoveByGranularity';
    mm.sendAsyncMessage(type, aDetails);
  },

  activateCurrent: function activateCurrent(aData, aActivateIfKey = false) {
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    let offset = aData && typeof aData.keyIndex === 'number' ?
                 aData.keyIndex - Output.brailleState.startOffset : -1;

    mm.sendAsyncMessage('AccessFu:Activate',
                        {offset: offset, activateIfKey: aActivateIfKey});
  },

  sendContextMenuMessage: function sendContextMenuMessage() {
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    mm.sendAsyncMessage('AccessFu:ContextMenu', {});
  },

  activateContextMenu: function activateContextMenu(aDetails) {
    if (Utils.MozBuildApp === 'mobile/android') {
      let p = AccessFu.adjustContentBounds(aDetails.bounds, Utils.CurrentBrowser,
                                           true, true).center();
      Services.obs.notifyObservers(null, 'Gesture:LongPress',
                                   JSON.stringify({x: p.x, y: p.y}));
    }
  },

  setEditState: function setEditState(aEditState) {
    this.editState = aEditState;
  },

  // XXX: This is here for backwards compatability with screen reader simulator
  // it should be removed when the extension is updated on amo.
  scroll: function scroll(aPage, aHorizontal) {
    this.sendScrollMessage(aPage, aHorizontal);
  },

  sendScrollMessage: function sendScrollMessage(aPage, aHorizontal) {
    let mm = Utils.getMessageManager(Utils.CurrentBrowser);
    mm.sendAsyncMessage('AccessFu:Scroll', {page: aPage, horizontal: aHorizontal, origin: 'top'});
  },

  doScroll: function doScroll(aDetails) {
    let horizontal = aDetails.horizontal;
    let page = aDetails.page;
    let p = AccessFu.adjustContentBounds(aDetails.bounds, Utils.CurrentBrowser,
                                         true, true).center();
    let wu = Utils.win.QueryInterface(Ci.nsIInterfaceRequestor).
      getInterface(Ci.nsIDOMWindowUtils);
    wu.sendWheelEvent(p.x, p.y,
                      horizontal ? page : 0, horizontal ? 0 : page, 0,
                      Utils.win.WheelEvent.DOM_DELTA_PAGE, 0, 0, 0, 0);
  },

  get keyMap() {
    delete this.keyMap;
    this.keyMap = {
      a: ['moveNext', 'Anchor'],
      A: ['movePrevious', 'Anchor'],
      b: ['moveNext', 'Button'],
      B: ['movePrevious', 'Button'],
      c: ['moveNext', 'Combobox'],
      C: ['movePrevious', 'Combobox'],
      d: ['moveNext', 'Landmark'],
      D: ['movePrevious', 'Landmark'],
      e: ['moveNext', 'Entry'],
      E: ['movePrevious', 'Entry'],
      f: ['moveNext', 'FormElement'],
      F: ['movePrevious', 'FormElement'],
      g: ['moveNext', 'Graphic'],
      G: ['movePrevious', 'Graphic'],
      h: ['moveNext', 'Heading'],
      H: ['movePrevious', 'Heading'],
      i: ['moveNext', 'ListItem'],
      I: ['movePrevious', 'ListItem'],
      k: ['moveNext', 'Link'],
      K: ['movePrevious', 'Link'],
      l: ['moveNext', 'List'],
      L: ['movePrevious', 'List'],
      p: ['moveNext', 'PageTab'],
      P: ['movePrevious', 'PageTab'],
      r: ['moveNext', 'RadioButton'],
      R: ['movePrevious', 'RadioButton'],
      s: ['moveNext', 'Separator'],
      S: ['movePrevious', 'Separator'],
      t: ['moveNext', 'Table'],
      T: ['movePrevious', 'Table'],
      x: ['moveNext', 'Checkbox'],
      X: ['movePrevious', 'Checkbox']
    };

    return this.keyMap;
  },

  quickNavMode: {
    get current() {
      return this.modes[this._currentIndex];
    },

    previous: function quickNavMode_previous() {
      if (--this._currentIndex < 0)
        this._currentIndex = this.modes.length - 1;
    },

    next: function quickNavMode_next() {
      if (++this._currentIndex >= this.modes.length)
        this._currentIndex = 0;
    },

    updateModes: function updateModes(aModes) {
      if (aModes) {
        this.modes = aModes.split(',');
      } else {
        this.modes = [];
      }
    },

    _currentIndex: -1
  }
};
AccessFu.Input = Input;