gecko/b2g/chrome/content/shell.js

/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- /
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* 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/. */

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cu = Components.utils;
const Cr = Components.results;

Cu.import('resource://gre/modules/XPCOMUtils.jsm');
Cu.import('resource://gre/modules/Services.jsm');
Cu.import('resource://gre/modules/ContactService.jsm');
Cu.import('resource://gre/modules/SettingsChangeNotifier.jsm');
#ifdef MOZ_B2G_FM
Cu.import('resource://gre/modules/DOMFMRadioParent.jsm');
#endif
Cu.import('resource://gre/modules/AlarmService.jsm');
Cu.import('resource://gre/modules/ActivitiesService.jsm');
Cu.import('resource://gre/modules/PermissionPromptHelper.jsm');
Cu.import('resource://gre/modules/PermissionSettings.jsm');
Cu.import('resource://gre/modules/ObjectWrapper.jsm');
Cu.import('resource://gre/modules/accessibility/AccessFu.jsm');
Cu.import('resource://gre/modules/Payment.jsm');

XPCOMUtils.defineLazyServiceGetter(Services, 'env',
                                   '@mozilla.org/process/environment;1',
                                   'nsIEnvironment');

XPCOMUtils.defineLazyServiceGetter(Services, 'ss',
                                   '@mozilla.org/content/style-sheet-service;1',
                                   'nsIStyleSheetService');

#ifdef MOZ_WIDGET_GONK
XPCOMUtils.defineLazyServiceGetter(Services, 'audioManager',
                                   '@mozilla.org/telephony/audiomanager;1',
                                   'nsIAudioManager');
#else
Services.audioManager = {
  'masterVolume': 0
};
#endif

XPCOMUtils.defineLazyServiceGetter(Services, 'fm',
                                   '@mozilla.org/focus-manager;1',
                                   'nsIFocusManager');

XPCOMUtils.defineLazyGetter(this, 'DebuggerServer', function() {
  Cu.import('resource://gre/modules/devtools/dbg-server.jsm');
  return DebuggerServer;
});

XPCOMUtils.defineLazyGetter(this, "ppmm", function() {
  return Cc["@mozilla.org/parentprocessmessagemanager;1"]
         .getService(Ci.nsIMessageListenerManager);
});

function getContentWindow() {
  return shell.contentBrowser.contentWindow;
}

var shell = {

  get CrashSubmit() {
    delete this.CrashSubmit;
    Cu.import("resource://gre/modules/CrashSubmit.jsm", this);
    return this.CrashSubmit;
  },

  reportCrash: function shell_reportCrash() {
    let crashID;
    try {
      crashID = Cc["@mozilla.org/xre/app-info;1"]
                .getService(Ci.nsIXULRuntime).lastRunCrashID;
    } catch(e) { }
    if (Services.prefs.getBoolPref('app.reportCrashes') &&
        crashID) {

      Services.obs.addObserver(function observer(subject, topic, state) {
          if (topic != "network:offline-status-changed")
            return;
          if (state == 'online') {
            shell.CrashSubmit.submit(crashID);
            Services.obs.removeObserver(observer, topic);
          }
        }
        , "network:offline-status-changed", false);
    }
  },

  get contentBrowser() {
    delete this.contentBrowser;
    return this.contentBrowser = document.getElementById('homescreen');
  },

  get homeURL() {
    try {
      let homeSrc = Services.env.get('B2G_HOMESCREEN');
      if (homeSrc)
        return homeSrc;
    } catch (e) {}

    return Services.prefs.getCharPref('browser.homescreenURL');
  },

  get manifestURL() {
    return Services.prefs.getCharPref('browser.manifestURL');
   },

  start: function shell_start() {

    // Dogfood id. We might want to remove it in the future.
    // see bug 789466
    try {
      let dogfoodId = Services.prefs.getCharPref('prerelease.dogfood.id');
      if (dogfoodId != "") {
        let cr = Cc["@mozilla.org/xre/app-info;1"]
                   .getService(Ci.nsICrashReporter);
        cr.annotateCrashReport("Email", dogfoodId);
      }
    }
    catch (e) { }

    let homeURL = this.homeURL;
    if (!homeURL) {
      let msg = 'Fatal error during startup: No homescreen found: try setting B2G_HOMESCREEN';
      alert(msg);
      return;
    }

    let manifestURL = this.manifestURL;
    // <html:iframe id="homescreen"
    //              mozbrowser="true" mozallowfullscreen="true"
    //              style="overflow: hidden; -moz-box-flex: 1; border: none;"
    //              src="data:text/html;charset=utf-8,%3C!DOCTYPE html>%3Cbody style='background:black;'>"/>
    let browserFrame =
      document.createElementNS('http://www.w3.org/1999/xhtml', 'html:iframe');
    browserFrame.setAttribute('id', 'homescreen');
    browserFrame.setAttribute('mozbrowser', 'true');
    browserFrame.setAttribute('mozapp', manifestURL);
    browserFrame.setAttribute('mozallowfullscreen', 'true');
    browserFrame.setAttribute('style', "overflow: hidden; -moz-box-flex: 1; border: none;");
    browserFrame.setAttribute('src', "data:text/html;charset=utf-8,%3C!DOCTYPE html>%3Cbody style='background:black;");
    document.getElementById('shell').appendChild(browserFrame);

    browserFrame.contentWindow
                .QueryInterface(Ci.nsIInterfaceRequestor)
                .getInterface(Ci.nsIWebNavigation)
                .sessionHistory = Cc["@mozilla.org/browser/shistory;1"]
                                    .createInstance(Ci.nsISHistory);

    // Capture all key events so we can filter out hardware buttons
    // And send them to Gaia via mozChromeEvents.
    // Ideally, hardware buttons wouldn't generate key events at all, or
    // if they did, they would use keycodes that conform to DOM 3 Events.
    // See discussion in https://bugzilla.mozilla.org/show_bug.cgi?id=762362
    window.addEventListener('keydown', this, true);
    window.addEventListener('keypress', this, true);
    window.addEventListener('keyup', this, true);
    window.addEventListener('MozApplicationManifest', this);
    window.addEventListener('mozfullscreenchange', this);
    window.addEventListener('sizemodechange', this);
    this.contentBrowser.addEventListener('mozbrowserloadstart', this, true);

    // Until the volume can be set from the content side, set it to a
    // a specific value when the device starts. This way the front-end
    // can display a notification when the volume change and show a volume
    // level modified from this point.
    // try catch block must be used since the emulator fails here. bug 746429
    try {
      Services.audioManager.masterVolume = 0.5;
    } catch(e) {
      dump('Error setting master volume: ' + e + '\n');
    }

    CustomEventManager.init();
    WebappsHelper.init();
    AccessFu.attach(window);

    // XXX could factor out into a settings->pref map.  Not worth it yet.
    SettingsListener.observe("debug.fps.enabled", false, function(value) {
      Services.prefs.setBoolPref("layers.acceleration.draw-fps", value);
    });
    SettingsListener.observe("debug.paint-flashing.enabled", false, function(value) {
      Services.prefs.setBoolPref("nglayout.debug.paint_flashing", value);
    });

    this.contentBrowser.src = homeURL;

    ppmm.addMessageListener("content-handler", this);
  },

  stop: function shell_stop() {
    window.removeEventListener('keydown', this, true);
    window.removeEventListener('keypress', this, true);
    window.removeEventListener('keyup', this, true);
    window.removeEventListener('MozApplicationManifest', this);
    window.removeEventListener('mozfullscreenchange', this);
    window.removeEventListener('sizemodechange', this);
    this.contentBrowser.removeEventListener('mozbrowserloadstart', this, true);
    ppmm.removeMessageListener("content-handler", this);
    if (this.timer) {
      this.timer.cancel();
      this.timer = null;
    }

#ifndef MOZ_WIDGET_GONK
    delete Services.audioManager;
#endif
  },

  // If this key event actually represents a hardware button, filter it here
  // and send a mozChromeEvent with detail.type set to xxx-button-press or
  // xxx-button-release instead.
  filterHardwareKeys: function shell_filterHardwareKeys(evt) {
    var type;
    switch (evt.keyCode) {
      case evt.DOM_VK_HOME:         // Home button
        type = 'home-button';
        break;
      case evt.DOM_VK_SLEEP:        // Sleep button
      case evt.DOM_VK_END:          // On desktop we don't have a sleep button
        type = 'sleep-button';
        break;
      case evt.DOM_VK_PAGE_UP:      // Volume up button
        type = 'volume-up-button';
        break;
      case evt.DOM_VK_PAGE_DOWN:    // Volume down button
        type = 'volume-down-button';
        break;
      case evt.DOM_VK_ESCAPE:       // Back button (should be disabled)
        type = 'back-button';
        break;
      case evt.DOM_VK_CONTEXT_MENU: // Menu button
        type = 'menu-button';
        break;
      default:                      // Anything else is a real key
        return;  // Don't filter it at all; let it propagate to Gaia
    }

    // If we didn't return, then the key event represents a hardware key
    // and we need to prevent it from propagating to Gaia
    evt.stopImmediatePropagation();
    evt.preventDefault(); // Prevent keypress events (when #501496 is fixed).

    // If it is a key down or key up event, we send a chrome event to Gaia.
    // If it is a keypress event we just ignore it.
    switch (evt.type) {
      case 'keydown':
        type = type + '-press';
        break;
      case 'keyup':
        type = type + '-release';
        break;
      case 'keypress':
        return;
    }

    // On my device, the physical hardware buttons (sleep and volume)
    // send multiple events (press press release release), but the
    // soft home button just sends one.  This hack is to manually
    // "debounce" the keys. If the type of this event is the same as
    // the type of the last one, then don't send it.  We'll never send
    // two presses or two releases in a row.
    // FIXME: https://bugzilla.mozilla.org/show_bug.cgi?id=761067
    if (type !== this.lastHardwareButtonEventType) {
      this.lastHardwareButtonEventType = type;
      this.sendChromeEvent({type: type});
    }
  },

  lastHardwareButtonEventType: null, // property for the hack above
  needBufferSysMsgs: true,
  bufferedSysMsgs: [],
  timer: null,

  handleEvent: function shell_handleEvent(evt) {
    let content = this.contentBrowser.contentWindow;
    switch (evt.type) {
      case 'keydown':
      case 'keyup':
      case 'keypress':
        this.filterHardwareKeys(evt);
        break;
      case 'mozfullscreenchange':
        // When the screen goes fullscreen make sure to set the focus to the
        // main window so noboby can prevent the ESC key to get out fullscreen
        // mode
        if (document.mozFullScreen)
          Services.fm.focusedWindow = window;
        break;
      case 'sizemodechange':
        if (window.windowState == window.STATE_MINIMIZED) {
          this.contentBrowser.setVisible(false);
        } else {
          this.contentBrowser.setVisible(true);
        }
        break;
      case 'mozbrowserloadstart':
        if (content.document.location == 'about:blank')
          return;

        this.contentBrowser.removeEventListener('mozbrowserloadstart', this, true);

        this.reportCrash();

        let chromeWindow = window.QueryInterface(Ci.nsIDOMChromeWindow);
        chromeWindow.browserDOMWindow = new nsBrowserAccess();

        Cu.import('resource://gre/modules/Webapps.jsm');
        DOMApplicationRegistry.allAppsLaunchable = true;

        this.sendEvent(window, 'ContentStart');
        break;
      case 'MozApplicationManifest':
        try {
          if (!Services.prefs.getBoolPref('browser.cache.offline.enable'))
            return;

          let contentWindow = evt.originalTarget.defaultView;
          let documentElement = contentWindow.document.documentElement;
          if (!documentElement)
            return;

          let manifest = documentElement.getAttribute('manifest');
          if (!manifest)
            return;

          let principal = contentWindow.document.nodePrincipal;
          if (Services.perms.testPermissionFromPrincipal(principal, 'offline-app') == Ci.nsIPermissionManager.UNKNOWN_ACTION) {
            if (Services.prefs.getBoolPref('browser.offline-apps.notify')) {
              // FIXME Bug 710729 - Add a UI for offline cache notifications
              return;
            }
            return;
          }

          Services.perms.addFromPrincipal(principal, 'offline-app',
                                          Ci.nsIPermissionManager.ALLOW_ACTION);

          let manifestURI = Services.io.newURI(manifest, null, documentURI);
          let updateService = Cc['@mozilla.org/offlinecacheupdate-service;1']
                              .getService(Ci.nsIOfflineCacheUpdateService);
          updateService.scheduleUpdate(manifestURI, documentURI, window);
        } catch (e) {
          dump('Error while creating offline cache: ' + e + '\n');
        }
        break;
    }
  },

  sendEvent: function shell_sendEvent(content, type, details) {
    let event = content.document.createEvent('CustomEvent');
    event.initCustomEvent(type, true, true, details ? details : {});
    content.dispatchEvent(event);
  },

  sendChromeEvent: function shell_sendChromeEvent(details) {
    this.sendEvent(getContentWindow(), "mozChromeEvent",
                   ObjectWrapper.wrap(details, getContentWindow()));
  },

  sendSystemMessage: function shell_sendSystemMessage(msg) {
    let origin = Services.io.newURI(msg.manifest, null, null).prePath;
    this.sendChromeEvent({
      type: 'open-app',
      url: msg.uri,
      manifestURL: msg.manifest,
      isActivity: (msg.type == 'activity'),
      target: msg.target
    });
  },

  receiveMessage: function shell_receiveMessage(message) {
    if (message.name != 'content-handler') {
      return;
    }
    let handler = message.json;
    new MozActivity({
      name: 'view',
      data: {
        type: handler.type,
        url: handler.url,
        extras: handler.extras
      }
    });
  }
};

function nsBrowserAccess() {
}

nsBrowserAccess.prototype = {
  QueryInterface: XPCOMUtils.generateQI([Ci.nsIBrowserDOMWindow]),

  openURI: function openURI(uri, opener, where, context) {
    // TODO This should be replaced by an 'open-browser-window' intent
    let content = shell.contentBrowser.contentWindow;
    let contentWindow = content.wrappedJSObject;
    if (!('getApplicationManager' in contentWindow))
      return null;

    let applicationManager = contentWindow.getApplicationManager();
    if (!applicationManager)
      return null;

    let url = uri ? uri.spec : 'about:blank';
    let window = applicationManager.launch(url, where);
    return window.contentWindow;
  },

  openURIInFrame: function openURIInFrame(uri, opener, where, context) {
    throw new Error('Not Implemented');
  },

  isTabContentWindow: function isTabContentWindow(contentWindow) {
    return contentWindow == window;
  }
};

// Listen for system messages and relay them to Gaia.
Services.obs.addObserver(function onSystemMessage(subject, topic, data) {
  let msg = JSON.parse(data);
  // Buffer non-activity messages until content starts to load for 10 seconds.
  // We'll revisit this later if new kind of messages don't need to be cached.
  if (shell.needBufferSysMsgs && msg.type !== 'activity') {
    shell.bufferedSysMsgs.push(msg);
    return;
  }
  shell.sendSystemMessage(msg);
}, 'system-messages-open-app', false);

Services.obs.addObserver(function(aSubject, aTopic, aData) {
  shell.sendChromeEvent({ type: "fullscreenoriginchange",
                          fullscreenorigin: aData });
}, "fullscreen-origin-change", false);

Services.obs.addObserver(function onWebappsReady(subject, topic, data) {
  shell.sendChromeEvent({ type: 'webapps-registry-ready' });
}, 'webapps-registry-ready', false);

Services.obs.addObserver(function onBluetoothVolumeChange(subject, topic, data) {
  if (data == 'up') {
    shell.sendChromeEvent({ type: 'volume-up-button-press' });
    shell.sendChromeEvent({ type: 'volume-up-button-release' });
  } else if (data == 'down') {
    shell.sendChromeEvent({ type: 'volume-down-button-press' });
    shell.sendChromeEvent({ type: 'volume-down-button-release' });
  }
}, 'bluetooth-volume-change', false);

(function Repl() {
  if (!Services.prefs.getBoolPref('b2g.remote-js.enabled')) {
    return;
  }
  const prompt = 'JS> ';
  let output;
  let reader = {
    onInputStreamReady : function repl_readInput(input) {
      let sin = Cc['@mozilla.org/scriptableinputstream;1']
                  .createInstance(Ci.nsIScriptableInputStream);
      sin.init(input);
      try {
        let val = eval(sin.read(sin.available()));
        let ret = (typeof val === 'undefined') ? 'undefined\n' : val + '\n';
        output.write(ret, ret.length);
        // TODO: check if socket has been closed
      } catch (e) {
        if (e.result === Cr.NS_BASE_STREAM_CLOSED ||
            (typeof e === 'object' && e.result === Cr.NS_BASE_STREAM_CLOSED)) {
          return;
        }
        let message = (typeof e === 'object') ? e.message + '\n' : e + '\n';
        output.write(message, message.length);
      }
      output.write(prompt, prompt.length);
      input.asyncWait(reader, 0, 0, Services.tm.mainThread);
    }
  }
  let listener = {
    onSocketAccepted: function repl_acceptConnection(serverSocket, clientSocket) {
      dump('Accepted connection on ' + clientSocket.host + '\n');
      let input = clientSocket.openInputStream(Ci.nsITransport.OPEN_BLOCKING, 0, 0)
                              .QueryInterface(Ci.nsIAsyncInputStream);
      output = clientSocket.openOutputStream(Ci.nsITransport.OPEN_BLOCKING, 0, 0);
      output.write(prompt, prompt.length);
      input.asyncWait(reader, 0, 0, Services.tm.mainThread);
    },
    onStopListening: function repl_onStopListening() {
      if (output) {
        output.close();
      }
    }
  }
  let serverPort = Services.prefs.getIntPref('b2g.remote-js.port');
  let serverSocket = Cc['@mozilla.org/network/server-socket;1']
                       .createInstance(Ci.nsIServerSocket);
  serverSocket.init(serverPort, true, -1);
  dump('Opened socket on ' + serverSocket.port + '\n');
  serverSocket.asyncListen(listener);
})();

var CustomEventManager = {
  init: function custevt_init() {
    window.addEventListener("ContentStart", (function(evt) {
      let content = shell.contentBrowser.contentWindow;
      content.addEventListener("mozContentEvent", this, false, true);

      // After content starts to load for 10 seconds, send and
      // clean up the buffered system messages if there is any.
      shell.timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
      shell.timer.initWithCallback(function timerCallback() {
        shell.bufferedSysMsgs.forEach(function sendSysMsg(msg) {
          shell.sendSystemMessage(msg);
        });
        shell.bufferedSysMsgs.length = 0;
        shell.needBufferSysMsgs = false;
        shell.timer = null;
      }, 10000, Ci.nsITimer.TYPE_ONE_SHOT);
    }).bind(this), false);
  },

  handleEvent: function custevt_handleEvent(evt) {
    let detail = evt.detail;
    dump('XXX FIXME : Got a mozContentEvent: ' + detail.type + "\n");

    switch(detail.type) {
      case 'desktop-notification-click':
      case 'desktop-notification-close':
        AlertsHelper.handleEvent(detail);
        break;
      case 'webapps-install-granted':
      case 'webapps-install-denied':
        WebappsHelper.handleEvent(detail);
        break;
      case 'select-choicechange':
        FormsHelper.handleEvent(detail);
        break;
      case 'system-message-listener-ready':
        Services.obs.notifyObservers(null, 'system-message-listener-ready', null);
        break;
    }
  }
}

var AlertsHelper = {
  _listeners: {},
  _count: 0,

  handleEvent: function alert_handleEvent(detail) {
    if (!detail || !detail.id)
      return;

    let listener = this._listeners[detail.id];
    let topic = detail.type == "desktop-notification-click" ? "alertclickcallback" : "alertfinished";
    listener.observer.observe(null, topic, listener.cookie);

    // we're done with this notification
    if (topic === "alertfinished")
      delete this._listeners[detail.id];
  },

  registerListener: function alert_registerListener(cookie, alertListener) {
    let id = "alert" + this._count++;
    this._listeners[id] = { observer: alertListener, cookie: cookie };
    return id;
  },

  showAlertNotification: function alert_showAlertNotification(imageUrl,
                                                              title,
                                                              text,
                                                              textClickable,
                                                              cookie,
                                                              alertListener,
                                                              name)
  {
    let id = this.registerListener(cookie, alertListener);
    shell.sendChromeEvent({
      type: "desktop-notification",
      id: id,
      icon: imageUrl,
      title: title,
      text: text
    });
  }
}

var WebappsHelper = {
  _installers: {},
  _count: 0,

  init: function webapps_init() {
    Services.obs.addObserver(this, "webapps-launch", false);
    Services.obs.addObserver(this, "webapps-ask-install", false);
  },

  registerInstaller: function webapps_registerInstaller(data) {
    let id = "installer" + this._count++;
    this._installers[id] = data;
    return id;
  },

  handleEvent: function webapps_handleEvent(detail) {
    if (!detail || !detail.id)
      return;

    let installer = this._installers[detail.id];
    switch (detail.type) {
      case "webapps-install-granted":
        DOMApplicationRegistry.confirmInstall(installer);
        break;
      case "webapps-install-denied":
        DOMApplicationRegistry.denyInstall(installer);
        break;
    }
  },

  observe: function webapps_observe(subject, topic, data) {
    let json = JSON.parse(data);
    json.mm = subject;

    switch(topic) {
      case "webapps-launch":
        DOMApplicationRegistry.getManifestFor(json.origin, function(aManifest) {
          if (!aManifest)
            return;

          let manifest = new DOMApplicationManifest(aManifest, json.origin);
          shell.sendChromeEvent({
            "type": "webapps-launch",
            "url": manifest.fullLaunchPath(json.startPoint),
            "manifestURL": json.manifestURL
          });
        });
        break;
      case "webapps-ask-install":
        let id = this.registerInstaller(json);
        shell.sendChromeEvent({
          type: "webapps-ask-install",
          id: id,
          app: json.app
        });
        break;
    }
  }
}

// Start the debugger server.
function startDebugger() {
  if (!DebuggerServer.initialized) {
    // Allow remote connections.
    DebuggerServer.init(function () { return true; });
    DebuggerServer.addBrowserActors();
    DebuggerServer.addActors('chrome://browser/content/dbg-browser-actors.js');
  }

  let port = Services.prefs.getIntPref('devtools.debugger.remote-port') || 6000;
  try {
    DebuggerServer.openListener(port);
  } catch (e) {
    dump('Unable to start debugger server: ' + e + '\n');
  }
}

window.addEventListener('ContentStart', function(evt) {
  if (Services.prefs.getBoolPref('devtools.debugger.remote-enabled')) {
    startDebugger();
  }
});

// This is the backend for Gaia's screenshot feature.  Gaia requests a
// screenshot by sending a mozContentEvent with detail.type set to
// 'take-screenshot'.  Then we take a screenshot and send a
// mozChromeEvent with detail.type set to 'take-screenshot-success'
// and detail.file set to the an image/png blob
window.addEventListener('ContentStart', function ss_onContentStart() {
  let content = shell.contentBrowser.contentWindow;
  content.addEventListener('mozContentEvent', function ss_onMozContentEvent(e) {
    if (e.detail.type !== 'take-screenshot')
      return;

    try {
      var canvas = document.createElementNS('http://www.w3.org/1999/xhtml',
                                            'canvas');
      var width = window.innerWidth;
      var height = window.innerHeight;
      canvas.setAttribute('width', width);
      canvas.setAttribute('height', height);

      var context = canvas.getContext('2d');
      var flags =
        context.DRAWWINDOW_DRAW_CARET |
        context.DRAWWINDOW_DRAW_VIEW |
        context.DRAWWINDOW_USE_WIDGET_LAYERS;
      context.drawWindow(window, 0, 0, width, height,
                         'rgb(255,255,255)', flags);

      // I can't use sendChromeEvent() here because it doesn't wrap
      // the blob in the detail object correctly. So I use __exposedProps__
      // instead to safely send the chrome detail object to content.
      shell.sendEvent(getContentWindow(), 'mozChromeEvent', {
        __exposedProps__: { type: 'r', file: 'r' },
        type: 'take-screenshot-success',
        file: canvas.mozGetAsFile('screenshot', 'image/png')
      });
    } catch (e) {
      dump('exception while creating screenshot: ' + e + '\n');
      shell.sendChromeEvent({
        type: 'take-screenshot-error',
        error: String(e)
      });
    }
  });
});

(function geolocationStatusTracker() {
  let gGeolocationActiveCount = 0;

  Services.obs.addObserver(function(aSubject, aTopic, aData) {
    let oldCount = gGeolocationActiveCount;
    if (aData == "starting") {
      gGeolocationActiveCount += 1;
    } else if (aData == "shutdown") {
      gGeolocationActiveCount -= 1;
    }

    // We need to track changes from 1 <-> 0
    if (gGeolocationActiveCount + oldCount == 1) {
      shell.sendChromeEvent({
        type: 'geolocation-status',
        active: (gGeolocationActiveCount == 1)
      });
    }
}, "geolocation-device-events", false);
})();

(function headphonesStatusTracker() {
  Services.obs.addObserver(function(aSubject, aTopic, aData) {
    shell.sendChromeEvent({
      type: 'headphones-status-changed',
      state: aData
    });
}, "headphones-status-changed", false);
})();

(function recordingStatusTracker() {
  let gRecordingActiveCount = 0;

  Services.obs.addObserver(function(aSubject, aTopic, aData) {
    let oldCount = gRecordingActiveCount;
    if (aData == "starting") {
      gRecordingActiveCount += 1;
    } else if (aData == "shutdown") {
      gRecordingActiveCount -= 1;
    }

    // We need to track changes from 1 <-> 0
    if (gRecordingActiveCount + oldCount == 1) {
      shell.sendChromeEvent({
        type: 'recording-status',
        active: (gRecordingActiveCount == 1)
      });
    }
}, "recording-device-events", false);
})();

(function volumeStateTracker() {
  Services.obs.addObserver(function(aSubject, aTopic, aData) {
    shell.sendChromeEvent({
      type: 'volume-state-changed',
      active: (aData == 'Shared')
    });
}, 'volume-state-changed', false);
})();