The Tor Browser / file revision

 /* 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";

 module.metadata = {

   "stability": "unstable"

 };

 const { EventEmitterTrait: EventEmitter } = require("../deprecated/events");

 const { WindowTracker, windowIterator } = require("../deprecated/window-utils");

 const { DOMEventAssembler } = require("../deprecated/events/assembler");

 const { Trait } = require("../deprecated/light-traits");

 // Event emitter objects used to register listeners and emit events on them

 // when they occur.

 const observer = Trait.compose(DOMEventAssembler, EventEmitter).create({

   /**

    * Method is implemented by `EventEmitter` and is used just for emitting

    * events on registered listeners.

    */

   _emit: Trait.required,

   /**

    * Events that are supported and emitted by the module.

    */

   supportedEventsTypes: [ "activate", "deactivate" ],

   /**

    * Function handles all the supported events on all the windows that are

    * observed. Method is used to proxy events to the listeners registered on

    * this event emitter.

    * @param {Event} event

    *    Keyboard event being emitted.

    */

   handleEvent: function handleEvent(event) {

     this._emit(event.type, event.target, event);

   }

 });

 // Using `WindowTracker` to track window events.

 WindowTracker({

   onTrack: function onTrack(chromeWindow) {

     observer._emit("open", chromeWindow);

     observer.observe(chromeWindow);

   },

   onUntrack: function onUntrack(chromeWindow) {

     observer._emit("close", chromeWindow);

     observer.ignore(chromeWindow);

   }

 });

 exports.observer = observer;