The Tor Browser: services/common/observers.js@b8a032363ba2 (annotated)

services/common/observers.js@b8a032363ba2 (annotated)

services/common/observers.js

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* 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/. */
 #ifndef MERGED_COMPARTMENT
 this.EXPORTED_SYMBOLS = ["Observers"];
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;
 const Cu = Components.utils;
 #endif
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 /**
  * A service for adding, removing and notifying observers of notifications.
  * Wraps the nsIObserverService interface.
  *
  * @version 0.2
  */
 this.Observers = {
   /**
    * Register the given callback as an observer of the given topic.
    *
    * @param   topic       {String}
    *          the topic to observe
    *
    * @param   callback    {Object}
    *          the callback; an Object that implements nsIObserver or a Function
    *          that gets called when the notification occurs
    *
    * @param   thisObject  {Object}  [optional]
    *          the object to use as |this| when calling a Function callback
    *
    * @returns the observer
    */
   add: function(topic, callback, thisObject) {
     let observer = new Observer(topic, callback, thisObject);
     this._cache.push(observer);
     this._service.addObserver(observer, topic, true);
     return observer;
   },
   /**
    * Unregister the given callback as an observer of the given topic.
    *
    * @param topic       {String}
    *        the topic being observed
    *
    * @param callback    {Object}
    *        the callback doing the observing
    *
    * @param thisObject  {Object}  [optional]
    *        the object being used as |this| when calling a Function callback
    */
   remove: function(topic, callback, thisObject) {
     // This seems fairly inefficient, but I'm not sure how much better
     // we can make it.  We could index by topic, but we can't index by callback
     // or thisObject, as far as I know, since the keys to JavaScript hashes
     // (a.k.a. objects) can apparently only be primitive values.
     let [observer] = this._cache.filter(function(v) v.topic      == topic    &&
                                                     v.callback   == callback &&
                                                     v.thisObject == thisObject);
     if (observer) {
       this._service.removeObserver(observer, topic);
       this._cache.splice(this._cache.indexOf(observer), 1);
     }
   },
   /**
    * Notify observers about something.
    *
    * @param topic   {String}
    *        the topic to notify observers about
    *
    * @param subject {Object}  [optional]
    *        some information about the topic; can be any JS object or primitive
    *
    * @param data    {String}  [optional] [deprecated]
    *        some more information about the topic; deprecated as the subject
    *        is sufficient to pass all needed information to the JS observers
    *        that this module targets; if you have multiple values to pass to
    *        the observer, wrap them in an object and pass them via the subject
    *        parameter (i.e.: { foo: 1, bar: "some string", baz: myObject })
    */
   notify: function(topic, subject, data) {
     subject = (typeof subject == "undefined") ? null : new Subject(subject);
        data = (typeof    data == "undefined") ? null : data;
     this._service.notifyObservers(subject, topic, data);
   },
   _service: Cc["@mozilla.org/observer-service;1"].
             getService(Ci.nsIObserverService),
   /**
    * A cache of observers that have been added.
    *
    * We use this to remove observers when a caller calls |remove|.
    *
    * XXX This might result in reference cycles, causing memory leaks,
    * if we hold a reference to an observer that holds a reference to us.
    * Could we fix that by making this an independent top-level object
    * rather than a property of this object?
    */
   _cache: []
 };
 function Observer(topic, callback, thisObject) {
   this.topic = topic;
   this.callback = callback;
   this.thisObject = thisObject;
 }
 Observer.prototype = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
   observe: function(subject, topic, data) {
     // Extract the wrapped object for subjects that are one of our wrappers
     // around a JS object.  This way we support both wrapped subjects created
     // using this module and those that are real XPCOM components.
     if (subject && typeof subject == "object" &&
         ("wrappedJSObject" in subject) &&
         ("observersModuleSubjectWrapper" in subject.wrappedJSObject))
       subject = subject.wrappedJSObject.object;
     if (typeof this.callback == "function") {
       if (this.thisObject)
         this.callback.call(this.thisObject, subject, data);
       else
         this.callback(subject, data);
     }
     else // typeof this.callback == "object" (nsIObserver)
       this.callback.observe(subject, topic, data);
   }
 }
 function Subject(object) {
   // Double-wrap the object and set a property identifying the wrappedJSObject
   // as one of our wrappers to distinguish between subjects that are one of our
   // wrappers (which we should unwrap when notifying our observers) and those
   // that are real JS XPCOM components (which we should pass through unaltered).
   this.wrappedJSObject = { observersModuleSubjectWrapper: true, object: object };
 }
 Subject.prototype = {
   QueryInterface: XPCOMUtils.generateQI([]),
   getHelperForLanguage: function() {},
   getInterfaces: function() {}
 };