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ObserverUtils.jsm
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/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 :miv */
/*
//
// BEGIN SONGBIRD GPL
//
// This file is part of the Songbird web player.
//
// Copyright(c) 2005-2008 POTI, Inc.
// http://songbirdnest.com
//
// This file may be licensed under the terms of of the
// GNU General Public License Version 2 (the "GPL").
//
// Software distributed under the License is distributed
// on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either
// express or implied. See the GPL for the specific language
// governing rights and limitations.
//
// You should have received a copy of the GPL along with this
// program. If not, go to http://www.gnu.org/licenses/gpl.html
// or write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
//
// END SONGBIRD GPL
//
*/
/**
* \file ObserverUtils.jsm
* \brief Javascript source for the observer utilities.
*/
//------------------------------------------------------------------------------
//
// Observer utilities configuration.
//
//------------------------------------------------------------------------------
EXPORTED_SYMBOLS = [ "ObserverSet" ];
//------------------------------------------------------------------------------
//
// Observer utility defs.
//
//------------------------------------------------------------------------------
const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results
const Cu = Components.utils
//------------------------------------------------------------------------------
//
// Observer set services.
//
// These services may be used to maintain a set of observers and to facilitate
// the removal of them.
//
//------------------------------------------------------------------------------
/**
* Construct an observer set object.
*/
function ObserverSet()
{
// Get the observer services.
this._observerSvc = Cc["@mozilla.org/observer-service;1"]
.getService(Ci.nsIObserverService);
// Initialize some fields.
this._observerList = {};
}
// Define the class.
ObserverSet.prototype = {
// Set the constructor.
constructor: ObserverSet,
//
// Observer set fields.
//
// _observerSvc Mozilla observer service.
// _observerList List of observers.
// _nextObserverID Next observer ID.
//
_observerSvc: null,
_observerList: null,
_nextObserverID: 0,
/**
* Add the observer object specified by aObserver as an observer of the event
* topic specified by aTopic with weak ownership as specified by aOwnsWeak.
* If aIsOneShot is true, the observer is removed after the first event is
* observed.
* Return an observer ID that may be used with remove.
*
* \param aObserver Observer object.
* \param aTopic Observer topic.
* \param aOwnsWeak Weak ownership.
* \param aIsOneShot True if observer should be removed after the
* first event.
*
* \return Observer ID.
*/
add: function ObserverSet_add(aObserver,
aTopic,
aOwnsWeak,
aIsOneShot) {
// Create the observer set entry object.
var observerEntry = {};
observerEntry.id = this._nextObserverID++;
observerEntry.observer = aObserver;
observerEntry.topic = aTopic;
observerEntry.ownsWeak = aOwnsWeak;
observerEntry.isOneShot = aIsOneShot;
// Use one-shot observer wrapper if observer is one-shot.
var observer = observerEntry.observer;
if (observerEntry.isOneShot) {
var _this = this;
observer = {
observe: function(aSubject, aTopic, aData) {
return _this._doOneShot(observerEntry, aSubject, aTopic, aData);
}
};
}
observerEntry.addedObserver = observer;
// Add the observer.
this._observerSvc.addObserver(observerEntry.addedObserver,
observerEntry.topic,
observerEntry.ownsWeak);
this._observerList[observerEntry.id] = observerEntry;
return observerEntry.id;
},
/**
* Remove the observer specified by aObserverID.
*
* \param aObserverID ID of observer to remove.
*/
remove: function ObserverSet_remove(aObserverID) {
// Get the observer set entry. Do nothing if not found.
var observerEntry = this._observerList[aObserverID];
if (!observerEntry)
return;
// Remove the observer.
this._observerSvc.removeObserver(observerEntry.addedObserver,
observerEntry.topic,
observerEntry.ownsWeak);
delete this._observerList[aObserverID];
},
/**
* Remove all observers.
*/
removeAll: function ObserverSet_removeAll() {
// Remove all observers.
for (var id in this._observerList) {
this.remove(id);
}
this._observerList = {};
},
//----------------------------------------------------------------------------
//
// Internal observer set services.
//
//----------------------------------------------------------------------------
/**
* Dispatch the observed event specified by aSubject, aTopic, and aData to the
* one-shot observer entry specified aObserverEntry and remove the observer.
*
* \param aObserverEntry One-shot observer entry.
* \param aSubject Event subject.
* \param aTopic Event topic.
* \param aData Event data.
*/
_doOneShot: function ObserverSet__doOneShot(aObserverEntry,
aSubject,
aTopic,
aData) {
// Dispatch event to observer.
return aObserverEntry.observer.observe(aSubject, aTopic, aData);
}
};