nsIPrefBranch2.idl
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- /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
- /* ***** BEGIN LICENSE BLOCK *****
- * Version: NPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Netscape Public License
- * Version 1.1 (the "License"); you may not use this file except in
- * compliance with the License. You may obtain a copy of the License at
- * http://www.mozilla.org/NPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is Mozilla Communicator client code.
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- * Alec Flett <alecf@netscape.com>
- * Brian Nesse <bnesse@netscape.com>
- * Benjamin Smedberg <benjamin@smedbergs.us>
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the NPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the NPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
- #include "nsIPrefBranch.idl"
- interface nsIObserver;
- /**
- * nsIPrefBranch2 allows clients to observe changes to pref values.
- *
- * @status FROZEN
- * @see nsIPrefBranch
- */
- [scriptable, uuid(74567534-eb94-4b1c-8f45-389643bfc555)]
- interface nsIPrefBranch2 : nsIPrefBranch
- {
- /**
- * Add a preference change observer. On preference changes, the following
- * arguments will be passed to the nsIObserver.observe() method:
- * aSubject - The nsIPrefBranch object (this)
- * aTopic - The string defined by NS_PREFBRANCH_PREFCHANGE_TOPIC_ID
- * aData - The preference which has changed
- *
- * @param aDomain The preference on which to listen for changes. This can
- * be the name of an entire branch to observe.
- * e.g. Holding the "root" prefbranch and calling
- * addObserver("foo.bar.", ...) will observe changes to
- * foo.bar.baz and foo.bar.bzip
- * @param aObserver The object to be notified if the preference changes.
- * @param aHoldWeak true Hold a weak reference to |aObserver|. The object
- * must implement the nsISupportsWeakReference
- * interface or this will fail.
- * false Hold a strong reference to |aObserver|.
- *
- * @note
- * Registering as a preference observer can open an object to potential
- * cyclical references which will cause memory leaks. These cycles generally
- * occur because an object both registers itself as an observer (causing the
- * branch to hold a reference to the observer) and holds a reference to the
- * branch object for the purpose of getting/setting preference values. There
- * are 3 approaches which have been implemented in an attempt to avoid these
- * situations.
- * 1) The nsPrefBranch object supports nsISupportsWeakReference. Any consumer
- * may hold a weak reference to it instead of a strong one.
- * 2) The nsPrefBranch object listens for xpcom-shutdown and frees all of the
- * objects currently in its observer list. This insures that long lived
- * objects (services for example) will be freed correctly.
- * 3) The observer can request to be held as a weak reference when it is
- * registered. This insures that shorter lived objects (say one tied to an
- * open window) will not fall into the cyclical reference trap.
- *
- * @see nsIObserver
- * @see removeObserver
- */
- void addObserver(in string aDomain, in nsIObserver aObserver,
- in boolean aHoldWeak);
- /**
- * Remove a preference change observer.
- *
- * @param aDomain The preference which is being observed for changes.
- * @param aObserver An observer previously registered with addObserver().
- *
- * @see nsIObserver
- * @see addObserver
- */
- void removeObserver(in string aDomain, in nsIObserver aObserver);
- };
- %{C++
- /**
- * Notification sent when a preference changes.
- */
- #define NS_PREFBRANCH_PREFCHANGE_TOPIC_ID "nsPref:changed"
- %}