| /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| /* ***** BEGIN LICENSE BLOCK ***** |
| * Version: MPL 1.1/GPL 2.0/LGPL 2.1 |
| * |
| * The contents of this file are subject to the Mozilla 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/MPL/ |
| * |
| * 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 MPL, 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 MPL, 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 name of the preference which has changed, relative to |
| * the |root| of the aSubject branch. |
| * |
| * aSubject.get*Pref(aData) will get the new value of the modified |
| * preference. For example, if your observer is registered with |
| * addObserver("bar.", ...) on a branch with root "foo.", modifying |
| * the preference "foo.bar.baz" will trigger the observer, and aData |
| * parameter will be "bar.baz". |
| * |
| * @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 ensures 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. |
| * |
| * @note |
| * The list of registered observers may be changed during the dispatch of |
| * nsPref:changed notification. However, the observers are not guaranteed |
| * to be notified in any particular order, so you can't be sure whether the |
| * added/removed observer will be called during the notification when it |
| * is added/removed. |
| * |
| * @note |
| * It is possible to change preferences during the notification. |
| * |
| * @note |
| * It is not safe to change observers during this callback in Gecko |
| * releases before 1.9. If you want a safe way to remove a pref observer, |
| * please use an nsITimer. |
| * |
| * @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(). |
| * |
| * @note |
| * Note that you must call removeObserver() on the same nsIPrefBranch2 |
| * instance on which you called addObserver() in order to remove aObserver; |
| * otherwise, the observer will not be removed. |
| * |
| * @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" |
| |
| %} |