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141 lines
6.0 KiB
Plaintext
141 lines
6.0 KiB
Plaintext
/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla Communicator client code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Alec Flett <alecf@netscape.com>
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* Brian Nesse <bnesse@netscape.com>
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* Benjamin Smedberg <benjamin@smedbergs.us>
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#include "nsIPrefBranch.idl"
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interface nsIObserver;
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/**
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* nsIPrefBranch2 allows clients to observe changes to pref values.
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*
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* @see nsIPrefBranch
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*/
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[scriptable, uuid(784de8e2-e72f-441a-ae74-9d5fdfe13be3)]
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interface nsIPrefBranch2 : nsIPrefBranch
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{
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/**
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* Add a preference change observer. On preference changes, the following
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* arguments will be passed to the nsIObserver.observe() method:
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* aSubject - The nsIPrefBranch object (this)
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* aTopic - The string defined by NS_PREFBRANCH_PREFCHANGE_TOPIC_ID
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* aData - The name of the preference which has changed, relative to
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* the |root| of the aSubject branch.
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*
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* aSubject.get*Pref(aData) will get the new value of the modified
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* preference. For example, if your observer is registered with
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* addObserver("bar.", ...) on a branch with root "foo.", modifying
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* the preference "foo.bar.baz" will trigger the observer, and aData
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* parameter will be "bar.baz".
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*
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* @param aDomain The preference on which to listen for changes. This can
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* be the name of an entire branch to observe.
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* e.g. Holding the "root" prefbranch and calling
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* addObserver("foo.bar.", ...) will observe changes to
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* foo.bar.baz and foo.bar.bzip
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* @param aObserver The object to be notified if the preference changes.
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* @param aHoldWeak true Hold a weak reference to |aObserver|. The object
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* must implement the nsISupportsWeakReference
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* interface or this will fail.
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* false Hold a strong reference to |aObserver|.
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*
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* @note
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* Registering as a preference observer can open an object to potential
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* cyclical references which will cause memory leaks. These cycles generally
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* occur because an object both registers itself as an observer (causing the
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* branch to hold a reference to the observer) and holds a reference to the
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* branch object for the purpose of getting/setting preference values. There
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* are 3 approaches which have been implemented in an attempt to avoid these
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* situations.
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* 1) The nsPrefBranch object supports nsISupportsWeakReference. Any consumer
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* may hold a weak reference to it instead of a strong one.
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* 2) The nsPrefBranch object listens for xpcom-shutdown and frees all of the
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* objects currently in its observer list. This ensures that long lived
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* objects (services for example) will be freed correctly.
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* 3) The observer can request to be held as a weak reference when it is
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* registered. This insures that shorter lived objects (say one tied to an
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* open window) will not fall into the cyclical reference trap.
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*
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* @note
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* The list of registered observers may be changed during the dispatch of
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* nsPref:changed notification. However, the observers are not guaranteed
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* to be notified in any particular order, so you can't be sure whether the
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* added/removed observer will be called during the notification when it
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* is added/removed.
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*
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* @note
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* It is possible to change preferences during the notification.
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*
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* @note
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* It is not safe to change observers during this callback in Gecko
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* releases before 1.9. If you want a safe way to remove a pref observer,
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* please use an nsITimer.
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*
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* @see nsIObserver
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* @see removeObserver
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*/
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void addObserver(in string aDomain, in nsIObserver aObserver,
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in boolean aHoldWeak);
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/**
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* Remove a preference change observer.
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*
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* @param aDomain The preference which is being observed for changes.
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* @param aObserver An observer previously registered with addObserver().
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*
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* @note
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* Note that you must call removeObserver() on the same nsIPrefBranch2
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* instance on which you called addObserver() in order to remove aObserver;
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* otherwise, the observer will not be removed.
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*
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* @see nsIObserver
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* @see addObserver
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*/
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void removeObserver(in string aDomain, in nsIObserver aObserver);
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};
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%{C++
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/**
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* Notification sent when a preference changes.
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*/
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#define NS_PREFBRANCH_PREFCHANGE_TOPIC_ID "nsPref:changed"
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%}
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