mirror of
https://github.com/mozilla/gecko-dev.git
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218 lines
7.2 KiB
C++
218 lines
7.2 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=2 sw=2 et tw=78: */
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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.org code.
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*
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* The Initial Developer of the Original Code is Mozilla.org.
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* Portions created by the Initial Developer are Copyright (C) 2008
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Robert O'Callahan <robert@ocallahan.org>
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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 of the GNU General Public License Version 2 or later (the "GPL"),
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* or 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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#ifndef NSREFERENCEDELEMENT_H_
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#define NSREFERENCEDELEMENT_H_
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#include "mozilla/dom/Element.h"
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#include "nsIAtom.h"
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#include "nsIDocument.h"
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#include "nsThreadUtils.h"
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#include "nsAutoPtr.h"
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class nsIURI;
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class nsCycleCollectionCallback;
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/**
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* Class to track what element is referenced by a given ID.
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*
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* To use it, call Reset() to set it up to watch a given URI. Call get()
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* anytime to determine the referenced element (which may be null if
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* the element isn't found). When the element changes, ElementChanged
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* will be called, so subclass this class if you want to receive that
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* notification. ElementChanged runs at safe-for-script time, i.e. outside
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* of the content update. Call Unlink() if you want to stop watching
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* for changes (get() will then return null).
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*
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* By default this is a single-shot tracker --- i.e., when ElementChanged
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* fires, we will automatically stop tracking. get() will continue to return
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* the changed-to element.
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* Override IsPersistent to return PR_TRUE if you want to keep tracking after
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* the first change.
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*/
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class nsReferencedElement {
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public:
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typedef mozilla::dom::Element Element;
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nsReferencedElement() {}
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~nsReferencedElement() {
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Unlink();
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}
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/**
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* Find which element, if any, is referenced.
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*/
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Element* get() { return mElement; }
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/**
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* Set up the reference. This can be called multiple times to
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* change which reference is being tracked, but these changes
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* do not trigger ElementChanged.
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* @param aFrom the source element for context
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* @param aURI the URI containing a hash-reference to the element
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* @param aWatch if false, then we do not set up the notifications to track
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* changes, so ElementChanged won't fire and get() will always return the same
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* value, the current element for the ID.
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* @param aReferenceImage whether the ID references image elements which are
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* subject to the document's mozSetImageElement overriding mechanism.
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*/
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void Reset(nsIContent* aFrom, nsIURI* aURI, bool aWatch = true,
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bool aReferenceImage = false);
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/**
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* A variation on Reset() to set up a reference that consists of the ID of
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* an element in the same document as aFrom.
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* @param aFrom the source element for context
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* @param aID the ID of the element
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* @param aWatch if false, then we do not set up the notifications to track
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* changes, so ElementChanged won't fire and get() will always return the same
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* value, the current element for the ID.
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*/
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void ResetWithID(nsIContent* aFrom, const nsString& aID,
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bool aWatch = true);
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/**
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* Clears the reference. ElementChanged is not triggered. get() will return
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* null.
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*/
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void Unlink();
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void Traverse(nsCycleCollectionTraversalCallback* aCB);
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protected:
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/**
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* Override this to be notified of element changes. Don't forget
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* to call this superclass method to change mElement. This is called
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* at script-runnable time.
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*/
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virtual void ElementChanged(Element* aFrom, Element* aTo) {
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mElement = aTo;
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}
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/**
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* Override this to convert from a single-shot notification to
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* a persistent notification.
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*/
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virtual bool IsPersistent() { return false; }
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/**
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* Set ourselves up with our new document. Note that aDocument might be
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* null. Either aWatch must be false or aRef must be empty.
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*/
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void HaveNewDocument(nsIDocument* aDocument, bool aWatch,
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const nsString& aRef);
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private:
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static bool Observe(Element* aOldElement,
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Element* aNewElement, void* aData);
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class Notification : public nsISupports {
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public:
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virtual void SetTo(Element* aTo) = 0;
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virtual void Clear() { mTarget = nsnull; }
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virtual ~Notification() {}
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protected:
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Notification(nsReferencedElement* aTarget)
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: mTarget(aTarget)
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{
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NS_PRECONDITION(aTarget, "Must have a target");
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}
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nsReferencedElement* mTarget;
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};
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class ChangeNotification : public nsRunnable,
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public Notification
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{
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public:
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ChangeNotification(nsReferencedElement* aTarget,
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Element* aFrom, Element* aTo)
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: Notification(aTarget), mFrom(aFrom), mTo(aTo)
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{}
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virtual ~ChangeNotification() {}
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NS_DECL_ISUPPORTS_INHERITED
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NS_IMETHOD Run() {
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if (mTarget) {
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mTarget->mPendingNotification = nsnull;
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mTarget->ElementChanged(mFrom, mTo);
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}
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return NS_OK;
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}
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virtual void SetTo(Element* aTo) { mTo = aTo; }
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virtual void Clear()
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{
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Notification::Clear(); mFrom = nsnull; mTo = nsnull;
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}
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protected:
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nsRefPtr<Element> mFrom;
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nsRefPtr<Element> mTo;
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};
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friend class ChangeNotification;
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class DocumentLoadNotification : public Notification,
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public nsIObserver
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{
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public:
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DocumentLoadNotification(nsReferencedElement* aTarget,
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const nsString& aRef) :
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Notification(aTarget)
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{
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if (!mTarget->IsPersistent()) {
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mRef = aRef;
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}
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}
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virtual ~DocumentLoadNotification() {}
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NS_DECL_ISUPPORTS
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NS_DECL_NSIOBSERVER
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private:
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virtual void SetTo(Element* aTo) { }
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nsString mRef;
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};
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friend class DocumentLoadNotification;
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nsCOMPtr<nsIAtom> mWatchID;
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nsCOMPtr<nsIDocument> mWatchDocument;
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nsRefPtr<Element> mElement;
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nsRefPtr<Notification> mPendingNotification;
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bool mReferencingImage;
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};
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#endif /*NSREFERENCEDELEMENT_H_*/
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