gecko/content/base/public/nsReferencedElement.h

198 lines
6.4 KiB
C++

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