gecko-dev/layout/style/nsDOMMediaQueryList.h

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/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
/* ***** 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 nsDOMMediaQueryList.
*
* The Initial Developer of the Original Code is the Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* L. David Baron <dbaron@dbaron.org>, Mozilla Corporation (original author)
*
* 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 ***** */
/* implements DOM interface for querying and observing media queries */
#ifndef nsDOMMediaQueryList_h_
#define nsDOMMediaQueryList_h_
#include "nsIDOMMediaQueryList.h"
#include "nsCycleCollectionParticipant.h"
#include "nsAutoPtr.h"
#include "nsCOMPtr.h"
#include "nsTArray.h"
#include "prclist.h"
class nsPresContext;
class nsMediaList;
class nsDOMMediaQueryList : public nsIDOMMediaQueryList,
public PRCList
{
public:
// The caller who constructs is responsible for calling Evaluate
// before calling any other methods.
nsDOMMediaQueryList(nsPresContext *aPresContext,
const nsAString &aMediaQueryList);
private:
~nsDOMMediaQueryList();
public:
NS_DECL_CYCLE_COLLECTING_ISUPPORTS
NS_DECL_CYCLE_COLLECTION_CLASS(nsDOMMediaQueryList)
NS_DECL_NSIDOMMEDIAQUERYLIST
struct HandleChangeData {
nsRefPtr<nsDOMMediaQueryList> mql;
nsCOMPtr<nsIDOMMediaQueryListListener> listener;
};
typedef FallibleTArray< nsCOMPtr<nsIDOMMediaQueryListListener> > ListenerList;
typedef FallibleTArray<HandleChangeData> NotifyList;
// Appends listeners that need notification to aListenersToNotify
void MediumFeaturesChanged(NotifyList &aListenersToNotify);
private:
void RecomputeMatches();
// We only need a pointer to the pres context to support lazy
// reevaluation following dynamic changes. However, this lazy
// reevaluation is perhaps somewhat important, since some usage
// patterns may involve the creation of large numbers of
// MediaQueryList objects which almost immediately become garbage
// (after a single call to the .matches getter).
//
// This pointer does make us a little more dependent on cycle
// collection.
//
// We have a non-null mPresContext for our entire lifetime except
// after cycle collection unlinking. Having a non-null mPresContext
// is equivalent to being in that pres context's mDOMMediaQueryLists
// linked list.
nsRefPtr<nsPresContext> mPresContext;
nsRefPtr<nsMediaList> mMediaList;
bool mMatches;
bool mMatchesValid;
ListenerList mListeners;
};
#endif /* !defined(nsDOMMediaQueryList_h_) */