gecko-dev/layout/style/nsDOMMediaQueryList.h

80 lines
2.5 KiB
C++

/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* 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"
#include "mozilla/Attributes.h"
class nsPresContext;
class nsMediaList;
class nsDOMMediaQueryList MOZ_FINAL : 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);
bool HasListeners() const { return !mListeners.IsEmpty(); }
void RemoveAllListeners();
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_) */