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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: sw=2 ts=8 et :
*/
/* 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/. */
#ifndef MOZILLA_LAYERS_MEMORYPRESSUREOBSERVER_H
#define MOZILLA_LAYERS_MEMORYPRESSUREOBSERVER_H
#include "nsIObserver.h"
namespace mozilla {
namespace layers {
// A simple memory pressure observer implementation born out of the realization
// that almost all of our memory pressure observers do exactly the same thing.
//
// The intended way to use it is to have the class that nees to react on memory
// pressure inherit the MemoryPressureListener interface and own a strong
// reference to a MemoryPressureListener object.
// Call Unregister on the listener in the destructor of your class or whenever
// you do not which to receive the notification anymore, otherwise the listener
// will be held alive by the observer service (leak) and keep a dangling pointer
// to your class.
/// See nsIMemory.idl
enum class MemoryPressureReason {
LOW_MEMORY,
LOW_MEMORY_ONGOING,
HEAP_MINIMIZE,
};
class MemoryPressureListener {
public:
virtual void OnMemoryPressure(MemoryPressureReason aWhy) = 0;
};
class MemoryPressureObserver final : public nsIObserver {
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIOBSERVER
// Returns null if anything goes wrong.
static already_AddRefed<MemoryPressureObserver> Create(
MemoryPressureListener* aListener);
void Unregister();
private:
explicit MemoryPressureObserver(MemoryPressureListener* aListener);
~MemoryPressureObserver();
MemoryPressureListener* mListener;
};
} // namespace layers
} // namespace mozilla
#endif
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