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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* vim: sw=2 ts=8 et :
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*/
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef MOZILLA_LAYERS_MEMORYPRESSUREOBSERVER_H
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#define MOZILLA_LAYERS_MEMORYPRESSUREOBSERVER_H
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#include "nsIObserver.h"
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namespace mozilla {
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namespace layers {
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// A simple memory pressure observer implementation born out of the realization
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// that almost all of our memory pressure observers do exactly the same thing.
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//
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// The intended way to use it is to have the class that nees to react on memory
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// pressure inherit the MemoryPressureListener interface and own a strong
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// reference to a MemoryPressureListener object.
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// Call Unregister on the listener in the destructor of your class or whenever
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// you do not which to receive the notification anymore, otherwise the listener
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// will be held alive by the observer service (leak) and keep a dangling pointer
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// to your class.
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/// See nsIMemory.idl
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enum class MemoryPressureReason {
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LOW_MEMORY,
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LOW_MEMORY_ONGOING,
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HEAP_MINIMIZE,
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};
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class MemoryPressureListener {
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public:
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virtual void OnMemoryPressure(MemoryPressureReason aWhy) = 0;
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};
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class MemoryPressureObserver final : public nsIObserver {
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public:
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NS_DECL_ISUPPORTS
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NS_DECL_NSIOBSERVER
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// Returns null if anything goes wrong.
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static already_AddRefed<MemoryPressureObserver> Create(
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MemoryPressureListener* aListener);
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void Unregister();
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private:
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explicit MemoryPressureObserver(MemoryPressureListener* aListener);
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virtual ~MemoryPressureObserver();
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MemoryPressureListener* mListener;
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};
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} // namespace layers
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} // namespace mozilla
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#endif