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/* 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_widget_AndroidVsync_h
#define mozilla_widget_AndroidVsync_h
#include <android/choreographer.h>
#include <memory>
#include "mozilla/DataMutex.h"
#include "mozilla/ThreadSafeWeakPtr.h"
#include "mozilla/TimeStamp.h"
#include "nsTArray.h"
namespace mozilla {
namespace widget {
/**
* A thread-safe way to listen to vsync notifications on Android. All methods
* can be called on any thread.
* Observers must keep a strong reference to the AndroidVsync instance until
* they unregister themselves.
*/
class AndroidVsync final : public SupportsThreadSafeWeakPtr<AndroidVsync> {
public:
MOZ_DECLARE_REFCOUNTED_TYPENAME(AndroidVsync)
static RefPtr<AndroidVsync> GetInstance();
class Observer {
public:
// Will be called on the Java UI thread.
virtual void OnVsync(const TimeStamp& aTimeStamp) = 0;
// Will be called on the Java UI thread.
virtual void OnMaybeUpdateRefreshRate() {}
// Called when the observer is unregistered, in case it wants to
// manage its own lifetime.
virtual void Dispose() {}
virtual ~Observer() = default;
};
// INPUT observers are called before RENDER observers.
enum ObserverType { INPUT, RENDER };
void RegisterObserver(Observer* aObserver, ObserverType aType);
void UnregisterObserver(Observer* aObserver, ObserverType aType);
void OnMaybeUpdateRefreshRate();
private:
AndroidVsync() = default;
// A heap allocated weak pointer to an AndroidVsync object, intended to be
// passed as the `data` argument to AChoreographer_postFrameCallback(64),
// allowing the callback functions to check whether the AndroidVsync is still
// alive. Unique ownership ensures we will only post a single callback at a
// time.
using CallbackToken = std::unique_ptr<ThreadSafeWeakPtr<AndroidVsync>>;
// Posts a frame callback if we have registered observers and one is not
// already pending.
void MaybePostFrameCallback();
static void PostFrameCallback(AChoreographer* aChoreographer,
CallbackToken aToken);
// Frame callback used on SDK levels prior to 28.
static void FrameCallback(long aFrameTimeNanos, void* aData);
// Frame callback used on SDK levels 29 onward.
static void FrameCallback64(int64_t aFrameTimeNanos, void* aData);
struct Impl {
// If we should and are able to post a frame callback then returns the data
// required to do so, transferring ownership of mToken to the caller.
Maybe<std::pair<AChoreographer*, CallbackToken>> ShouldPostFrameCallback();
nsTArray<Observer*> mInputObservers;
nsTArray<Observer*> mRenderObservers;
// Must be initialized on the Android UI thread. Never modified or destroyed
// after initialization.
AChoreographer* mChoreographer = nullptr;
// If null, indicates that a frame callback is pending and another should
// not be scheduled. If non-null, we are allowed to post a new callback.
// This is set to point to the owning AndroidVsync on initialization, and
// ownership is transferred by ShouldPostFrameCallback(). It is the
// callback's responsibility to restore this field when finished with the
// token.
CallbackToken mToken;
};
DataMutex<Impl> mImpl{"AndroidVsync.mImpl"};
static StaticDataMutex<ThreadSafeWeakPtr<AndroidVsync>> sInstance;
};
} // namespace widget
} // namespace mozilla
#endif // mozilla_widget_AndroidVsync_h