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compositor_lock.h
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compositor_lock.h
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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_COMPOSITOR_COMPOSITOR_LOCK_H_
#define UI_COMPOSITOR_COMPOSITOR_LOCK_H_
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "ui/compositor/compositor_export.h"
namespace ui {
class Compositor;
class CompositorLock;
class CompositorLockClient {
public:
virtual ~CompositorLockClient() {}
// Called if the CompositorLock ends before being destroyed due to timeout.
virtual void CompositorLockTimedOut() = 0;
};
class CompositorLockDelegate {
public:
virtual ~CompositorLockDelegate() {}
// Called to perform the unlock operation.
virtual void RemoveCompositorLock(CompositorLock*) = 0;
};
// This class represents a lock on the compositor, that can be used to prevent
// commits to the compositor tree while we're waiting for an asynchronous
// event. The typical use case is when waiting for a renderer to produce a frame
// at the right size. The caller keeps a reference on this object, and drops the
// reference once it desires to release the lock.
// By default, the lock will be cancelled after a short timeout to ensure
// responsiveness of the UI, so the compositor tree should be kept in a
// "reasonable" state while the lock is held. The timeout length, or no timeout,
// can be requested at the time the lock is created.
// Don't instantiate this class directly, use Compositor::GetCompositorLock.
class COMPOSITOR_EXPORT CompositorLock {
public:
// The |client| is informed about events from the CompositorLock. The
// |delegate| is used to perform actual unlocking. If |timeout| is zero then
// no timeout is scheduled, else a timeout is scheduled on the |task_runner|.
explicit CompositorLock(CompositorLockClient* client,
base::WeakPtr<CompositorLockDelegate> delegate);
~CompositorLock();
private:
friend class Compositor;
friend class FakeCompositorLock;
// Causes the CompositorLock to end due to a timeout.
void TimeoutLock();
CompositorLockClient* const client_;
base::WeakPtr<CompositorLockDelegate> delegate_;
DISALLOW_COPY_AND_ASSIGN(CompositorLock);
};
} // namespace ui
#endif // UI_COMPOSITOR_COMPOSITOR_LOCK_H_