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// Copyright 2014 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.
#include "base/memory/ref_counted.h"
#include "base/observer_list.h"
#include "base/synchronization/lock.h"
#include "base/time/time.h"
#include "ui/compositor/compositor_export.h"
namespace ui {
// This class manages vsync parameters for a compositor. It merges updates of
// the parameters from different sources and sends the merged updates to
// observers which register to it.
class COMPOSITOR_EXPORT CompositorVSyncManager
: public base::RefCounted<CompositorVSyncManager> {
class Observer {
virtual void OnUpdateVSyncParameters(base::TimeTicks timebase,
base::TimeDelta interval) = 0;
// The "authoritative" vsync interval, if provided, will override |interval|
// as reported by UpdateVSyncParameters() whenever it is called. This is
// typically the value reported by a more reliable source, e.g. the platform
// display configuration. In the particular case of ChromeOS -- this is the
// value queried through XRandR, which is more reliable than the value
// queried through the 3D context.
void SetAuthoritativeVSyncInterval(base::TimeDelta interval);
// The vsync parameters consist of |timebase|, which is the platform timestamp
// of the last vsync, and |interval|, which is the interval between vsyncs.
// |interval| may be overriden by SetAuthoritativeVSyncInterval() above.
void UpdateVSyncParameters(base::TimeTicks timebase,
base::TimeDelta interval);
void AddObserver(Observer* observer);
void RemoveObserver(Observer* observer);
friend class base::RefCounted<CompositorVSyncManager>;
void NotifyObservers(base::TimeTicks timebase, base::TimeDelta interval);
ObserverList<Observer> observer_list_;
base::TimeTicks last_timebase_;
base::TimeDelta last_interval_;
base::TimeDelta authoritative_vsync_interval_;
} // namespace ui