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// Copyright 2013 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_GFX_VSYNC_PROVIDER_H_
#define UI_GFX_VSYNC_PROVIDER_H_
#include "base/callback.h"
#include "base/time/time.h"
#include "ui/gfx/gfx_export.h"
namespace gfx {
class GFX_EXPORT VSyncProvider {
public:
virtual ~VSyncProvider() {}
typedef base::Callback<
void(const base::TimeTicks timebase, const base::TimeDelta interval)>
UpdateVSyncCallback;
// Get the time of the most recent screen refresh, along with the time
// between consecutive refreshes. The callback is called as soon as
// the data is available: it could be immediately from this method,
// later via a PostTask to the current MessageLoop, or never (if we have
// no data source). We provide the strong guarantee that the callback will
// not be called once the instance of this class is destroyed.
virtual void GetVSyncParameters(const UpdateVSyncCallback& callback) = 0;
// Similar to GetVSyncParameters(). It returns true, if the data is available.
// Otherwise false is returned.
virtual bool GetVSyncParametersIfAvailable(base::TimeTicks* timebase,
base::TimeDelta* interval) = 0;
// Returns true, if GetVSyncParametersIfAvailable is supported.
virtual bool SupportGetVSyncParametersIfAvailable() const = 0;
// Returns true, if VSyncProvider gets VSync timebase from HW.
virtual bool IsHWClock() const = 0;
};
// Provides a constant timebase and interval.
class GFX_EXPORT FixedVSyncProvider : public VSyncProvider {
public:
FixedVSyncProvider(base::TimeTicks timebase, base::TimeDelta interval)
: timebase_(timebase), interval_(interval) {
}
~FixedVSyncProvider() override {}
void GetVSyncParameters(const UpdateVSyncCallback& callback) override;
bool GetVSyncParametersIfAvailable(base::TimeTicks* timebase,
base::TimeDelta* interval) override;
bool SupportGetVSyncParametersIfAvailable() const override;
bool IsHWClock() const override;
private:
base::TimeTicks timebase_;
base::TimeDelta interval_;
};
} // namespace gfx
#endif // UI_GFX_VSYNC_PROVIDER_H_
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