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      1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef UI_GL_VSYNC_PROVIDER_H_
      6 #define UI_GL_VSYNC_PROVIDER_H_
      7 
      8 #include <queue>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/callback.h"
     12 #include "base/time/time.h"
     13 #include "ui/gl/gl_export.h"
     14 
     15 namespace gfx {
     16 
     17 class GL_EXPORT VSyncProvider {
     18  public:
     19   VSyncProvider();
     20   virtual ~VSyncProvider();
     21 
     22   typedef base::Callback<void(const base::TimeTicks timebase,
     23                               const base::TimeDelta interval)>
     24       UpdateVSyncCallback;
     25 
     26   // Get the time of the most recent screen refresh, along with the time
     27   // between consecutive refreshes. The callback is called as soon as
     28   // the data is available: it could be immediately from this method,
     29   // later via a PostTask to the current MessageLoop, or never (if we have
     30   // no data source). We provide the strong guarantee that the callback will
     31   // not be called once the instance of this class is destroyed.
     32   virtual void GetVSyncParameters(const UpdateVSyncCallback& callback) = 0;
     33 
     34  private:
     35   DISALLOW_COPY_AND_ASSIGN(VSyncProvider);
     36 };
     37 
     38 // Base class for providers based on extensions like GLX_OML_sync_control and
     39 // EGL_CHROMIUM_sync_control.
     40 class SyncControlVSyncProvider : public VSyncProvider {
     41  public:
     42   SyncControlVSyncProvider();
     43   virtual ~SyncControlVSyncProvider();
     44 
     45   virtual void GetVSyncParameters(
     46       const UpdateVSyncCallback& callback) OVERRIDE;
     47 
     48  protected:
     49   virtual bool GetSyncValues(int64* system_time,
     50                              int64* media_stream_counter,
     51                              int64* swap_buffer_counter) = 0;
     52 
     53   virtual bool GetMscRate(int32* numerator, int32* denominator) = 0;
     54 
     55  private:
     56   base::TimeTicks last_timebase_;
     57   uint64 last_media_stream_counter_;
     58   base::TimeDelta last_good_interval_;
     59 
     60   // A short history of the last few computed intervals.
     61   // We use this to filter out the noise in the computation resulting
     62   // from configuration change (monitor reconfiguration, moving windows
     63   // between monitors, suspend and resume, etc.).
     64   std::queue<base::TimeDelta> last_computed_intervals_;
     65 
     66   DISALLOW_COPY_AND_ASSIGN(SyncControlVSyncProvider);
     67 };
     68 
     69 }  // namespace gfx
     70 
     71 #endif  // UI_GL_VSYNC_PROVIDER_H_
     72