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      1 // Copyright 2012 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 CC_DEBUG_FRAME_RATE_COUNTER_H_
      6 #define CC_DEBUG_FRAME_RATE_COUNTER_H_
      7 
      8 #include "base/basictypes.h"
      9 #include "base/memory/scoped_ptr.h"
     10 #include "base/time/time.h"
     11 #include "cc/debug/ring_buffer.h"
     12 
     13 namespace cc {
     14 
     15 // This class maintains a history of timestamps, and provides functionality to
     16 // intelligently compute average frames per second.
     17 class FrameRateCounter {
     18  public:
     19   static scoped_ptr<FrameRateCounter> Create(bool has_impl_thread);
     20 
     21   int current_frame_number() const { return ring_buffer_.CurrentIndex(); }
     22   int dropped_frame_count() const { return dropped_frame_count_; }
     23   size_t time_stamp_history_size() const { return ring_buffer_.BufferSize(); }
     24 
     25   void SaveTimeStamp(base::TimeTicks timestamp, bool software);
     26 
     27   // n = 0 returns the oldest frame interval retained in the history, while n =
     28   // time_stamp_history_size() - 1 returns the most recent frame interval.
     29   base::TimeDelta RecentFrameInterval(size_t n) const;
     30 
     31   // This is a heuristic that can be used to ignore frames in a reasonable way.
     32   // Returns true if the given frame interval is too fast or too slow, based on
     33   // constant thresholds.
     34   bool IsBadFrameInterval(
     35       base::TimeDelta interval_between_consecutive_frames) const;
     36 
     37   void GetMinAndMaxFPS(double* min_fps, double* max_fps) const;
     38   double GetAverageFPS() const;
     39 
     40   typedef RingBuffer<base::TimeTicks, 136> RingBufferType;
     41   RingBufferType::Iterator begin() const { return ring_buffer_.Begin(); }
     42   RingBufferType::Iterator end() const { return ring_buffer_.End(); }
     43 
     44  private:
     45   explicit FrameRateCounter(bool has_impl_thread);
     46 
     47   RingBufferType ring_buffer_;
     48 
     49   bool has_impl_thread_;
     50   int dropped_frame_count_;
     51 
     52   DISALLOW_COPY_AND_ASSIGN(FrameRateCounter);
     53 };
     54 
     55 }  // namespace cc
     56 
     57 #endif  // CC_DEBUG_FRAME_RATE_COUNTER_H_
     58