| // Copyright 2012 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 CC_FRAME_RATE_COUNTER_H_ |
| #define CC_FRAME_RATE_COUNTER_H_ |
| |
| #include "base/basictypes.h" |
| #include "base/memory/scoped_ptr.h" |
| #include "base/time.h" |
| |
| namespace cc { |
| |
| // This class maintains a history of timestamps, and provides functionality to |
| // intelligently compute average frames per second. |
| class FrameRateCounter { |
| public: |
| static scoped_ptr<FrameRateCounter> create(bool hasImplThread); |
| |
| void markBeginningOfFrame(base::TimeTicks timestamp); |
| void markEndOfFrame(); |
| int currentFrameNumber() const { return m_currentFrameNumber; } |
| double getAverageFPS() const; |
| int timeStampHistorySize() const { return kTimeStampHistorySize; } |
| |
| // n = 0 returns the oldest frame retained in the history, |
| // while n = timeStampHistorySize() - 1 returns the timestamp most recent frame. |
| // FIXME: Returns most recent timestamp for n = 0 when called between markBeginningOfFrame and markEndOfFrame calls. |
| base::TimeTicks timeStampOfRecentFrame(int n) const; |
| |
| // This is a heuristic that can be used to ignore frames in a reasonable way. Returns |
| // true if the given frame interval is too fast or too slow, based on constant thresholds. |
| bool isBadFrameInterval(base::TimeDelta intervalBetweenConsecutiveFrames) const; |
| |
| int droppedFrameCount() const { return m_droppedFrameCount; } |
| |
| private: |
| explicit FrameRateCounter(bool hasImplThread); |
| |
| base::TimeDelta frameInterval(int frameNumber) const; |
| int frameIndex(int frameNumber) const; |
| bool isBadFrame(int frameNumber) const; |
| |
| // Two thresholds (measured in seconds) that describe what is considered to be a "no-op frame" that should not be counted. |
| // - if the frame is too fast, then given our compositor implementation, the frame probably was a no-op and did not draw. |
| // - if the frame is too slow, then there is probably not animating content, so we should not pollute the average. |
| static const double kFrameTooFast; |
| static const double kFrameTooSlow; |
| |
| // If a frame takes longer than this threshold (measured in seconds) then we |
| // (naively) assume that it missed a screen refresh; that is, we dropped a frame. |
| // FIXME: Determine this threshold based on monitor refresh rate, crbug.com/138642. |
| static const double kDroppedFrameTime; |
| |
| static const int kTimeStampHistorySize = 170; |
| |
| bool m_hasImplThread; |
| |
| int m_currentFrameNumber; |
| base::TimeTicks m_timeStampHistory[kTimeStampHistorySize]; |
| |
| int m_droppedFrameCount; |
| |
| DISALLOW_COPY_AND_ASSIGN(FrameRateCounter); |
| }; |
| |
| } // namespace cc |
| |
| #endif // CC_FRAME_RATE_COUNTER_H_ |