// 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 CCFrameRateCounter_h #define CCFrameRateCounter_h #if USE(ACCELERATED_COMPOSITING) #include #include namespace cc { // This class maintains a history of timestamps, and provides functionality to // intelligently compute average frames per second (and standard deviation). class CCFrameRateCounter { WTF_MAKE_NONCOPYABLE(CCFrameRateCounter); public: static PassOwnPtr create() { return adoptPtr(new CCFrameRateCounter()); } void markBeginningOfFrame(double timestamp); void markEndOfFrame(); int currentFrameNumber() const { return m_currentFrameNumber; } void getAverageFPSAndStandardDeviation(double& averageFPS, double& standardDeviation) 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. double timeStampOfRecentFrame(int /* n */); // 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(double intervalBetweenConsecutiveFrames) const; int droppedFrameCount() const { return m_droppedFrameCount; } private: CCFrameRateCounter(); double 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 = 120; int m_currentFrameNumber; double m_timeStampHistory[kTimeStampHistorySize]; int m_droppedFrameCount; }; } // namespace cc #endif // USE(ACCELERATED_COMPOSITING) #endif