michael@0: /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_layers_opengl_FPSCounter_h_
michael@0: #define mozilla_layers_opengl_FPSCounter_h_
michael@0: 
michael@0: #include <stddef.h>                     // for size_t
michael@0: #include <algorithm>                    // for min
michael@0: #include "GLDefs.h"                     // for GLuint
michael@0: #include "mozilla/TimeStamp.h"          // for TimeStamp, TimeDuration
michael@0: #include "nsTArray.h"                   // for nsAutoTArray, nsTArray_Impl, etc
michael@0: #include "VBOArena.h"                   // for gl::VBOArena
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace gl {
michael@0: class GLContext;
michael@0: }
michael@0: namespace layers {
michael@0: 
michael@0: class DataTextureSource;
michael@0: class ShaderProgramOGL;
michael@0: 
michael@0: const double kFpsWindowMs = 250.0;
michael@0: const size_t kNumFrameTimeStamps = 16;
michael@0: struct FPSCounter {
michael@0:   FPSCounter() : mCurrentFrameIndex(0) {
michael@0:       mFrames.SetLength(kNumFrameTimeStamps);
michael@0:   }
michael@0: 
michael@0:   // We keep a circular buffer of the time points at which the last K
michael@0:   // frames were drawn.  To estimate FPS, we count the number of
michael@0:   // frames we've drawn within the last kFPSWindowMs milliseconds and
michael@0:   // divide by the amount time since the first of those frames.
michael@0:   nsAutoTArray<TimeStamp, kNumFrameTimeStamps> mFrames;
michael@0:   size_t mCurrentFrameIndex;
michael@0: 
michael@0:   void AddFrame(TimeStamp aNewFrame) {
michael@0:     mFrames[mCurrentFrameIndex] = aNewFrame;
michael@0:     mCurrentFrameIndex = (mCurrentFrameIndex + 1) % kNumFrameTimeStamps;
michael@0:   }
michael@0: 
michael@0:   double AddFrameAndGetFps(TimeStamp aCurrentFrame) {
michael@0:     AddFrame(aCurrentFrame);
michael@0:     return EstimateFps(aCurrentFrame);
michael@0:   }
michael@0: 
michael@0:   double GetFpsAt(TimeStamp aNow) {
michael@0:     return EstimateFps(aNow);
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   double EstimateFps(TimeStamp aNow) {
michael@0:     TimeStamp beginningOfWindow =
michael@0:       (aNow - TimeDuration::FromMilliseconds(kFpsWindowMs));
michael@0:     TimeStamp earliestFrameInWindow = aNow;
michael@0:     size_t numFramesDrawnInWindow = 0;
michael@0:     for (size_t i = 0; i < kNumFrameTimeStamps; ++i) {
michael@0:       const TimeStamp& frame = mFrames[i];
michael@0:       if (!frame.IsNull() && frame > beginningOfWindow) {
michael@0:         ++numFramesDrawnInWindow;
michael@0:         earliestFrameInWindow = std::min(earliestFrameInWindow, frame);
michael@0:       }
michael@0:     }
michael@0:     double realWindowSecs = (aNow - earliestFrameInWindow).ToSeconds();
michael@0:     if (realWindowSecs == 0.0 || numFramesDrawnInWindow == 1) {
michael@0:       return 0.0;
michael@0:     }
michael@0:     return double(numFramesDrawnInWindow - 1) / realWindowSecs;
michael@0:   }
michael@0: };
michael@0: 
michael@0: struct FPSState {
michael@0:   FPSCounter mCompositionFps;
michael@0:   FPSCounter mTransactionFps;
michael@0: 
michael@0:   FPSState() {}
michael@0: 
michael@0:   void DrawFPS(TimeStamp, unsigned, Compositor* aCompositor);
michael@0: 
michael@0:   void NotifyShadowTreeTransaction() {
michael@0:     mTransactionFps.AddFrame(TimeStamp::Now());
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   RefPtr<DataTextureSource> mFPSTextureSource;
michael@0: };
michael@0: 
michael@0: }
michael@0: }
michael@0: 
michael@0: #endif // mozilla_layers_opengl_FPSCounter_h_