gecko-dev/gfx/layers/opengl/FPSCounter.h

80 lines
2.3 KiB
C++

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