Function ovr_GetPredictedDisplayTime

ReviveXR/REV_CAPI.cpp:1241–1282

}

OVR_PUBLIC_FUNCTION(double) ovr_GetPredictedDisplayTime(ovrSession session, long long frameIndex)
{
	if (!session)
		return ovr_GetTimeInSeconds();

	REV_TRACE(ovr_GetPredictedDisplayTime);
	XR_FUNCTION(session->Instance, ConvertTimeToWin32PerformanceCounterKHR);

	MICROPROFILE_META_CPU("Predict Frame", (int)frameIndex);

	XrIndexedFrameState* CurrentFrame = session->CurrentFrame;
	XrTime displayTime = CurrentFrame->predictedDisplayTime;
	if (frameIndex > CurrentFrame->frameIndex)
	{
		// There is no predicted display period for this frame yet, synthesize one
		displayTime += CurrentFrame->predictedDisplayPeriod * (frameIndex - CurrentFrame->frameIndex);
	}
	else if (frameIndex < CurrentFrame->frameIndex)
	{
		// We keep a history of older frames, check if this is within the history range
		// If not, then synthesize an older display time
		long long delta = CurrentFrame->frameIndex - frameIndex;
		if (delta < ovrMaxProvidedFrameStats)
			displayTime = session->FrameStats[frameIndex % ovrMaxProvidedFrameStats].predictedDisplayTime;
		else
			displayTime -= CurrentFrame->predictedDisplayPeriod * delta;
	}

	static double PerfFrequencyInverse = 0.0;
	if (PerfFrequencyInverse == 0.0)
	{
		LARGE_INTEGER freq;
		QueryPerformanceFrequency(&freq);
		PerfFrequencyInverse = 1.0 / (double)freq.QuadPart;
	}

	LARGE_INTEGER li;
	if (XR_FAILED(ConvertTimeToWin32PerformanceCounterKHR(session->Instance, displayTime, &li)))
		return 0.0;

	return li.QuadPart * PerfFrequencyInverse;
}

OVR_PUBLIC_FUNCTION(double) ovr_GetTimeInSeconds()
{