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…mits The limiter waited in Present while GTA measures its frame delta in CTimer::Update, so everything between the two leaked into the delta and the game clock, which only adds whole milliseconds per frame, became an uneven mix of ticks. The wait now runs right before GTA samples its clock, where 1.6 waited. Present only paces frames the game timer never saw. The waitable timer is high resolution where available and the spin margin may grow to 2 ms when the timer keeps waking up late.
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Summary
The frame limiter waited in
Present, but GTA measures its frame delta inCTimer::Update. Everything between the two (message pump, input, pre frame pulse) takes a different amount of time every frame, and all of it leaked into the delta GTA saw.CTimer::UpdateVariablesaddsfloor(delta_ms)to the game clock, so at 240 FPS the 4.17 ms frames turned into a random mix of 4 and 5 ms ticks. That is the aim jitter, and it is why 144 with VSync looked fine while 240 did not.The wait now runs in
CCore::OnGameTimerUpdate, right before the clock is sampled, which is exactly where 1.6 waited.Presentonly paces frames the game timer never ticked for (minimized, loading). The waitable timer is created high resolution where Windows supports it, and the spin margin may grow to 2 ms when the timer keeps waking up late instead of being capped below what it actually needs.Unlimited FPS has no pacing at all, so any jitter there is the game running above 300 FPS and is outside the limiter.
Fixes #5335
Test plan
Cap at 240 on a machine that reaches it, aim with a weapon and strafe. Repeat at 120 and 144. Frame times in the frame graph stay flat and the camera stays smooth. Minimize and restore, alt-tab, join and disconnect, the limiter keeps working through all of it.
Checklist