Simulator Responds Poorly to High Poll Rate Mice

areddan · August 16, 2025, 9:25pm

Simulator drops a lot of frames when using a high poll rate mouse on windows. My mouse is only 1000Hz but still we get the slowdown, see this video (only happens when you mouse over the simulator):

I know this is an issue with SDL2. Here's some relevant links:

github.com/libsdl-org/SDL

Mice with high polling rate causes significant lag on Windows

opened 06:35PM - 28 Dec 23 UTC

closed 04:41AM - 02 Jan 24 UTC

AnAkkk

There was already a ticket about a similar issue but it was closed https://githu…b.com/libsdl-org/SDL/issues/4376 I have a Razer Viper 8Khz and when playing CS2, the game gets very laggy on Windows when moving the mouse. This does not happen when playing on the Linux version of CS2. I think this is because SDL is using `GetRawInputData`, this is known to not work properly with mice that have a high polling rate. GetRawInputData is acquiring a lock on every call, and this causes significant performance loss because a high number of calls are needed when there is a high polling rate. The way to fix this issue would be to use `GetRawInputBuffer` https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getrawinputbuffer which can retrieves multiple input events at once. Valorant had the same issue (they were using GetRawInputData), and they later added a game setting called "Raw Input Buffer" to make use of GetRawInputBuffer, and it fixes this same issue. See here for more information https://www.reddit.com/r/VALORANT/comments/r5w10e/comment/hmplvwh/?utm_source=reddit&utm_medium=web2x&context=3 https://www.thespike.gg/valorant/tips/what-is-raw-input-buffer-in-valorant It has also became the default setting in Valorant. EDIT: Also, the Unity game engine was affected by the same issue. More information here: https://forum.unity.com/threads/windows-mouse-raw-input-mouse-handling-broken-in-rewired.1172786/#post-7514816

github.com/libsdl-org/SDL

Improved SDL_PollEvent usage

main ← 0x1F9F1:better_poll_cycle

opened 11:13PM - 28 Sep 21 UTC

0x1F9F1

+52 -3

This PR changes the behaviour of `SDL_WaitEventTimeout` (used by `SDL_PollEvent`…) to reduce overhead, and avoid infinite loops. ## Description Currently when polling for events you can end up in an infinite loop. There are two main reasons for this: * `SDL_WaitEventTimeout` unconditionally calls `SDL_PumpEvents`, even if there are already events available. * `SDL_WaitEventTimeout` has no understanding of a poll cycle. To fix this, there are two main changes: * Avoid calling `SDL_PumpEvents` unless the event queue is actually empty. * Use a sentinel event to mark the end of a poll cycle. ## Alternatives Unfortunately both of these changes could alter the behaviour of existing applications, so the following changes may be needed: * Add a hint to preserve some/all of the previous behaviour. * Only avoid pumping if `timeout == 0`. * If you reach the sentinel, but there are more non-pump events (added in the middle of a poll loop), add the sentinel back to the end of the queue. ## Existing Issue(s) #4792 and #4376 describe the problems with the current event-poll cycle, though I felt part of #4792's approach is sub-optimal.

I used a similar approach to this in order to fix the problem for a personal project and it seemed to work - but not sure if applicable in PD Simulator case.

This isn't a big problem as we don't use mouse often when the simulator is open, I only just realized the reason today - I thought there was something slow in my code

willco · August 18, 2025, 4:12pm

Thanks for the report, my gamer son has a 1000 hz mouse I can borrow to test this with.

areddan · August 18, 2025, 4:27pm

Hahah thank you. Worth noting that my framerate is fully uncapped (setRefreshRate(0)) and I'm manually updating the frame buffer / marking updated rows so the refresh rate is absurdly high for this trivial example (~750fps). Not sure if this is still an issue at 50hz - I'll confirm tonight.

willco · August 18, 2025, 8:42pm

I can't reproduce this with a simple test app. Could you post the app you're testing with?

areddan · August 18, 2025, 9:39pm

Sure thing, do you just want the compiled binary or do you need me to provide source?

willco · August 18, 2025, 10:16pm

Binary is fine, thanks!

areddan · August 19, 2025, 3:18am

pd1.pdx.zip (17.7 KB)
Here you go! Its Debug x64!

willco · August 20, 2025, 9:11pm

Thanks so much, I was able to reproduce the issue. It wasn't SDL related but rather Windows being Windows. It was updating the mouse position so much it was starving the UI of drawing events even though the UI was being told to redraw. I'm now being a bit more aggressive with redrawing the screen which fixes the issue.

areddan · August 20, 2025, 9:29pm

Really nice catch! Classic windows

Thank you for the rapid response willco, you're a legend.