This isn't obvious, but makes sense when thinking about how games actually use it. This is also in line with how Windows mouse relative mode is implemented.
Fixes https://github.com/libsdl-org/SDL/issues/5340
Here's an IRC dump that hopefully explains the issue this fixes:
> I'm debugging something odd where, for a libre game,
unvanquished.net (a FPS), relative mouse input in fullscreen is
buggy
> it's like, working mostly ok, but it has a weird
performance/cleanup bug
> after some time in relative mouse input mode, some time as low
as 15s, usually more, the SDL sends A LOT of relative mouse
input per frame
> almost all of which have xrel==0 && yrel==0
> by A LOT, I mean that after ~1min, it's usually in the
thousands per frame
> each frame, a while ( SDL_PollEvent( &e)) loop reads the
inputs, but it seems SDL is not clearing the list.
> one way to clear the list is to open the in-game console or
menu, which switches the input mode to absolute, then close it
which gets a working relative input mode (for some time at least)
> I've shown the issue to be present with SDL2.0.20 but not with
2.0.14 on my system
> some other players on Arch Linux (SDL2.0.20) report a possibly
related issue, where some keys seem to be pressed at random
> I've did some bisection on SDL master, and I've found that
there are actually two commits involved, one breaking it
totally (no input at all), and one fixing it partially (with
the problem described above)
First related commit that breaks it totally:
commit 82793ac279
Author: Sam Lantinga <slouken@libsdl.org>
Date: Thu Oct 14 14:26:21 2021 -0700
Fixed mouse warping while in relative mode
We should get a mouse event with an absolute position and no relative motion and shouldn't change the OS cursor position at all
Second related commit, that halfway fixes it:
commit 31f8c3ef44
Author: Sam Lantinga <slouken@libsdl.org>
Date: Thu Jan 6 11:27:44 2022 -0800
Fixed event pump starvation if the application frequently pushes its own events
Reverting the first commit did fix the issue for me, but would
probably reintroduce the bug it was fixing(?). This patch should
fix it for everyone hopefully.
https://github.com/DaemonEngine/Daemon/issues/600 is the upstream
bug, and contains some early investigation.
According to MSDN, we can also get SIZE_MAXHIDE and SIZE_MAXSHOW,
based on state changes to other windows. It's not clear under
what circumstances this will happen (I saw some docs indicating
it may require multiple application windows), but it doesn't seem
right to treat them as RESTORED.
- no need to keep the error in a static variable
- always print the error code
- reduce the required stack-size
- reduce the number of snprintf calls (and code size)
Sam Lantinga
Ryan C. Gordon
Christian Kündig
SDL Wiki Bot
Ethan Lee
Antoine Fontaine
Esme Povirk
uyjulian
pionere
Ozkan Sezer
Sylvain
staphen
Wohlstand