`SDL_GetCurrentRenderOutputSize()` sometimes reports the wrong size

[klartext]

I used SDL_GetCurrentRenderOutputSize() in conjunction with SDL_SetWindowFullscreen().

My first impression was, that toggling the fullscreen does not work properly.

After some exploration and experimentation I came to the conclusion, that the problem comes from
SDL_GetCurrentRenderOutputSize() which sometimes reports the wrong size.

I then also used SDL_SyncWindow() (which I think should not be necessary to be used, but hoped it can give a hint for locating the problem)... and my first impression was it helps, but then it turned out that the problem still occurs.
So the syncing does not help.
In the end I think, that the problem really comes from SDL_GetCurrentRenderOutputSize().

This is happening on Arch-Linux, and it is package version 3.2.28-1.

I saw some other Issues that mentioned problems with setting the Size... and without looking into details of these issues, I wonder if some of them are related to wrong size reporting by SDL_GetCurrentRenderOutputSize().

[klartext]

winsizetest.c

[klartext]

CC=gcc
    
CPPFLAGS=$(shell pkg-config --cflags sdl2) # this boils down to: -I/usr/include/SDL2 -D_GNU_SOURCE=1 -D_REENTRANT
LDLIBS=-lm -lSDL3 -pthread

CFLAGS = -Wall -W

winsizetest:  winsizetest.c
        $(CC) -o winsizetest winsizetest.c $(CPPFLAGS) $(LDFLAGS) $(LDLIBS)

[klartext]

Just testet it again.
Looks like the problem occurs, when moving the mouse from outside the window onto the window or the other way around.
(This runs on i3.)

[klartext]

output.txt

[Kontrabant]

If I had to guess, this is probably due to the window size being delayed when leaving fullscreen due to waiting for the borders to come back on before reporting the window size (borders on X are racy, but we have to wait for them when leaving fullscreen, or the reported window size will be incorrect).

I can replicate this in a VM, and it's goes away if I raise the synchronization timeout value from 100ms to 200ms.

[Kontrabant]

Can you try this branch on your system and see if it fixes the issue?

https://github.com/Kontrabant/SDL/tree/x_delay