SDL2 2.30.2 fullscreen shows only blank screen on Debian Linux testing (trixie)

[cslr]

On Linux, SDL 2.30.3 shows only blank screen when fullscreen. I'm using multithreaded code and using mutex to synchronize SDL access (mostly from one thread). In windowed mode screen is updated without problems.

uname -a:
Linux whiteice 6.7.12-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.7.12-1 (2024-04-24) x86_64 GNU/Linux

dpkg -l libsdl2-2.0-0:
ii libsdl2-2.0-0:amd64 2.30.3+dfsg-1 amd64 Simple DirectMedia Layer
ii libsdl2-2.0-0:i386 2.30.3+dfsg-1 i386 Simple DirectMedia Layer

dpkg -l libsdl2-dev:
ii libsdl2-dev:amd64 2.30.3+dfsg-1 amd64 Simple DirectMedia Layer development files

[haydentech]

Are you checking the return value on your update calls? I had a very similar problem, and it was due to calling SDL functions from different threads. In my case, the SDL update calls were failing with a "Unable to make GL context current" error.

[cslr]

I'm calling SDL_update() from the main thread which initializes SDL and opens the window. I'm also calling SDL_update() from another thread which updates/draws the window surface. The SDL_update() from the second thread fails but the main thread SDL_update() should work ok and update the screen correctly, at least in windowed mode it works without problems.

[slouken]

You must call update from the main thread.