Created attachment 110034 [details]
GZDoom with background bleeding
I've seen this on GZDoom run with the SDL_VIDEODRIVER=wayland, at least. Xonotic shows no discernible issues, in this regard.
I'm not entirely sure what it is, but it looks vaguely something to do with alpha transparency? It causes what's rendered behind the window to show up.
For a moment, I thought that it might be related to my having the transparency effect enabled, but disabling that changed nothing.
Created attachment 110035 [details]
GZDoom menu with more alpha bleeding
Note that this doesn't occur when I run this on Weston. Alpha transparency works as expected.
Running with SDL_VIDEODRIVER=x11 also avoids the problem.
Is that a free game?
GZDoom is free, and should be in your distro's repositories.
You can also download the game files for Doom for free from here:
(In reply to Kyle Devir from comment #4)
> GZDoom is free, and should be in your distro's repositories.
By any chance do you know the package name in debian? Searching for doom gives me many things but not gzdoom.
(In reply to Martin Flöser from comment #5)
> (In reply to Kyle Devir from comment #4)
> > GZDoom is free, and should be in your distro's repositories.
> By any chance do you know the package name in debian? Searching for doom
> gives me many things but not gzdoom.
Didn't realize Debian didn't package it. Precompiled binaries are available, though:
apt-add-repository 'deb http://debian.drdteam.org/ stable multiverse'
Then download and import the gpg key from here:
Then, update and install gzdoom.
Can reproduce alpha transparency bug in Brutal Doom game from AUR https://aur.archlinux.org/packages/brutal-doom/
OS: Netrunner Rolling
Video: Intel 4400
Driver: xf86-video-intel 1:2.99.917+823+gd9bf46e4-1
Hmm, I used the flatpak, set the env var and confirmed it was running on Wayland via xeyes.
It doesn't seem reproducible here.
This sounds like it's a well-known issue with the game / SDL's understanding of rendering to buffers with alpha channels.
Basically, on X11 the alpha channel was ignored, and on Wayland it's used (to be able to provide nicely alpha-blended windows with interesting shapes, etc). There's been an EGL extension proposed to allow SDL to request the alpha channel is ignored:
SDL already has support for this extension, though it's not yet part of a release:
There's an in-progress implementation for Mesa:
So I doubt this is actually a KWin bug, but I could be wrong…
Marking as RESOLVED UPSTREAM. FWIW, EGL_EXT_present_opaque patches have been merged in Mesa.