[Pkg-utopia-maintainers] Bug#1107749: flatpak: Vulkan not working on dual-GPU system after upgrade to trixie

[David Hoces Pérez]

Hi Simon, thanks for your reply.

Today I have tested running flatpak applications again on the same 
computer, and it looks like they are displayed without any issue now 
(no more white windows). I can still see the same warning messages I 
mentioned earlier, when I start the applications from the console but 
the applications are displayed as expected. On the other hand, these 
messages can be avoided by setting the environment variable 
GSK_RENDERER=gl, as you pointed out. Thank you very much for your help.

I don't know why these applications are properly displayed now and not 
before. Maybe this has been fixed after rebooting the computer, 
although I am pretty sure that I rebooted the computer just after 
upgrading to Trixie. I think that I even rebooted it once again, when I 
found this issue, just to see if the it remained the same. Maybe the 
reason why it works now is that today I have installed some package 
updates, although I can't see any relation between this issue and the 
packages that have been updated today:

Start-Date: 2025-06-16  09:19:10
Commandline: apt upgrade
Upgrade: coreutils:amd64 (9.7-2, 9.7-3), busybox:amd64 (1:1.37.0-5, 
1:1.37.0-6), libslf4j-java:amd64 (1.7.32-1, 1.7.32-2), 
libcommons-logging-java:amd64 (1.3.0-1, 1.3.0-2), fonts-wine:amd64 
(10.0~repack-4, 10.0~repack-5), libnautilus-extension4:amd64 (48.1-2, 
48.2-3), gnome-control-center-data:amd64 (1:48.1-2, 1:48.2-2), 
gnome-control-center:amd64 (1:48.1-2, 1:48.2-2), nautilus:amd64 
(48.1-2, 48.2-3), nautilus-data:amd64 (48.1-2, 48.2-3)

Thank you very much for your support. If I face the same issue again 
then I think that I could let you know about it, but for now I suppose 
that you can close the bug.

Regads,
David.

El vie, 13 de jun de 2025 a las 20:04:05 P. M., Simon McVittie 
<smcv at debian.org> escribió:
> Control: retitle -1 flatpak: Vulkan not working on dual-GPU system 
> after upgrade to trixie
> Control: tags -1 + moreinfo help
> 
> On Fri, 13 Jun 2025 at 18:42:57 +0100, David Hoces Pérez wrote:
>> My computer has two graphic cards available:
>> 
>> $ DRI_PRIME=0 glxinfo | grep "OpenGL renderer"
>> OpenGL renderer string: Mesa Intel(R) HD Graphics 4000 (IVB GT2)
>> 
>> $ DRI_PRIME=1 glxinfo | grep "OpenGL renderer"
>> OpenGL renderer string: AMD TURKS (DRM 2.50.0 / 6.12.30-amd64, LLVM 
>> 19.1.7)
>> 
>> However the environment variable seems to be ignored by Flatpak when 
>> I try to
>> switch to the other graphic card:
>> 
>> $ flatpak run --env=DRI_PRIME=1 de.haeckerfelix.Shortwave
>> MESA-INTEL: warning: Ivy Bridge Vulkan support is incomplete
> 
> Dual-GPU has traditionally been a disaster area. I don't have a 
> dual-GPU system myself and am not familiar with the necessary 
> workarounds.
> 
> Note that DRI_PRIME affects OpenGL, not Vulkan, but the error and 
> warning messages that you quoted would indicate use of Vulkan. There 
> are other mechanisms for selecting a preferred GPU for Vulkan, but 
> I'm not familiar with what the preferred/least-hackish of those 
> mechanisms is.
> 
> Listing available GPUs with `switcherooctl list`, then comparing the 
> output of `switcherooctl launch --gpu=GPU env` for each one, might be 
> helpful?
> 
>> The same applications work well in the desktop environment (GNOME and
>> Wayland) when they have been installed from a Debian package.
> 
> Note that upstream GTK (as found in the GNOME runtime and used by 
> Flatpak apps) defaults to rendering using Vulkan, but Debian's GTK 
> has been patched to keep its old default of rendering using OpenGL.
> 
> A more apples-to-apples comparison would be to use environment 
> variable GSK_RENDERER=vulkan or GSK_RENDERER=gl to force a specific 
> renderer:
> 
>     GSK_RENDERER=gl gnome-recipes
>     flatpak run --env=GSK_RENDERER=gl org.gnome.Recipes
> 
>     GSK_RENDERER=vulkan gnome-recipes
>     flatpak run --env=GSK_RENDERER=vulkan org.gnome.Recipes
> 
> If you can reproduce this with a GTK app that is small, simple and 
> doesn't have extraneous permissions, that would help to concentrate 
> debugging effort onto one specific scenario. GNOME Recipes is usually 
> the one I use for debugging if the specific app doesn't matter.
> 
> flatpak(1) and Debian don't have control over the content, choice or 
> precise behaviour of the graphics drivers inside the Flatpak 
> container: those are chosen by the runtime maintainer. In the case of 
> the GNOME runtime, they're inherited from the freedesktop SDK, 
> <<https://gitlab.com/freedesktop-sdk/freedesktop-sdk/>> (more 
> precisely, the 'org.freedesktop.Platform.GL.default' extension).
> 
> The exact behaviour of Vulkan rendering is likely to be an 
> interaction between:
> 
> * the kernel drivers, which were previously from bookworm but are now
>   from trixie (but you could potentially try installing a bookworm
>   kernel and rebooting back into it in order to check whether this is
>   relevant)
> 
> * the Wayland compositor, in your case GNOME Shell, which was 
> previously
>   from bookworm but is now from trixie, and the libraries it depends 
> on
> 
> * the app itself and the libraries and user-space graphics drivers it
>   depends on, which in the case of GNOME apps under Flatpak come from
>   org.gnome.Platform and org.freedesktop.Platform.GL.default
> 
> Running Flatpak as, for example, `flatpak run -vv org.gnome.Recipes` 
> would give more information about precisely what app, runtimes and 
> drivers are in use, and how Flatpak is sharing device nodes with the 
> container.
> 
>     smcv

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