Qt apps broken on nVidia/Wayland (Event thread blocked)

[David Gow]

Qt apps (particularly those using QtQuick) — including the KDE Plasma desktop — are broken on nVidia/Wayland systems since the nVidia egl-wayland library was updated to 1.1.8.

https://github.com/NVIDIA/egl-wayland/issues/40

The fix for this has landed in upstream Qt:
https://codereview.qt-project.org/c/qt/qtwayland/+/301712

But backports from upstream Qt are heavily delayed to non-commercial users.

The KDE project has backported the fix to their branch, and there is a Merge Request available in debian:
https://salsa.debian.org/qt-kde-team/qt/qtwayland/-/merge_requests/5

Without this fix, KDE Plasma is totally unusable under Wayland, and some Qt applications will likely break under Gnome, too, which could be a problem if nVidia/Wayland will be the default for Gnome in 22.04.

Most other distros have either backported this fixed, or switched to packaging the KDE-maintained branch of QtWayland, which contains it.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Erich Eickmeyer (eeickmeyer)]

I can confirm this. I have no problem launching the KDE Wayland Session under Intel graphics, but switching my system to the dGPU (Nvidia graphics) causes the entire session to crash and several processes hang.

[Erich Eickmeyer (eeickmeyer)]

David, inspecting the merge request you pointed to, you'll notice that one of those commenters is one of the people I subscribed to this bug. This means we are very well aware of the issue.

Also, notice that this package does not contain an ubuntu suffix. This means the package is directly sync'd from Debian. Therefore, while well-placed, this bug report may have been unnecessary. :)

I can confirm that GNOME/Wayland sessions aren't affected by this, so that's not the issue here. Remember, Wayland is a protocol, not a display server/library that everything talks to. Each window manager has its own implementation, so what happens with Wayland in KDE does not affect Wayland in GNOME.

[Rik Mills (rikmills)]

Plasma Wayland sessions will not be a supported option in 22.04 LTS. Saying that, bug reports are appreciated to get future support better, but will not be high priority.

[David Gow (david-ingeniumdigital)]

Thanks for the response. Hopefully just having this bug reported so that there's some search result for "ubuntu plasma wayland nvidia bug" or similar will make things easier.

My concern re: the gnome session was that — as I understand it — this should affect any applications which are written against Qt Quick, and while I don't think Gnome includes any by default, it's still possible that people will see regressions running such applications under Gnome. (Though I agree that this is obviously not as critical as the whole DE being broken.)

In any case, hopefully this will act as the appropriate gentle nudge to encourage Debian/Ubuntu to switch to the KDE-maintained Qt branch or otherwise find a way get these sorts of fixes in sooner. :-) (Alas, I've had to move my nVidia/Wayland experiments over to openSUSE, which is a bit more usable on the bleeding edge at the moment.)

Thanks,
— David

[Launchpad Janitor (janitor)]

This bug was fixed in the package qtwayland-opensource-src - 5.15.4-1

---------------
qtwayland-opensource-src (5.15.4-1) experimental; urgency=medium

  * New upstream release.
  * Bump Qt build-dependencies to 5.15.4.
  * Bump ABI version to 5-15-4.
  * Drop fix_dead_keys.diff, included in the new release.
  * Add patches from KDE's Qt 5 Patch Collection up to 2022-05-14
    (LP: #1967659).
  * Update debian/libqt5waylandclient5.symbols.
  * Update Homepage field.
  * Bump Standards-Version to 4.6.1, no changes needed.

 -- Dmitry Shachnev <email address hidden> Sat, 14 May 2022 16:07:42 +0300