Package: qt6-wayland
Version: 6.8.2-4
Severity: normal
Tags: upstream
While building & testing the current stable Flightgear application with
Qt6 on my Wayland-only Sway desktop, on Debian stable (trixie), the Qt
based launcher GUI of Flightgear aborts at startup with a message that
indicates an unexpected event has occurred on the XDG Toplevel window of
the launcher.
'xdg_toplevel' has no event 3
I expect the application to run correctly and display the Flightgear
launcher GUI.
Investigating the failure, I find that event 3 (wm_capabilities) has
been part of Wayland XDG shell protocol since version 5, which is the
version offered by my Sway compositor.
https://wayland.app/protocols/xdg-shell#xdg_toplevel:event:wm_capabilities
Running with WAYLAND_DEBUG=1 I see the Qt6 library bind to version 5 of
the XDG shell protocol (xdg_wm_base), but it seems unable to process the
wm_capabilities event. I turn to the source for Qt6 to establish why it
is requesting a version that it cannot process and discover what I
believe to be a long term bug (still present in unstable, as below):
https://sources.debian.org/src/qt6-wayland/6.9.2-3/src/plugins/shellintegration/xdg-shell/qwaylandxdgshellintegration.cpp#L17
which hard-codes the supported protocol version at '6', but the Toplevel
implementation only supports event handlers for events 0,1,2 (configure,
close, configure_bounds):
https://sources.debian.org/src/qt6-wayland/6.9.2-3/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell_p.h#L87
To prove this is the problem, I patch the plugin library for qt6-wayland
/usr/lib/x86_64-linux-gnu/qt6/plugins/wayland-shell-integration/libxdg-shell.so)
to lower the hard-coded protocol value to '4' (using Ghidra and tweak)
which lowers the negotiated and bound protocol version with Sway.
After refreshing the ld.so.cache Flightgear now runs it's launcher as
expected.
-- System Information:
Debian Release: 13.1
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500,
'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 6.12.48+deb13-amd64 (SMP w/8 CPU threads; PREEMPT)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE
not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages qt6-wayland depends on:
ii libc6 2.41-12
ii libegl1 1.7.0-1+b2
ii libopengl0 1.7.0-1+b2
ii libqt6core6t64 [qt6-base-private-abi]
6.8.2+dfsg-9
ii libqt6dbus6
6.8.2+dfsg-9
ii libqt6gui6
6.8.2+dfsg-9
ii libqt6opengl6
6.8.2+dfsg-9
ii libqt6svg6 6.8.2-3
ii libqt6waylandclient6 [qt6-waylandclient-private-abi] 6.8.2-4
ii libqt6waylandcompositor6 [qt6-waylandcompositor-private-abi] 6.8.2-4
ii libqt6wlshellintegration6 6.8.2-4
ii libstdc++6 14.2.0-19
ii libwayland-client0 1.23.1-3
ii libwayland-egl1 1.23.1-3
ii libwayland-server0 1.23.1-3
qt6-wayland recommends no packages.
qt6-wayland suggests no packages.
-- no debconf information
