Bug#954781: libqt5core5a: QT will not use Wayland on Gnome
Hi, Dmitry and other maintainers,
I've came accross this problem a couple months ago because I maintain a
QT application (Kristall). It was pretty hard to pinpoint the need to
install qtwayland5 to make everything work when setting the variable.
Besides the message displayed when running the program via cli, it also
goes to journalctl if running via Icon so users might be worried. To try
to help them, I created a bug against kristall [1] and I'm going to ship
a debian/README to explain the situation.
Thanks to sergiodj, we discovered this bug and that fedora is patching
qt base to run wayland natively in gnome since december of 2019 [2] - so
they've had a lot of time to test and find bugs. The rationale and
benefits are:
"Qt Wayland plugin has been available for a long time, but it hasn't
been in condition where it could be enabled by default. With Qt 5.12 the
state of the Wayland plugin is much better and it's becoming more and
more reliable. It now supports all the needed protocols and has been
enabled by default for non-Gnome Wayland sessions. With Qt Wayland on
Gnome Wayland session we need to support CSD, it's actually the only way
how decorations are going to work in Qt apps right now. Qt Wayland
implements basic decorations, which really doesn't match Gnome Adwaita
theme, therefore there are new CSD being implemented as part of
QGnomePlatform.
To make Qt applications run natively on Wayland we need to modify Qt 5,
specifically qt5-qtbase module, where we allow the Wayland plugin to be
used also for Gnome sessions. The new decorations from QGnomePlatform
will be used automatically once they are fully implemented and updated
in Fedora.
Qt applications running with the Wayland plugin run generally faster and
smoother on Wayland enabled sessions like Gnome Wayland and better
support HiDPI displays (respects desktop scale)."
On Mon, 23 Mar 2020 15:33:40 +0300 Dmitry Shachnev <mitya57@debian.org>
wrote:
> On Mon, Mar 23, 2020 at 01:23:43PM +0100, Norbert Lange wrote:
> > Runnin any QT Application on Gnome will blacklist Wayland. You see
> > the explicit message when starting an application from the terminal.
> >
> > % wireshark Warning: Ignoring
> > XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to
> > run on Wayland anyway.
> >
> > (for me this is really annoying as I have a HiDPI and a normal
> > Monitor, X11 doesnt allow different scaling).
> >
> > Fedora considers QT 5.12+ ready to enable this by default, see the
> > two used pathes under [1], Section "Scope".
> >
> > I'd hope debian could follow here, and use those patches in testing.
>
> The problem is that upstream Qt considers GNOME/Wayland support not
> yet ready.
>
> There is an umbrella bug (QTBUG-68619) which depends on some other
> bugs. At the moment only one of them is open (QTBUG-68636), so I think
> as soon as someone fixes it, it will be possible to enable that
> support.
The QTBUG-68619 has been closed because QTBUG-68636 has also been
closed. But the latter has been fixed only in qt 6.2.3 so it won't be
extended to our current qt5 version. It seems to me that this bug is
pretty minor regarding its impact, and I found a lot of matchs in
Debian's bug db regarding the QT_QPA_PLATFORM [3].
That's why I'd like to know if you would consider changing the
qtwayland5 to Recommends or Depends in order to alleviate users burden
if they decide to run wayland natively via the envvar. It's also an
alternative to follow Fedora's approach, though I think the first option
would be preferred.
Thanks and best regards,
Charles
[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1018251
[2]
https://fedoraproject.org/wiki/Changes/Qt_Wayland_By_Default_On_Gnome
[3]
https://www.mail-archive.com/search?q=QT_QPA_PLATFORM%3Dwayland&l=debian-bugs-dist%40lists.debian.org
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