re-enable wayland

[Gigadoc2]

Type of change

(not sure what the appropriate type is)

• ✅ New feature (non-breaking change which adds functionality)

Description and Context

This removes the unsetting of XDG_SESSION_TYPE, and thus restores QTs behaviour of choosing the platform backend according to OS and desktop used.

Rationale:
For one, the wayland backend of QT is quite stable nowadays, and with current QT, KPXC works fine under GNOME and sway (and probably KDE as well), file open dialog and clipboard included. Of course, auto-type does not work as with X, but that is an intentional limitation of wayland, and using KPXC under XWayland will not change this.
But even if there are distributions or desktops where QT-wayland does not work well, this problem will affect not only KPXC, but any other QT app as well (and it is likely that the user is using at least one other QT application). Thus, the user will have to override QTs backend anyway, to make all their other applications work. On the other hand, there is a big downside to setting QT_QPA_PLATFORM explicitly (which KPXC requires without this change): Forcing QT to one specific backend will not work when regularly switching between wayland and X11 desktops. But when QT_QPA_PLATFORM is unset, QT will choose the proper backend according to the desktop in use.

Testing strategy

Tested this change with GNOME Shell 3.32.2 and sway version 1.2, everything seems to be working (including file open dialogs and clipboard).

Checklist:

• ✅ I have read the CONTRIBUTING document. [REQUIRED]
• ✅ My code follows the code style of this project. [REQUIRED]
• ☐ All new and existing tests passed. [REQUIRED]
• ☐ I have compiled and verified my code with -DWITH_ASAN=ON. [REQUIRED]

Two tests fail because of memory leaks detected, but the tests also fail without my change.

[droidmonkey]

I'm ok with this as long as we show that Auto-Type is disabled due to incompatibility with Wayland at this time

[droidmonkey]

This can be a message on the Auto-Type settings

[Gigadoc2]

That is a good idea, though I'd say that it is technically unrelated to this change, as Auto-Type is not possible with XWayland either (well, it might be possible for other XWayland windows, but for a user it is not obvious which applications are native wayland and which are Xwayland).

But in any case, I'll look at how to do this :)

I also realized that I might want to run more tests: Apart from not having tested KDE as a prominent Wayland desktop, I did have QT_QPA_PLATFORMTHEME=qt5ct set, which while not affection functionality might very well hide graphical inconsistencies.

[droidmonkey]

#2635 introduced this change

[Gigadoc2]

I am currently testing the behaviour under GNOME with a fresh Fedora 30 install. The theming issues have become less severe (you can nicely compare a F30 with and without updates), but the mouse cursor size is still off (of course, the window decoration is also different, but that is a deliberate design descision by GNOME).

However, it turns out that exactly this workaround has become part of QT meanwhile, just limited to only force X11 under GNOME (and not other desktops).

This is the more sensible approach (though IMO the most sensible approach would be to just not disable anything and let GNOME sort out it's theme handling), so I feel like this further deprecates the workaround included here in KPXC. The version present in QT also does not prevent the usage on wayland on other Desktops (which are without theming issues).

I would argue that this can now be merged, even without the warning in the Auto-Type settings, as Auto-Type is also broken as it is now: When forcing KPXC to run with the X11 backend under wayland, Auto-Type will only work for other XWayland windows (and this might even be compositor-specific). I'd argue this is almost worse than not working at all, because you cannot see which window is native wayland and which is XWayland without digging deep into the details of your desktop, thus the Auto-Type feature will seem completely unreliable to the normal user.

[Gigadoc2]

I just tested with KDE as well, there the theming works better (sort of expected with KPXC being a QT app), just the favicon is missing, which is an interesting bug.

BTW, I just noticed that the entire Auto-Type tab is missing anyway when native wayland is in use. Maybe this behaviour should be extended to XWayland as well (instead of the warning message)?

[GabrielPrototype]

It looks like AutoType in wayland is possible via a virtual keyboard device, someone has already implemented a prototype for KeepassX, please take a look at the code he wrote https://github.com/rockihack/keepassx/tree/wayland-autotype/src/autotype/wayland

cc: @rockihack

[droidmonkey]

Wow nice!

[phoerious]

Yeah, I thought about something like that. There are onscreen keyboards for Wayland after all. The standardisation and implementation of protocol extensions to enable assistive technologies are still lacking a lot, however.