Bug 467507

Created attachment 157373 [details]
photo of PP when plasma-mobile does not start on kwin 5.27.2

SUMMARY
Hi and thank you for developing kwin!
On my OG PP with Mobian bookworm, plasma-mobile 5.27.2 is no more working since kwin 5.27.2 hit the testing repo. Please note, plasma-mobile 5.27.2 was working correctly on top of kwin 5.26.90 and downgrading kwin back to 5.26.90 reverts back to a working state. Additionally, another Mobian user reported this on Matrix on their Pinetab.

After logging in, a white rectangle in the top right corner appears on top of black background. Nothing else happens, GUI never appears.
By comparing the journalctl log with a previous one, the following line seems new
mar 12 21:10:59 mobian kwin_wayland_wrapper[977]: libkwinglutils: Shaders are not supported

Furthermore, by git bisecting kwin, problems starts happening after commit eef9bd5c [1].
Looks to me, that commit is identifying if some low-spec devices are present, thus setting some flags to disable features which run smoothly on higher-spec systems only. Driver for OG PP video rendering (Lima) is also mentioned in that commit.

Just guessing, that commit is setting device as unable to do a bunch of things (including shaders, as of error message), but it's failing to keep some other part of kwin from triggering those things?

Is there a way to tell plasma-mobile to not use shaders, like [2] for blur? That could be a temporary workaround

[1] https://invent.kde.org/plasma/kwin/-/commit/eef9bd5c4e564e9cbca6188c52cb3cee5ab9c825
[2] https://invent.kde.org/plasma-mobile/plasma-phone-settings/-/blob/master/etc/xdg/kwinrc#L6

SOFTWARE/OS VERSIONS
Linux: 6.1-sunxi64
KDE Plasma Version: 5.27.2
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8