Dear maintainers,

First off, thanks for maintaining KDE in Debian, I enjoy using it.

Since a recent upgrade (after the issues we had with only half (or
less) of the stack migrating to testing) I'm experiencing issues with
drawing of windows. The issue is that it seems that windows
(e.g. konsole) are only drawn after some delay or after switching back
and forth to another window. Especially the cursor position is often
at a different place that it shows, making typing mistakes very
difficult to correct. Also e.g. scrolling through messages in
Thunderbird is difficult, as the window is only properly refreshed
after I stop scrolling, until then the window is messed up. I tried to
make a screen shot of the situation, but it seems that also the
screenshot tool (Spectacle) ensures that the window is properly
refresh the moment it takes the screenshot. The issue is less of a
problem in Emacs, as that seems to force the refresh by itself much
more often (although I do see glitches with the cursor jumping).

I'm aware that the issue may not be with kwin, but it's the package I
thought of first, please reassign if you think the issue is more
likely to be elsewhere. Also please let me know if I can provide you
with more information to help solve the issue.

My system is an up-to-date testing environment. I delayed reporting
this issue in the hope that it was caused by other to-be-migrated
packages from unstable, but the issue is annoying me now for more than
a week (I estimate) and I have no clue which package from unstable I
should be looking out for.

Paul

Hi Paul,

Can you check whether
  Start compositor on startup
is selected in the Plasma settings?

Thanks

Norbert

Hi Norbert,

It was disabled. Immediately after enabling it, the issues seem to be gone.

I don't believe I ever changed the setting, so it got into this state
somehow without me being involved I think.

Paul

I/We have now seen this several times, so I decided to check what it was on my
system even though I'm not experiencing issues.
And it's not enabled with me too and I also have no recollection of disabling
it. But the attached screenshot gives a (pretty good) hint as to why it got
disabled: (apparent) previous KWin crashes.
I have a Radeon RX Vega 64 card and afaik the drivers are in the kernel.
I do run Sid though ... ;-)

Cheers,
  Diederik

Hi Diederik,

Nice screenshot. For the record, that hint wasn't there on my system.
The other settings are the same, minus I have "OpenGL 2.0" as "Rendering
backend".

Paul

PS
lshw says this about my display
             description: VGA compatible controller
             product: CometLake-U GT2 [UHD Graphics]
             vendor: Intel Corporation
             physical id: 2
             bus info: pci@0000:00:02.0
             logical name: /dev/fb0
             version: 02
             width: 64 bits
             clock: 33MHz
             capabilities: pciexpress msi pm vga_controller bus_master
cap_list fb
             configuration: depth=32 driver=i915 latency=0
mode=1920x1080 resolution=1920,1080 visual=truecolor xres=1920 yres=1080
             resources: iomemory:600-5ff iomemory:400-3ff irq:148
memory:6022000000-6022ffffff memory:4000000000-400fffffff
ioport:4000(size=64) memory:c0000-dffff

Hi Paul,

It was my assumption that you (and others) didn't get that hint, otherwise you
(and others) would (very) likely have mentioned it.
The hint I got explains why the setting was/got disabled, without people
recollecting that they had disabled it and that's why I shared it :-)

Cheers,
  Diederik