Bug 445088

Summary: Dual monitor setup: Program window display gets mashed up when small old monitor is configured left (aside new higher dpi monitor)
Product: [Plasma] kwin Reporter: t061
Component: multi-screenAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED UNMAINTAINED    
Severity: normal CC: nate
Priority: NOR    
Version First Reported In: 5.18.7   
Target Milestone: ---   
Platform: openSUSE   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Screenshot
Screenshot old monitor right=OK

Description t061 2021-11-06 17:19:27 UTC
Created attachment 143288 [details]
Screenshot

SUMMARY
The program window display of some programs (VLC at video playback, Kontact, LibreOffice) gets mashed up when small old monitor is configured left (aside new higher dpi monitor). (Settings-Display and monitor). When the old small monitor is configured right aside the new one, everything works fine.


STEPS TO REPRODUCE
1. Open Settings - Display and monitor
2. Move the box representing the old monitor to the left 
3. Start Kontact, VLC player (video playback) or LibreOffice

--> program window display will be mashed up. :(

4. Move the box representing the old monitor to the right (no restart required)
5. Start Kontact, VLC player or LibreOffice again

--> everything works fine :)

See screenshots.


Workaround:
a) Libre Office: remove libreoffice-qt5 and libreoffice-gtk2 package, install libreoffice-gtk3 package instead (?!)
b) VLC: use custom skin ("avs 95 beta")

Hardware: 
Main display: Eizo 27" 2560 x 1440 (144ish-dpi)
2nd display: Acer 19" 1280x1024
Geforce GT 610

Software:
OpenSuse Leap 15.3
KDE 5.18 LTS
NVIDIA 390.144-lp153.31.1 graphics driver (closed source)
libqt* 5.12.7*
KDE Framework: 5.76
Comment 1 t061 2021-11-06 17:26:13 UTC
Created attachment 143289 [details]
Screenshot old monitor right=OK
Comment 2 Nate Graham 2021-11-08 21:21:07 UTC
Very likely an issue specific to the proprietary NVIDIA driver.
Comment 3 t061 2021-11-09 17:33:21 UTC
(In reply to Nate Graham from comment #2)
> Very likely an issue specific to the proprietary NVIDIA driver.

But why does it work with LibreOffice in GTK3 mode then, or VLC with custom skin? GTK3 programs seem to be always rendered correctly, no matter where the small monitor is configured.
Comment 4 Nate Graham 2021-11-09 17:36:45 UTC
Because GTK apps draw using the CPU, not the GPU. The trade-off there is higher CPU and energy usage, but protection from GPU driver bugs.
Comment 5 David Edmundson 2023-09-06 10:38:17 UTC
This bug was reported against an outdated version of KWin. We have made many changes since the. 
If the issue persists in newer versions can you reopen the bug report updating the version number.