Bug 509442

Summary: Windows previews don't work with openGL+egl-wayland2, also don't work with vulkan backend
Product: [Plasma] plasmashell Reporter: nsmcclellan
Component: Task Manager and Icons-Only Task Manager widgetsAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: aleixpol, kdedev, nate, qydwhotmail
Priority: NOR    
Version First Reported In: 6.4.5   
Target Milestone: 1.0   
Platform: CachyOS   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description nsmcclellan 2025-09-12 23:46:48 UTC 
SUMMARY

Task Manager / Icons-Only Task Manager - Window previews do not work (they are a black square) when using the vulkan backend. Additionally, when using egl-wayland2 instead of the older egl-wayland, previews are broken with all backends, including openGL. Previews only work when using openGL backend plus the older egl-wayland. (egl-wayland2 is desired because it fixes an nvidia bug that distorts the taskbar tooltips, and presumably it will eventually replace egl-wayland).

STEPS TO REPRODUCE
1. run kcmshell6 kcm_qtquicksettings, switch to vulkan renderer, restart plasma shell (Alt-F2, kquitapp6 plasmashell; kstart plasmashell)

or....

2. Install egl-wayland 2 from https://github.com/NVIDIA/egl-wayland2, and reboot after setting the following inside of /etc/environment:

__EGL_EXTERNAL_PLATFORM_CONFIG_FILENAMES=/usr/share/egl/egl_external_platform.d/09_nvidia_wayland2.json:/usr/share/egl/egl_external_platform.d/15_nvidia_gbm.json:/usr/share/egl/egl_external_platform.d/20_nvidia_xcb.json:/usr/share/egl/egl_external_platform.d/20_nvidia_xlib.json

OBSERVED RESULT

No window previews, just a black box where the preview would be.

EXPECTED RESULT

Working window previews.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  6.16.6-3-cachyos and Plasma on Wayland
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.2

ADDITIONAL INFORMATION

FYI, Alt-Tab still shows previews in all of these scenarios, even though task manager previews don't work.
Comment 1 TraceyC 2025-09-17 21:55:53 UTC 
As it says in kcm_qtquicksettings

> These settings adjust the QtQuick settings used by Plasma. Modifying these settings can break your desktop. Only adjust these settings if you know what you are doing.

If you reset these to defaults, and remove the customization to /etc/environment, do window previews work normally?

I note that on https://github.com/NVIDIA/egl-wayland2 there's the note
> This library is still in development.
For any bugs caused by using that library, you'd need to report it to that project.
Comment 2 nsmcclellan 2025-09-20 17:52:14 UTC 
Ok, I have reported it on the github for egl-wayland2. Yes, window previews work fine with the openGL backend with the older egl-wayland.
Comment 3 TraceyC 2025-09-20 18:01:47 UTC 
OK, I'll close this out since this will be handled upstream. Thanks!