SUMMARY

I have filed a similar bug report to Mesa, and they have directed me here: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4913. Apologies if this is the wrong component to file the report to

When running Vulkan applications in fullscreen via XWayland with an Intel iGPU, the application window becomes corrupted. This only appears to happen if the window is in-focus, uses XCB, and (as far as I can test) uses Vulkan.

STEPS TO REPRODUCE
1. Clone Sascha Willem's Vulkan examples, and build the samples in XCB mode (without specifying any flags in CMake)
2. Run any example in fullscreen (e.g. ./gltfscenerendering --fullscreen)

OBSERVED RESULT
The window becomes corrupted when in-focus. When out-of-focus, the application window renders correctly. Capturing the application window via other software (e.g. OBS Studio and Spectacle) will also cause it to output correctly.

EXPECTED RESULT
No visual corruption.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.12.10-arch1-1
(available in About System)
KDE Plasma Version: 5.22.0
KDE Frameworks Version: 5.83.0
Qt Version: 5.12.2

ADDITIONAL INFORMATION

This bug was originally filed to Mesa (https://gitlab.freedesktop.org/mesa/mesa/-/issues/4913). It can only be reproduced using an Intel iGPU and not an AMD iGPU or dGPU.