XnViewMP (Linux) is much slower on Wayland than X11

[winnylinny]

Navigating through images is much slower and laggier on Wayland than X11. Using XnViewMP on X11 is instant and fast without any problems. When I switch to Wayland, it's much slower. I can still "use" the application, but it's more frustrating. Panning a zoomed image is also obviously slower too.

I am on KDE Plasma 6.6.5.

I have tried XnViewMP 1.11.5 and older versions. The behavior is the same. Navigating images is fast and smooth with X11, but sluggish with Wayland. It doesn't matter that the files are on a fast local NVMe.

I have tried the following variables which don't help too much.
QT_QPA_PLATFORM=xcb
QT_SELECT=qt6

I have tried the qt6 beta of XnViewMP.

I have tried the "system-libs" version.

The only solution is to switch back to X11. This is a problem because soon KDE will no longer support X11 as everyone is being forced to use Wayland.

What else can I try?

[xnview]

qt6 beta has same problems? which Linux?

[winnylinny]

qt6 beta has same problems? which Linux?

Yes. I tried qt6 beta from here: viewtopic.php?t=50710

This happens on 2 PC's. Arch Linux and Manjaro Linux. This happens on Nvidia GPU and Intel GPU.

XnViewMP on an old slow laptop with Intel GPU on X11 is faster than a new PC with Nvidia GPU on Wayland. There is an obvious difference in performance. It doesn't only affect navigating images with the mouse wheel and arrow keys, but also affects performance when panning an image that is zoomed.

I will try any advice you have so that XnviewMP is fast and smooth on Wayland like it is with X11.