[Bug] Cursor position incorrect in titlebar/window decorations in Plasma 6.7.2, possibly 6.7.1

Karousel version: 0.17
Plasma version: 6.7.2
X11 / Wayland: Wayland

Description:

I've been loving Karousel since I discovered it and it's become pretty integral to my workflow. As of the end of last week though, Karousel is sadly broken for me :(

Basically it looks like an incompatibility between something in Plasma 6.7.2 and Karousel. What's happening is that the cursor position in the titlebar is being registered incorrectly, at too high a position: about ~0.5 cm, or around ~32 physical pixels, on my monitor, which with the 165% scaling I have works out at about 20 virtual pixels.

The position is only registered as being in the titlebar when it actually is though – if it's within the window, the position is interpreted correctly. This means I can't click anything in the lower 0.5 cm / 32 physical px / 20 virtual px of the titlebar/window decorations.

The result is that in Qt applications I have a very very narrow, off-centre target area for titlebar buttons, and on apps that use their own window decorations this sometimes results in the buttons not being clickable at all, if they are smaller than the native ones.

If I toggle the float status of a window, everything works fine when it's floating. Equally, if I turn off Karousel, everything works perfectly fine.

With Plasma 6.7.0 there was no issue, it's since I updated. It was also already a problem in Karousel 0.16, updating to 0.17 didn't fix it.

I've attached my package update history in June and July so that you can see what upgrades might have caused the issue, in case it's not to do with Plasma/KWin.

zypp_history.md

Start by reproducing the titlebar cursor-position problem on Wayland with Plasma 6.7.2 and Karousel 0.17, comparing tiled and floating windows and Karousel enabled or disabled. Trace the window-decoration pointer handling in the Karousel source and compare behavior with Plasma 6.7.0. Done means titlebar controls are clickable across the full decoration area without breaking floating windows.