Bug 495296

SUMMARY
When running JOSM (Java app, Flatpak, XWayland) in Wayland session and trying to access the toplevel menu bar while having its window maximized, there is an out of sync situation of the visible position of the mouse cursor and the position that the app (JOSM) actually is "seeing", making it hard to actually use the menu.

STEPS TO REPRODUCE
1. Run JOSM (Flatpak) in a Wayland session, build from master.
2. Maximize the main window.
3. Click on an element of the toplevel menu bar (File, Edit, View etc.).
4. The menu only appears as long as the left mouse button is being pressed, otherwise it will just flash briefly.
5. While holding the mouse button pressed and the menu is open, hover around with the cursor until one of the menu items gets highlighted.
6. Release the mouse button. The menu will now stay visible.

OBSERVED RESULT
The visible cursor appears to be somewhere else than over the highlighted item – out of sync with the cursor position as "seen" by JOSM. Activating/launching a menu item while it is highlighted works as usual despite the visible cursor being somewhere else.

EXPECTED RESULT
* When clickling on an element of the toplevel menu bar,  the menu should stay open instead of just flashing briefly.
* The visible cursor position should stay in sync with the one that the app sees: Highlighting/ Activating a menu item should work when the visible cursor is actually placed at the respective item, not when it is placed somewhere else.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.2.80
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.1

ADDITIONAL INFORMATION
Reproduced with the following setups:
* Plasma 6.2.80 build from master atop of Kubuntu 24.10 on real HW.
* Neon Unstable installation with current updates in a Gnome Boxes/QEMU VM.

Could NOT reproduce with one of the following conditions:
* Plasma X11 session
* JOSM window being not maximized
* Wayland session on a VM with Kubuntu 24.10 and distro packages: Plasma 6.1.5, Qt 6.6.2, Frameworks 6.6.0