QCursor::pos stuck at (0, 0) until mouse click/move (wayland, kwin)

On wayland (kde), `QCursor::pos()` always returns `(0,0)`, until the first mouse click or mouse move.

Running the program with `WAYLAND_DEBUG=1`, I can verify that `wl_pointer enter` is generated with the correct cursor position. Tabbing in and tabbing out, I see the correct `wl_pointer` enter and leave events, but `QCursor::pos()` still reports `(0, 0)`. The correct cursor positions are reported after mouse press, or mouse move.

Example code is attached.

I did not test on earlier Qt versions.