Hi all, since i don't have much time to look in it the next few days, i'm dumping here some interesting findings i did on an issue i'm having on kwin/wayland (qt 5.9) I'll continue to look into that, but if this immediately rings a bell to someone, even better.
Sometimes shadows (especially of plasma tooltips and sometimes QMenu submenus) are wrong, usually a bit taller than the window is. putting some debug around, i see in kwin, shadow.cpp geometrychanged() i see m_toplevel having indeed the wrong geometry (few pixels too tall, the same anount the graphical artifact is) while if i put debug statements on every resize event of the same plasma tooltip, it never gets resized to that size, but always stays less tall. if really some times the geometry of a toplevel in kwin is not the real one, that's indeed a problem that could explain other potential bugs other than the artifact often appearing for shadows -- Marco Martin
