Comment 1 for bug 1521586

This affects gtk3 indicator in Xubuntu (xfwm or mutter as wm). Usually the black borders in the attached screenshot are transparent shadows, but it represents exactly the area which is sometimes not clickable.

To reproduce:
* click a gtk3 indicator
* hover over the expanded indicator menu
* try to click the indicator or any neighbors
=> only clicks in the upper ~1/3 of the button show a reaction, the lower 2/3 do nothing.

The same thing happens with some gtk3 window shadows, e.g. the gnome calculator: Underlying windows cannot be brought into focus near the window border in the shadow area.