GtkMenuButton: disable focus-on-click
As general rule, all buttons that launch a menu should not grab focus on click, because otherwise when the menu is closed the focus goes back to the button instead of the previously focused widget, which is the one the user was interacting with.
GtkScaleButton
and GtkVolumeButton
set focus-on-click
to FALSE
for this same reason.
Fixes #2557 (closed)
Edited by Nelson Ben