In this case we have a bunch of interactive main children
of the overlay, and then a centered overlay that contains both
non-interactive (labels) and interactive (entry) widgets.
This shows off a problem where the non-interactive parts (the labels)
steals input from the overlay main children (breaks button click and
hover effects).
https://bugzilla.gnome.org/show_bug.cgi?id=750568https://bugs.freedesktop.org/show_bug.cgi?id=90917