The check in _windowsRestacked checks for
windows[i].x >= primary.x
and
windows[i].x <= primary.x + primary.width
(likewise for y).
This is wrong because a fullscreen window on the secondary screen is likely
to have windows[i].x == primary.x + primary.width which means that the checks
for _both_ screens would be valid, but the first one would win due to
the "break;" statement.
But here the window isn't really on the primary but on the secondary one.
Fix that by using < instead of <= for those checks.
https://bugzilla.gnome.org/show_bug.cgi?id=614509
f262473a3f