Clients using _NET_WM_MOVERESIZE to start a drag operation may encounter
a race condition if the user presses and releases a mouse button very
fast, getting "stuck" in a grab state. While this is easily fixed with
the user pressing the button or hitting Escape as the EWMH spec suggests,
its's still a bit of annoyance for users.
After starting a grab operation, check that the button is actually pressed
by the client, and if not, cancel the grab operation. This prevents the
stuck grab in a race-free way, although it requires an extra round-trip
to the server.
With client-side decorations becoming more popular, the use of
_NET_WM_MOVERESIZE is on the rise, thus this bug is seen more frequently
than before.
https://bugzilla.gnome.org/show_bug.cgi?id=699777
a487d4dd01
