Function bounded_roundtrip 

pub(crate) fn bounded_roundtrip<S>(
    conn: &Connection,
    queue: &mut EventQueue<S>,
    state: &mut S,
) -> Result<(), String>
where
    S: SyncState + Dispatch<WlCallback, ()> + 'static,

EventQueue::roundtrip with a deadline: a wedged compositor becomes an error instead of hanging the calling thread (and everything queued behind it).