ignore every event except Enter in receiving mode (#65)

Modifier or other key events are still sent by some compositors after leaving the window which causes them to be pressed on both devices.
Now an Enter event must be produced before any further events are sent out (except disconnect)

src/server.rs

@@ -824,6 +824,11 @@ impl Server {
                 start_timer = true;
                 log::trace!("STATE ===> AwaitingLeave");
                 enter = true;
+            } else {
+                // ignore any potential events in receiving mode
+                if self.state.get() == State::Receiving && e != Event::Disconnect() {
+                    return Ok(());
+                }
             }
 
             (client_state.active_addr, enter, start_timer)