Toggle Connect/Disconnect on the same button once connected

MessageDispatcherSync gains an optional on_connect_changed(bool)
callback, fired from the websocket client's background loop once the
connection is actually live/lost, so the button only flips state on a
real connection change rather than optimistically on click.

ws/message.py

@@ -103,6 +103,10 @@ class MessageDispatcherSync(IConnection):
 		self.state = None
 		self.state = queue.Queue()
 		self.auto_subscribe = auto_subscribe
+		# Optional callback(connected: bool), invoked from the websocket
+		# client's background thread/loop - e.g. for a GUI to toggle a
+		# Connect/Disconnect button once the connection is actually live.
+		self.on_connect_changed = None
 
 	def msgio_get(self, key):
 		obj = MsgIoSync(key, self.send)
@@ -114,6 +118,8 @@ class MessageDispatcherSync(IConnection):
 	async def on_connect(self):
 		if self.auto_subscribe:
 			asyncio.get_event_loop().run_in_executor(None, self.subscribe)
+		if self.on_connect_changed is not None:
+			self.on_connect_changed(True)
 
 	def subscribe(self):
 		for handler in self.msg_handlers:
@@ -122,7 +128,8 @@ class MessageDispatcherSync(IConnection):
 			self.send({'+': key})
 
 	async def on_disconnect(self):
-		pass
+		if self.on_connect_changed is not None:
+			self.on_connect_changed(False)
 
 	async def on_recv(self, data):
 		d = json.loads(data)