Add an experimental shutdown handler

gui.py

@@ -1629,6 +1629,7 @@ class GUIManager:
         root.iconbitmap(resource_path("pickaxe.ico"))  # window icon
         root.title(WINDOW_TITLE)  # window title
         root.protocol("WM_DELETE_WINDOW", self.close)  # hook the X window closing button
+        root.protocol("WM_ENDSESSION", self.close)  # hook the Windows shutdown signal
         root.bind_all("<KeyPress-Escape>", self.unfocus)  # pressing ESC unfocuses selection
         # Image cache for displaying images
         self._cache = ImageCache(self)
@@ -1781,7 +1782,7 @@ class GUIManager:
             await asyncio.sleep(0.05)
         self._poll_task = None
 
-    def close(self):
+    def close(self, *args):
         """
         Requests the GUI application to close.
         The window itself will be closed in the closing sequence later.

main.py

@@ -160,8 +160,8 @@ exit_status = 0
 loop = asyncio.new_event_loop()
 asyncio.set_event_loop(loop)
 client = Twitch(settings)
-signal.signal(signal.SIGINT, lambda *_: client.signal_close())
-signal.signal(signal.SIGTERM, lambda *_: client.signal_close())
+signal.signal(signal.SIGINT, lambda *_: client.gui.close())
+signal.signal(signal.SIGTERM, lambda *_: client.gui.close())
 try:
     loop.run_until_complete(client.run())
 except CaptchaRequired:

twitch.py

@@ -121,14 +121,6 @@ class Twitch:
         # perfect for GUI usage
         return partial(self.change_state, state)
 
-    def signal_close(self):
-        """
-        Called when the application is requested to close by the operating system,
-        usually by receiving a SIGINT or SIGTERM.
-        """
-        # delegate this to the same action as the user clicking on the X in the GUI window
-        self.gui.close()
-
     def close(self):
         """
         Called when the application is requested to close by the user,