Show system messages when users join/leave room

desktop-client/room_widget.py

@@ -29,6 +29,8 @@ class RoomWidget(QWidget):
         self.room_code = ""
         self.expected_vlc_events = []
         self.last_reported_time_ms = 0
+        self.current_users = []
+        self._is_first_user_update = True
         
         self._setup_ui()
         
@@ -176,6 +178,8 @@ class RoomWidget(QWidget):
         self.set_room_code_display(room_code)
         self.room_file_badge.setText(f"📄 {file_name}")
         self.chat_messages.setHtml("Welcome to the room! 👋")
+        self.current_users = []
+        self._is_first_user_update = True
         
         if file_path:
             self.vlc_player.load_media(file_path, start_time_s)
@@ -183,6 +187,8 @@ class RoomWidget(QWidget):
             
     def cleanup(self):
         self.vlc_player.stop()
+        self.current_users = []
+        self._is_first_user_update = True
 
     def set_room_code_display(self, text: str):
         self.room_code_display.setText(f"Room: {text}")
@@ -339,6 +345,21 @@ class RoomWidget(QWidget):
                 self.add_system_message(f"{username} seeked to {fmt(position_s)}")
 
     def update_users(self, users: list):
+        if self._is_first_user_update:
+            self._is_first_user_update = False
+        else:
+            joined = set(users) - set(self.current_users)
+            left = set(self.current_users) - set(users)
+            
+            for user in joined:
+                if user != self.username:
+                    self.add_system_message(f"👋 {user} joined the room")
+                    
+            for user in left:
+                if user != self.username:
+                    self.add_system_message(f"🚪 {user} left the room")
+                    
+        self.current_users = users
         self.users_lbl.setText(f"{len(users)} watching: {', '.join(users)}")
 
     def add_chat_message(self, author: str, text: str, timestamp: int):