Add ability to handle user join/leave/kick events in MultiplayerComposites

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -33,6 +33,12 @@ namespace osu.Game.Online.Multiplayer
         /// </summary>
         public event Action? RoomUpdated;
 
+        public event Action<MultiplayerRoomUser>? UserJoined;
+
+        public event Action<MultiplayerRoomUser>? UserLeft;
+
+        public event Action<MultiplayerRoomUser>? UserKicked;
+
         /// <summary>
         /// Invoked when the multiplayer server requests the current beatmap to be loaded into play.
         /// </summary>
@@ -366,11 +372,26 @@ namespace osu.Game.Online.Multiplayer
 
                 Room.Users.Add(user);
 
+                UserJoined?.Invoke(user);
                 RoomUpdated?.Invoke();
             }, false);
         }
 
-        Task IMultiplayerClient.UserLeft(MultiplayerRoomUser user)
+        Task IMultiplayerClient.UserLeft(MultiplayerRoomUser user) =>
+            handleUserLeft(user, UserLeft);
+
+        Task IMultiplayerClient.UserKicked(MultiplayerRoomUser user)
+        {
+            if (LocalUser == null)
+                return Task.CompletedTask;
+
+            if (user.Equals(LocalUser))
+                LeaveRoom();
+
+            return handleUserLeft(user, UserKicked);
+        }
+
+        private Task handleUserLeft(MultiplayerRoomUser user, Action<MultiplayerRoomUser>? callback)
         {
             if (Room == null)
                 return Task.CompletedTask;
@@ -383,24 +404,13 @@ namespace osu.Game.Online.Multiplayer
                 Room.Users.Remove(user);
                 PlayingUserIds.Remove(user.UserID);
 
+                callback?.Invoke(user);
                 RoomUpdated?.Invoke();
             }, false);
 
             return Task.CompletedTask;
         }
 
-        Task IMultiplayerClient.UserKicked(MultiplayerRoomUser user)
-        {
-            if (LocalUser == null)
-                return Task.CompletedTask;
-
-            if (user.Equals(LocalUser))
-                LeaveRoom();
-
-            // TODO: also inform users of the kick operation.
-            return ((IMultiplayerClient)this).UserLeft(user);
-        }
-
         Task IMultiplayerClient.HostChanged(int userId)
         {
             if (Room == null)

osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerRoomComposite.cs

@@ -20,9 +20,38 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
             base.LoadComplete();
 
             Client.RoomUpdated += OnRoomUpdated;
+
+            Client.UserLeft += UserLeft;
+            Client.UserKicked += UserKicked;
+            Client.UserJoined += UserJoined;
+
             OnRoomUpdated();
         }
 
+        /// <summary>
+        /// Invoked when a user has joined the room.
+        /// </summary>
+        /// <param name="user">The user.</param>
+        protected virtual void UserJoined(MultiplayerRoomUser user)
+        {
+        }
+
+        /// <summary>
+        /// Invoked when a user has been kicked from the room (including the local user).
+        /// </summary>
+        /// <param name="user">The user.</param>
+        protected virtual void UserKicked(MultiplayerRoomUser user)
+        {
+        }
+
+        /// <summary>
+        /// Invoked when a user has left the room.
+        /// </summary>
+        /// <param name="user">The user.</param>
+        protected virtual void UserLeft(MultiplayerRoomUser user)
+        {
+        }
+
         /// <summary>
         /// Invoked when any change occurs to the multiplayer room.
         /// </summary>
@@ -33,7 +62,12 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
         protected override void Dispose(bool isDisposing)
         {
             if (Client != null)
+            {
+                Client.UserLeft -= UserLeft;
+                Client.UserKicked -= UserKicked;
+                Client.UserJoined -= UserJoined;
                 Client.RoomUpdated -= OnRoomUpdated;
+            }
 
             base.Dispose(isDisposing);
         }