Make Room.RecentParticipants non-bindable

osu.Game.Tests/Visual/Multiplayer/TestSceneDrawableRoom.cs

@@ -199,11 +199,11 @@ namespace osu.Game.Tests.Visual.Multiplayer
 
             if (room.RecentParticipants.Count == 0)
             {
-                room.RecentParticipants.AddRange(Enumerable.Range(0, 20).Select(i => new APIUser
+                room.RecentParticipants = Enumerable.Range(0, 20).Select(i => new APIUser
                 {
                     Id = i,
                     Username = $"User {i}"
-                }));
+                }).ToArray();
             }
 
             return new DrawableLoungeRoom(room)

osu.Game.Tests/Visual/Multiplayer/TestSceneDrawableRoomParticipantsList.cs

@@ -138,17 +138,17 @@ namespace osu.Game.Tests.Visual.Multiplayer
 
         private void addUser(int id)
         {
-            SelectedRoom.Value.RecentParticipants.Add(new APIUser
+            SelectedRoom.Value.RecentParticipants = SelectedRoom.Value.RecentParticipants.Append(new APIUser
             {
                 Id = id,
                 Username = $"User {id}"
-            });
+            }).ToArray();
             SelectedRoom.Value.ParticipantCount++;
         }
 
         private void removeUserAt(int index)
         {
-            SelectedRoom.Value.RecentParticipants.RemoveAt(index);
+            SelectedRoom.Value.RecentParticipants = SelectedRoom.Value.RecentParticipants.Where(u => !u.Equals(SelectedRoom.Value.RecentParticipants[index])).ToArray();
             SelectedRoom.Value.ParticipantCount--;
         }
     }

osu.Game.Tests/Visual/Playlists/TestScenePlaylistsParticipantsList.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Graphics;
 using osu.Game.Online.API.Requests.Responses;
@@ -19,17 +20,16 @@ namespace osu.Game.Tests.Visual.Playlists
 
             AddStep("create list", () =>
             {
-                SelectedRoom.Value = new Room { RoomID = 7 };
+                SelectedRoom.Value = new Room
-
-                for (int i = 0; i < 50; i++)
                 {
-                    SelectedRoom.Value.RecentParticipants.Add(new APIUser
+                    RoomID = 7,
+                    RecentParticipants = Enumerable.Range(0, 50).Select(_ => new APIUser
                     {
                         Username = "peppy",
                         Statistics = new UserStatistics { GlobalRank = 1234 },
                         Id = 2
-                    });
+                    }).ToArray()
-                }
+                };
             });
         }
 

osu.Game.Tests/Visual/Playlists/TestScenePlaylistsRoomCreation.cs

@@ -62,7 +62,7 @@ namespace osu.Game.Tests.Visual.Playlists
             {
                 room.Name = "my awesome room";
                 room.Host = API.LocalUser.Value;
-                room.RecentParticipants.Add(room.Host);
+                room.RecentParticipants = [room.Host];
                 room.EndDate = DateTimeOffset.Now.AddMinutes(5);
                 room.Playlist.Add(new PlaylistItem(importedBeatmap.Beatmaps.First())
                 {
@@ -86,7 +86,7 @@ namespace osu.Game.Tests.Visual.Playlists
                 room.Name = "my awesome room";
                 room.MaxAttempts = 5;
                 room.Host = API.LocalUser.Value;
-                room.RecentParticipants.Add(room.Host);
+                room.RecentParticipants = [room.Host];
                 room.EndDate = DateTimeOffset.Now.AddMinutes(5);
                 room.Playlist.Add(new PlaylistItem(importedBeatmap.Beatmaps.First())
                 {

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -487,11 +487,11 @@ namespace osu.Game.Online.Multiplayer
         {
             Debug.Assert(APIRoom != null);
 
-            APIRoom.RecentParticipants.Add(user.User ?? new APIUser
+            APIRoom.RecentParticipants = APIRoom.RecentParticipants.Append(user.User ?? new APIUser
             {
                 Id = user.UserID,
                 Username = "[Unresolved]"
-            });
+            }).ToArray();
             APIRoom.ParticipantCount++;
         }
 
@@ -506,7 +506,7 @@ namespace osu.Game.Online.Multiplayer
                 PlayingUserIds.Remove(user.UserID);
 
                 Debug.Assert(APIRoom != null);
-                APIRoom.RecentParticipants.RemoveAll(u => u.Id == user.UserID);
+                APIRoom.RecentParticipants = APIRoom.RecentParticipants.Where(u => u.Id != user.UserID).ToArray();
                 APIRoom.ParticipantCount--;
 
                 callback?.Invoke(user);

osu.Game/Online/Rooms/Room.cs

@@ -137,6 +137,15 @@ namespace osu.Game.Online.Rooms
             set => SetField(ref participantCount, value);
         }
 
+        /// <summary>
+        /// The set of most recent participants in the room.
+        /// </summary>
+        public IReadOnlyList<APIUser> RecentParticipants
+        {
+            get => recentParticipants;
+            set => SetList(ref recentParticipants, value);
+        }
+
         /// <summary>
         /// The match type.
         /// </summary>
@@ -282,6 +291,9 @@ namespace osu.Game.Online.Rooms
         [JsonProperty("participant_count")]
         private int participantCount;
 
+        [JsonProperty("recent_participants")]
+        private IReadOnlyList<APIUser> recentParticipants = [];
+
         [JsonProperty("max_attempts", DefaultValueHandling = DefaultValueHandling.Ignore)]
         private int? maxAttempts;
 
@@ -324,10 +336,6 @@ namespace osu.Game.Online.Rooms
         [JsonProperty("playlist")]
         public readonly BindableList<PlaylistItem> Playlist = new BindableList<PlaylistItem>();
 
-        [Cached]
-        [JsonProperty("recent_participants")]
-        public readonly BindableList<APIUser> RecentParticipants = new BindableList<APIUser>();
-
         /// <summary>
         /// Copies values from another <see cref="Room"/> into this one.
         /// </summary>
@@ -369,11 +377,7 @@ namespace osu.Game.Online.Rooms
                 Playlist.AddRange(other.Playlist);
             }
 
-            if (!RecentParticipants.SequenceEqual(other.RecentParticipants))
+            RecentParticipants = other.RecentParticipants;
-            {
-                RecentParticipants.Clear();
-                RecentParticipants.AddRange(other.RecentParticipants);
-            }
         }
 
         public void RemoveExpiredPlaylistItems()
@@ -411,6 +415,16 @@ namespace osu.Game.Online.Rooms
         protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null!)
             => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
 
+        protected bool SetList<T>(ref IReadOnlyList<T> list, IReadOnlyList<T> value, [CallerMemberName] string propertyName = null!)
+        {
+            if (list.SequenceEqual(value))
+                return false;
+
+            list = value;
+            OnPropertyChanged(propertyName);
+            return true;
+        }
+
         protected bool SetField<T>(ref T field, T value, [CallerMemberName] string propertyName = null!)
         {
             if (EqualityComparer<T>.Default.Equals(field, value))

osu.Game/Screens/OnlinePlay/Components/ParticipantsDisplay.cs

@@ -23,7 +23,7 @@ namespace osu.Game.Screens.OnlinePlay.Components
 
             AddInternal(scroll = new OsuScrollContainer(direction)
             {
-                Child = list = new ParticipantsList()
+                Child = list = new ParticipantsList(room)
             });
 
             switch (direction)

osu.Game/Screens/OnlinePlay/Components/ParticipantsList.cs

@@ -1,15 +1,14 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
+using System.ComponentModel;
-
-using osu.Framework.Allocation;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Threading;
 using osu.Game.Online.API.Requests.Responses;
+using osu.Game.Online.Rooms;
 using osu.Game.Users.Drawables;
 using osuTK;
 
@@ -57,15 +56,29 @@ namespace osu.Game.Screens.OnlinePlay.Components
             }
         }
 
-        [BackgroundDependencyLoader]
+        private readonly Room room;
-        private void load()
+
+        public ParticipantsList(Room room)
         {
-            RecentParticipants.CollectionChanged += (_, _) => updateParticipants();
+            this.room = room;
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            room.PropertyChanged += onRoomPropertyChanged;
             updateParticipants();
         }
 
-        private ScheduledDelegate scheduledUpdate;
+        private void onRoomPropertyChanged(object? sender, PropertyChangedEventArgs e)
-        private FillFlowContainer<UserTile> tiles;
+        {
+            if (e.PropertyName == nameof(Room.RecentParticipants))
+                updateParticipants();
+        }
+
+        private ScheduledDelegate? scheduledUpdate;
+        private FillFlowContainer<UserTile>? tiles;
 
         private void updateParticipants()
         {
@@ -83,8 +96,8 @@ namespace osu.Game.Screens.OnlinePlay.Components
                     Spacing = Vector2.One
                 };
 
-                for (int i = 0; i < RecentParticipants.Count; i++)
+                for (int i = 0; i < room.RecentParticipants.Count; i++)
-                    tiles.Add(new UserTile { User = RecentParticipants[i] });
+                    tiles.Add(new UserTile { User = room.RecentParticipants[i] });
 
                 AddInternal(tiles);
 
@@ -92,9 +105,15 @@ namespace osu.Game.Screens.OnlinePlay.Components
             });
         }
 
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+            room.PropertyChanged -= onRoomPropertyChanged;
+        }
+
         private partial class UserTile : CompositeDrawable
         {
-            public APIUser User
+            public APIUser? User
             {
                 get => avatar.User;
                 set => avatar.User = value;

osu.Game/Screens/OnlinePlay/Lounge/Components/DrawableRoomParticipantsList.cs

@@ -1,9 +1,8 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using System.Collections.Specialized;
+using System.Collections.Generic;
 using System.ComponentModel;
-using System.Diagnostics;
 using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
@@ -165,12 +164,11 @@ namespace osu.Game.Screens.OnlinePlay.Lounge.Components
         {
             base.LoadComplete();
 
-            RecentParticipants.BindCollectionChanged(onParticipantsChanged, true);
-
             room.PropertyChanged += onRoomPropertyChanged;
 
             updateRoomHost();
             updateRoomParticipantCount();
+            updateRoomParticipants();
         }
 
         private int numberOfCircles = 4;
@@ -190,44 +188,39 @@ namespace osu.Game.Screens.OnlinePlay.Lounge.Components
 
                 // Reinitialising the list looks janky, but this is unlikely to be used in a setting where it's visible.
                 clearUsers();
-                foreach (var u in RecentParticipants)
+                foreach (var u in room.RecentParticipants)
                     addUser(u);
 
                 updateHiddenUsers();
             }
         }
 
-        private void onParticipantsChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        private void updateRoomParticipants()
         {
-            switch (e.Action)
+            HashSet<APIUser> newUsers = room.RecentParticipants.ToHashSet();
+
+            avatarFlow.RemoveAll(a =>
             {
-                case NotifyCollectionChangedAction.Add:
+                // Avatar with no user. Really shouldn't ever be the case but asserting it correctly is difficult.
-                    Debug.Assert(e.NewItems != null);
+                if (a.User == null)
+                    return false;
 
-                    foreach (var added in e.NewItems.OfType<APIUser>())
+                // User was previously and still is a participant. Keep them around but remove them from the new set.
-                        addUser(added);
+                // This will be useful when we add all remaining users (now just the new participants) to the flow.
-                    break;
+                if (newUsers.Contains(a.User))
-
+                {
-                case NotifyCollectionChangedAction.Remove:
+                    newUsers.Remove(a.User);
-                    Debug.Assert(e.OldItems != null);
+                    return false;
-
-                    foreach (var removed in e.OldItems.OfType<APIUser>())
-                        removeUser(removed);
-                    break;
-
-                case NotifyCollectionChangedAction.Reset:
-                    clearUsers();
-                    break;
-
-                case NotifyCollectionChangedAction.Replace:
-                case NotifyCollectionChangedAction.Move:
-                    // Easiest is to just reinitialise the whole list. These are unlikely to ever be use cases.
-                    clearUsers();
-                    foreach (var u in RecentParticipants)
-                        addUser(u);
-                    break;
                 }
 
+                // User is no longer a participant. Remove them from the flow.
+                return true;
+            }, true);
+
+            // Add all remaining users to the flow.
+            foreach (var u in newUsers)
+                addUser(u);
+
             updateHiddenUsers();
         }
 
@@ -239,11 +232,6 @@ namespace osu.Game.Screens.OnlinePlay.Lounge.Components
                 avatarFlow.Add(new CircularAvatar { User = user });
         }
 
-        private void removeUser(APIUser user)
-        {
-            avatarFlow.RemoveAll(a => a.User == user, true);
-        }
-
         private void clearUsers()
         {
             avatarFlow.Clear();
@@ -253,7 +241,7 @@ namespace osu.Game.Screens.OnlinePlay.Lounge.Components
         private void updateHiddenUsers()
         {
             int hiddenCount = 0;
-            if (RecentParticipants.Count > NumberOfCircles)
+            if (room.RecentParticipants.Count > NumberOfCircles)
                 hiddenCount = room.ParticipantCount - NumberOfCircles + 1;
 
             hiddenUsers.Count = hiddenCount;
@@ -262,7 +250,7 @@ namespace osu.Game.Screens.OnlinePlay.Lounge.Components
                 avatarFlow.Remove(avatarFlow.Last(), true);
             else if (displayedCircles < NumberOfCircles)
             {
-                var nextUser = RecentParticipants.FirstOrDefault(u => avatarFlow.All(a => a.User != u));
+                var nextUser = room.RecentParticipants.FirstOrDefault(u => avatarFlow.All(a => a.User != u));
                 if (nextUser != null) addUser(nextUser);
             }
         }
@@ -278,6 +266,10 @@ namespace osu.Game.Screens.OnlinePlay.Lounge.Components
                 case nameof(Room.ParticipantCount):
                     updateRoomParticipantCount();
                     break;
+
+                case nameof(Room.RecentParticipants):
+                    updateRoomParticipants();
+                    break;
             }
         }
 

osu.Game/Screens/OnlinePlay/OnlinePlayComposite.cs

@@ -4,7 +4,6 @@
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics.Containers;
-using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Online.Rooms;
 
 namespace osu.Game.Screens.OnlinePlay
@@ -16,8 +15,5 @@ namespace osu.Game.Screens.OnlinePlay
     {
         [Resolved(typeof(Room))]
         protected BindableList<PlaylistItem> Playlist { get; private set; } = null!;
-
-        [Resolved(typeof(Room))]
-        protected BindableList<APIUser> RecentParticipants { get; private set; } = null!;
     }
 }

osu.Game/Tests/Visual/OnlinePlay/TestRoomRequestsHandler.cs

@@ -280,7 +280,7 @@ namespace osu.Game.Tests.Visual.OnlinePlay
             responseRoom.Password = responseRoom.HasPassword ? Guid.NewGuid().ToString() : null;
 
             if (!withParticipants)
-                responseRoom.RecentParticipants.Clear();
+                responseRoom.RecentParticipants = [];
 
             return responseRoom;
         }