Make StatefulMultiplayerClient control current playlist item

osu.Game/Online/Multiplayer/MultiplayerRoomSettings.cs

@@ -36,18 +36,26 @@ namespace osu.Game.Online.Multiplayer
         [Key(5)]
         public IEnumerable<APIMod> AllowedMods { get; set; } = Enumerable.Empty<APIMod>();
 
+        /// <summary>
+        /// Only used for client-side mutation.
+        /// </summary>
+        [Key(6)]
+        public int PlaylistItemId { get; set; }
+
         public bool Equals(MultiplayerRoomSettings other)
             => BeatmapID == other.BeatmapID
                && BeatmapChecksum == other.BeatmapChecksum
                && RequiredMods.SequenceEqual(other.RequiredMods)
                && AllowedMods.SequenceEqual(other.AllowedMods)
                && RulesetID == other.RulesetID
-               && Name.Equals(other.Name, StringComparison.Ordinal);
+               && Name.Equals(other.Name, StringComparison.Ordinal)
+               && PlaylistItemId == other.PlaylistItemId;
 
         public override string ToString() => $"Name:{Name}"
                                              + $" Beatmap:{BeatmapID} ({BeatmapChecksum})"
                                              + $" RequiredMods:{string.Join(',', RequiredMods)}"
                                              + $" AllowedMods:{string.Join(',', AllowedMods)}"
-                                             + $" Ruleset:{RulesetID}";
+                                             + $" Ruleset:{RulesetID}"
+                                             + $" Item:{PlaylistItemId}";
     }
 }

osu.Game/Online/Multiplayer/StatefulMultiplayerClient.cs

@@ -66,6 +66,8 @@ namespace osu.Game.Online.Multiplayer
         /// </summary>
         public readonly BindableList<int> CurrentMatchPlayingUserIds = new BindableList<int>();
 
+        public readonly Bindable<PlaylistItem?> CurrentMatchPlayingItem = new Bindable<PlaylistItem?>();
+
         /// <summary>
         /// The <see cref="MultiplayerRoomUser"/> corresponding to the local player, if available.
         /// </summary>
@@ -94,9 +96,6 @@ namespace osu.Game.Online.Multiplayer
 
         private Room? apiRoom;
 
-        // Todo: This is temporary, until the multiplayer server returns the item id on match start or otherwise.
-        private int playlistItemId;
-
         [BackgroundDependencyLoader]
         private void load()
         {
@@ -142,7 +141,6 @@ namespace osu.Game.Online.Multiplayer
                 {
                     Room = joinedRoom;
                     apiRoom = room;
-                    playlistItemId = room.Playlist.SingleOrDefault()?.ID ?? 0;
                 }, cancellationSource.Token);
 
                 // Update room settings.
@@ -218,7 +216,8 @@ namespace osu.Game.Online.Multiplayer
                 BeatmapChecksum = item.GetOr(existingPlaylistItem).Beatmap.Value.MD5Hash,
                 RulesetID = item.GetOr(existingPlaylistItem).RulesetID,
                 RequiredMods = item.HasValue ? item.Value.AsNonNull().RequiredMods.Select(m => new APIMod(m)).ToList() : Room.Settings.RequiredMods,
-                AllowedMods = item.HasValue ? item.Value.AsNonNull().AllowedMods.Select(m => new APIMod(m)).ToList() : Room.Settings.AllowedMods
+                AllowedMods = item.HasValue ? item.Value.AsNonNull().AllowedMods.Select(m => new APIMod(m)).ToList() : Room.Settings.AllowedMods,
+                PlaylistItemId = Room.Settings.PlaylistItemId,
             });
         }
 
@@ -506,14 +505,13 @@ namespace osu.Game.Online.Multiplayer
             Room.Settings = settings;
             apiRoom.Name.Value = Room.Settings.Name;
 
-            // The playlist update is delayed until an online beatmap lookup (below) succeeds.
+            // The current item update is delayed until an online beatmap lookup (below) succeeds.
-            // In-order for the client to not display an outdated beatmap, the playlist is forcefully cleared here.
+            // In-order for the client to not display an outdated beatmap, the current item is forcefully cleared here.
-            apiRoom.Playlist.Clear();
+            CurrentMatchPlayingItem.Value = null;
 
             RoomUpdated?.Invoke();
 
             var req = new GetBeatmapSetRequest(settings.BeatmapID, BeatmapSetLookupType.BeatmapId);
-
             req.Success += res =>
             {
                 if (cancellationToken.IsCancellationRequested)
@@ -540,18 +538,21 @@ namespace osu.Game.Online.Multiplayer
             var mods = settings.RequiredMods.Select(m => m.ToMod(ruleset));
             var allowedMods = settings.AllowedMods.Select(m => m.ToMod(ruleset));
 
-            PlaylistItem playlistItem = new PlaylistItem
+            // Update an existing playlist item from the API room, or create a new item.
-            {
+            var playlistItem = apiRoom.Playlist.FirstOrDefault(i => i.ID == settings.PlaylistItemId);
-                ID = playlistItemId,
-                Beatmap = { Value = beatmap },
-                Ruleset = { Value = ruleset.RulesetInfo },
-            };
 
+            if (playlistItem == null)
+                apiRoom.Playlist.Add(playlistItem = new PlaylistItem());
+
+            playlistItem.ID = settings.PlaylistItemId;
+            playlistItem.Beatmap.Value = beatmap;
+            playlistItem.Ruleset.Value = ruleset.RulesetInfo;
+            playlistItem.RequiredMods.Clear();
             playlistItem.RequiredMods.AddRange(mods);
+            playlistItem.AllowedMods.Clear();
             playlistItem.AllowedMods.AddRange(allowedMods);
 
-            apiRoom.Playlist.Clear(); // Clearing should be unnecessary, but here for sanity.
+            CurrentMatchPlayingItem.Value = playlistItem;
-            apiRoom.Playlist.Add(playlistItem);
         }
 
         /// <summary>

osu.Game/Screens/OnlinePlay/Match/RoomSubScreen.cs

@@ -28,9 +28,6 @@ namespace osu.Game.Screens.OnlinePlay.Match
 
         private Sample sampleStart;
 
-        [Resolved(typeof(Room), nameof(Room.Playlist))]
-        protected BindableList<PlaylistItem> Playlist { get; private set; }
-
         /// <summary>
         /// Any mods applied by/to the local user.
         /// </summary>
@@ -74,7 +71,6 @@ namespace osu.Game.Screens.OnlinePlay.Match
             base.LoadComplete();
 
             SelectedItem.BindValueChanged(_ => Scheduler.AddOnce(selectedItemChanged));
-            SelectedItem.Value = Playlist.FirstOrDefault();
 
             managerUpdated = beatmapManager.ItemUpdated.GetBoundCopy();
             managerUpdated.BindValueChanged(beatmapUpdated);

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

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Specialized;
 using System.Diagnostics;
 using System.Linq;
 using JetBrains.Annotations;
@@ -269,7 +268,9 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
         {
             base.LoadComplete();
 
-            Playlist.BindCollectionChanged(onPlaylistChanged, true);
+            SelectedItem.BindValueChanged(onSelectedItemChanged);
+            SelectedItem.BindTo(client.CurrentMatchPlayingItem);
+
             BeatmapAvailability.BindValueChanged(updateBeatmapAvailability, true);
             UserMods.BindValueChanged(onUserModsChanged);
 
@@ -300,11 +301,9 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
             return base.OnBackButton();
         }
 
-        private void onPlaylistChanged(object sender, NotifyCollectionChangedEventArgs e)
+        private void onSelectedItemChanged(ValueChangedEvent<PlaylistItem> item)
         {
-            SelectedItem.Value = Playlist.LastOrDefault();
+            if (item.NewValue?.AllowedMods.Any() != true)
-
-            if (SelectedItem.Value?.AllowedMods.Any() != true)
             {
                 userModsSection.Hide();
                 userModsSelectOverlay.Hide();
@@ -313,7 +312,7 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
             else
             {
                 userModsSection.Show();
-                userModsSelectOverlay.IsValidMod = m => SelectedItem.Value.AllowedMods.Any(a => a.GetType() == m.GetType());
+                userModsSelectOverlay.IsValidMod = m => item.NewValue.AllowedMods.Any(a => a.GetType() == m.GetType());
             }
         }
 

osu.Game/Screens/OnlinePlay/Playlists/PlaylistsRoomSubScreen.cs

@@ -27,6 +27,9 @@ namespace osu.Game.Screens.OnlinePlay.Playlists
         [Resolved(typeof(Room), nameof(Room.RoomID))]
         private Bindable<int?> roomId { get; set; }
 
+        [Resolved(typeof(Room), nameof(Room.Playlist))]
+        private BindableList<PlaylistItem> playlist { get; set; }
+
         private MatchSettingsOverlay settingsOverlay;
         private MatchLeaderboard leaderboard;
 
@@ -117,7 +120,7 @@ namespace osu.Game.Screens.OnlinePlay.Playlists
                                                                         new DrawableRoomPlaylistWithResults
                                                                         {
                                                                             RelativeSizeAxes = Axes.Both,
-                                                                            Items = { BindTarget = Playlist },
+                                                                            Items = { BindTarget = playlist },
                                                                             SelectedItem = { BindTarget = SelectedItem },
                                                                             RequestShowResults = item =>
                                                                             {
@@ -222,7 +225,7 @@ namespace osu.Game.Screens.OnlinePlay.Playlists
 
                     // Set the first playlist item.
                     // This is scheduled since updating the room and playlist may happen in an arbitrary order (via Room.CopyFrom()).
-                    Schedule(() => SelectedItem.Value = Playlist.FirstOrDefault());
+                    Schedule(() => SelectedItem.Value = playlist.FirstOrDefault());
                 }
             }, true);
         }