From 6eddc6c59e6c63c219798bc0fb92a59e0d3c3b96 Mon Sep 17 00:00:00 2001
From: smoogipoo <smoogipoo@smgi.me>
Date: Fri, 9 Apr 2021 21:03:45 +0900
Subject: [PATCH] Enable spectating multiplayer matches

---
 .../Online/Multiplayer/MultiplayerClient.cs   |  3 ---
 .../Screens/OnlinePlay/Match/RoomSubScreen.cs |  6 ++++--
 .../Multiplayer/MultiplayerMatchSubScreen.cs  | 20 +++++++++++++++----
 3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/osu.Game/Online/Multiplayer/MultiplayerClient.cs b/osu.Game/Online/Multiplayer/MultiplayerClient.cs
index 37e11cc576..4529dfd0a7 100644
--- a/osu.Game/Online/Multiplayer/MultiplayerClient.cs
+++ b/osu.Game/Online/Multiplayer/MultiplayerClient.cs
@@ -96,9 +96,6 @@ namespace osu.Game.Online.Multiplayer
             if (!IsConnected.Value)
                 return Task.CompletedTask;
 
-            if (newState == MultiplayerUserState.Spectating)
-                return Task.CompletedTask; // Not supported yet.
-
             return connection.InvokeAsync(nameof(IMultiplayerServer.ChangeState), newState);
         }
 
diff --git a/osu.Game/Screens/OnlinePlay/Match/RoomSubScreen.cs b/osu.Game/Screens/OnlinePlay/Match/RoomSubScreen.cs
index 706da05d15..0d1ed5d88e 100644
--- a/osu.Game/Screens/OnlinePlay/Match/RoomSubScreen.cs
+++ b/osu.Game/Screens/OnlinePlay/Match/RoomSubScreen.cs
@@ -148,10 +148,12 @@ namespace osu.Game.Screens.OnlinePlay.Match
             return base.OnExiting(next);
         }
 
-        protected void StartPlay(Func<Player> player)
+        protected void StartPlay(Func<Player> player) => PushTopLevelScreen(() => new PlayerLoader(player));
+
+        protected void PushTopLevelScreen(Func<Screen> screen)
         {
             sampleStart?.Play();
-            ParentScreen?.Push(new PlayerLoader(player));
+            ParentScreen?.Push(screen());
         }
 
         private void selectedItemChanged()
diff --git a/osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSubScreen.cs b/osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSubScreen.cs
index 90cef0107c..035eba4f30 100644
--- a/osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSubScreen.cs
+++ b/osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSubScreen.cs
@@ -25,6 +25,7 @@ using osu.Game.Screens.OnlinePlay.Match;
 using osu.Game.Screens.OnlinePlay.Match.Components;
 using osu.Game.Screens.OnlinePlay.Multiplayer.Match;
 using osu.Game.Screens.OnlinePlay.Multiplayer.Participants;
+using osu.Game.Screens.OnlinePlay.Multiplayer.Spectate;
 using osu.Game.Screens.Play.HUD;
 using osu.Game.Users;
 using osuTK;
@@ -405,11 +406,22 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
             }
         }
 
-        private void onRoomUpdated()
+        private void onRoomUpdated() => Scheduler.Add(() =>
         {
-            // user mods may have changed.
-            Scheduler.AddOnce(UpdateMods);
-        }
+            if (client.Room == null)
+                return;
+
+            Debug.Assert(client.LocalUser != null);
+
+            UpdateMods();
+
+            if (client.LocalUser.State == MultiplayerUserState.Spectating
+                && (client.Room.State == MultiplayerRoomState.Playing || client.Room.State == MultiplayerRoomState.WaitingForLoad)
+                && ParentScreen.IsCurrentScreen())
+            {
+                PushTopLevelScreen(() => new MultiplayerSpectator(client.CurrentMatchPlayingUserIds.ToArray()));
+            }
+        });
 
         private void onLoadRequested()
         {