Fix OnUserBeganPlaying not being invoked if already watching

osu.Game.Tests/Visual/Gameplay/TestSceneSpectator.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;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -204,6 +205,29 @@ namespace osu.Game.Tests.Visual.Gameplay
             AddAssert("screen didn't change", () => Stack.CurrentScreen is SoloSpectator);
         }
 
+        [Test]
+        public void OnUserBeganPlayingCallbackInvokedOnNewAdd()
+        {
+            bool callbackInvoked = false;
+            Action<int, SpectatorState> callbackAction = (_, __) => callbackInvoked = true;
+
+            AddStep("bind first event", () => testSpectatorStreamingClient.OnUserBeganPlaying += callbackAction);
+            start();
+            AddAssert("callback invoked", () => callbackInvoked);
+
+            AddStep("reset", () =>
+            {
+                testSpectatorStreamingClient.OnUserBeganPlaying -= callbackAction;
+                callbackInvoked = false;
+            });
+
+            AddStep("bind event again", () => testSpectatorStreamingClient.OnUserBeganPlaying += callbackAction);
+            AddAssert("callback invoked", () => callbackInvoked);
+
+            // Don't leave the event bound if test run succeeded.
+            AddStep("reset", () => testSpectatorStreamingClient.OnUserBeganPlaying -= callbackAction);
+        }
+
         private OsuFramedReplayInputHandler replayHandler =>
             (OsuFramedReplayInputHandler)Stack.ChildrenOfType<OsuInputManager>().First().ReplayInputHandler;
 

osu.Game/Online/Spectator/SpectatorStreamingClient.cs

@@ -60,6 +60,7 @@ namespace osu.Game.Online.Spectator
         private IBindable<IReadOnlyList<Mod>> currentMods { get; set; }
 
         private readonly SpectatorState currentState = new SpectatorState();
+        private readonly Dictionary<int, SpectatorState> currentUserStates = new Dictionary<int, SpectatorState>();
 
         private bool isPlaying;
 
@@ -68,10 +69,25 @@ namespace osu.Game.Online.Spectator
         /// </summary>
         public event Action<int, FrameDataBundle> OnNewFrames;
 
+        private event Action<int, SpectatorState> onUserBeganPlaying;
+
         /// <summary>
-        /// Called whenever a user starts a play session.
+        /// Called whenever a user starts a play session, or immediately if the user is being watched and currently in a play session.
         /// </summary>
-        public event Action<int, SpectatorState> OnUserBeganPlaying;
+        public event Action<int, SpectatorState> OnUserBeganPlaying
+        {
+            add
+            {
+                onUserBeganPlaying += value;
+
+                lock (userLock)
+                {
+                    foreach (var (userId, state) in currentUserStates)
+                        value?.Invoke(userId, state);
+                }
+            }
+            remove => onUserBeganPlaying -= value;
+        }
 
         /// <summary>
         /// Called whenever a user finishes a play session.
@@ -134,7 +150,10 @@ namespace osu.Game.Online.Spectator
             if (!playingUsers.Contains(userId))
                 playingUsers.Add(userId);
 
-            OnUserBeganPlaying?.Invoke(userId, state);
+            lock (userLock)
+                currentUserStates[userId] = state;
+
+            onUserBeganPlaying?.Invoke(userId, state);
 
             return Task.CompletedTask;
         }
@@ -143,6 +162,9 @@ namespace osu.Game.Online.Spectator
         {
             playingUsers.Remove(userId);
 
+            lock (userLock)
+                currentUserStates.Remove(userId);
+
             OnUserFinishedPlaying?.Invoke(userId, state);
 
             return Task.CompletedTask;