Make lobby song update occur at round end (#19303)

Content.Client/GameTicking/Managers/ClientGameTicker.cs

@@ -1,4 +1,3 @@
-using Content.Client.Audio;
 using Content.Client.Gameplay;
 using Content.Client.Lobby;
 using Content.Client.RoundEnd;
@@ -8,7 +7,6 @@ using Content.Shared.GameWindow;
 using JetBrains.Annotations;
 using Robust.Client.Graphics;
 using Robust.Client.State;
-using Robust.Shared.Audio;
 using Robust.Shared.Configuration;
 using Robust.Shared.Player;
 using Robust.Shared.Utility;
@@ -21,7 +19,6 @@ namespace Content.Client.GameTicking.Managers
         [Dependency] private readonly IStateManager _stateManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
         [Dependency] private readonly IConfigurationManager _configManager = default!;
-        [Dependency] private readonly BackgroundAudioSystem _backgroundAudio = default!;
         [Dependency] private readonly SharedAudioSystem _audio = default!;
 
         [ViewVariables] private bool _initialized;
@@ -49,6 +46,7 @@ namespace Content.Client.GameTicking.Managers
 
         public event Action? InfoBlobUpdated;
         public event Action? LobbyStatusUpdated;
+        public event Action? LobbySongUpdated;
         public event Action? LobbyLateJoinStatusUpdated;
         public event Action<IReadOnlyDictionary<EntityUid, Dictionary<string, uint?>>>? LobbyJobsAvailableUpdated;
 
@@ -73,6 +71,16 @@ namespace Content.Client.GameTicking.Managers
             _initialized = true;
         }
 
+        public void SetLobbySong(string? song, bool forceUpdate = false)
+        {
+            var updated = song != LobbySong;
+
+            LobbySong = song;
+
+            if (updated || forceUpdate)
+                LobbySongUpdated?.Invoke();
+        }
+
         private void LateJoinStatus(TickerLateJoinStatusEvent message)
         {
             DisallowedLateJoin = message.Disallowed;
@@ -97,7 +105,7 @@ namespace Content.Client.GameTicking.Managers
             RoundStartTimeSpan = message.RoundStartTimeSpan;
             IsGameStarted = message.IsRoundStarted;
             AreWeReady = message.YouAreReady;
-            LobbySong = message.LobbySong;
+            SetLobbySong(message.LobbySong);
             LobbyBackground = message.LobbyBackground;
             Paused = message.Paused;
 
@@ -124,12 +132,8 @@ namespace Content.Client.GameTicking.Managers
 
         private void RoundEnd(RoundEndMessageEvent message)
         {
-            if (message.LobbySong != null)
-            {
-                LobbySong = message.LobbySong;
-                _backgroundAudio.StartLobbyMusic();
-            }
-
+            // Force an update in the event of this song being the same as the last.
+            SetLobbySong(message.LobbySong, true);
             RestartSound = message.RestartSound;
 
             // Don't open duplicate windows (mainly for replays).