Use BeforeGameStart to remove mission browser UI on game start.

OpenRA.Game/Game.cs

@@ -197,7 +197,7 @@ namespace OpenRA
 				CreateAndStartLocalServer(lobbyInfo.GlobalSettings.Map, orders);
 		}
 
-		public static void CreateAndStartLocalServer(string mapUID, IEnumerable<Order> setupOrders, Action onStart = null)
+		public static void CreateAndStartLocalServer(string mapUID, IEnumerable<Order> setupOrders)
 		{
 			OrderManager om = null;
 
@@ -207,10 +207,8 @@ namespace OpenRA
 				LobbyInfoChanged -= lobbyReady;
 				foreach (var o in setupOrders)
 					om.IssueOrder(o);
-
-				if (onStart != null)
-					onStart();
 			};
+
 			LobbyInfoChanged += lobbyReady;
 
 			om = JoinServer(IPAddress.Loopback.ToString(), CreateLocalServer(mapUID), "");

OpenRA.Mods.Common/Widgets/Logic/MissionBrowserLogic.cs

@@ -55,6 +55,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 		{
 			this.modData = modData;
 			this.onStart = onStart;
+			Game.BeforeGameStart += OnGameStart;
 
 			missionList = widget.Get<ScrollPanelWidget>("MISSION_LIST");
 
@@ -151,6 +152,24 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			};
 		}
 
+		void OnGameStart()
+		{
+			Ui.CloseWindow();
+			onStart();
+		}
+
+		bool disposed;
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing && !disposed)
+			{
+				disposed = true;
+				Game.BeforeGameStart -= OnGameStart;
+			}
+
+			base.Dispose(disposing);
+		}
+
 		void CreateMissionGroup(string title, IEnumerable<MapPreview> previews)
 		{
 			var header = ScrollItemWidget.Setup(headerTemplate, () => true, () => { });
@@ -344,11 +363,11 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				PlayVideo(fsPlayer, missionData.StartVideo, PlayingVideo.GameStart, () =>
 				{
 					StopVideo(fsPlayer);
-					Game.CreateAndStartLocalServer(selectedMap.Uid, orders, onStart);
+					Game.CreateAndStartLocalServer(selectedMap.Uid, orders);
 				});
 			}
 			else
-				Game.CreateAndStartLocalServer(selectedMap.Uid, orders, onStart);
+				Game.CreateAndStartLocalServer(selectedMap.Uid, orders);
 		}
 
 		class DropDownOption