Merge pull request #13375 from smoogipoo/fix-multi-nullref

Fix possible nullref when exiting song select too fast

osu.Game.Tests/Visual/Navigation/TestSceneScreenNavigation.cs

@@ -9,16 +9,19 @@ using osu.Framework.Screens;
 using osu.Framework.Testing;
 using osu.Game.Beatmaps;
 using osu.Game.Graphics.UserInterface;
+using osu.Game.Online.Multiplayer;
 using osu.Game.Overlays;
 using osu.Game.Overlays.Mods;
 using osu.Game.Overlays.Toolbar;
 using osu.Game.Rulesets.Mods;
 using osu.Game.Rulesets.Osu.Mods;
+using osu.Game.Screens.OnlinePlay.Components;
 using osu.Game.Screens.Play;
 using osu.Game.Screens.Ranking;
 using osu.Game.Screens.Select;
 using osu.Game.Screens.Select.Options;
 using osu.Game.Tests.Beatmaps.IO;
+using osu.Game.Tests.Visual.Multiplayer;
 using osuTK;
 using osuTK.Input;
 
@@ -152,6 +155,14 @@ namespace osu.Game.Tests.Visual.Navigation
             AddUntilStep("wait for track", () => !Game.MusicController.CurrentTrack.IsDummyDevice && Game.MusicController.IsPlaying);
         }
 
+        [Test]
+        public void TestPushSongSelectAndPressBackButtonImmediately()
+        {
+            AddStep("push song select", () => Game.ScreenStack.Push(new TestPlaySongSelect()));
+            AddStep("press back button", () => Game.ChildrenOfType<BackButton>().First().Action());
+            AddWaitStep("wait two frames", 2);
+        }
+
         [Test]
         public void TestExitSongSelectWithClick()
         {
@@ -298,6 +309,18 @@ namespace osu.Game.Tests.Visual.Navigation
             AddAssert("Toolbar is hidden", () => Game.Toolbar.State.Value == Visibility.Hidden);
         }
 
+        [Test]
+        public void TestPushMatchSubScreenAndPressBackButtonImmediately()
+        {
+            TestMultiplayer multiplayer = null;
+
+            PushAndConfirm(() => multiplayer = new TestMultiplayer());
+
+            AddStep("open room", () => multiplayer.OpenNewRoom());
+            AddStep("press back button", () => Game.ChildrenOfType<BackButton>().First().Action());
+            AddWaitStep("wait two frames", 2);
+        }
+
         private void pushEscape() =>
             AddStep("Press escape", () => InputManager.Key(Key.Escape));
 
@@ -322,5 +345,18 @@ namespace osu.Game.Tests.Visual.Navigation
 
             protected override bool DisplayStableImportPrompt => false;
         }
+
+        private class TestMultiplayer : Screens.OnlinePlay.Multiplayer.Multiplayer
+        {
+            [Cached(typeof(MultiplayerClient))]
+            public readonly TestMultiplayerClient Client;
+
+            public TestMultiplayer()
+            {
+                Client = new TestMultiplayerClient((TestMultiplayerRoomManager)RoomManager);
+            }
+
+            protected override RoomManager CreateRoomManager() => new TestMultiplayerRoomManager();
+        }
     }
 }

osu.Game/OsuGame.cs

@@ -651,9 +651,10 @@ namespace osu.Game
                                     Origin = Anchor.BottomLeft,
                                     Action = () =>
                                     {
-                                        var currentScreen = ScreenStack.CurrentScreen as IOsuScreen;
+                                        if (!(ScreenStack.CurrentScreen is IOsuScreen currentScreen))
+                                            return;
 
-                                        if (currentScreen?.AllowBackButton == true && !currentScreen.OnBackButton())
+                                        if (!((Drawable)currentScreen).IsLoaded || (currentScreen.AllowBackButton && !currentScreen.OnBackButton()))
                                             ScreenStack.Exit();
                                     }
                                 },

osu.Game/Screens/IOsuScreen.cs

@@ -67,8 +67,11 @@ namespace osu.Game.Screens
         /// Invoked when the back button has been pressed to close any overlays before exiting this <see cref="IOsuScreen"/>.
         /// </summary>
         /// <remarks>
+        /// If this <see cref="IOsuScreen"/> has not yet finished loading, the exit will occur immediately without this method being invoked.
+        /// <para>
         /// Return <c>true</c> to block this <see cref="IOsuScreen"/> from being exited after closing an overlay.
         /// Return <c>false</c> if this <see cref="IOsuScreen"/> should continue exiting.
+        /// </para>
         /// </remarks>
         bool OnBackButton();
     }

osu.Game/Screens/OnlinePlay/OnlinePlayScreen.cs

@@ -253,7 +253,10 @@ namespace osu.Game.Screens.OnlinePlay
 
         public override bool OnBackButton()
         {
-            if ((screenStack.CurrentScreen as IOnlinePlaySubScreen)?.OnBackButton() == true)
+            if (!(screenStack.CurrentScreen is IOnlinePlaySubScreen onlineSubScreen))
+                return false;
+
+            if (((Drawable)onlineSubScreen).IsLoaded && onlineSubScreen.AllowBackButton && onlineSubScreen.OnBackButton())
                 return true;
 
             if (screenStack.CurrentScreen != null && !(screenStack.CurrentScreen is LoungeSubScreen))