From e9d4e4d1d5bb5c6df13474c867c81b4d516cd61d Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Wed, 6 Jan 2021 15:26:13 +0900
Subject: [PATCH] Add xmldoc and throw a local exception on null background

---
 osu.Game/Screens/BackgroundScreen.cs |  4 ++++
 osu.Game/Screens/OsuScreen.cs        | 14 ++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/osu.Game/Screens/BackgroundScreen.cs b/osu.Game/Screens/BackgroundScreen.cs
index ea220c2f82..c81362eebe 100644
--- a/osu.Game/Screens/BackgroundScreen.cs
+++ b/osu.Game/Screens/BackgroundScreen.cs
@@ -34,6 +34,10 @@ namespace osu.Game.Screens
             return false;
         }
 
+        /// <summary>
+        /// Apply arbitrary changes to this background in a thread safe manner.
+        /// </summary>
+        /// <param name="action">The operation to perform.</param>
         public void ApplyToBackground(Action<BackgroundScreen> action) => Schedule(() => action.Invoke(this));
 
         protected override void Update()
diff --git a/osu.Game/Screens/OsuScreen.cs b/osu.Game/Screens/OsuScreen.cs
index d1cdb9f1de..11467db6c8 100644
--- a/osu.Game/Screens/OsuScreen.cs
+++ b/osu.Game/Screens/OsuScreen.cs
@@ -115,8 +115,6 @@ namespace osu.Game.Screens
             Mods = screenDependencies.Mods;
         }
 
-        public void ApplyToBackground(Action<BackgroundScreen> action) => background.ApplyToBackground(action);
-
         /// <summary>
         /// The background created and owned by this screen. May be null if the background didn't change.
         /// </summary>
@@ -148,6 +146,18 @@ namespace osu.Game.Screens
             Activity.Value ??= InitialActivity;
         }
 
+        /// <summary>
+        /// Apply arbitrary changes to the current background screen in a thread safe manner.
+        /// </summary>
+        /// <param name="action">The operation to perform.</param>
+        public void ApplyToBackground(Action<BackgroundScreen> action)
+        {
+            if (background == null)
+                throw new InvalidOperationException("Attempted to apply to background before screen is pushed");
+
+            background.ApplyToBackground(action);
+        }
+
         public override void OnResuming(IScreen last)
         {
             if (PlayResumeSound)