From 59e2478b0ec8e3a4a0ebaf615489224c88b38fd3 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Wed, 19 Oct 2022 16:01:07 +0900
Subject: [PATCH] Fix some older beatmaps having missing backgrounds

Closes https://github.com/ppy/osu/issues/20824.

Note that this will require a reimport of beatmaps as it is baked into the database. Probably not worth making a migration for at this point in time.
---
 osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs b/osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs
index 75500fbc4e..5f5749dc73 100644
--- a/osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs
+++ b/osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs
@@ -355,6 +355,14 @@ namespace osu.Game.Beatmaps.Formats
 
             switch (type)
             {
+                case LegacyEventType.Sprite:
+                    // Generally, the background is the first thing defined in a beatmap file.
+                    // In some older beatmaps, it is not present and replaced by a storyboard-level background instead.
+                    // Allow the first sprite (by file order) to act as the background in such cases.
+                    if (string.IsNullOrEmpty(beatmap.BeatmapInfo.Metadata.BackgroundFile))
+                        beatmap.BeatmapInfo.Metadata.BackgroundFile = CleanFilename(split[3]);
+                    break;
+
                 case LegacyEventType.Background:
                     beatmap.BeatmapInfo.Metadata.BackgroundFile = CleanFilename(split[2]);
                     break;