Fix taiko beatmap scroll speed increasing after every save in editor

osu.Game.Rulesets.Taiko.Tests/Editor/TestSceneEditorSaving.cs

@@ -0,0 +1,91 @@
+// Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Input;
+using osu.Framework.Testing;
+using osu.Framework.Utils;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets.Edit;
+using osu.Game.Rulesets.Taiko.Beatmaps;
+using osu.Game.Screens.Edit;
+using osu.Game.Screens.Edit.Setup;
+using osu.Game.Screens.Menu;
+using osu.Game.Screens.Select;
+using osu.Game.Tests.Visual;
+using osuTK.Input;
+
+namespace osu.Game.Rulesets.Taiko.Tests.Editor
+{
+    public class TestSceneEditorSaving : OsuGameTestScene
+    {
+        private Screens.Edit.Editor editor => Game.ChildrenOfType<Screens.Edit.Editor>().FirstOrDefault();
+
+        private EditorBeatmap editorBeatmap => (EditorBeatmap)editor.Dependencies.Get(typeof(EditorBeatmap));
+
+        /// <summary>
+        /// Tests the general expected flow of creating a new beatmap, saving it, then loading it back from song select.
+        /// Emphasis is placed on <see cref="BeatmapDifficulty.SliderMultiplier"/>, since taiko has special handling for it to keep compatibility with stable.
+        /// </summary>
+        [Test]
+        public void TestNewBeatmapSaveThenLoad()
+        {
+            AddStep("set default beatmap", () => Game.Beatmap.SetDefault());
+            AddStep("set taiko ruleset", () => Ruleset.Value = new TaikoRuleset().RulesetInfo);
+
+            PushAndConfirm(() => new EditorLoader());
+
+            AddUntilStep("wait for editor load", () => editor?.IsLoaded == true);
+
+            AddUntilStep("wait for metadata screen load", () => editor.ChildrenOfType<MetadataSection>().FirstOrDefault()?.IsLoaded == true);
+
+            // We intentionally switch away from the metadata screen, else there is a feedback loop with the textbox handling which causes metadata changes below to get overwritten.
+
+            AddStep("Enter compose mode", () => InputManager.Key(Key.F1));
+            AddUntilStep("Wait for compose mode load", () => editor.ChildrenOfType<HitObjectComposer>().FirstOrDefault()?.IsLoaded == true);
+
+            AddStep("Set slider multiplier", () => editorBeatmap.Difficulty.SliderMultiplier = 2);
+            AddStep("Set artist and title", () =>
+            {
+                editorBeatmap.BeatmapInfo.Metadata.Artist = "artist";
+                editorBeatmap.BeatmapInfo.Metadata.Title = "title";
+            });
+            AddStep("Set difficulty name", () => editorBeatmap.BeatmapInfo.Version = "difficulty");
+
+            checkMutations();
+
+            AddStep("Save", () => InputManager.Keys(PlatformAction.Save));
+
+            checkMutations();
+
+            AddStep("Exit", () => InputManager.Key(Key.Escape));
+
+            AddUntilStep("Wait for main menu", () => Game.ScreenStack.CurrentScreen is MainMenu);
+
+            PushAndConfirm(() => new PlaySongSelect());
+
+            AddUntilStep("Wait for beatmap selected", () => !Game.Beatmap.IsDefault);
+            AddStep("Open options", () => InputManager.Key(Key.F3));
+            AddStep("Enter editor", () => InputManager.Key(Key.Number5));
+
+            AddUntilStep("Wait for editor load", () => editor != null);
+
+            checkMutations();
+        }
+
+        private void checkMutations()
+        {
+            AddAssert("Beatmap has correct slider multiplier", () =>
+            {
+                // we can only assert value correctness on TaikoMultiplierAppliedDifficulty, because that is the final difficulty converted taiko beatmaps use.
+                // therefore, ensure that we have that difficulty type by calling .CopyFrom(), which is a no-op if the type is already correct.
+                var taikoDifficulty = new TaikoBeatmapConverter.TaikoMultiplierAppliedDifficulty();
+                taikoDifficulty.CopyFrom(editorBeatmap.Difficulty);
+                return Precision.AlmostEquals(taikoDifficulty.SliderMultiplier, 2);
+            });
+            AddAssert("Beatmap has correct metadata", () => editorBeatmap.BeatmapInfo.Metadata.Artist == "artist" && editorBeatmap.BeatmapInfo.Metadata.Title == "title");
+            AddAssert("Beatmap has correct difficulty name", () => editorBeatmap.BeatmapInfo.Version == "difficulty");
+        }
+    }
+}

osu.Game.Rulesets.Taiko/Beatmaps/TaikoBeatmapConverter.cs

@@ -191,7 +191,7 @@ private bool shouldConvertSliderToHits(HitObject obj, IBeatmap beatmap, IHasDist
 
         protected override Beatmap<TaikoHitObject> CreateBeatmap() => new TaikoBeatmap();
 
-        private class TaikoMultiplierAppliedDifficulty : BeatmapDifficulty
+        internal class TaikoMultiplierAppliedDifficulty : BeatmapDifficulty
         {
             public TaikoMultiplierAppliedDifficulty(IBeatmapDifficultyInfo difficulty)
             {
@@ -209,7 +209,7 @@ public override void CopyTo(BeatmapDifficulty other)
             {
                 base.CopyTo(other);
                 if (!(other is TaikoMultiplierAppliedDifficulty))
-                    SliderMultiplier /= LegacyBeatmapEncoder.LEGACY_TAIKO_VELOCITY_MULTIPLIER;
+                    other.SliderMultiplier /= LegacyBeatmapEncoder.LEGACY_TAIKO_VELOCITY_MULTIPLIER;
             }
 
             public override void CopyFrom(IBeatmapDifficultyInfo other)

osu.Game/Beatmaps/BeatmapModelManager.cs

@@ -189,7 +189,11 @@ public virtual void Save(BeatmapInfo beatmapInfo, IBeatmap beatmapContent, ISkin
 
             // Difficulty settings must be copied first due to the clone in `Beatmap<>.BeatmapInfo_Set`.
             // This should hopefully be temporary, assuming said clone is eventually removed.
-            beatmapInfo.BaseDifficulty.CopyFrom(beatmapContent.Difficulty);
+
+            // Warning: The directionality here is important. Changes have to be copied *from* beatmapContent (which comes from editor and is being saved)
+            // *to* the beatmapInfo (which is a database model and needs to receive values without the taiko slider velocity multiplier for correct operation).
+            // CopyTo() will undo such adjustments, while CopyFrom() will not.
+            beatmapContent.Difficulty.CopyTo(beatmapInfo.BaseDifficulty);
 
             // All changes to metadata are made in the provided beatmapInfo, so this should be copied to the `IBeatmap` before encoding.
             beatmapContent.BeatmapInfo = beatmapInfo;