Expose skin sources via ISkinSource and revert to consuming based on hierarchy

osu.Game.Rulesets.Osu.Tests/TestSceneCursorTrail.cs

@@ -2,6 +2,8 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Audio.Sample;
@@ -114,6 +116,8 @@ namespace osu.Game.Rulesets.Osu.Tests
 
             public ISkin FindProvider(Func<ISkin, bool> lookupFunction) => null;
 
+            public IEnumerable<ISkin> AllSources => Enumerable.Empty<ISkin>();
+
             public event Action SourceChanged
             {
                 add { }

osu.Game.Rulesets.Osu.Tests/TestSceneSkinFallbacks.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Allocation;
@@ -146,6 +147,8 @@ namespace osu.Game.Rulesets.Osu.Tests
 
             public ISkin FindProvider(Func<ISkin, bool> lookupFunction) => null;
 
+            public IEnumerable<ISkin> AllSources => Enumerable.Empty<ISkin>();
+
             public event Action SourceChanged;
 
             private bool enabled = true;

osu.Game.Tests/Visual/Gameplay/TestSceneSkinnableDrawable.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using NUnit.Framework;
@@ -330,6 +331,8 @@ namespace osu.Game.Tests.Visual.Gameplay
 
             public ISkin FindProvider(Func<ISkin, bool> lookupFunction) => throw new NotImplementedException();
 
+            public IEnumerable<ISkin> AllSources => Enumerable.Empty<ISkin>();
+
             public event Action SourceChanged
             {
                 add { }

osu.Game.Tests/Visual/Gameplay/TestSceneSkinnableSound.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Allocation;
@@ -147,6 +148,7 @@ namespace osu.Game.Tests.Visual.Gameplay
             public ISample GetSample(ISampleInfo sampleInfo) => source?.GetSample(sampleInfo);
             public IBindable<TValue> GetConfig<TLookup, TValue>(TLookup lookup) => source?.GetConfig<TLookup, TValue>(lookup);
             public ISkin FindProvider(Func<ISkin, bool> lookupFunction) => source?.FindProvider(lookupFunction);
+            public IEnumerable<ISkin> AllSources => source.AllSources;
 
             public void TriggerSourceChanged()
             {

osu.Game/Skinning/ISkinSource.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using JetBrains.Annotations;
 
 namespace osu.Game.Skinning
@@ -20,5 +21,10 @@ namespace osu.Game.Skinning
         /// <returns>The skin to be used for subsequent lookups, or <c>null</c> if none is available.</returns>
         [CanBeNull]
         ISkin FindProvider(Func<ISkin, bool> lookupFunction);
+
+        /// <summary>
+        /// Retrieve all sources available for lookup, with highest priority source first.
+        /// </summary>
+        IEnumerable<ISkin> AllSources { get; }
     }
 }

osu.Game/Skinning/RulesetSkinProvidingContainer.cs

@@ -26,7 +26,6 @@ namespace osu.Game.Skinning
         /// Therefore disallow falling back to any parent <see cref="ISkinSource"/> any further.
         /// </remarks>
         protected override bool AllowFallingBackToParent => false;
-
         protected override Container<Drawable> Content { get; }
 
         public RulesetSkinProvidingContainer(Ruleset ruleset, IBeatmap beatmap, [CanBeNull] ISkin beatmapSkin)
@@ -44,13 +43,13 @@ namespace osu.Game.Skinning
         }
 
         [Resolved]
-        private SkinManager skinManager { get; set; }
+        private ISkinSource skinSource { get; set; }
 
         [BackgroundDependencyLoader]
         private void load()
         {
             UpdateSkins();
-            skinManager.SourceChanged += OnSourceChanged;
+            skinSource.SourceChanged += OnSourceChanged;
         }
 
         protected override void OnSourceChanged()
@@ -63,25 +62,19 @@ namespace osu.Game.Skinning
         {
             SkinSources.Clear();
 
-            // TODO: we also want to insert a DefaultLegacySkin here if the current *beatmap* is providing any skinned elements.
+            foreach (var skin in skinSource.AllSources)
-
-            switch (skinManager.CurrentSkin.Value)
             {
-                case LegacySkin currentLegacySkin:
+                switch (skin)
-                    SkinSources.Add(GetLegacyRulesetTransformedSkin(currentLegacySkin));
+                {
+                    case LegacySkin legacySkin:
+                        SkinSources.Add(GetLegacyRulesetTransformedSkin(legacySkin));
+                        break;
 
-                    if (currentLegacySkin != skinManager.DefaultLegacySkin)
+                    default:
-                        SkinSources.Add(GetLegacyRulesetTransformedSkin(skinManager.DefaultLegacySkin));
+                        SkinSources.Add(skin);
-
+                        break;
-                    break;
+                }
-
-                default:
-                    SkinSources.Add(skinManager.CurrentSkin.Value);
-                    break;
             }
-
-            if (skinManager.CurrentSkin.Value != skinManager.DefaultSkin)
-                SkinSources.Add(skinManager.DefaultSkin);
         }
 
         protected ISkin GetLegacyRulesetTransformedSkin(ISkin legacySkin)
@@ -100,8 +93,8 @@ namespace osu.Game.Skinning
         {
             base.Dispose(isDisposing);
 
-            if (skinManager != null)
+            if (skinSource != null)
-                skinManager.SourceChanged -= OnSourceChanged;
+                skinSource.SourceChanged -= OnSourceChanged;
         }
     }
 }

osu.Game/Skinning/SkinManager.cs

@@ -248,17 +248,29 @@ namespace osu.Game.Skinning
             return null;
         }
 
+        public IEnumerable<ISkin> AllSources
+        {
+            get
+            {
+                yield return CurrentSkin.Value;
+
+                if (CurrentSkin.Value is LegacySkin)
+                    yield return DefaultLegacySkin;
+
+                yield return DefaultSkin;
+            }
+        }
+
         private T lookupWithFallback<T>(Func<ISkin, T> lookupFunction)
             where T : class
         {
-            if (lookupFunction(CurrentSkin.Value) is T skinSourced)
+            foreach (var source in AllSources)
-                return skinSourced;
+            {
+                if (lookupFunction(source) is T skinSourced)
+                    return skinSourced;
+            }
 
-            if (CurrentSkin.Value is LegacySkin && lookupFunction(DefaultLegacySkin) is T legacySourced)
+            return null;
-                return legacySourced;
-
-            // Finally fall back to the (non-legacy) default.
-            return lookupFunction(DefaultSkin);
         }
 
         #region IResourceStorageProvider

osu.Game/Skinning/SkinProvidingContainer.cs

@@ -131,6 +131,21 @@ namespace osu.Game.Skinning
             return fallbackSource?.FindProvider(lookupFunction);
         }
 
+        public IEnumerable<ISkin> AllSources
+        {
+            get
+            {
+                foreach (var skin in SkinSources)
+                    yield return skin;
+
+                if (fallbackSource != null)
+                {
+                    foreach (var skin in fallbackSource.AllSources)
+                        yield return skin;
+                }
+            }
+        }
+
         public Drawable GetDrawableComponent(ISkinComponent component)
         {
             foreach (var skin in SkinSources)

osu.Game/Tests/Beatmaps/LegacyBeatmapSkinColourTest.cs

@@ -146,6 +146,7 @@ namespace osu.Game.Tests.Beatmaps
             }
 
             public ISkin FindProvider(Func<ISkin, bool> lookupFunction) => null;
+            public IEnumerable<ISkin> AllSources => Enumerable.Empty<ISkin>();
         }
     }
 }