Merge d6e5a47e52 into f09d8f097a

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Templates/Rulesets/ruleset-empty/osu.Game.Rulesets.EmptyFreeform/EmptyFreeformDifficultyCalculator.cs

@@ -19,9 +19,9 @@ namespace osu.Game.Rulesets.EmptyFreeform
         {
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
-            return new DifficultyAttributes(mods, 0);
+            return new DifficultyAttributes();
         }
 
         protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate) => Enumerable.Empty<DifficultyHitObject>();

Templates/Rulesets/ruleset-example/osu.Game.Rulesets.Pippidon/PippidonDifficultyCalculator.cs

@@ -19,9 +19,9 @@ namespace osu.Game.Rulesets.Pippidon
         {
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
-            return new DifficultyAttributes(mods, 0);
+            return new DifficultyAttributes();
         }
 
         protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate) => Enumerable.Empty<DifficultyHitObject>();

Templates/Rulesets/ruleset-scrolling-empty/osu.Game.Rulesets.EmptyScrolling/EmptyScrollingDifficultyCalculator.cs

@@ -19,9 +19,9 @@ namespace osu.Game.Rulesets.EmptyScrolling
         {
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
-            return new DifficultyAttributes(mods, 0);
+            return new DifficultyAttributes();
         }
 
         protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate) => Enumerable.Empty<DifficultyHitObject>();

Templates/Rulesets/ruleset-scrolling-example/osu.Game.Rulesets.Pippidon/PippidonDifficultyCalculator.cs

@@ -19,9 +19,9 @@ namespace osu.Game.Rulesets.Pippidon
         {
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
-            return new DifficultyAttributes(mods, 0);
+            return new DifficultyAttributes();
         }
 
         protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate) => Enumerable.Empty<DifficultyHitObject>();

osu.Game.Benchmarks/BenchmarkDifficultyCalculation.cs

@@ -0,0 +1,96 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.IO;
+using BenchmarkDotNet.Attributes;
+using osu.Framework.IO.Stores;
+using osu.Game.Beatmaps;
+using osu.Game.Beatmaps.Formats;
+using osu.Game.IO;
+using osu.Game.IO.Archives;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Catch;
+using osu.Game.Rulesets.Difficulty;
+using osu.Game.Rulesets.Mania;
+using osu.Game.Rulesets.Osu;
+using osu.Game.Rulesets.Taiko;
+using osu.Game.Scoring;
+using osu.Game.Tests.Resources;
+
+namespace osu.Game.Benchmarks
+{
+    public class BenchmarkDifficultyCalculation : BenchmarkTest
+    {
+        private FlatWorkingBeatmap beatmap = null!;
+
+        private IDifficultyAttributes osuAttributes = null!;
+        private IDifficultyAttributes taikoAttributes = null!;
+        private IDifficultyAttributes catchAttributes = null!;
+        private IDifficultyAttributes maniaAttributes = null!;
+
+        public override void SetUp()
+        {
+            using var resources = new DllResourceStore(typeof(TestResources).Assembly);
+            using var archive = resources.GetStream("Resources/Archives/241526 Soleily - Renatus.osz");
+            using var zipReader = new ZipArchiveReader(archive);
+
+            using var beatmapStream = new MemoryStream();
+            zipReader.GetStream("Soleily - Renatus (Gamu) [Insane].osu").CopyTo(beatmapStream);
+            beatmapStream.Seek(0, SeekOrigin.Begin);
+            var reader = new LineBufferedReader(beatmapStream);
+            var decoder = Decoder.GetDecoder<Beatmap>(reader);
+
+            beatmap = new FlatWorkingBeatmap(decoder.Decode(reader));
+
+            // Prepare difficulty attributes for an isolated performance calculation in every mode.
+            osuAttributes = DifficultyOsu();
+            taikoAttributes = DifficultyTaiko();
+            catchAttributes = DifficultyCatch();
+            maniaAttributes = DifficultyMania();
+        }
+
+        [Benchmark]
+        public IDifficultyAttributes DifficultyOsu() => new OsuRuleset().CreateDifficultyCalculator(beatmap).Calculate();
+
+        [Benchmark]
+        public IDifficultyAttributes DifficultyTaiko() => new TaikoRuleset().CreateDifficultyCalculator(beatmap).Calculate();
+
+        [Benchmark]
+        public IDifficultyAttributes DifficultyCatch() => new CatchRuleset().CreateDifficultyCalculator(beatmap).Calculate();
+
+        [Benchmark]
+        public IDifficultyAttributes DifficultyMania() => new ManiaRuleset().CreateDifficultyCalculator(beatmap).Calculate();
+
+        [Benchmark]
+        public void PerformanceOsu()
+        {
+            Ruleset ruleset = new OsuRuleset();
+            ScoreInfo score = new ScoreInfo(beatmap.BeatmapInfo, ruleset.RulesetInfo);
+            ruleset.CreatePerformanceCalculator()!.Calculate(score, osuAttributes);
+        }
+
+        [Benchmark]
+        public void PerformanceTaiko()
+        {
+            Ruleset ruleset = new TaikoRuleset();
+            ScoreInfo score = new ScoreInfo(beatmap.BeatmapInfo, ruleset.RulesetInfo);
+            ruleset.CreatePerformanceCalculator()!.Calculate(score, taikoAttributes);
+        }
+
+        [Benchmark]
+        public void PerformanceCatch()
+        {
+            Ruleset ruleset = new CatchRuleset();
+            ScoreInfo score = new ScoreInfo(beatmap.BeatmapInfo, ruleset.RulesetInfo);
+            ruleset.CreatePerformanceCalculator()!.Calculate(score, catchAttributes);
+        }
+
+        [Benchmark]
+        public void PerformanceMania()
+        {
+            Ruleset ruleset = new ManiaRuleset();
+            ScoreInfo score = new ScoreInfo(beatmap.BeatmapInfo, ruleset.RulesetInfo);
+            ruleset.CreatePerformanceCalculator()!.Calculate(score, maniaAttributes);
+        }
+    }
+}

osu.Game.Rulesets.Catch/Difficulty/CatchDifficultyAttributes.cs

@@ -8,8 +8,15 @@ using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Catch.Difficulty
 {
-    public class CatchDifficultyAttributes : DifficultyAttributes
+    [JsonObject(MemberSerialization.OptIn)]
+    public struct CatchDifficultyAttributes : IDifficultyAttributes
     {
+        /// <inheritdoc/>
+        public double StarRating { get; set; }
+
+        /// <inheritdoc/>
+        public int MaxCombo { get; set; }
+
         /// <summary>
         /// The perceived approach rate inclusive of rate-adjusting mods (DT/HT/etc).
         /// </summary>
@@ -19,22 +26,19 @@ namespace osu.Game.Rulesets.Catch.Difficulty
         [JsonProperty("approach_rate")]
         public double ApproachRate { get; set; }
 
-        public override IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
+        public IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
         {
-            foreach (var v in base.ToDatabaseAttributes())
+            yield return (IDifficultyAttributes.ATTRIB_ID_MAX_COMBO, MaxCombo);
-                yield return v;
-
             // Todo: osu!catch should not output star rating in the 'aim' attribute.
-            yield return (ATTRIB_ID_AIM, StarRating);
+            yield return (IDifficultyAttributes.ATTRIB_ID_AIM, StarRating);
-            yield return (ATTRIB_ID_APPROACH_RATE, ApproachRate);
+            yield return (IDifficultyAttributes.ATTRIB_ID_APPROACH_RATE, ApproachRate);
         }
 
-        public override void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
+        public void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
         {
-            base.FromDatabaseAttributes(values, onlineInfo);
+            MaxCombo = (int)values[IDifficultyAttributes.ATTRIB_ID_MAX_COMBO];
-
+            StarRating = values[IDifficultyAttributes.ATTRIB_ID_AIM];
-            StarRating = values[ATTRIB_ID_AIM];
+            ApproachRate = values[IDifficultyAttributes.ATTRIB_ID_APPROACH_RATE];
-            ApproachRate = values[ATTRIB_ID_APPROACH_RATE];
         }
     }
 }

osu.Game.Rulesets.Catch/Difficulty/CatchDifficultyCalculator.cs

@@ -30,10 +30,10 @@ namespace osu.Game.Rulesets.Catch.Difficulty
         {
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
             if (beatmap.HitObjects.Count == 0)
-                return new CatchDifficultyAttributes { Mods = mods };
+                return new CatchDifficultyAttributes();
 
             // this is the same as osu!, so there's potential to share the implementation... maybe
             double preempt = IBeatmapDifficultyInfo.DifficultyRange(beatmap.Difficulty.ApproachRate, 1800, 1200, 450) / clockRate;
@@ -41,7 +41,6 @@ namespace osu.Game.Rulesets.Catch.Difficulty
             CatchDifficultyAttributes attributes = new CatchDifficultyAttributes
             {
                 StarRating = Math.Sqrt(skills[0].DifficultyValue()) * difficulty_multiplier,
-                Mods = mods,
                 ApproachRate = preempt > 1200.0 ? -(preempt - 1800.0) / 120.0 : -(preempt - 1200.0) / 150.0 + 5.0,
                 MaxCombo = beatmap.GetMaxCombo(),
             };

osu.Game.Rulesets.Catch/Difficulty/CatchPerformanceAttributes.cs

@@ -1,11 +1,23 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Collections.Generic;
+using Newtonsoft.Json;
 using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Catch.Difficulty
 {
-    public class CatchPerformanceAttributes : PerformanceAttributes
+    public struct CatchPerformanceAttributes : IPerformanceAttributes
     {
+        /// <summary>
+        /// Calculated score performance points.
+        /// </summary>
+        [JsonProperty("pp")]
+        public double Total { get; set; }
+
+        public IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
+        {
+            yield return new PerformanceDisplayAttribute(nameof(Total), "Achieved PP", Total);
+        }
     }
 }

osu.Game.Rulesets.Catch/Difficulty/CatchPerformanceCalculator.cs

@@ -23,7 +23,7 @@ namespace osu.Game.Rulesets.Catch.Difficulty
         {
         }
 
-        protected override PerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, DifficultyAttributes attributes)
+        protected override IPerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, IDifficultyAttributes attributes)
         {
             var catchAttributes = (CatchDifficultyAttributes)attributes;
 

osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyAttributes.cs

@@ -8,8 +8,15 @@ using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Mania.Difficulty
 {
-    public class ManiaDifficultyAttributes : DifficultyAttributes
+    [JsonObject(MemberSerialization.OptIn)]
+    public struct ManiaDifficultyAttributes : IDifficultyAttributes
     {
+        /// <inheritdoc/>
+        public double StarRating { get; set; }
+
+        /// <inheritdoc/>
+        public int MaxCombo { get; set; }
+
         /// <summary>
         /// The hit window for a GREAT hit inclusive of rate-adjusting mods (DT/HT/etc).
         /// </summary>
@@ -19,21 +26,18 @@ namespace osu.Game.Rulesets.Mania.Difficulty
         [JsonProperty("great_hit_window")]
         public double GreatHitWindow { get; set; }
 
-        public override IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
+        public IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
         {
-            foreach (var v in base.ToDatabaseAttributes())
+            yield return (IDifficultyAttributes.ATTRIB_ID_MAX_COMBO, MaxCombo);
-                yield return v;
+            yield return (IDifficultyAttributes.ATTRIB_ID_DIFFICULTY, StarRating);
-
+            yield return (IDifficultyAttributes.ATTRIB_ID_GREAT_HIT_WINDOW, GreatHitWindow);
-            yield return (ATTRIB_ID_DIFFICULTY, StarRating);
-            yield return (ATTRIB_ID_GREAT_HIT_WINDOW, GreatHitWindow);
         }
 
-        public override void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
+        public void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
         {
-            base.FromDatabaseAttributes(values, onlineInfo);
+            MaxCombo = (int)values[IDifficultyAttributes.ATTRIB_ID_MAX_COMBO];
-
+            StarRating = values[IDifficultyAttributes.ATTRIB_ID_DIFFICULTY];
-            StarRating = values[ATTRIB_ID_DIFFICULTY];
+            GreatHitWindow = values[IDifficultyAttributes.ATTRIB_ID_GREAT_HIT_WINDOW];
-            GreatHitWindow = values[ATTRIB_ID_GREAT_HIT_WINDOW];
         }
     }
 }

osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyCalculator.cs

@@ -38,10 +38,10 @@ namespace osu.Game.Rulesets.Mania.Difficulty
             originalOverallDifficulty = beatmap.BeatmapInfo.Difficulty.OverallDifficulty;
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
             if (beatmap.HitObjects.Count == 0)
-                return new ManiaDifficultyAttributes { Mods = mods };
+                return new ManiaDifficultyAttributes();
 
             HitWindows hitWindows = new ManiaHitWindows();
             hitWindows.SetDifficulty(beatmap.Difficulty.OverallDifficulty);
@@ -49,7 +49,6 @@ namespace osu.Game.Rulesets.Mania.Difficulty
             ManiaDifficultyAttributes attributes = new ManiaDifficultyAttributes
             {
                 StarRating = skills[0].DifficultyValue() * difficulty_multiplier,
-                Mods = mods,
                 // In osu-stable mania, rate-adjustment mods don't affect the hit window.
                 // This is done the way it is to introduce fractional differences in order to match osu-stable for the time being.
                 GreatHitWindow = Math.Ceiling((int)(getHitWindow300(mods) * clockRate) / clockRate),

osu.Game.Rulesets.Mania/Difficulty/ManiaPerformanceAttributes.cs

@@ -7,16 +7,20 @@ using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Mania.Difficulty
 {
-    public class ManiaPerformanceAttributes : PerformanceAttributes
+    public struct ManiaPerformanceAttributes : IPerformanceAttributes
     {
+        /// <summary>
+        /// Calculated score performance points.
+        /// </summary>
+        [JsonProperty("pp")]
+        public double Total { get; set; }
+
         [JsonProperty("difficulty")]
         public double Difficulty { get; set; }
 
-        public override IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
+        public IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
         {
-            foreach (var attribute in base.GetAttributesForDisplay())
+            yield return new PerformanceDisplayAttribute(nameof(Total), "Achieved PP", Total);
-                yield return attribute;
-
             yield return new PerformanceDisplayAttribute(nameof(Difficulty), "Difficulty", Difficulty);
         }
     }

osu.Game.Rulesets.Mania/Difficulty/ManiaPerformanceCalculator.cs

@@ -26,7 +26,7 @@ namespace osu.Game.Rulesets.Mania.Difficulty
         {
         }
 
-        protected override PerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, DifficultyAttributes attributes)
+        protected override IPerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, IDifficultyAttributes attributes)
         {
             var maniaAttributes = (ManiaDifficultyAttributes)attributes;
 

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

@@ -34,6 +34,18 @@ namespace osu.Game.Rulesets.Osu.Tests
         public void TestClassicMod(double expectedStarRating, int expectedMaxCombo, string name)
             => Test(expectedStarRating, expectedMaxCombo, name, new OsuModClassic());
 
+        [Test]
+        public void TestFlashlightDifficultyNullability()
+        {
+            IWorkingBeatmap beatmap = GetBeatmap("diffcalc-test");
+
+            OsuDifficultyAttributes attributes = (OsuDifficultyAttributes)CreateDifficultyCalculator(beatmap).Calculate();
+            Assert.IsNull(attributes.FlashlightDifficulty);
+
+            attributes = (OsuDifficultyAttributes)CreateDifficultyCalculator(GetBeatmap("diffcalc-test")).Calculate([new OsuModFlashlight()]);
+            Assert.IsNotNull(attributes.FlashlightDifficulty);
+        }
+
         protected override DifficultyCalculator CreateDifficultyCalculator(IWorkingBeatmap beatmap) => new OsuDifficultyCalculator(new OsuRuleset().RulesetInfo, beatmap);
 
         protected override Ruleset CreateRuleset() => new OsuRuleset();

osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyAttributes.cs

@@ -2,17 +2,22 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
-using System.Linq;
 using JetBrains.Annotations;
 using Newtonsoft.Json;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Difficulty;
-using osu.Game.Rulesets.Mods;
 
 namespace osu.Game.Rulesets.Osu.Difficulty
 {
-    public class OsuDifficultyAttributes : DifficultyAttributes
+    [JsonObject(MemberSerialization.OptIn)]
+    public struct OsuDifficultyAttributes : IDifficultyAttributes
     {
+        /// <inheritdoc/>
+        public double StarRating { get; set; }
+
+        /// <inheritdoc/>
+        public int MaxCombo { get; set; }
+
         /// <summary>
         /// The difficulty corresponding to the aim skill.
         /// </summary>
@@ -33,10 +38,10 @@ namespace osu.Game.Rulesets.Osu.Difficulty
         public double SpeedNoteCount { get; set; }
 
         /// <summary>
-        /// The difficulty corresponding to the flashlight skill.
+        /// The difficulty corresponding to the flashlight skill. A null value indicates the non-existence of <see cref="Mods.OsuModFlashlight"/>.
         /// </summary>
         [JsonProperty("flashlight_difficulty")]
-        public double FlashlightDifficulty { get; set; }
+        public double? FlashlightDifficulty { get; set; }
 
         /// <summary>
         /// Describes how much of <see cref="AimDifficulty"/> is contributed to by hitcircles or sliders.
@@ -90,41 +95,38 @@ namespace osu.Game.Rulesets.Osu.Difficulty
         /// </summary>
         public int SpinnerCount { get; set; }
 
-        public override IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
+        public IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
         {
-            foreach (var v in base.ToDatabaseAttributes())
+            yield return (IDifficultyAttributes.ATTRIB_ID_MAX_COMBO, MaxCombo);
-                yield return v;
+            yield return (IDifficultyAttributes.ATTRIB_ID_AIM, AimDifficulty);
-
+            yield return (IDifficultyAttributes.ATTRIB_ID_SPEED, SpeedDifficulty);
-            yield return (ATTRIB_ID_AIM, AimDifficulty);
+            yield return (IDifficultyAttributes.ATTRIB_ID_OVERALL_DIFFICULTY, OverallDifficulty);
-            yield return (ATTRIB_ID_SPEED, SpeedDifficulty);
+            yield return (IDifficultyAttributes.ATTRIB_ID_APPROACH_RATE, ApproachRate);
-            yield return (ATTRIB_ID_OVERALL_DIFFICULTY, OverallDifficulty);
+            yield return (IDifficultyAttributes.ATTRIB_ID_DIFFICULTY, StarRating);
-            yield return (ATTRIB_ID_APPROACH_RATE, ApproachRate);
-            yield return (ATTRIB_ID_DIFFICULTY, StarRating);
 
             if (ShouldSerializeFlashlightDifficulty())
-                yield return (ATTRIB_ID_FLASHLIGHT, FlashlightDifficulty);
+                yield return (IDifficultyAttributes.ATTRIB_ID_FLASHLIGHT, FlashlightDifficulty!);
 
-            yield return (ATTRIB_ID_SLIDER_FACTOR, SliderFactor);
+            yield return (IDifficultyAttributes.ATTRIB_ID_SLIDER_FACTOR, SliderFactor);
 
-            yield return (ATTRIB_ID_AIM_DIFFICULT_STRAIN_COUNT, AimDifficultStrainCount);
+            yield return (IDifficultyAttributes.ATTRIB_ID_AIM_DIFFICULT_STRAIN_COUNT, AimDifficultStrainCount);
-            yield return (ATTRIB_ID_SPEED_DIFFICULT_STRAIN_COUNT, SpeedDifficultStrainCount);
+            yield return (IDifficultyAttributes.ATTRIB_ID_SPEED_DIFFICULT_STRAIN_COUNT, SpeedDifficultStrainCount);
-            yield return (ATTRIB_ID_SPEED_NOTE_COUNT, SpeedNoteCount);
+            yield return (IDifficultyAttributes.ATTRIB_ID_SPEED_NOTE_COUNT, SpeedNoteCount);
         }
 
-        public override void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
+        public void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
         {
-            base.FromDatabaseAttributes(values, onlineInfo);
+            MaxCombo = (int)values[IDifficultyAttributes.ATTRIB_ID_MAX_COMBO];
-
+            AimDifficulty = values[IDifficultyAttributes.ATTRIB_ID_AIM];
-            AimDifficulty = values[ATTRIB_ID_AIM];
+            SpeedDifficulty = values[IDifficultyAttributes.ATTRIB_ID_SPEED];
-            SpeedDifficulty = values[ATTRIB_ID_SPEED];
+            OverallDifficulty = values[IDifficultyAttributes.ATTRIB_ID_OVERALL_DIFFICULTY];
-            OverallDifficulty = values[ATTRIB_ID_OVERALL_DIFFICULTY];
+            ApproachRate = values[IDifficultyAttributes.ATTRIB_ID_APPROACH_RATE];
-            ApproachRate = values[ATTRIB_ID_APPROACH_RATE];
+            StarRating = values[IDifficultyAttributes.ATTRIB_ID_DIFFICULTY];
-            StarRating = values[ATTRIB_ID_DIFFICULTY];
+            FlashlightDifficulty = values.GetValueOrDefault(IDifficultyAttributes.ATTRIB_ID_FLASHLIGHT);
-            FlashlightDifficulty = values.GetValueOrDefault(ATTRIB_ID_FLASHLIGHT);
+            SliderFactor = values[IDifficultyAttributes.ATTRIB_ID_SLIDER_FACTOR];
-            SliderFactor = values[ATTRIB_ID_SLIDER_FACTOR];
+            AimDifficultStrainCount = values[IDifficultyAttributes.ATTRIB_ID_AIM_DIFFICULT_STRAIN_COUNT];
-            AimDifficultStrainCount = values[ATTRIB_ID_AIM_DIFFICULT_STRAIN_COUNT];
+            SpeedDifficultStrainCount = values[IDifficultyAttributes.ATTRIB_ID_SPEED_DIFFICULT_STRAIN_COUNT];
-            SpeedDifficultStrainCount = values[ATTRIB_ID_SPEED_DIFFICULT_STRAIN_COUNT];
+            SpeedNoteCount = values[IDifficultyAttributes.ATTRIB_ID_SPEED_NOTE_COUNT];
-            SpeedNoteCount = values[ATTRIB_ID_SPEED_NOTE_COUNT];
             DrainRate = onlineInfo.DrainRate;
             HitCircleCount = onlineInfo.CircleCount;
             SliderCount = onlineInfo.SliderCount;
@@ -138,7 +140,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty
         // unless the fields are also renamed.
 
         [UsedImplicitly]
-        public bool ShouldSerializeFlashlightDifficulty() => Mods.Any(m => m is ModFlashlight);
+        public bool ShouldSerializeFlashlightDifficulty() => FlashlightDifficulty is not null;
 
         #endregion
     }

osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyCalculator.cs

@@ -31,17 +31,17 @@ namespace osu.Game.Rulesets.Osu.Difficulty
         {
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
             if (beatmap.HitObjects.Count == 0)
-                return new OsuDifficultyAttributes { Mods = mods };
+                return new OsuDifficultyAttributes();
 
             double aimRating = Math.Sqrt(skills[0].DifficultyValue()) * difficulty_multiplier;
             double aimRatingNoSliders = Math.Sqrt(skills[1].DifficultyValue()) * difficulty_multiplier;
             double speedRating = Math.Sqrt(skills[2].DifficultyValue()) * difficulty_multiplier;
             double speedNotes = ((Speed)skills[2]).RelevantNoteCount();
 
-            double flashlightRating = 0.0;
+            double flashlightRating = 0;
 
             if (mods.Any(h => h is OsuModFlashlight))
                 flashlightRating = Math.Sqrt(skills[3].DifficultyValue()) * difficulty_multiplier;
@@ -97,11 +97,10 @@ namespace osu.Game.Rulesets.Osu.Difficulty
             OsuDifficultyAttributes attributes = new OsuDifficultyAttributes
             {
                 StarRating = starRating,
-                Mods = mods,
                 AimDifficulty = aimRating,
                 SpeedDifficulty = speedRating,
                 SpeedNoteCount = speedNotes,
-                FlashlightDifficulty = flashlightRating,
+                FlashlightDifficulty = mods.Any(x => x is OsuModFlashlight) ? flashlightRating : null,
                 SliderFactor = sliderFactor,
                 AimDifficultStrainCount = aimDifficultyStrainCount,
                 SpeedDifficultStrainCount = speedDifficultyStrainCount,

osu.Game.Rulesets.Osu/Difficulty/OsuPerformanceAttributes.cs

@@ -7,8 +7,14 @@ using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Osu.Difficulty
 {
-    public class OsuPerformanceAttributes : PerformanceAttributes
+    public struct OsuPerformanceAttributes : IPerformanceAttributes
     {
+        /// <summary>
+        /// Calculated score performance points.
+        /// </summary>
+        [JsonProperty("pp")]
+        public double Total { get; set; }
+
         [JsonProperty("aim")]
         public double Aim { get; set; }
 
@@ -24,11 +30,9 @@ namespace osu.Game.Rulesets.Osu.Difficulty
         [JsonProperty("effective_miss_count")]
         public double EffectiveMissCount { get; set; }
 
-        public override IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
+        public IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
         {
-            foreach (var attribute in base.GetAttributesForDisplay())
+            yield return new PerformanceDisplayAttribute(nameof(Total), "Achieved PP", Total);
-                yield return attribute;
-
             yield return new PerformanceDisplayAttribute(nameof(Aim), "Aim", Aim);
             yield return new PerformanceDisplayAttribute(nameof(Speed), "Speed", Speed);
             yield return new PerformanceDisplayAttribute(nameof(Accuracy), "Accuracy", Accuracy);

osu.Game.Rulesets.Osu/Difficulty/OsuPerformanceCalculator.cs

@@ -45,7 +45,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty
         {
         }
 
-        protected override PerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, DifficultyAttributes attributes)
+        protected override IPerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, IDifficultyAttributes attributes)
         {
             var osuAttributes = (OsuDifficultyAttributes)attributes;
 
@@ -285,7 +285,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty
             if (!score.Mods.Any(h => h is OsuModFlashlight))
                 return 0.0;
 
-            double flashlightValue = Flashlight.DifficultyToPerformance(attributes.FlashlightDifficulty);
+            double flashlightValue = Flashlight.DifficultyToPerformance(attributes.FlashlightDifficulty!.Value);
 
             // Penalize misses by assessing # of misses relative to the total # of objects. Default a 3% reduction for any # of misses.
             if (effectiveMissCount > 0)

osu.Game.Rulesets.Taiko/Difficulty/TaikoDifficultyAttributes.cs

@@ -8,8 +8,15 @@ using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Taiko.Difficulty
 {
-    public class TaikoDifficultyAttributes : DifficultyAttributes
+    [JsonObject(MemberSerialization.OptIn)]
+    public struct TaikoDifficultyAttributes : IDifficultyAttributes
     {
+        /// <inheritdoc/>
+        public double StarRating { get; set; }
+
+        /// <inheritdoc/>
+        public int MaxCombo { get; set; }
+
         /// <summary>
         /// The difficulty corresponding to the stamina skill.
         /// </summary>
@@ -58,25 +65,22 @@ namespace osu.Game.Rulesets.Taiko.Difficulty
         [JsonProperty("ok_hit_window")]
         public double OkHitWindow { get; set; }
 
-        public override IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
+        public IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
         {
-            foreach (var v in base.ToDatabaseAttributes())
+            yield return (IDifficultyAttributes.ATTRIB_ID_MAX_COMBO, MaxCombo);
-                yield return v;
+            yield return (IDifficultyAttributes.ATTRIB_ID_DIFFICULTY, StarRating);
-
+            yield return (IDifficultyAttributes.ATTRIB_ID_GREAT_HIT_WINDOW, GreatHitWindow);
-            yield return (ATTRIB_ID_DIFFICULTY, StarRating);
+            yield return (IDifficultyAttributes.ATTRIB_ID_OK_HIT_WINDOW, OkHitWindow);
-            yield return (ATTRIB_ID_GREAT_HIT_WINDOW, GreatHitWindow);
+            yield return (IDifficultyAttributes.ATTRIB_ID_MONO_STAMINA_FACTOR, MonoStaminaFactor);
-            yield return (ATTRIB_ID_OK_HIT_WINDOW, OkHitWindow);
-            yield return (ATTRIB_ID_MONO_STAMINA_FACTOR, MonoStaminaFactor);
         }
 
-        public override void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
+        public void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
         {
-            base.FromDatabaseAttributes(values, onlineInfo);
+            MaxCombo = (int)values[IDifficultyAttributes.ATTRIB_ID_MAX_COMBO];
-
+            StarRating = values[IDifficultyAttributes.ATTRIB_ID_DIFFICULTY];
-            StarRating = values[ATTRIB_ID_DIFFICULTY];
+            GreatHitWindow = values[IDifficultyAttributes.ATTRIB_ID_GREAT_HIT_WINDOW];
-            GreatHitWindow = values[ATTRIB_ID_GREAT_HIT_WINDOW];
+            OkHitWindow = values[IDifficultyAttributes.ATTRIB_ID_OK_HIT_WINDOW];
-            OkHitWindow = values[ATTRIB_ID_OK_HIT_WINDOW];
+            MonoStaminaFactor = values[IDifficultyAttributes.ATTRIB_ID_MONO_STAMINA_FACTOR];
-            MonoStaminaFactor = values[ATTRIB_ID_MONO_STAMINA_FACTOR];
         }
     }
 }

osu.Game.Rulesets.Taiko/Difficulty/TaikoDifficultyCalculator.cs

@@ -72,10 +72,10 @@ namespace osu.Game.Rulesets.Taiko.Difficulty
             return difficultyHitObjects;
         }
 
-        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+        protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
         {
             if (beatmap.HitObjects.Count == 0)
-                return new TaikoDifficultyAttributes { Mods = mods };
+                return new TaikoDifficultyAttributes();
 
             Colour colour = (Colour)skills.First(x => x is Colour);
             Rhythm rhythm = (Rhythm)skills.First(x => x is Rhythm);
@@ -106,7 +106,6 @@ namespace osu.Game.Rulesets.Taiko.Difficulty
             TaikoDifficultyAttributes attributes = new TaikoDifficultyAttributes
             {
                 StarRating = starRating,
-                Mods = mods,
                 StaminaDifficulty = staminaRating,
                 MonoStaminaFactor = monoStaminaFactor,
                 RhythmDifficulty = rhythmRating,

osu.Game.Rulesets.Taiko/Difficulty/TaikoPerformanceAttributes.cs

@@ -7,8 +7,14 @@ using osu.Game.Rulesets.Difficulty;
 
 namespace osu.Game.Rulesets.Taiko.Difficulty
 {
-    public class TaikoPerformanceAttributes : PerformanceAttributes
+    public struct TaikoPerformanceAttributes : IPerformanceAttributes
     {
+        /// <summary>
+        /// Calculated score performance points.
+        /// </summary>
+        [JsonProperty("pp")]
+        public double Total { get; set; }
+
         [JsonProperty("difficulty")]
         public double Difficulty { get; set; }
 
@@ -21,11 +27,9 @@ namespace osu.Game.Rulesets.Taiko.Difficulty
         [JsonProperty("estimated_unstable_rate")]
         public double? EstimatedUnstableRate { get; set; }
 
-        public override IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
+        public IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
         {
-            foreach (var attribute in base.GetAttributesForDisplay())
+            yield return new PerformanceDisplayAttribute(nameof(Total), "Achieved PP", Total);
-                yield return attribute;
-
             yield return new PerformanceDisplayAttribute(nameof(Difficulty), "Difficulty", Difficulty);
             yield return new PerformanceDisplayAttribute(nameof(Accuracy), "Accuracy", Accuracy);
         }

osu.Game.Rulesets.Taiko/Difficulty/TaikoPerformanceCalculator.cs

@@ -28,7 +28,7 @@ namespace osu.Game.Rulesets.Taiko.Difficulty
         {
         }
 
-        protected override PerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, DifficultyAttributes attributes)
+        protected override IPerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, IDifficultyAttributes attributes)
         {
             var taikoAttributes = (TaikoDifficultyAttributes)attributes;
 

osu.Game.Tests/NonVisual/DifficultyAdjustmentModCombinationsTest.cs

@@ -222,7 +222,7 @@ namespace osu.Game.Tests.NonVisual
 
             protected override Mod[] DifficultyAdjustmentMods { get; }
 
-            protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+            protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
             {
                 throw new NotImplementedException();
             }

osu.Game.Tests/NonVisual/TestSceneTimedDifficultyCalculation.cs

@@ -172,7 +172,7 @@ namespace osu.Game.Tests.NonVisual
             {
             }
 
-            protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+            protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
                 => new TestDifficultyAttributes { Objects = beatmap.HitObjects.ToArray() };
 
             protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate)

osu.Game.Tests/Visual/UserInterface/TestSceneBeatmapAttributeText.cs

@@ -208,8 +208,8 @@ namespace osu.Game.Tests.Visual.UserInterface
             {
             }
 
-            protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
+            protected override IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
-                => new DifficultyAttributes(mods, mods.OfType<TestMod>().SingleOrDefault()?.Difficulty.Value ?? 0);
+                => new DifficultyAttributes { StarRating = mods.OfType<TestMod>().SingleOrDefault()?.Difficulty.Value ?? 0 };
 
             protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate)
                 => Array.Empty<DifficultyHitObject>();
@@ -225,7 +225,7 @@ namespace osu.Game.Tests.Visual.UserInterface
             {
             }
 
-            protected override PerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, DifficultyAttributes attributes)
+            protected override IPerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, IDifficultyAttributes attributes)
                 => new PerformanceAttributes { Total = score.Mods.OfType<TestMod>().SingleOrDefault()?.Performance.Value ?? 0 };
         }
 

osu.Game/Beatmaps/StarDifficulty.cs

@@ -22,18 +22,18 @@ namespace osu.Game.Beatmaps
         /// The difficulty attributes computed for the given beatmap.
         /// Might not be available if the star difficulty is associated with a beatmap that's not locally available.
         /// </summary>
-        public readonly DifficultyAttributes? DifficultyAttributes;
+        public readonly IDifficultyAttributes? DifficultyAttributes;
 
         /// <summary>
         /// The performance attributes computed for a perfect score on the given beatmap.
         /// Might not be available if the star difficulty is associated with a beatmap that's not locally available.
         /// </summary>
-        public readonly PerformanceAttributes? PerformanceAttributes;
+        public readonly IPerformanceAttributes? PerformanceAttributes;
 
         /// <summary>
         /// Creates a <see cref="StarDifficulty"/> structure.
         /// </summary>
-        public StarDifficulty(DifficultyAttributes difficulty, PerformanceAttributes performance)
+        public StarDifficulty(IDifficultyAttributes difficulty, IPerformanceAttributes performance)
         {
             Stars = double.IsFinite(difficulty.StarRating) ? difficulty.StarRating : 0;
             MaxCombo = difficulty.MaxCombo;
@@ -44,7 +44,7 @@ namespace osu.Game.Beatmaps
 
         /// <summary>
         /// Creates a <see cref="StarDifficulty"/> structure with a pre-populated star difficulty and max combo
-        /// in scenarios where computing <see cref="Rulesets.Difficulty.DifficultyAttributes"/> is not feasible (i.e. when working with online sources).
+        /// in scenarios where computing <see cref="IDifficultyAttributes"/> is not feasible (i.e. when working with online sources).
         /// </summary>
         public StarDifficulty(double starDifficulty, int maxCombo)
         {

osu.Game/Localisation/GeneralSettingsStrings.cs

@@ -44,6 +44,11 @@ namespace osu.Game.Localisation
         /// </summary>
         public static LocalisableString CheckUpdate => new TranslatableString(getKey(@"check_update"), @"Check for updates");
 
+        /// <summary>
+        /// "Checking for updates"
+        /// </summary>
+        public static LocalisableString CheckingForUpdates => new TranslatableString(getKey(@"checking_for_updates"), @"Checking for updates");
+
         /// <summary>
         /// "Open osu! folder"
         /// </summary>

osu.Game/Overlays/Settings/Sections/General/UpdateSettings.cs

@@ -4,7 +4,6 @@
 using System.Threading.Tasks;
 using osu.Framework;
 using osu.Framework.Allocation;
-using osu.Framework.Extensions;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Localisation;
 using osu.Framework.Logging;
@@ -13,6 +12,7 @@ using osu.Framework.Screens;
 using osu.Framework.Statistics;
 using osu.Game.Configuration;
 using osu.Game.Localisation;
+using osu.Game.Online.Multiplayer;
 using osu.Game.Overlays.Notifications;
 using osu.Game.Overlays.Settings.Sections.Maintenance;
 using osu.Game.Updater;
@@ -36,8 +36,11 @@ namespace osu.Game.Overlays.Settings.Sections.General
         [Resolved]
         private Storage storage { get; set; } = null!;
 
+        [Resolved]
+        private OsuGame? game { get; set; }
+
         [BackgroundDependencyLoader]
-        private void load(OsuConfigManager config, OsuGame? game)
+        private void load(OsuConfigManager config)
         {
             Add(new SettingsEnumDropdown<ReleaseStream>
             {
@@ -50,23 +53,7 @@ namespace osu.Game.Overlays.Settings.Sections.General
                 Add(checkForUpdatesButton = new SettingsButton
                 {
                     Text = GeneralSettingsStrings.CheckUpdate,
-                    Action = () =>
+                    Action = () => checkForUpdates().FireAndForget()
-                    {
-                        checkForUpdatesButton.Enabled.Value = false;
-                        Task.Run(updateManager.CheckForUpdateAsync).ContinueWith(task => Schedule(() =>
-                        {
-                            if (!task.GetResultSafely())
-                            {
-                                notifications?.Post(new SimpleNotification
-                                {
-                                    Text = GeneralSettingsStrings.RunningLatestRelease(game!.Version),
-                                    Icon = FontAwesome.Solid.CheckCircle,
-                                });
-                            }
-
-                            checkForUpdatesButton.Enabled.Value = true;
-                        }));
-                    }
                 });
             }
 
@@ -94,6 +81,44 @@ namespace osu.Game.Overlays.Settings.Sections.General
             }
         }
 
+        private async Task checkForUpdates()
+        {
+            if (updateManager == null || game == null)
+                return;
+
+            checkForUpdatesButton.Enabled.Value = false;
+
+            var checkingNotification = new ProgressNotification
+            {
+                Text = GeneralSettingsStrings.CheckingForUpdates,
+            };
+            notifications?.Post(checkingNotification);
+
+            try
+            {
+                bool foundUpdate = await updateManager.CheckForUpdateAsync().ConfigureAwait(true);
+
+                if (!foundUpdate)
+                {
+                    notifications?.Post(new SimpleNotification
+                    {
+                        Text = GeneralSettingsStrings.RunningLatestRelease(game.Version),
+                        Icon = FontAwesome.Solid.CheckCircle,
+                    });
+                }
+            }
+            catch
+            {
+            }
+            finally
+            {
+                // This sequence allows the notification to be immediately dismissed.
+                checkingNotification.State = ProgressNotificationState.Cancelled;
+                checkingNotification.Close(false);
+                checkForUpdatesButton.Enabled.Value = true;
+            }
+        }
+
         private void exportLogs()
         {
             ProgressNotification notification = new ProgressNotification

osu.Game/Rulesets/Difficulty/DifficultyCalculator.cs

@@ -51,7 +51,7 @@ namespace osu.Game.Rulesets.Difficulty
         /// </summary>
         /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>A structure describing the difficulty of the beatmap.</returns>
-        public DifficultyAttributes Calculate(CancellationToken cancellationToken = default)
+        public IDifficultyAttributes Calculate(CancellationToken cancellationToken = default)
             => Calculate(Array.Empty<Mod>(), cancellationToken);
 
         /// <summary>
@@ -60,7 +60,7 @@ namespace osu.Game.Rulesets.Difficulty
         /// <param name="mods">The mods that should be applied to the beatmap.</param>
         /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>A structure describing the difficulty of the beatmap.</returns>
-        public DifficultyAttributes Calculate([NotNull] IEnumerable<Mod> mods, CancellationToken cancellationToken = default)
+        public IDifficultyAttributes Calculate([NotNull] IEnumerable<Mod> mods, CancellationToken cancellationToken = default)
         {
             cancellationToken.ThrowIfCancellationRequested();
             preProcess(mods, cancellationToken);
@@ -140,7 +140,7 @@ namespace osu.Game.Rulesets.Difficulty
         /// This can only be used to compute difficulties for legacy mod combinations.
         /// </remarks>
         /// <returns>A collection of structures describing the difficulty of the beatmap for each mod combination.</returns>
-        public IEnumerable<DifficultyAttributes> CalculateAllLegacyCombinations(CancellationToken cancellationToken = default)
+        public IEnumerable<(Mod[] Mods, IDifficultyAttributes Attributes)> CalculateAllLegacyCombinations(CancellationToken cancellationToken = default)
         {
             var rulesetInstance = ruleset.CreateInstance();
 
@@ -148,11 +148,13 @@ namespace osu.Game.Rulesets.Difficulty
             {
                 Mod classicMod = rulesetInstance.CreateMod<ModClassic>();
 
-                var finalCombination = ModUtils.FlattenMod(combination);
+                IEnumerable<Mod> finalCombination = ModUtils.FlattenMod(combination);
                 if (classicMod != null)
                     finalCombination = finalCombination.Append(classicMod);
 
-                yield return Calculate(finalCombination.ToArray(), cancellationToken);
+                Mod[] finalMods = finalCombination.ToArray();
+
+                yield return (finalMods, Calculate(finalMods, cancellationToken));
             }
         }
 
@@ -263,14 +265,14 @@ namespace osu.Game.Rulesets.Difficulty
         protected virtual Mod[] DifficultyAdjustmentMods => Array.Empty<Mod>();
 
         /// <summary>
-        /// Creates <see cref="DifficultyAttributes"/> to describe beatmap's calculated difficulty.
+        /// Creates <see cref="IDifficultyAttributes"/> to describe beatmap's calculated difficulty.
         /// </summary>
         /// <param name="beatmap">The <see cref="IBeatmap"/> whose difficulty was calculated.
         /// This may differ from <see cref="Beatmap"/> in the case of timed calculation.</param>
         /// <param name="mods">The <see cref="Mod"/>s that difficulty was calculated with.</param>
         /// <param name="skills">The skills which processed the beatmap.</param>
         /// <param name="clockRate">The rate at which the gameplay clock is run at.</param>
-        protected abstract DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate);
+        protected abstract IDifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate);
 
         /// <summary>
         /// Enumerates <see cref="DifficultyHitObject"/>s to be processed from <see cref="HitObject"/>s in the <see cref="IBeatmap"/>.

osu.Game/Rulesets/Difficulty/IDifficultyAttributes.cs

@@ -1,19 +1,16 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using System;
 using System.Collections.Generic;
 using Newtonsoft.Json;
 using osu.Game.Beatmaps;
-using osu.Game.Rulesets.Mods;
 
 namespace osu.Game.Rulesets.Difficulty
 {
     /// <summary>
     /// Describes the difficulty of a beatmap, as output by a <see cref="DifficultyCalculator"/>.
     /// </summary>
-    [JsonObject(MemberSerialization.OptIn)]
+    public interface IDifficultyAttributes
-    public class DifficultyAttributes
     {
         protected const int ATTRIB_ID_AIM = 1;
         protected const int ATTRIB_ID_SPEED = 3;
@@ -31,11 +28,6 @@ namespace osu.Game.Rulesets.Difficulty
         protected const int ATTRIB_ID_OK_HIT_WINDOW = 27;
         protected const int ATTRIB_ID_MONO_STAMINA_FACTOR = 29;
 
-        /// <summary>
-        /// The mods which were applied to the beatmap.
-        /// </summary>
-        public Mod[] Mods { get; set; } = Array.Empty<Mod>();
-
         /// <summary>
         /// The combined star rating of all skills.
         /// </summary>
@@ -49,42 +41,40 @@ namespace osu.Game.Rulesets.Difficulty
         public int MaxCombo { get; set; }
 
         /// <summary>
-        /// Creates new <see cref="DifficultyAttributes"/>.
+        /// Converts this <see cref="IDifficultyAttributes"/> to osu-web compatible database attribute mappings.
-        /// </summary>
-        public DifficultyAttributes()
-        {
-        }
-
-        /// <summary>
-        /// Creates new <see cref="DifficultyAttributes"/>.
-        /// </summary>
-        /// <param name="mods">The mods which were applied to the beatmap.</param>
-        /// <param name="starRating">The combined star rating of all skills.</param>
-        public DifficultyAttributes(Mod[] mods, double starRating)
-        {
-            Mods = mods;
-            StarRating = starRating;
-        }
-
-        /// <summary>
-        /// Converts this <see cref="DifficultyAttributes"/> to osu-web compatible database attribute mappings.
         /// </summary>
         /// <remarks>
         /// See: osu_difficulty_attribs table.
         /// </remarks>
-        public virtual IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
+        public IEnumerable<(int attributeId, object value)> ToDatabaseAttributes();
-        {
-            yield return (ATTRIB_ID_MAX_COMBO, MaxCombo);
-        }
 
         /// <summary>
-        /// Reads osu-web database attribute mappings into this <see cref="DifficultyAttributes"/> object.
+        /// Reads osu-web database attribute mappings into this <see cref="IDifficultyAttributes"/> object.
         /// </summary>
         /// <param name="values">The attribute mappings.</param>
         /// <param name="onlineInfo">The <see cref="IBeatmapOnlineInfo"/> where more information about the beatmap may be extracted from (such as AR/CS/OD/etc).</param>
-        public virtual void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
+        public void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo);
+    }
+
+    /// <summary>
+    /// Represents a full, minimal implementation of <see cref="IDifficultyAttributes"/>.
+    /// </summary>
+    public class DifficultyAttributes : IDifficultyAttributes
     {
-            MaxCombo = (int)values[ATTRIB_ID_MAX_COMBO];
+        public double StarRating { get; set; }
+
+        public int MaxCombo { get; set; }
+
+        public IEnumerable<(int attributeId, object value)> ToDatabaseAttributes()
+        {
+            yield return (IDifficultyAttributes.ATTRIB_ID_MAX_COMBO, MaxCombo);
+            yield return (IDifficultyAttributes.ATTRIB_ID_AIM, StarRating);
+        }
+
+        public void FromDatabaseAttributes(IReadOnlyDictionary<int, double> values, IBeatmapOnlineInfo onlineInfo)
+        {
+            MaxCombo = (int)values[IDifficultyAttributes.ATTRIB_ID_MAX_COMBO];
+            StarRating = values[IDifficultyAttributes.ATTRIB_ID_AIM];
         }
     }
 }

osu.Game/Rulesets/Difficulty/IPerformanceAttributes.cs

@@ -6,7 +6,7 @@ using Newtonsoft.Json;
 
 namespace osu.Game.Rulesets.Difficulty
 {
-    public class PerformanceAttributes
+    public interface IPerformanceAttributes
     {
         /// <summary>
         /// Calculated score performance points.
@@ -19,7 +19,17 @@ namespace osu.Game.Rulesets.Difficulty
         /// Some attributes may be omitted if they are not meant for display.
         /// </summary>
         /// <returns></returns>
-        public virtual IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
+        public IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay();
+    }
+
+    /// <summary>
+    /// Represents a full, minimal implementation of <see cref="IPerformanceAttributes"/>.
+    /// </summary>
+    public class PerformanceAttributes : IPerformanceAttributes
+    {
+        public double Total { get; set; }
+
+        public IEnumerable<PerformanceDisplayAttribute> GetAttributesForDisplay()
         {
             yield return new PerformanceDisplayAttribute(nameof(Total), "Achieved PP", Total);
         }

osu.Game/Rulesets/Difficulty/PerformanceBreakdown.cs

@@ -11,19 +11,19 @@ namespace osu.Game.Rulesets.Difficulty
         /// <summary>
         /// Actual gameplay performance.
         /// </summary>
-        public PerformanceAttributes Performance { get; set; }
+        public IPerformanceAttributes Performance { get; set; }
 
         /// <summary>
         /// Performance of a perfect play for comparison.
         /// </summary>
-        public PerformanceAttributes PerfectPerformance { get; set; }
+        public IPerformanceAttributes PerfectPerformance { get; set; }
 
         /// <summary>
         /// Create a new performance breakdown.
         /// </summary>
         /// <param name="performance">Actual gameplay performance.</param>
         /// <param name="perfectPerformance">Performance of a perfect play for comparison.</param>
-        public PerformanceBreakdown(PerformanceAttributes performance, PerformanceAttributes perfectPerformance)
+        public PerformanceBreakdown(IPerformanceAttributes performance, IPerformanceAttributes perfectPerformance)
         {
             Performance = performance;
             PerfectPerformance = perfectPerformance;

osu.Game/Rulesets/Difficulty/PerformanceCalculator.cs

@@ -17,20 +17,20 @@ namespace osu.Game.Rulesets.Difficulty
             Ruleset = ruleset;
         }
 
-        public Task<PerformanceAttributes> CalculateAsync(ScoreInfo score, DifficultyAttributes attributes, CancellationToken cancellationToken)
+        public Task<IPerformanceAttributes> CalculateAsync(ScoreInfo score, IDifficultyAttributes attributes, CancellationToken cancellationToken)
             => Task.Run(() => CreatePerformanceAttributes(score, attributes), cancellationToken);
 
-        public PerformanceAttributes Calculate(ScoreInfo score, DifficultyAttributes attributes)
+        public IPerformanceAttributes Calculate(ScoreInfo score, IDifficultyAttributes attributes)
             => CreatePerformanceAttributes(score, attributes);
 
-        public PerformanceAttributes Calculate(ScoreInfo score, IWorkingBeatmap beatmap)
+        public IPerformanceAttributes Calculate(ScoreInfo score, IWorkingBeatmap beatmap)
             => Calculate(score, Ruleset.CreateDifficultyCalculator(beatmap).Calculate(score.Mods));
 
         /// <summary>
-        /// Creates <see cref="PerformanceAttributes"/> to describe a score's performance.
+        /// Creates <see cref="IPerformanceAttributes"/> to describe a score's performance.
         /// </summary>
         /// <param name="score">The score to create the attributes for.</param>
         /// <param name="attributes">The difficulty attributes for the beatmap relating to the score.</param>
-        protected abstract PerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, DifficultyAttributes attributes);
+        protected abstract IPerformanceAttributes CreatePerformanceAttributes(ScoreInfo score, IDifficultyAttributes attributes);
     }
 }

osu.Game/Rulesets/Difficulty/PerformanceDisplayAttribute.cs

@@ -9,7 +9,7 @@ namespace osu.Game.Rulesets.Difficulty
     public class PerformanceDisplayAttribute
     {
         /// <summary>
-        /// Name of the attribute property in <see cref="PerformanceAttributes"/>.
+        /// Name of the attribute property in <see cref="IPerformanceAttributes"/>.
         /// </summary>
         public string PropertyName { get; }
 

osu.Game/Rulesets/Difficulty/TimedDifficultyAttributes.cs

@@ -8,7 +8,7 @@ using System;
 namespace osu.Game.Rulesets.Difficulty
 {
     /// <summary>
-    /// Wraps a <see cref="DifficultyAttributes"/> object and adds a time value for which the attribute is valid.
+    /// Wraps a <see cref="IDifficultyAttributes"/> object and adds a time value for which the attribute is valid.
     /// Output by DifficultyCalculator.CalculateTimed methods.
     /// </summary>
     public class TimedDifficultyAttributes : IComparable<TimedDifficultyAttributes>
@@ -21,14 +21,14 @@ namespace osu.Game.Rulesets.Difficulty
         /// <summary>
         /// The attributes.
         /// </summary>
-        public readonly DifficultyAttributes Attributes;
+        public readonly IDifficultyAttributes Attributes;
 
         /// <summary>
         /// Creates new <see cref="TimedDifficultyAttributes"/>.
         /// </summary>
         /// <param name="time">The non-clock-adjusted time value at which the attributes take effect.</param>
         /// <param name="attributes">The attributes.</param>
-        public TimedDifficultyAttributes(double time, DifficultyAttributes attributes)
+        public TimedDifficultyAttributes(double time, IDifficultyAttributes attributes)
         {
             Time = time;
             Attributes = attributes;

osu.Game/Screens/Play/HUD/PerformancePointsCounter.cs

@@ -106,7 +106,7 @@ namespace osu.Game.Screens.Play.HUD
         }
 
         [CanBeNull]
-        private DifficultyAttributes getAttributeAtTime(JudgementResult judgement)
+        private IDifficultyAttributes getAttributeAtTime(JudgementResult judgement)
         {
             if (timedAttributes == null || timedAttributes.Count == 0)
                 return null;

osu.Game/Screens/Ranking/Statistics/PerformanceBreakdownChart.cs

@@ -176,8 +176,8 @@ namespace osu.Game.Screens.Ranking.Statistics
             var perfectDisplayAttributes = breakdown.PerfectPerformance.GetAttributesForDisplay();
 
             setTotalValues(
-                displayAttributes.First(a => a.PropertyName == nameof(PerformanceAttributes.Total)),
+                displayAttributes.First(a => a.PropertyName == nameof(IPerformanceAttributes.Total)),
-                perfectDisplayAttributes.First(a => a.PropertyName == nameof(PerformanceAttributes.Total))
+                perfectDisplayAttributes.First(a => a.PropertyName == nameof(IPerformanceAttributes.Total))
             );
 
             var rowDimensions = new List<Dimension>();
@@ -185,7 +185,7 @@ namespace osu.Game.Screens.Ranking.Statistics
 
             foreach (PerformanceDisplayAttribute attr in displayAttributes)
             {
-                if (attr.PropertyName == nameof(PerformanceAttributes.Total)) continue;
+                if (attr.PropertyName == nameof(IPerformanceAttributes.Total)) continue;
 
                 var row = createAttributeRow(attr, perfectDisplayAttributes.First(a => a.PropertyName == attr.PropertyName));
 

osu.Game/Tests/Beatmaps/DifficultyCalculatorTest.cs

@@ -25,14 +25,14 @@ namespace osu.Game.Tests.Beatmaps
 
         protected void Test(double expectedStarRating, int expectedMaxCombo, string name, params Mod[] mods)
         {
-            var attributes = CreateDifficultyCalculator(getBeatmap(name)).Calculate(mods);
+            var attributes = CreateDifficultyCalculator(GetBeatmap(name)).Calculate(mods);
 
             // Platform-dependent math functions (Pow, Cbrt, Exp, etc) may result in minute differences.
             Assert.That(attributes.StarRating, Is.EqualTo(expectedStarRating).Within(0.00001));
             Assert.That(attributes.MaxCombo, Is.EqualTo(expectedMaxCombo));
         }
 
-        private IWorkingBeatmap getBeatmap(string name)
+        protected IWorkingBeatmap GetBeatmap(string name)
         {
             using (var resStream = openResource($"{resource_namespace}.{name}.osu"))
             using (var stream = new LineBufferedReader(resStream))