Add adaptive speed mod

osu.Game.Rulesets.Mania/ManiaRuleset.cs

@@ -258,6 +258,7 @@ public override IEnumerable<Mod> GetModsFor(ModType type)
                     {
                         new MultiMod(new ModWindUp(), new ModWindDown()),
                         new ManiaModMuted(),
+                        new ModAdaptiveSpeed()
                     };
 
                 default:

osu.Game.Rulesets.Osu/OsuRuleset.cs

@@ -195,6 +195,7 @@ public override IEnumerable<Mod> GetModsFor(ModType type)
                         new OsuModMuted(),
                         new OsuModNoScope(),
                         new OsuModAimAssist(),
+                        new ModAdaptiveSpeed()
                     };
 
                 case ModType.System:

osu.Game.Rulesets.Taiko/TaikoRuleset.cs

@@ -151,6 +151,7 @@ public override IEnumerable<Mod> GetModsFor(ModType type)
                     {
                         new MultiMod(new ModWindUp(), new ModWindDown()),
                         new TaikoModMuted(),
+                        new ModAdaptiveSpeed()
                     };
 
                 default:

osu.Game/Rulesets/Mods/ModAdaptiveSpeed.cs

@@ -0,0 +1,122 @@
+// 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 System.Linq;
+using osu.Framework.Audio;
+using osu.Framework.Audio.Track;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics.Audio;
+using osu.Framework.Utils;
+using osu.Game.Beatmaps;
+using osu.Game.Configuration;
+using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Drawables;
+
+namespace osu.Game.Rulesets.Mods
+{
+    public class ModAdaptiveSpeed : Mod, IApplicableToRate, IApplicableToDrawableHitObject, IApplicableToBeatmap
+    {
+        private const double fastest_rate = 2f;
+
+        private const double slowest_rate = 0.5f;
+
+        /// <summary>
+        /// Adjust track rate using the average speed of the last x hits
+        /// </summary>
+        private const int average_count = 10;
+
+        public override string Name => "Adaptive Speed";
+
+        public override string Acronym => "AS";
+
+        public override string Description => "Let track speed adapt to you.";
+
+        public override ModType Type => ModType.Fun;
+
+        public override double ScoreMultiplier => 1;
+
+        public override Type[] IncompatibleMods => new[] { typeof(ModRateAdjust), typeof(ModTimeRamp) };
+
+        [SettingSource("Adjust pitch", "Should pitch be adjusted with speed")]
+        public BindableBool AdjustPitch { get; } = new BindableBool
+        {
+            Default = true,
+            Value = true
+        };
+
+        public BindableNumber<double> SpeedChange { get; } = new BindableDouble
+        {
+            Default = 1,
+            Value = 1,
+            Precision = 0.01,
+        };
+
+        private ITrack track;
+
+        private readonly List<double> recentRates = Enumerable.Range(0, average_count).Select(x => 1d).ToList();
+
+        // rates are calculated using the end time of the previous hit object
+        // caching them here for easy access
+        private readonly Dictionary<HitObject, double> previousEndTimes = new Dictionary<HitObject, double>();
+
+        public ModAdaptiveSpeed()
+        {
+            AdjustPitch.BindValueChanged(applyPitchAdjustment);
+        }
+
+        public void ApplyToTrack(ITrack track)
+        {
+            this.track = track;
+
+            AdjustPitch.TriggerChange();
+        }
+
+        public void ApplyToSample(DrawableSample sample)
+        {
+            sample.AddAdjustment(AdjustableProperty.Frequency, SpeedChange);
+        }
+
+        public double ApplyToRate(double time, double rate = 1) => rate;
+
+        private void applyPitchAdjustment(ValueChangedEvent<bool> adjustPitchSetting)
+        {
+            // remove existing old adjustment
+            track?.RemoveAdjustment(adjustmentForPitchSetting(adjustPitchSetting.OldValue), SpeedChange);
+
+            track?.AddAdjustment(adjustmentForPitchSetting(adjustPitchSetting.NewValue), SpeedChange);
+        }
+
+        private AdjustableProperty adjustmentForPitchSetting(bool adjustPitchSettingValue)
+            => adjustPitchSettingValue ? AdjustableProperty.Frequency : AdjustableProperty.Tempo;
+
+        public void ApplyToDrawableHitObject(DrawableHitObject drawable)
+        {
+            drawable.OnNewResult += (o, result) =>
+            {
+                if (!result.IsHit) return;
+                if (!previousEndTimes.ContainsKey(result.HitObject)) return;
+
+                double prevEndTime = previousEndTimes[result.HitObject];
+
+                recentRates.Add(Math.Clamp((result.HitObject.GetEndTime() - prevEndTime) / (result.TimeAbsolute - prevEndTime) * SpeedChange.Value, slowest_rate, fastest_rate));
+                if (recentRates.Count > average_count)
+                    recentRates.RemoveAt(0);
+
+                SpeedChange.Value = recentRates.Average();
+            };
+        }
+
+        public void ApplyToBeatmap(IBeatmap beatmap)
+        {
+            for (int i = 1; i < beatmap.HitObjects.Count; i++)
+            {
+                var hitObject = beatmap.HitObjects[i];
+                var previousObject = beatmap.HitObjects.Take(i).LastOrDefault(o => !Precision.AlmostBigger(o.GetEndTime(), hitObject.GetEndTime()));
+
+                if (previousObject != null)
+                    previousEndTimes.Add(hitObject, previousObject.GetEndTime());
+            }
+        }
+    }
+}

osu.Game/Rulesets/Mods/ModRateAdjust.cs

@@ -25,7 +25,7 @@ public virtual void ApplyToSample(DrawableSample sample)
 
         public double ApplyToRate(double time, double rate) => rate * SpeedChange.Value;
 
-        public override Type[] IncompatibleMods => new[] { typeof(ModTimeRamp) };
+        public override Type[] IncompatibleMods => new[] { typeof(ModTimeRamp), typeof(ModAdaptiveSpeed) };
 
         public override string SettingDescription => SpeedChange.IsDefault ? string.Empty : $"{SpeedChange.Value:N2}x";
     }

osu.Game/Rulesets/Mods/ModTimeRamp.cs

@@ -30,7 +30,7 @@ public abstract class ModTimeRamp : Mod, IUpdatableByPlayfield, IApplicableToBea
         [SettingSource("Adjust pitch", "Should pitch be adjusted with speed")]
         public abstract BindableBool AdjustPitch { get; }
 
-        public override Type[] IncompatibleMods => new[] { typeof(ModRateAdjust) };
+        public override Type[] IncompatibleMods => new[] { typeof(ModRateAdjust), typeof(ModAdaptiveSpeed) };
 
         public override string SettingDescription => $"{InitialRate.Value:N2}x to {FinalRate.Value:N2}x";