From d99c60adc7cf97d11de29631ec46c1c652a1b62e Mon Sep 17 00:00:00 2001
From: smoogipoo <smoogipoo@smgi.me>
Date: Mon, 26 Aug 2019 12:51:13 +0900
Subject: [PATCH] Provide a way to scale beat lengths relative to each other

---
 .../Rulesets/Timing/MultiplierControlPoint.cs |  8 +++-
 .../UI/Scrolling/DrawableScrollingRuleset.cs  | 38 +++++++++++++++----
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs b/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs
index 9bab065d1e..ffa35c24cd 100644
--- a/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs
+++ b/osu.Game/Rulesets/Timing/MultiplierControlPoint.cs
@@ -20,7 +20,13 @@ namespace osu.Game.Rulesets.Timing
         /// <summary>
         /// The aggregate multiplier which this <see cref="MultiplierControlPoint"/> provides.
         /// </summary>
-        public double Multiplier => Velocity * DifficultyPoint.SpeedMultiplier * 1000 / TimingPoint.BeatLength;
+        public double Multiplier => Velocity * DifficultyPoint.SpeedMultiplier * BaseBeatLength / TimingPoint.BeatLength;
+
+        /// <summary>
+        /// The base beat length to scale the <see cref="TimingPoint"/> provided multiplier relative to.
+        /// </summary>
+        /// <example>For a <see cref="BaseBeatLength"/> of 1000, a <see cref="TimingPoint"/> with a beat length of 500 will increase the multiplier by 2.</example>
+        public double BaseBeatLength = 1000;
 
         /// <summary>
         /// The velocity multiplier.
diff --git a/osu.Game/Rulesets/UI/Scrolling/DrawableScrollingRuleset.cs b/osu.Game/Rulesets/UI/Scrolling/DrawableScrollingRuleset.cs
index 42ec0b79b9..385f824ef5 100644
--- a/osu.Game/Rulesets/UI/Scrolling/DrawableScrollingRuleset.cs
+++ b/osu.Game/Rulesets/UI/Scrolling/DrawableScrollingRuleset.cs
@@ -69,6 +69,11 @@ namespace osu.Game.Rulesets.UI.Scrolling
         /// </summary>
         protected virtual bool UserScrollSpeedAdjustment => true;
 
+        /// <summary>
+        /// Whether <see cref="TimingControlPoint"/> beat lengths should scale relative to the most common beat length in the <see cref="Beatmap"/>.
+        /// </summary>
+        protected virtual bool RelativeScaleBeatLengths => false;
+
         /// <summary>
         /// Provides the default <see cref="MultiplierControlPoint"/>s that adjust the scrolling rate of <see cref="HitObject"/>s
         /// inside this <see cref="DrawableRuleset{TObject}"/>.
@@ -107,16 +112,35 @@ namespace osu.Game.Rulesets.UI.Scrolling
         [BackgroundDependencyLoader]
         private void load()
         {
-            // Calculate default multiplier control points
+            double lastObjectTime = (Objects.LastOrDefault() as IHasEndTime)?.EndTime ?? Objects.LastOrDefault()?.StartTime ?? double.MaxValue;
+            double baseBeatLength = 1000;
+
+            if (RelativeScaleBeatLengths)
+            {
+                IReadOnlyList<TimingControlPoint> timingPoints = Beatmap.ControlPointInfo.TimingPoints;
+                double maxDuration = 0;
+
+                for (int i = 0; i < timingPoints.Count; i++)
+                {
+                    double endTime = i < timingPoints.Count - 1 ? timingPoints[i + 1].Time : lastObjectTime;
+                    double duration = endTime - timingPoints[i].Time;
+
+                    if (duration > maxDuration)
+                    {
+                        maxDuration = duration;
+                        baseBeatLength = timingPoints[i].BeatLength;
+                    }
+                }
+            }
+
+            // Merge sequences of timing and difficulty control points to create the aggregate "multiplier" control point
             var lastTimingPoint = new TimingControlPoint();
             var lastDifficultyPoint = new DifficultyControlPoint();
-
-            // Merge timing + difficulty points
             var allPoints = new SortedList<ControlPoint>(Comparer<ControlPoint>.Default);
             allPoints.AddRange(Beatmap.ControlPointInfo.TimingPoints);
             allPoints.AddRange(Beatmap.ControlPointInfo.DifficultyPoints);
 
-            // Generate the timing points, making non-timing changes use the previous timing change
+            // Generate the timing points, making non-timing changes use the previous timing change and vice-versa
             var timingChanges = allPoints.Select(c =>
             {
                 var timingPoint = c as TimingControlPoint;
@@ -131,14 +155,13 @@ namespace osu.Game.Rulesets.UI.Scrolling
                 return new MultiplierControlPoint(c.Time)
                 {
                     Velocity = Beatmap.BeatmapInfo.BaseDifficulty.SliderMultiplier,
+                    BaseBeatLength = baseBeatLength,
                     TimingPoint = lastTimingPoint,
                     DifficultyPoint = lastDifficultyPoint
                 };
             });
 
-            double lastObjectTime = (Objects.LastOrDefault() as IHasEndTime)?.EndTime ?? Objects.LastOrDefault()?.StartTime ?? double.MaxValue;
-
-            // Perform some post processing of the timing changes
+            // Trim unwanted sequences of timing changes
             timingChanges = timingChanges
                             // Collapse sections after the last hit object
                             .Where(s => s.StartTime <= lastObjectTime)
@@ -147,7 +170,6 @@ namespace osu.Game.Rulesets.UI.Scrolling
 
             controlPoints.AddRange(timingChanges);
 
-            // If we have no control points, add a default one
             if (controlPoints.Count == 0)
                 controlPoints.Add(new MultiplierControlPoint { Velocity = Beatmap.BeatmapInfo.BaseDifficulty.SliderMultiplier });
         }