Make notes scroll with beat length.

osu.Game.Rulesets.Mania/Timing/TimeRelativeContainer.cs

@@ -29,9 +29,13 @@ namespace osu.Game.Rulesets.Mania.Timing
             set { RelativeCoordinateSpace = new Vector2(1, (float)value); }
         }
 
+        private readonly List<DrawableTimingSection> drawableTimingSections;
+
         public TimeRelativeContainer(IEnumerable<TimingSection> timingSections)
         {
-            Children = timingSections.Select(t => new DrawableTimingSection(t));
+            drawableTimingSections = timingSections.Select(t => new DrawableTimingSection(t)).ToList();
+
+            Children = drawableTimingSections;
         }
 
         /// <summary>
@@ -48,7 +52,7 @@ namespace osu.Game.Rulesets.Mania.Timing
                 return;
             }
 
-            var section = (Children.LastOrDefault(t => t.Y >= drawable.Y) ?? Children.First()) as DrawableTimingSection;
+            var section = drawableTimingSections.LastOrDefault(t => t.CanContain(drawable)) ?? drawableTimingSections.First();
 
             if (section == null)
                 throw new Exception("Could not find suitable timing section to add object to.");
@@ -59,13 +63,28 @@ namespace osu.Game.Rulesets.Mania.Timing
         /// <summary>
         /// A container that contains drawables within the time span of a timing section.
         /// <para>
-        /// Scrolls relative to the current time.
+        /// The content of this container will scroll relative to the current time.
         /// </para>
         /// </summary>
         private class DrawableTimingSection : Container
         {
+            protected override Container<Drawable> Content => content;
+            /// <summary>
+            /// The container which will scroll relative to the current time.
+            /// </summary>
+            private readonly Container content;
+
             private readonly TimingSection section;
 
+            /// <summary>
+            /// Creates a drawable timing section. The height of this container will be proportional
+            /// to the beat length of the timing section and the timespan of its parent at all times.
+            /// <para>
+            /// This is so that, e.g. a beat length of 500ms results in this container being twice as high as its parent,
+            /// which means that the content container will scroll at twice the normal rate.
+            /// </para>
+            /// </summary>
+            /// <param name="section">The section to create the drawable timing section for.</param>
             public DrawableTimingSection(TimingSection section)
             {
                 this.section = section;
@@ -73,18 +92,30 @@ namespace osu.Game.Rulesets.Mania.Timing
                 Anchor = Anchor.BottomCentre;
                 Origin = Anchor.BottomCentre;
 
-                RelativePositionAxes = Axes.Y;
-                Y = -(float)section.StartTime;
-
                 RelativeSizeAxes = Axes.Both;
-                Height = (float)section.Duration;
 
-                RelativeCoordinateSpace = new Vector2(1, Height);
+                AddInternal(content = new Container
+                {
+                    Anchor = Anchor.BottomCentre,
+                    Origin = Anchor.BottomCentre,
+                    RelativePositionAxes = Axes.Both,
+                    RelativeSizeAxes = Axes.Both,
+                    Y = -(float)section.StartTime,
+                    Height = (float)section.Duration,
+                    RelativeCoordinateSpace = new Vector2(1, (float)section.Duration)
+                });
             }
 
             protected override void Update()
             {
-                Y = (float)(Time.Current - section.StartTime);
+                var parent = (TimeRelativeContainer)Parent;
+
+                // Adjust our height to account for the speed changes
+                Height = (float)(parent.TimeSpan * 1000 / section.BeatLength);
+                RelativeCoordinateSpace = new Vector2(1, (float)parent.TimeSpan);
+
+                // Scroll the content
+                content.Y = (float)(Time.Current - section.StartTime);
             }
 
             public override void Add(Drawable drawable)
@@ -93,10 +124,12 @@ namespace osu.Game.Rulesets.Mania.Timing
                 // we need to offset it back by our position so that it becomes correctly relatively-positioned to us
                 // This can be removed if hit objects were stored such that either their StartTime or their "beat offset" was relative to the timing section
                 // they belonged to, but this requires a radical change to the beatmap format which we're not ready to do just yet
-                drawable.Y -= Y;
+                drawable.Y += (float)section.StartTime;
 
                 base.Add(drawable);
             }
+
+            public bool CanContain(Drawable drawable) => content.Y >= drawable.Y;
         }
     }
 }

osu.Game.Rulesets.Mania/UI/ManiaPlayfield.cs

@@ -27,10 +27,10 @@ namespace osu.Game.Rulesets.Mania.UI
     {
         public const float HIT_TARGET_POSITION = 50;
 
-        private const float time_span_default = 500;
+        private const float time_span_default = 20000;
         private const float time_span_min = 10;
-        private const float time_span_max = 20000;
+        private const float time_span_max = 50000;
-        private const float time_span_step = 100;
+        private const float time_span_step = 1000;
 
         /// <summary>
         /// Default column keys, expanding outwards from the middle as more column are added.