From 074dee3a83a9d456378a91518f4daa8bb9b26e40 Mon Sep 17 00:00:00 2001
From: smoogipoo <smoogipoo@smgi.me>
Date: Thu, 5 Apr 2018 18:37:51 +0900
Subject: [PATCH] Re-implement mousewheel zoom

---
 .../Timeline/ScrollingTimelineContainer.cs    | 73 +++++++++++++++++--
 1 file changed, 68 insertions(+), 5 deletions(-)

diff --git a/osu.Game/Screens/Edit/Screens/Compose/Timeline/ScrollingTimelineContainer.cs b/osu.Game/Screens/Edit/Screens/Compose/Timeline/ScrollingTimelineContainer.cs
index 07896d63be..e4b19fc2c5 100644
--- a/osu.Game/Screens/Edit/Screens/Compose/Timeline/ScrollingTimelineContainer.cs
+++ b/osu.Game/Screens/Edit/Screens/Compose/Timeline/ScrollingTimelineContainer.cs
@@ -4,8 +4,12 @@
 using osu.Framework.Configuration;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Transforms;
+using osu.Framework.Input;
+using osu.Framework.MathUtils;
 using osu.Game.Beatmaps;
 using osu.Game.Graphics;
+using OpenTK;
 
 namespace osu.Game.Screens.Edit.Screens.Compose.Timeline
 {
@@ -15,13 +19,15 @@ namespace osu.Game.Screens.Edit.Screens.Compose.Timeline
         public readonly Bindable<WorkingBeatmap> Beatmap = new Bindable<WorkingBeatmap>();
 
         private readonly Container waveformContainer;
-        private readonly BeatmapWaveformGraph waveform;
+
+        private float currentZoom = 10;
 
         public ScrollingTimelineContainer()
             : base(Direction.Horizontal)
         {
             Masking = true;
 
+            BeatmapWaveformGraph waveform;
             Child = waveformContainer = new Container
             {
                 RelativeSizeAxes = Axes.Y,
@@ -34,18 +40,75 @@ namespace osu.Game.Screens.Edit.Screens.Compose.Timeline
             };
 
             waveform.Beatmap.BindTo(Beatmap);
-            
+
             WaveformVisible.ValueChanged += visible => waveform.FadeTo(visible ? 1 : 0, 200, Easing.OutQuint);
         }
 
-        private float zoom = 10;
-
         protected override void Update()
         {
             base.Update();
 
             waveformContainer.Margin = new MarginPadding { Horizontal = DrawWidth / 2 };
-            waveformContainer.Width = DrawWidth * zoom;
+            waveformContainer.Width = DrawWidth * currentZoom;
+        }
+
+        protected override bool OnWheel(InputState state)
+        {
+            if (!state.Keyboard.ControlPressed)
+                return base.OnWheel(state);
+
+            setZoomTarget(zoomTarget + state.Mouse.WheelDelta, waveformContainer.ToLocalSpace(state.Mouse.NativeState.Position).X);
+            return true;
+        }
+
+        private float zoomTarget = 10;
+        private void setZoomTarget(float newZoom, float focusPoint)
+        {
+            zoomTarget = MathHelper.Clamp(newZoom, 1, 60);
+            transformZoomTo(zoomTarget, focusPoint, 200, Easing.OutQuint);
+        }
+
+        private void transformZoomTo(float newZoom, float focusPoint, double duration = 0, Easing easing = Easing.None)
+            => this.TransformTo(this.PopulateTransform(new TransformZoom(focusPoint, waveformContainer.DrawWidth, DrawWidth, Current), newZoom, duration, easing));
+
+        private class TransformZoom : Transform<float, ScrollingTimelineContainer>
+        {
+            private readonly float focusPoint;
+            private readonly float focusSize;
+            private readonly float sizeReference;
+            private readonly float scrollOffset;
+
+            public TransformZoom(float focusPoint, float focusSize, float sizeReference, float scrollOffset)
+            {
+                this.focusPoint = focusPoint;
+                this.focusSize = focusSize;
+                this.sizeReference = sizeReference;
+                this.scrollOffset = scrollOffset;
+            }
+
+            public override string TargetMember => nameof(currentZoom);
+
+            private float valueAt(double time)
+            {
+                if (time < StartTime) return StartValue;
+                if (time >= EndTime) return EndValue;
+
+                return Interpolation.ValueAt(time, StartValue, EndValue, StartTime, EndTime, Easing);
+            }
+
+            protected override void Apply(ScrollingTimelineContainer d, double time)
+            {
+                float newZoom = valueAt(time);
+
+                float focusOffset = focusPoint - scrollOffset;
+                float expectedWidth = sizeReference * newZoom;
+                float targetOffset = expectedWidth * (focusPoint / focusSize) - focusOffset;
+
+                d.currentZoom = newZoom;
+                d.ScrollTo(targetOffset, false);
+            }
+
+            protected override void ReadIntoStartValue(ScrollingTimelineContainer d) => StartValue = d.currentZoom;
         }
     }
 }