From 14a77a8f16d849483a59c68cf726e7784966052a Mon Sep 17 00:00:00 2001
From: Andrei Zavatski <megaman9919@gmail.com>
Date: Sat, 21 Dec 2019 16:08:28 +0300
Subject: [PATCH] Improve animations

---
 .../HUD/HitErrorMeters/ColourHitErrorMeter.cs | 83 +++++++++++++++----
 1 file changed, 69 insertions(+), 14 deletions(-)

diff --git a/osu.Game/Screens/Play/HUD/HitErrorMeters/ColourHitErrorMeter.cs b/osu.Game/Screens/Play/HUD/HitErrorMeters/ColourHitErrorMeter.cs
index 6775b98f84..649f29810e 100644
--- a/osu.Game/Screens/Play/HUD/HitErrorMeters/ColourHitErrorMeter.cs
+++ b/osu.Game/Screens/Play/HUD/HitErrorMeters/ColourHitErrorMeter.cs
@@ -1,6 +1,10 @@
 // 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 System.Linq;
+using osu.Framework.Bindables;
+using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
@@ -13,35 +17,86 @@ namespace osu.Game.Screens.Play.HUD.HitErrorMeters
 {
     public class ColourHitErrorMeter : HitErrorMeter
     {
-        private const int bar_height = 200;
+        private const int max_available_judgements = 20;
 
-        private readonly FillFlowContainer judgementsFlow;
+        private readonly JudgementFlow judgementsFlow;
+        private readonly BindableList<(Color4 colour, JudgementResult result)> judgements = new BindableList<(Color4 colour, JudgementResult result)>();
 
         public ColourHitErrorMeter(HitWindows hitWindows)
             : base(hitWindows)
         {
             AutoSizeAxes = Axes.Both;
-            InternalChild = judgementsFlow = new FillFlowContainer
-            {
-                AutoSizeAxes = Axes.X,
-                Height = bar_height,
-                Direction = FillDirection.Vertical,
-                Spacing = new Vector2(0, 2),
-                Masking = true,
-            };
+            InternalChild = judgementsFlow = new JudgementFlow();
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+            judgementsFlow.Judgements.BindTo(judgements);
         }
 
         public override void OnNewJudgement(JudgementResult judgement)
         {
-            judgementsFlow.Add(new DrawableJudgement(GetColourForHitResult(HitWindows.ResultFor(judgement.TimeOffset))));
+            judgements.Add((GetColourForHitResult(HitWindows.ResultFor(judgement.TimeOffset)), judgement));
+
+            if (judgements.Count > max_available_judgements)
+                judgements.RemoveAt(0);
         }
 
-        private class DrawableJudgement : CircularContainer
+        private class JudgementFlow : Container<DrawableResult>
         {
-            public DrawableJudgement(Color4 colour)
+            private const int drawable_judgement_size = 8;
+            private const int spacing = 2;
+            private const int animation_duration = 200;
+
+            public readonly BindableList<(Color4 colour, JudgementResult result)> Judgements = new BindableList<(Color4 colour, JudgementResult result)>();
+
+            public JudgementFlow()
             {
+                AutoSizeAxes = Axes.X;
+                Height = max_available_judgements * (drawable_judgement_size + spacing);
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+                Judgements.ItemsAdded += push;
+                Judgements.ItemsRemoved += pop;
+            }
+
+            private void push(IEnumerable<(Color4 colour, JudgementResult result)> judgements)
+            {
+                Children.ForEach(c => c.FinishTransforms());
+
+                var (colour, result) = judgements.Single();
+                var drawableJudgement = new DrawableResult(colour, result, drawable_judgement_size)
+                {
+                    Alpha = 0,
+                    Y = -(drawable_judgement_size + spacing)
+                };
+
+                Add(drawableJudgement);
+                drawableJudgement.FadeInFromZero(animation_duration, Easing.OutQuint);
+
+                Children.ForEach(c => c.MoveToOffset(new Vector2(0, drawable_judgement_size + spacing), animation_duration, Easing.OutQuint));
+            }
+
+            private void pop(IEnumerable<(Color4 colour, JudgementResult result)> judgements)
+            {
+                Children.FirstOrDefault(c => c.Result == judgements.Single().result).FadeOut(animation_duration, Easing.OutQuint).Expire();
+            }
+        }
+
+        private class DrawableResult : CircularContainer
+        {
+            public JudgementResult Result { get; private set; }
+
+            public DrawableResult(Color4 colour, JudgementResult result, int size)
+            {
+                Result = result;
+
                 Masking = true;
-                Size = new Vector2(8);
+                Size = new Vector2(size);
                 Child = new Box
                 {
                     RelativeSizeAxes = Axes.Both,