From 82ba545358723a8560de4444568b107f029a6bfa Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 2 Oct 2023 17:01:56 +0900
Subject: [PATCH] Add initial animation for health bars

---
 .../Screens/Play/HUD/ArgonHealthDisplay.cs    |  4 +-
 osu.Game/Screens/Play/HUD/HealthDisplay.cs    | 42 ++++++++++++++++++-
 osu.Game/Skinning/LegacyHealthDisplay.cs      |  1 +
 3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/osu.Game/Screens/Play/HUD/ArgonHealthDisplay.cs b/osu.Game/Screens/Play/HUD/ArgonHealthDisplay.cs
index 6cf1daa10264..68685d7eb599 100644
--- a/osu.Game/Screens/Play/HUD/ArgonHealthDisplay.cs
+++ b/osu.Game/Screens/Play/HUD/ArgonHealthDisplay.cs
@@ -212,7 +212,7 @@ protected override void Flash(JudgementResult result)
             }
         }
 
-        private double missBarValue = 1.0;
+        private double missBarValue;
         private readonly List<Vector2> missBarVertices = new List<Vector2>();
 
         public double MissBarValue
@@ -228,7 +228,7 @@ public double MissBarValue
             }
         }
 
-        private double healthBarValue = 1.0;
+        private double healthBarValue;
         private readonly List<Vector2> healthBarVertices = new List<Vector2>();
 
         public double HealthBarValue
diff --git a/osu.Game/Screens/Play/HUD/HealthDisplay.cs b/osu.Game/Screens/Play/HUD/HealthDisplay.cs
index 5131f93ca29e..e4bb91e7ca96 100644
--- a/osu.Game/Screens/Play/HUD/HealthDisplay.cs
+++ b/osu.Game/Screens/Play/HUD/HealthDisplay.cs
@@ -6,7 +6,9 @@
 using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Framework.Threading;
 using osu.Game.Rulesets.Judgements;
+using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Scoring;
 using osu.Game.Rulesets.UI;
 
@@ -23,12 +25,16 @@ public abstract partial class HealthDisplay : CompositeDrawable
         [Resolved]
         protected HealthProcessor HealthProcessor { get; private set; } = null!;
 
-        public Bindable<double> Current { get; } = new BindableDouble(1)
+        public Bindable<double> Current { get; } = new BindableDouble
         {
             MinValue = 0,
             MaxValue = 1
         };
 
+        private BindableNumber<double> health = null!;
+
+        private ScheduledDelegate? initialIncrease;
+
         /// <summary>
         /// Triggered when a <see cref="Judgement"/> is a successful hit, signaling the health display to perform a flash animation (if designed to do so).
         /// </summary>
@@ -52,14 +58,46 @@ protected override void LoadComplete()
         {
             base.LoadComplete();
 
-            Current.BindTo(HealthProcessor.Health);
             HealthProcessor.NewJudgement += onNewJudgement;
 
+            // Don't bind directly so we can animate the startup procedure.
+            health = HealthProcessor.Health.GetBoundCopy();
+            health.BindValueChanged(h =>
+            {
+                Current.Value = h.NewValue;
+                finishInitialAnimation();
+            });
+
             if (hudOverlay != null)
                 showHealthBar.BindTo(hudOverlay.ShowHealthBar);
 
             // this probably shouldn't be operating on `this.`
             showHealthBar.BindValueChanged(healthBar => this.FadeTo(healthBar.NewValue ? 1 : 0, HUDOverlay.FADE_DURATION, HUDOverlay.FADE_EASING), true);
+
+            startInitialAnimation();
+        }
+
+        private void startInitialAnimation()
+        {
+            // TODO: this should run in gameplay time, including showing a larger increase when skipping.
+            // TODO: it should also start increasing relative to the first hitobject.
+            const double increase_delay = 150;
+
+            initialIncrease = Scheduler.AddDelayed(() =>
+            {
+                double newValue = Current.Value + 0.05f;
+                this.TransformBindableTo(Current, newValue, increase_delay);
+                Flash(new JudgementResult(new HitObject(), new Judgement()));
+
+                if (newValue >= 1)
+                    finishInitialAnimation();
+            }, increase_delay, true);
+        }
+
+        private void finishInitialAnimation()
+        {
+            initialIncrease?.Cancel();
+            initialIncrease = null;
         }
 
         private void onNewJudgement(JudgementResult judgement)
diff --git a/osu.Game/Skinning/LegacyHealthDisplay.cs b/osu.Game/Skinning/LegacyHealthDisplay.cs
index f785022f8416..08add79fc161 100644
--- a/osu.Game/Skinning/LegacyHealthDisplay.cs
+++ b/osu.Game/Skinning/LegacyHealthDisplay.cs
@@ -66,6 +66,7 @@ private void load(ISkinSource source)
             marker.Current.BindTo(Current);
 
             maxFillWidth = fill.Width;
+            fill.Width = 0;
         }
 
         protected override void Update()