From d7fede96ef98c1139960c5e15e9bb885e0a039ba Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Sat, 5 Aug 2017 11:09:34 +0900
Subject: [PATCH] Fix shadow on SpriteIcon being a bit off

---
 osu.Game/Graphics/SpriteIcon.cs | 46 +++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 11 deletions(-)

diff --git a/osu.Game/Graphics/SpriteIcon.cs b/osu.Game/Graphics/SpriteIcon.cs
index 345c6e7639..4bf4af922a 100644
--- a/osu.Game/Graphics/SpriteIcon.cs
+++ b/osu.Game/Graphics/SpriteIcon.cs
@@ -1,6 +1,7 @@
 // Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Sprites;
@@ -18,18 +19,19 @@ namespace osu.Game.Graphics
 
         public SpriteIcon()
         {
+            spriteShadow = new Sprite
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                RelativeSizeAxes = Axes.Both,
+                FillMode = FillMode.Fit,
+                Depth = 2,
+                Y = 2,
+                Colour = new Color4(0f, 0f, 0f, 0.2f),
+            };
+
             InternalChildren = new[]
             {
-                spriteShadow = new Sprite
-                {
-                    Anchor = Anchor.Centre,
-                    Origin = Anchor.Centre,
-                    RelativeSizeAxes = Axes.Both,
-                    FillMode = FillMode.Fit,
-                    Position = new Vector2(0, 0.06f),
-                    Colour = new Color4(0f, 0f, 0f, 0.2f),
-                    Alpha = 0
-                },
                 spriteMain = new Sprite
                 {
                     Anchor = Anchor.Centre,
@@ -60,10 +62,32 @@ namespace osu.Game.Graphics
                 Size = new Vector2(texture?.DisplayWidth ?? 0, texture?.DisplayHeight ?? 0);
         }
 
+        public override bool Invalidate(Invalidation invalidation = Invalidation.All, Drawable source = null, bool shallPropagate = true)
+        {
+            if ((invalidation & Invalidation.Colour) > 0)
+            {
+                //adjust shadow alpha based on highest component intensity to avoid muddy display of darker text.
+                //squared result for quadratic fall-off seems to give the best result.
+                var avgColour = (Color4)DrawInfo.Colour.AverageColour;
+
+                spriteShadow.Alpha = (float)Math.Pow(Math.Max(Math.Max(avgColour.R, avgColour.G), avgColour.B), 2);
+            }
+
+            return base.Invalidate(invalidation, source, shallPropagate);
+        }
+
         public bool Shadow
         {
             get { return spriteShadow.IsPresent; }
-            set { spriteShadow.Alpha = value ? 1 : 0; }
+            set
+            {
+                if (value == (spriteShadow.IsAlive && spriteShadow.IsLoaded)) return;
+
+                if (value)
+                    AddInternal(spriteShadow);
+                else
+                    RemoveInternal(spriteShadow);
+            }
         }
 
         private FontAwesome icon;