From f70f25098b2b64999708d1771dce0189e4a4f029 Mon Sep 17 00:00:00 2001
From: Sebastian Krajewski <mail@wieku.me>
Date: Mon, 6 Jan 2020 00:32:13 +0100
Subject: [PATCH] Change visible triangles colour when dark or light colour is
 changed

---
 osu.Game/Graphics/Backgrounds/Triangles.cs | 46 ++++++++++++++++++++--
 1 file changed, 42 insertions(+), 4 deletions(-)

diff --git a/osu.Game/Graphics/Backgrounds/Triangles.cs b/osu.Game/Graphics/Backgrounds/Triangles.cs
index 6d88808150..cbb50f7ddb 100644
--- a/osu.Game/Graphics/Backgrounds/Triangles.cs
+++ b/osu.Game/Graphics/Backgrounds/Triangles.cs
@@ -29,8 +29,29 @@ namespace osu.Game.Graphics.Backgrounds
         /// </summary>
         private const float edge_smoothness = 1;
 
-        public Color4 ColourLight = Color4.White;
-        public Color4 ColourDark = Color4.Black;
+        private Color4 colourLight = Color4.White;
+
+        public Color4 ColourLight
+        {
+            get => colourLight;
+            set
+            {
+                colourLight = value;
+                updateColours();
+            }
+        }
+
+        private Color4 colourDark = Color4.Black;
+
+        public Color4 ColourDark
+        {
+            get => colourDark;
+            set
+            {
+                colourDark = value;
+                updateColours();
+            }
+        }
 
         /// <summary>
         /// Whether we want to expire triangles as they exit our draw area completely.
@@ -151,7 +172,8 @@ namespace osu.Game.Graphics.Backgrounds
             TriangleParticle particle = CreateTriangle();
 
             particle.Position = new Vector2(RNG.NextSingle(), randomY ? RNG.NextSingle() : 1);
-            particle.Colour = CreateTriangleShade();
+            particle.ColourShade = RNG.NextSingle();
+            particle.Colour = CreateTriangleShade(particle.ColourShade);
 
             return particle;
         }
@@ -177,7 +199,17 @@ namespace osu.Game.Graphics.Backgrounds
         /// Creates a shade of colour for the triangles.
         /// </summary>
         /// <returns>The colour.</returns>
-        protected virtual Color4 CreateTriangleShade() => Interpolation.ValueAt(RNG.NextSingle(), ColourDark, ColourLight, 0, 1);
+        protected virtual Color4 CreateTriangleShade(float shade) => Interpolation.ValueAt(shade, colourDark, colourLight, 0, 1);
+
+        private void updateColours()
+        {
+            for (int i = 0; i < parts.Count; i++)
+            {
+                TriangleParticle newParticle = parts[i];
+                newParticle.Colour = CreateTriangleShade(newParticle.ColourShade);
+                parts[i] = newParticle;
+            }
+        }
 
         protected override DrawNode CreateDrawNode() => new TrianglesDrawNode(this);
 
@@ -264,6 +296,12 @@ namespace osu.Game.Graphics.Backgrounds
             /// </summary>
             public Vector2 Position;
 
+            /// <summary>
+            /// The colour shade of the triangle.
+            /// This is needed for colour recalculation of visible triangles when <see cref="ColourDark"/> or <see cref="ColourLight"/> is changed.
+            /// </summary>
+            public float ColourShade;
+
             /// <summary>
             /// The colour of the triangle.
             /// </summary>