generalize and simplify animation

osu.Game/Graphics/Sprites/HueAnimation.cs

@@ -0,0 +1,75 @@
+// 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;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.OpenGL.Vertices;
+using osu.Framework.Graphics.Shaders;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.Textures;
+using osuTK;
+
+namespace osu.Game.Graphics.Sprites
+{
+    public class HueAnimation : Sprite
+    {
+        public HueAnimation()
+        {
+            Size = new Vector2(960);
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(ShaderManager shaders, TextureStore textures)
+        {
+            TextureShader = shaders.Load(VertexShaderDescriptor.TEXTURE_2, @"HueAnimation");
+            RoundedTextureShader = shaders.Load(VertexShaderDescriptor.TEXTURE_2, @"HueAnimation"); // Masking isn't supported for now
+        }
+
+        private float animationProgress;
+
+        public float AnimationProgress
+        {
+            get => animationProgress;
+            set
+            {
+                if (animationProgress == value) return;
+
+                animationProgress = value;
+                Invalidate(Invalidation.DrawInfo);
+            }
+        }
+
+        public override bool IsPresent => true;
+
+        protected override DrawNode CreateDrawNode() => new HueAnimationDrawNode(this);
+
+        private class HueAnimationDrawNode : SpriteDrawNode
+        {
+            protected new HueAnimation Source => (HueAnimation)base.Source;
+
+            private float progress;
+
+            public HueAnimationDrawNode(HueAnimation source)
+                : base(source)
+            {
+            }
+
+            public override void ApplyState()
+            {
+                base.ApplyState();
+
+                progress = Source.animationProgress;
+            }
+
+            protected override void Blit(Action<TexturedVertex2D> vertexAction)
+            {
+                Shader.GetUniform<float>("progress").UpdateValue(ref progress);
+
+                base.Blit(vertexAction);
+            }
+
+            protected override bool CanDrawOpaqueInterior => false;
+        }
+    }
+}