add the damn shader

osu.Framework.Font/Graphics/Shaders/DefaultKaraokeLyricShader.cs

@@ -9,7 +9,7 @@ namespace osu.Framework.Graphics.Shaders
 {
     public class DefaultKaraokeLyricShader : InternalShader
     {
-        public override string ShaderName => "DefaultKaraokeFont";
+        public override string ShaderName => "DefaultKaraokeLyric";
 
         public Color4 Colour { get; set; }
 
@@ -21,6 +21,10 @@ public class DefaultKaraokeLyricShader : InternalShader
 
         public int ShaderSize { get; set; }
 
+        public int ShaderSigma { get; set; }
+
+        public Vector2 ShaderColour { get; set; }
+
         public override void ApplyValue(FrameBuffer current)
         {
             var radius = Radius;

osu.Framework.Font/Resources/Shaders/sh_DefaultKaraokeLyric.fs

@@ -0,0 +1,44 @@
+#include "sh_Utils.h"
+
+#define INV_SQRT_2PI 0.39894
+
+varying mediump vec2 v_TexCoord;
+
+uniform lowp sampler2D m_Sampler;
+
+uniform mediump vec2 g_TexSize;
+uniform int g_Radius;
+
+uniform mediump float g_Sigma;
+uniform highp vec2 g_BlurDirection;
+
+mediump float computeGauss(in mediump float x, in mediump float sigma)
+{
+	return INV_SQRT_2PI * exp(-0.5*x*x / (sigma*sigma)) / sigma;
+}
+
+lowp vec4 blur(sampler2D tex, int radius, highp vec2 direction, mediump vec2 texCoord, mediump vec2 texSize, mediump float sigma)
+{
+	mediump float factor = computeGauss(0.0, sigma);
+	mediump vec4 sum = texture2D(tex, texCoord) * factor;
+
+	mediump float totalFactor = factor;
+
+	for (int i = 2; i <= 200; i += 2)
+	{
+		mediump float x = float(i) - 0.5;
+		factor = computeGauss(x, sigma) * 2.0;
+		totalFactor += 2.0 * factor;
+		sum += texture2D(tex, texCoord + direction * x / texSize) * factor;
+		sum += texture2D(tex, texCoord - direction * x / texSize) * factor;
+		if (i >= radius)
+			break;
+	}
+
+    return toSRGB(sum / totalFactor);
+}
+
+void main(void)
+{
+	gl_FragColor = blur(m_Sampler, g_Radius, g_BlurDirection, v_TexCoord, g_TexSize, g_Sigma);
+}