split shader and make use of more inbuilt functions

osu.Game.Resources/Shaders/sh_CircularFlashlight.fs

@@ -0,0 +1,9 @@
+#include "sh_Flashlight.h"
+
+vec4 getColourAt(vec2 diff, vec2 size, vec4 originalColour)
+{
+    float dist = length(diff);
+    float flashlightRadius = length(size);
+
+    return vec4(originalColour.xyz, smoothstep(flashlightRadius, flashlightRadius * smoothness, dist));
+}

osu.Game.Resources/Shaders/sh_Flashlight.fs

@@ -1,34 +0,0 @@
-#ifdef GL_ES
-    precision mediump float;
-#endif
-
-varying vec2 v_Position;
-varying vec4 v_Colour;
-
-uniform bool rectangular;
-uniform vec2 flashlightPos;
-uniform float circularFlashlightSize;
-uniform vec2 rectangularFlashlightSize;
-
-const float smoothness = 1.1;
-
-void main(void)
-{
-    if(rectangular)
-    {
-        vec2 diff = abs(v_Position - flashlightPos);
-
-        float alpha = 1.0 - smoothstep(rectangularFlashlightSize.x, rectangularFlashlightSize.x * smoothness, diff.x);
-        alpha *= 1.0 - smoothstep(rectangularFlashlightSize.y, rectangularFlashlightSize.y * smoothness, diff.y);
-
-        gl_FragColor  = v_Colour * vec4(1.0, 1.0, 1.0, 1.0 - alpha);
-    }
-    else
-    {
-        vec2 diff = flashlightPos - v_Position;
-
-        float dist = sqrt(diff.x * diff.x + diff.y * diff.y);
-
-        gl_FragColor = v_Colour * vec4(1.0, 1.0, 1.0, smoothstep(circularFlashlightSize, circularFlashlightSize * smoothness, dist));
-    }
-}

osu.Game.Resources/Shaders/sh_Flashlight.h

@@ -0,0 +1,18 @@
+#ifdef GL_ES
+    precision mediump float;
+#endif
+
+varying vec2 v_Position;
+varying vec4 v_Colour;
+
+uniform vec2 flashlightPos;
+uniform vec2 flashlightSize;
+
+const float smoothness = 1.1;
+
+vec4 getColourAt(vec2, vec2, vec4);
+
+void main(void)
+{
+    gl_FragColor = getColourAt(flashlightPos - v_Position, flashlightSize, v_Colour);
+}

osu.Game.Resources/Shaders/sh_RectangularFlashlight.fs

@@ -0,0 +1,10 @@
+#include "sh_Flashlight.h"
+
+vec4 getColourAt(vec2 diff, vec2 size, vec4 originalColour)
+{
+    diff = abs(diff);
+
+    float alpha = length(smoothstep(size, size * smoothness, diff));
+
+    return vec4(originalColour.xyz, alpha);
+}