DRYer

kitty/alpha_blend.glsl

@@ -0,0 +1,22 @@
+vec4 alpha_blend(vec4 over, vec4 under) {
+    // Alpha blend two colors returning the resulting color pre-multiplied by its alpha
+    // and its alpha.
+    // See https://en.wikipedia.org/wiki/Alpha_compositing
+    float alpha = mix(under.a, 1.0f, over.a);
+    vec3 combined_color = mix(under.rgb * under.a, over.rgb, over.a);
+    return vec4(combined_color, alpha);
+}
+
+vec4 alpha_blend_premul(vec4 over, vec4 under) {
+    // Same as alpha_blend() except that it assumes over and under are both premultiplied.
+    float inv_over_alpha = 1.0f - over.a;
+    float alpha = over.a + under.a * inv_over_alpha;
+    return vec4(over.rgb + under.rgb * inv_over_alpha, alpha);
+}
+
+vec4 alpha_blend_premul(vec4 over, vec3 under) {
+    // same as alpha_blend_premul with under_alpha = 1 outputs a blended color
+    // with alpha 1 which is effectively pre-multiplied since alpha is 1
+    float inv_over_alpha = 1.0f - over.a;
+    return vec4(over.rgb + under.rgb * inv_over_alpha, 1.0);
+}

kitty/cell_fragment.glsl

@@ -1,3 +1,4 @@
+#pragma kitty_include_shader <alpha_blend.glsl>
 #pragma kitty_include_shader <linear2srgb.glsl>
 
 #define {WHICH_PROGRAM}
@@ -40,29 +41,6 @@ in float colored_sprite;
 out vec4 final_color;
 
 // Util functions {{{
-vec4 alpha_blend(vec4 over, vec4 under) {
-    // Alpha blend two colors returning the resulting color pre-multiplied by its alpha
-    // and its alpha.
-    // See https://en.wikipedia.org/wiki/Alpha_compositing
-    float alpha = mix(under.a, 1.0f, over.a);
-    vec3 combined_color = mix(under.rgb * under.a, over.rgb, over.a);
-    return vec4(combined_color, alpha);
-}
-
-vec4 alpha_blend_premul(vec4 over, vec4 under) {
-    // Same as alpha_blend() except that it assumes over and under are both premultiplied.
-    float inv_over_alpha = 1.0f - over.a;
-    float alpha = over.a + under.a * inv_over_alpha;
-    return vec4(over.rgb + under.rgb * inv_over_alpha, alpha);
-}
-
-vec4 alpha_blend_premul(vec4 over, vec3 under) {
-    // same as alpha_blend_premul with under_alpha = 1 outputs a blended color
-    // with alpha 1 which is effectively pre-multiplied since alpha is 1
-    float inv_over_alpha = 1.0f - over.a;
-    return vec4(over.rgb + under.rgb * inv_over_alpha, 1.0);
-}
-
 vec4 vec4_premul(vec3 rgb, float a) {
     return vec4(rgb * a, a);
 }

kitty/graphics_fragment.glsl

@@ -1,3 +1,4 @@
+#pragma kitty_include_shader <alpha_blend.glsl>
 #define ALPHA_TYPE
 
 uniform sampler2D image;
@@ -11,15 +12,6 @@ uniform float inactive_text_alpha;
 in vec2 texcoord;
 out vec4 color;
 
-#ifdef ALPHA_MASK
-vec4 alpha_blend_premul(vec4 over, vec4 under) {
-    // Same as alpha_blend() except that it assumes over and under are both premultiplied.
-    float inv_over_alpha = 1.0f - over.a;
-    float alpha = over.a + under.a * inv_over_alpha;
-    return vec4(over.rgb + under.rgb * inv_over_alpha, alpha);
-}
-#endif
-
 void main() {
     color = texture(image, texcoord);
 #ifdef ALPHA_MASK