Fix incorrect text-antialiasing when using very low background opacity

Fix #1005

docs/changelog.rst

@@ -86,6 +86,9 @@ Changelog
 
 - Add a terminfo entry for full keyboard mode.
 
+- Fix incorrect text-antialiasing when using very low background opacity
+  (:iss:`1005`)
+
 0.12.3 [2018-09-29]
 ------------------------------
 

kitty/cell_fragment.glsl

@@ -102,7 +102,7 @@ void main() {
     // SIMPLE
 #ifdef TRANSPARENT
     final_color = alpha_blend_premul(fg.rgb, fg.a, background * bg_alpha, bg_alpha);
-    final_color = vec4(final_color.rgb / final_color.a, final_color.a);
+    final_color = vec4(final_color.rgb, final_color.a);
 #else
     // since background alpha is 1.0, it is effectively pre-multiplied
     final_color = vec4(premul_blend(fg.rgb, fg.a, background), 1.0f);