[gtk/ngl-less-shaders: 7/10] ngl: Improve the coloring shader

[Matthias Clasen <matthiasc src gnome org>]

commit 8aac574d630e7e6b72a0b8f151f305369362ce1d
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Mar 13 18:04:26 2021 -0500

    ngl: Improve the coloring shader
    
    Since we are now passing a float anyway, we can avoid
    the branch in the fragment shader.

 gsk/ngl/resources/coloring.glsl | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)
---
diff --git a/gsk/ngl/resources/coloring.glsl b/gsk/ngl/resources/coloring.glsl
index 15e8203b8a..007c54d562 100644
--- a/gsk/ngl/resources/coloring.glsl
+++ b/gsk/ngl/resources/coloring.glsl
@@ -12,7 +12,7 @@ void main() {
   // We use this shader for both plain glyphs (used as mask)
   // and color glpyhs (used as source). The renderer sets
   // aColor to vec4(-1) for color glyhs.
-  if (distance(aColor, vec4(-1)) < 0.001)
+  if (distance(aColor,vec4(-1)) < 0.1)
     use_color = 0.0;
   else
     use_color = 1.0;
@@ -29,8 +29,5 @@ _IN_ float use_color;
 void main() {
   vec4 diffuse = GskTexture(u_source, vUv);
 
-  if (use_color > 0.0)
-    gskSetOutputColor(final_color * diffuse.a);
-  else
-    gskSetOutputColor(diffuse * u_alpha);
+  gskSetOutputColor(mix(diffuse * u_alpha, final_color * diffuse.a, use_color));
 }