1 files changed, 17 insertions, 3 deletions
diff --git a/gsk/ngl/resources/unblurred_outset_shadow.glsl b/gsk/ngl/resources/unblurred_outset_shadow.glsl
index 56f0750e6d..0ce6790e98 100644
--- a/gsk/ngl/resources/unblurred_outset_shadow.glsl
+++ b/gsk/ngl/resources/unblurred_outset_shadow.glsl
@@ -1,4 +1,6 @@
 // VERTEX_SHADER:
+// unblurred_outset_shadow.glsl
+
 uniform float u_spread;
 uniform vec2 u_offset;
 uniform vec4[3] u_outline_rect;
@@ -25,16 +27,28 @@ void main() {
 }
 
 // FRAGMENT_SHADER:
+// unblurred_outset_shadow.glsl
 _IN_ vec4 final_color;
 _IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
 _IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
   vec2 frag = gsk_get_frag_coord();
+  float inside_coverage;
+
+  inside_coverage = gsk_rounded_rect_coverage(gsk_decode_rect(transformed_inside_outline), frag);
+  float alpha;
+
+  if (inside_coverage == 1.0)
+    alpha = 0.0;
+  else
+    {
+      float outside_coverage;
+
+      outside_coverage = gsk_rounded_rect_coverage(gsk_decode_rect(transformed_outside_outline), frag);
 
-  float alpha = clamp(gsk_rounded_rect_coverage(gsk_decode_rect(transformed_outside_outline), frag) -
-                      gsk_rounded_rect_coverage(gsk_decode_rect(transformed_inside_outline), frag),
-                      0.0, 1.0);
+      alpha = clamp(outside_coverage - inside_coverage, 0.0, 1.0);
+    }
 
   gskSetOutputColor(final_color * alpha);
 }