Unify circular corner geometry and shader masks

compositor/src/render/shaders/blur_shader.frag

@@ -19,11 +19,11 @@ uniform float presentation_alpha;
 uniform float background_opacity;
 uniform vec4 tint;
 varying vec2 v_coords;
+//_CORNERS_
+
 void main() {
-    vec2 half_size = visible_rect.zw * 0.5;
-    vec2 d = abs(gl_FragCoord.xy - visible_rect.xy - half_size) - (half_size - vec2(material_radius));
-    float sdf = length(max(d, 0.0)) + min(max(d.x, d.y), 0.0) - material_radius;
-    float coverage = alpha * presentation_alpha * (1.0 - smoothstep(-0.5, 0.5, sdf));
+    float sdf = rounded_rect_distance(gl_FragCoord.xy, visible_rect, material_radius);
+    float coverage = alpha * presentation_alpha * edge_coverage(sdf);
     if (coverage <= 0.0) { gl_FragColor = vec4(0.0); return; }
     vec2 coords = (gl_FragCoord.xy - capture_origin) / texture_size;
     vec4 color = vec4(0.0);