-uniform vec2 PREFIX(offset);
-uniform vec2 PREFIX(scale);
-uniform vec2 PREFIX(texcoord_min);
-uniform vec2 PREFIX(texcoord_max);
+// Implicit uniforms:
+// uniform vec2 PREFIX(offset);
+// uniform vec2 PREFIX(scale);
+//
+// uniform vec2 PREFIX(normalized_coords_to_texels);
+// uniform vec2 PREFIX(offset_bottomleft);
+// uniform vec2 PREFIX(offset_topright);
vec4 FUNCNAME(vec2 tc) {
tc -= PREFIX(offset);
tc *= PREFIX(scale);
-#if 1
- if (any(lessThan(tc, PREFIX(texcoord_min))) ||
- any(greaterThan(tc, PREFIX(texcoord_max)))) {
- return PREFIX(border_color);
- }
-#endif
- if (any(lessThan(tc, vec2(0.0))) ||
- any(greaterThan(tc, vec2(1.0)))) {
- return PREFIX(border_color);
- }
-#if 0
- // In theory, maybe we should test on the outmost textel centers
- // (e.g. (0.5/width, 0.5/height) for the top-left) instead of the
- // texture border. However, since we only support integer padding
- if (any(lessThan(tc, vec2(0.0))) || any(greaterThan(tc, vec2(1.0)))) {
+ vec2 tc_texels = tc * PREFIX(normalized_coords_to_texels);
+ vec2 coverage_bottomleft = clamp(tc_texels + PREFIX(offset_bottomleft), 0.0f, 1.0f);
+ vec2 coverare_topright = clamp(PREFIX(offset_topright) - tc_texels, 0.0f, 1.0f);
+ vec2 coverage_both = coverage_bottomleft * coverare_topright;
+ float coverage = coverage_both.x * coverage_both.y;
+
+ if (coverage <= 0.0f) {
+ // Short-circuit in case the underlying function is expensive to call.
return PREFIX(border_color);
+ } else {
+ return mix(PREFIX(border_color), INPUT(tc), coverage);
}
-#endif
-
- return INPUT(tc);
}