tests/sksl/blend/BlendOverlay.metal

#include <metal_stdlib>
#include <simd/simd.h>
using namespace metal;
struct Inputs {
    float4 src;
    float4 dst;
};
struct Outputs {
    float4 sk_FragColor [[color(0)]];
};
float _blend_overlay_component(float2 s, float2 d) {
    return 2.0 * d.x <= d.y ? (2.0 * s.x) * d.x : s.y * d.y - (2.0 * (d.y - d.x)) * (s.y - s.x);
}
float4 blend_overlay(float4 src, float4 dst) {
    float4 result = float4(_blend_overlay_component(src.xw, dst.xw), _blend_overlay_component(src.yw, dst.yw), _blend_overlay_component(src.zw, dst.zw), src.w + (1.0 - src.w) * dst.w);
    result.xyz = result.xyz + dst.xyz * (1.0 - src.w) + src.xyz * (1.0 - dst.w);
    return result;
}

fragment Outputs fragmentMain(Inputs _in [[stage_in]], bool _frontFacing [[front_facing]], float4 _fragCoord [[position]]) {
    Outputs _out;
    (void)_out;
    _out.sk_FragColor = blend_overlay(_in.src, _in.dst);
    return _out;
}