half4 blend_src_over(half4 src, half4 dst) {
    return src + (1 - src.a)*dst;
}

half4 main(half4 src, half4 dst) {
    return blend_src_over(src, half4(1) - dst);
}

/*%%*
function 'half4 blend_src_over(half4 src, half4 dst)' was already defined
shader 'main' must be main() or main(float2)
unknown identifier 'src'
unknown identifier 'dst'
*%%*/