check_c_source_compiles([=[
    #include <png.h>
    #if !defined(PNG_APNG_SUPPORTED) || !defined(PNG_READ_APNG_SUPPORTED) || !defined(PNG_READ_APNG_SUPPORTED)
    #error "APNG support is required"
    #endif
    int main() {}
]=] LIBPNG_HAS_APNG)