Function ncvisual_decode_loop 

pub unsafe extern "C" fn ncvisual_decode_loop(
    nc: *mut ncvisual,
) -> c_int

decode the next frame ala ncvisual_decode(), but if we have reached the end, rewind to the first frame of the ncvisual. a subsequent ‘ncvisual_blit()’ will render the first frame, as if the ncvisual had been closed and reopened. the return values remain the same as those of ncvisual_decode().