fn convert_shm_row(src: &[u8], dst: &mut [u8], src_bpp: usize, swap_rb: bool)Expand description
Convert one source row to a BGRA destination row per (src_bpp, swap_rb) from
shm_src_layout: a 4-byte source either copies straight or swaps R/B keeping alpha, a 3-byte
source fills opaque alpha and swaps R/B only when the layout calls for it.