Function harfbuzz_ft_sys::hb_ft_create_referenced

pub unsafe extern "C" fn hb_ft_create_referenced(
    ft_face: FT_Face
) -> *mut hb_face_t

Official harfbuzz documentation:

This version is like hb_ft_face_create(), except that it calls FT_Reference_Face() on ft-face, as such keeping ft-face alive as long as the hb-face is.

This is the most convenient version to use. Use it unless you have very good reasons not to.