pub unsafe extern "C" fn cairo_show_text_glyphs(
    cr: *mut cairo_t,
    utf8: *const c_char,
    utf8_len: c_int,
    glyphs: *const Glyph,
    num_glyphs: c_int,
    clusters: *const TextCluster,
    num_clusters: c_int,
    cluster_flags: cairo_text_cluster_flags_t
)