scm_set_smob_print (surface_tag, print_surface);
scm_c_define_gsubr ("surface-w", 1, 0, 0, get_surface_width);
scm_c_define_gsubr ("surface-h", 1, 0, 0, get_surface_height);
scm_set_smob_print (surface_tag, print_surface);
scm_c_define_gsubr ("surface-w", 1, 0, 0, get_surface_width);
scm_c_define_gsubr ("surface-h", 1, 0, 0, get_surface_height);