static bool has_interface (Grob*);
DECLARE_SCHEME_CALLBACK (force_shift_callback, (SCM ,SCM));
DECLARE_SCHEME_CALLBACK (side_position, (SCM ,SCM));
static bool has_interface (Grob*);
DECLARE_SCHEME_CALLBACK (force_shift_callback, (SCM ,SCM));
DECLARE_SCHEME_CALLBACK (side_position, (SCM ,SCM));