DECLARE_SCHEME_CALLBACK (calc_x_offset, (SCM));
DECLARE_SCHEME_CALLBACK (calc_y_offset, (SCM));
DECLARE_SCHEME_CALLBACK (calc_cross_staff, (SCM));
DECLARE_SCHEME_CALLBACK (calc_x_offset, (SCM));
DECLARE_SCHEME_CALLBACK (calc_y_offset, (SCM));
DECLARE_SCHEME_CALLBACK (calc_cross_staff, (SCM));