+ DECLARE_SCHEME_CALLBACK (calc_average_anchor, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_extent_aligned_anchor, (SCM));
+ DECLARE_SCHEME_CALLBACK (calc_break_visibility, (SCM));
+ DECLARE_GROB_INTERFACE();
+};
+
+struct Break_alignable_interface
+{
+ DECLARE_SCHEME_CALLBACK (self_align_callback, (SCM element));
+ DECLARE_GROB_INTERFACE();