struct Crescendo ;
struct Decresc_req;
struct Directional_spanner;
+struct Disallow_break_req;
struct Durational_req;
struct Dynamic;
struct Dynamic_req;
struct Global_translator;
struct Group_change_req;
struct Group_feature_req;
+struct Head_column;
struct Horizontal_align_item;
struct Horizontal_group;
struct Horizontal_group_item;
struct Lily_stream;
struct Line_of_score;
struct Line_of_staff;
+struct Line_spacer;
struct Linestaff;
struct Local_key;
struct Local_key_item;
struct Slur_engraver;
struct Slur_req;
struct Spacing_req ;
-struct Spacing_problem;
struct Span_dynamic_req;
struct Span_req;
struct Spanner;
+struct Spring_spacer;
struct Staff_performer;
struct Staff_side;
struct Staff_symbol;