in Snippets - LilyPond

Contexts and engravers 370
%%%
%%% Grob utilities
%%%
%%% These are literal rewrites of some C++ methods used by the ambitus engraver.
#(define (ly:separation-item::add-conditional-item grob grob-item)
"Add @var{grob-item} to the array of conditional elements of @var{grob}.
Rewrite of @code{Separation_item::add_conditional_item} from @file{lily/separation-item.cc}.
(ly:pointer-group-interface::add-grob grob 'conditional-elements grob-item))
#(define (ly:accidental-placement::accidental-pitch accidental-grob)
"Get the pitch from the grob cause of @var{accidental-grob}.
Rewrite of @code{accidental_pitch} from @file{lily/accidental-placement.cc}."
(ly:event-property (ly:grob-property (ly:grob-parent accidental-grob Y) 'cause)
'pitch))
#(define (ly:accidental-placement::add-accidental grob accidental-grob)
"Add @var{accidental-grob}, an @code{Accidental} grob, to the
list of the accidental grobs of @var{grob}, an @code{AccidentalPlacement}
grob.
Rewrite of @code{Accidental_placement::add_accidental} from @file{lily/accidental-placement.
(let ((pitch (ly:accidental-placement::accidental-pitch accidental-grob)))
(set! (ly:grob-parent accidental-grob X) grob)
(set! (ly:grob-property accidental-grob 'X-offset)
ly:grob::x-parent-positioning)
(let* ((accidentals (ly:grob-object grob 'accidental-grobs))
(handle (assq (ly:pitch-notename pitch) accidentals))
(entry (if handle (cdr handle) '())))
(set! (ly:grob-object grob 'accidental-grobs)
(assq-set! accidentals
(ly:pitch-notename pitch)
(cons accidental-grob entry))))))
%%%
%%% Ambitus data structure
%%%
%%% The class holds the various grobs that are created
%%% to print an ambitus:
%%% - ambitus-group: the grob that groups all the components of an ambitus
%%% (Ambitus grob);
%%% - ambitus-line: the vertical line between the upper and lower ambitus
%%% notes (AmbitusLine grob);
%%% - ambitus-up-note and ambitus-down-note: the note head and accidental
%%% for the lower and upper note of the ambitus (see class
%%% below).
%%% The other slots define the key and clef context of the engraver:
%%% - start-c0: position of middle c at the beginning of the piece. It
%%% is used to place the ambitus notes according to their pitch;
%%% - start-key-sig: the key signature at the beginning of the piece. It
%%% is used to determine if accidentals shall be printed next to ambitus
%%% notes.