I was delighted to learn that Lilypond allows one to use custodes. I was wondering how they really work, namely, how one can, upon a linebreak, check what the next pitch is. I have limited Scheme experience. I first tried the code for the first example from here:
http://www.lilypond.org/doc/v2.19/Documentation/notation/typesetting-mensural-music and enclosed it (that is, the part inside "\score { } ") in "\displayMusic{ }" . But this, while enlightening in some respects, didn't really tell me what's going on when the custos is to be displayed. So I downloaded the source code, and after grepping found two files of interest: custos.cc and custos-engraver.cc . In the latter I found an _expression_ headed by
"void
Custos_engraver::acknowledge_note_head (Grob_info info)"
(line 83). Could anyone tell me if I'm on the right track? My problem is that, while I'm willing to learn, I have a very limited experience with C++ and with any object programming whatsoever (having spent much time decades ago with Turbo Pascal 5 :-)). I'd be very grateful for any pointers regarding what happens during a linebreak (and, in general, how one should learn such things).
Best regards,
Leszek Wronski.