Re: Generation of Notation Videos with Lilypond Tool Chain

[Knut Petersen]

Three months ago you wrote:

A weakness of the approach is that the page turning times
for the score are gained by parsing the Postscript output
file of lilypond.  This approach is fragile and might break
when the font set is changed or whenever lilypond changes
its rendering philosophy.

David Nalesnik demonstrated how to teach lilypond to generate a list of bar numbers at line breaks,
see his original message at https://lists.gnu.org/archive/html/bug-lilypond/2015-01/msg00051.html.

Add the following code to the top of your ly file:
============================

#(define out (open-output-file "line-breaks.txt"))

#(define (display-breaks grob)
   (if (and (grob::has-interface grob 'paper-column-interface)
            (eq? #t (ly:grob-property grob 'non-musical)))
       (if (eq? 1 (ly:item-break-dir grob))
           (let* ((location (ly:grob-property grob 'rhythmic-location))
                  (m (car location)))
             (format out "Line beginning at measure ~a~%" m)))
       (ly:message "Need NonMusicalPaperColumn grob to determine line breaks.")))

Then activate the code as shown below:
========================

\score {
   [...]
    \layout{
        \context {
            \Score
            \override NonMusicalPaperColumn #'after-line-breaking = #display-breaks
        }
    }
}

Best regards,

Knut