Re: Four Bars per Line/System, again :)

[Janek Warchoł]

David,

a couple of thoughts:
- what about looping the break pattern?  I.e. \consists
#(custom-line-breaks-engraver '(2 3 4)) = \consists
#(custom-line-breaks-engraver '(2 3 4 2 3 4 2 3 4 ... 2 3 4))?
- i'm not sure if this is desired or not, but changing current
barNumber confuses your function:

\version "2.15.38"

#(define (custom-line-breaks-engraver bar-list)
  (let ((total (1+ (car bar-list)))) ;; not sure why increment necessary
    (lambda (context)
      (make-engraver
        (acknowledgers ((paper-column-interface engraver grob source-engraver)
          (let ((current-bar (ly:context-property context 'currentBarNumber)))
            (if (and (pair? bar-list)
                     (= (remainder current-bar total) 0)
                     (eq? #t (ly:grob-property grob 'non-musical)))
                (begin
                  (set! (ly:grob-property grob 'line-break-permission) 'force)
                  (if (not (null? (cdr bar-list)))
                      (begin
                        (set! bar-list (cdr bar-list))
                        (set! total (+ total (car bar-list))))
                      (set! bar-list '())))))))))))

\relative c' {
  \set Score.currentBarNumber = #4
  c4 c c c c c c c c c c c c2 c
  c4 c c c c c c c c c c c c2 c
  c4 c c c c c c c c c c c c2 c
}

\layout {
  \context {
    \Score
    \consists #(custom-line-breaks-engraver '(4 4 4))  % the break
occurs after measure with number 4, not after 4 measures
  }
}

cheers,
Janek