\version "2.19.56"

%% Two overrides, attempting to demonstrate/trigger how embedding lily in guile
%% and vice versa works.
%% Both doing some simple string-operations

foo = {
\override Score.BarNumber.break-visibility = ##(#t #t #t)
\override Score.BarNumber.before-line-breaking =
  #(lambda (grob)
     (let ((b-nmbr 
             (string->number (markup->string (ly:grob-property grob 'text)))))
  
       (ly:grob-set-property! grob 'self-alignment-X CENTER)
       (ly:grob-set-property! grob 'text
         #{ 
            \markup 
             #(if (and (number? b-nmbr) (odd? b-nmbr))
                  (format #f "guile ~a" (version))
                  (format #f "lilypond ~a" (lilypond-version)))
         #})))
}

fooII =
\override NoteHead.after-line-breaking =
#(lambda (grob)
  (if (positive? 
        (ly:pitch-octave 
          (ly:prob-property (ly:grob-property grob 'cause) 'pitch)))
      (begin
        (ly:grob-set-property! grob 'stencil
          (ly:stencil-aligned-to
            (grob-interpret-markup grob
              #{ 
                 \markup #(string-concatenate '("名" "字" "-" "♥" "-" "字" "名")) 
              #})
            CENTER 
            X))
        (ly:grob-set-property! grob 'color red))
      (ly:grob-set-property! grob 'color green)))
  
{
    %% successively uncomment:
    %\foo
    %\fooII
    \repeat unfold 20 { \repeat unfold 4 { c'4 e' g' c'' } \break }
}