\version "2.17.25"

\header {
  snippet-title = "Bracket repeats"
  snippet-author = "David Nalesnik"
  snippet-description = \markup {
    \wordwrap {
      This snippet is a workaround which creates a representation
      for repeats which consists of a bracket above a measure.  The
      number of repeats is expressed by a number centered within
      the bracket and formatted as "2x".  This is not a true
      solution as it creates an arbitrary stencil which does not
      convey a repeat structure understood by LilyPond.  Currently,
      the workaround will not accomodate repeats lasting more than
      a single bar and measures split across lines.
    }
  }
  tags = "repeats, scheme"
  status = "unfinished"
}

%%%%%%%%%%%%%%%%%%%
%   THE SNIPPET   %
%%%%%%%%%%%%%%%%%%%

% The following procedure is a modification of the function
% `measure-counter-stencil' found in the file
% `scm/music-functions.scm' in the LilyPond distribution.

#(define (test-stencil grob text)
   (let* ((orig (ly:grob-original grob))
          (siblings (ly:spanner-broken-into orig)) ; have we been split?
          (bounds (ly:grob-array->list (ly:grob-object grob 'columns)))
          (refp (ly:grob-system grob))
          ;; we use the first and/or last NonMusicalPaperColumn grob(s) of
          ;; a system in the event that a MeasureCounter spanner is broken
          (all-cols (ly:grob-array->list (ly:grob-object refp 'columns)))
          (all-cols
           (filter
            (lambda (col) (eq? #t (ly:grob-property col 'non-musical)))
            all-cols))
          (left-bound
           (if (or (null? siblings) ; spanner is unbroken
                   (eq? grob (car siblings))) ; or the first piece
               (car bounds)
               (car all-cols)))
          (right-bound
           (if (or (null? siblings)
                   (eq? grob (car (reverse siblings))))
               (car (reverse bounds))
               (car (reverse all-cols))))
          (elts-L (ly:grob-array->list (ly:grob-object left-bound 'elements)))
          (elts-R (ly:grob-array->list (ly:grob-object right-bound 'elements)))
          (break-alignment-L
           (filter
            (lambda (elt) (grob::has-interface elt 'break-alignment-interface))
            elts-L))
          (break-alignment-R
           (filter
            (lambda (elt) (grob::has-interface elt 'break-alignment-interface))
            elts-R))
          (break-alignment-L-ext (ly:grob-extent (car break-alignment-L) refp X))
          (break-alignment-R-ext (ly:grob-extent (car break-alignment-R) refp X))
          (num
           (markup text))
          (num
           (if (or (null? siblings)
                   (eq? grob (car siblings)))
               num
               (make-parenthesize-markup num)))
          (num (grob-interpret-markup grob num))
          (num-stil-ext-X (ly:stencil-extent num X))
          (num-stil-ext-Y (ly:stencil-extent num Y))
          (num (ly:stencil-aligned-to num X (ly:grob-property grob 'self-alignment-X)))
          (num
           (ly:stencil-translate-axis
            num
            (+ (interval-length break-alignment-L-ext)
              (* 0.5
                (- (car break-alignment-R-ext)
                  (cdr break-alignment-L-ext))))
            X))
          (bracket-L
           (markup
            #:path
            0.1 ; line-thickness
            `((moveto 0.5 ,(* 0.5 (interval-length num-stil-ext-Y)))
              (lineto ,(* 0.5
                         (- (car break-alignment-R-ext)
                           (cdr break-alignment-L-ext)
                           (interval-length num-stil-ext-X)))
                ,(* 0.5 (interval-length num-stil-ext-Y)))
              (closepath)
              (rlineto 0.0 -1.0))))
          (bracket-R
           (markup
            #:path
            0.1
            `((moveto ,(* 0.5
                         (- (car break-alignment-R-ext)
                           (cdr break-alignment-L-ext)
                           (interval-length num-stil-ext-X)))
                ,(* 0.5 (interval-length num-stil-ext-Y)))
              (lineto 0.5
                ,(* 0.5 (interval-length num-stil-ext-Y)))
              (closepath)
              (rlineto 0.0 -1.0))))
          (bracket-L (grob-interpret-markup grob bracket-L))
          (bracket-R (grob-interpret-markup grob bracket-R))
          (num (ly:stencil-combine-at-edge num X LEFT bracket-L 0.4))
          (num (ly:stencil-combine-at-edge num X RIGHT bracket-R 0.4)))
     num))

%%%%%%%%%%%%%%%%%%%%%
%   USAGE EXAMPLE   %
%%%%%%%%%%%%%%%%%%%%%
<<
  \new Voice = "notes" {
    \relative c'' {
      
      \time 3/4
      s2.
      \override Staff.MeasureCounter.font-encoding = #'latin1
      \override Staff.MeasureCounter.font-size = 0
      \override Staff.MeasureCounter.stencil =
      #(lambda (grob) (test-stencil grob #{ \markup \italic "Safety" #} ))
      \once \override Staff.MeasureCounter.count-from = 3
      \override Staff.DynamicLineSpanner.padding = 2
      \repeat volta 1 {
        \startMeasureCount
        a4 g f
        \stopMeasureCount
      }
    }
  }
  \new Lyrics \lyricsto "notes" {
    He had this
  }
>>

\layout {
  \context {
    \Staff
    \consists #Measure_counter_engraver
  }
}