nested-repeats, BarNumbers and unfoldRepeats

[Thomas Morley]

Hi all,

the challenge: start a repeat with alternative endings in the second
volta of a previous repeat _and_ do BarNumbers correctly with
'numbers-with-letters _and_ correct midi while using \unfoldRepeats.

First attempt:

mus-tst = {
  \set Score.alternativeNumberingStyle = #'numbers-with-letters
  \override Score.BarNumber.break-visibility = #end-of-line-invisible
  \repeat volta 2 { cis'1 }
  \alternative {
    { d'1 }
    {
      \set Score.voltaSpannerDuration = #(ly:make-moment 4/4)
      \repeat volta 2 {
        e'1
        #(make-music 'AlternativeEvent 'alternative-dir 1
'alternative-increment 0)
        f'1
        \unset Score.voltaSpannerDuration
      }
      \alternative {
        { g'1 a' }
        { b'1 c'' }
      }
    }
  }
  d''1
  \bar "|."
}

\score {
  { \new Staff \mus-tst }
  \layout {}
  %\midi {}
}

\score {
  \unfoldRepeats
  { \new Staff \mus-tst }
  \layout {}
  %\midi {}
}

It does all as desired but
#(make-music 'AlternativeEvent 'alternative-dir 1 'alternative-increment 0)
is not really nice. How to do it more elegant?
This came up in the german forum:
http://www.lilypondforum.de/index.php?topic=2229.msg12386#msg12386

My own attempt:

\version "2.18.2"

#(define ((my-make-volta-set l1 l2) mus)
  (let* ((music (ly:music-deep-copy mus))
         (alts (ly:music-property music 'elements))
         (lalts (length alts))
         (times (ly:music-property music 'repeat-count)))
    (map (lambda (x y xx yy)

           (make-music
            'SequentialMusic
            'elements
            ;; set properties for proper bar numbering
            (append
             (list (make-music 'AlternativeEvent
                               'alternative-dir xx
                               'alternative-increment yy))
             (list x)
             (if (= y (1- lalts))
                 (list (make-music 'AlternativeEvent
                                   'alternative-dir 1
                                   'alternative-increment 0))
                 '()))))
         alts
         (iota lalts)
         l1
         l2)))

mus-tst = {
  \set Score.alternativeNumberingStyle = #'numbers-with-letters
  \override Score.BarNumber.break-visibility = #end-of-line-invisible
  \withMusicProperty #'elements-callback #(my-make-volta-set '(-1 0) '(1 0))
  \repeat volta 2 { cis'1 }
  \alternative {
    { d'1 }
    {
      \set Score.voltaSpannerDuration = #(ly:make-moment 4/4)
      \repeat volta 2 {
        e'1
        f'1
        \unset Score.voltaSpannerDuration
      }
      \alternative {
        { g'1 a' }
        { b'1 c'' }
      }
    }
  }
  d''1
  \bar "|."
}

\score {
  { \new Staff \mus-tst }
  \layout {}
  %\midi {}
}

\score {
  \unfoldRepeats
  { \new Staff \mus-tst }
  \layout {}
  %\midi {}
}

Is slightly different in printed output, but with recent
devel-versions the unfoldRepeats-version is terrible.


Hence the other question:
I suspect
https://sourceforge.net/p/testlilyissues/issues/4252/
being responsible for the difference compared with 2.18.

Though,
is my coding that bad?
Or is bordercase triggered not covered by 4252?


Thanks,
  Harm