Re: Changing volta number text

[Aaron Hill]

On 2021-05-14 6:40 pm, Ralph Palmer wrote:
> Excellent! Thank you, Aaron. I wish I could understand what your 
> function
> does - how it works.

The technique involves querying the current Score.repeatCommands and 
replacing any existing (volta "...") command with the user-provided 
version.  This preserves the other repeat commands such as (end-repeat) 
and (volta #f).

Here is a minorly-refactored version with some documentation, comments, 
and a helpful usage warning:

%%%%
\version "2.22.0"
\include "english.ly"

changeVoltaText =
#(define-music-function
  (text) (markup?)
  (_i "Replaces the volta text within the currently-set 
@code{repeatCommands}.")

  (define (volta-text? cmd)
   ;; Look for the (volta "...") pattern.
   (and (pair? cmd)
        (eq? 'volta (car cmd))
        (markup? (cadr cmd))))
  (define (replacer cmd)
   (if (volta-text? cmd) `(volta ,text) cmd))
  (define (proc ctxt)
   (let ((cmds (ly:context-property ctxt 'repeatCommands '())))
    (if (any volta-text? cmds)
     (ly:context-set-property! ctxt 'repeatCommands (map replacer cmds))
     (ly:input-warning (*location*) "No volta text was replaced."))))

  #{ \context Score \applyContext #proc #})

test = {
  \time 3/4
  \repeat volta 3
  {
    a'4 b' c' |
    \changeVoltaText "dud"
    #(ly:expect-warning "No volta text was replaced.")
    b'4 c' d' |
  }
  \alternative {
    {
      \changeVoltaText "1., 3."
      e'4 f' g' |
    }
    {
      d'4 c' b' |
    }
    {
      \changeVoltaText \markup \with-color #red "4."
      g'4 a' b' |
    }
  }
  c'1
}

\score {
  \test
}
%%%%



-- Aaron Hill