Re: arbitrary repeat counter

[Simon Bailey]

Hi Jean,

thanks for that example. Is it supposed to print any numbers? It's not
doing so in 2.23.9 (windows, frescobaldi).

I've come up with a slightly different approach, that's not quite
finished (and not as fancy as creating a new engraver):

#(set-object-property! 'phrase-length 'backend-type? integer?)
#(define (counter-stencil grob)
   (let* ((counter (string->number (ly:grob-property grob 'text)))
          (phrase-length (ly:grob-property grob 'phrase-length)))
     (if (and (eq? (modulo counter phrase-length) 1) (>= counter phrase-length))
         (ly:stencil-aligned-to
          (grob-interpret-markup grob
            (markup (number->string (ceiling (/ counter phrase-length)))))
          Y
          CENTER))))

\relative c' {
  \set countPercentRepeats = ##t
  \override PercentRepeatCounter.phrase-length = 4
  \override PercentRepeatCounter.stencil = #counter-stencil
  \repeat percent 12 { c d e f }
}

I intend to wrap that in a music function that does all the override
magic and will take the music as a parameter (maybe work out the
phrase length from that, or pass it manually) and number of repeats.

Thanks, kind regards,
sb

On Wed, 1 Jun 2022 at 13:51, Jean Abou Samra <jean@abou-samra.fr> wrote:
>
> Le 01/06/2022 à 12:25, Simon Bailey a écrit :
> > Hi,
> >
> > with a little bit of digging through your manual, i have solved some
> > of my questions:
> >
> > #(define (counter-stencil grob)
> >     (let* ((counter (ly:grob-property grob 'text)))  ; get the value of
> > the counter
> >       (ly:stencil-aligned-to
> >         (grob-interpret-markup grob
> >           (markup counter "!")) ; print the counter back with !
> >         Y
> >         CENTER)))
> >
> > This basically replicates the behaviour of the regular percent counter
> > and adds an exclamation mark. so now i can just add some if/mod/div
> > magic and it should do what I want. Getting there… ;)
>
>
>
> Well, you have two possible approaches. The one you sketch above is
> the backend approach: override the measure counter's alignment so
> it aligns within the first measure rather than the whole span.
> The other is the translation approach: arrange to create the
> counter so that it has the right bound you want from the start.
> I think that is simpler in this case, so I'd do something like
>
> \version "2.22.2"
>
> newRepeatMarker = #(make-music 'MeasureCounterEvent 'mark-new-repeat #t)
>
> repeatCounting =
> #(define-music-function (n music) (index? ly:music?)
>     #{
>       \startMeasureCount
>       \repeat unfold #n { \newRepeatMarker #music }
>     #})
>
> #(define (My_counter_engraver context)
>     (let ((count 1)
>           (count-here #f)
>           (spanner #f)
>           (spanner-to-end #f))
>       (make-engraver
>        (listeners
>         ((measure-counter-event engraver event)
>          (cond
>           ((eqv? LEFT (ly:event-property event 'span-direction))
>            (set! count 1))
>           ((ly:event-property event 'mark-new-repeat #f)
>            (set! count-here #t)))))
>        ((process-music engraver)
>         (if count-here
>             (let ((col (ly:context-property context 'currentCommandColumn)))
>               (set! spanner (ly:engraver-make-grob engraver
> 'MeasureCounter '()))
>               (ly:spanner-set-bound! spanner LEFT col)
>               (ly:grob-set-property! spanner 'count-from count)
>               (set! count (1+ count)))))
>        (acknowledgers
>         ((bar-line-interface engraver grob source-engraver)
>          (if spanner-to-end
>              (let ((col (ly:context-property context
> 'currentCommandColumn)))
>               (ly:spanner-set-bound! spanner-to-end RIGHT col)
>               (ly:engraver-announce-end-grob engraver spanner-to-end '())
>               (set! spanner-to-end #f)))))
>        ((stop-translation-timestep engraver)
>         (if spanner
>             (set! spanner-to-end spanner))
>         (set! spanner #f)
>         (set! count-here #f)))))
>
> \layout {
>    \context {
>      \Staff
>      \consists #My_counter_engraver
>    }
> }
>
> \new Staff \relative c' {
>    \repeatCounting 4 { c4. 8 r4 8 r | d4. 4. 4 | 1 }
> }
>
>
> Best,
> Jean
>


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