Re: Thanks to David Nalesnik and Jan-Peter Voigt

[David Nalesnik]

Hi Jay,

On Sun, Sep 28, 2014 at 12:48 PM, David Nalesnik <address@hidden> wrote:

On Sun, Sep 28, 2014 at 10:30 AM, Jay Vara <address@hidden> wrote:

I wanted to get bar lines after each sub-meter of a compound meter, and
to have Completion_heads_engraver recognize these bar lines and split
and tie notes as needed.

Thanks to David and Jan-Peter, I was able to change their
doubleBarlinesAfterTimeSig engraver to achieve this effect. I still have
a little more work to do since some of the moment variables currently
have fixed values.

Here's an idea to make the engraver more flexible:

 \version "2.18.0"

meter = #'((3 4) (5 4) (2 4))

#(define (to-moment arg)

   (ly:make-moment (car arg) (cadr arg)))

alternateTiming =

#(lambda (sig)

   (lambda (context)

     (let ((last-bnum 0))

       `((process-music

          . ,(lambda (trans)

               (let* ((bnum (ly:context-property context 'currentBarNumber))

                      (len (length sig)) ; how many terms in compound meter

                      (pos (modulo bnum len)) 

                      (pos (if (= 0 pos) len pos)) ; first bar in pattern, second...

                      (pos-in-list (1- pos)) ; because elements of list are numbered from 0

                      (desired-measure-len (to-moment (list-ref sig pos-in-list)))) 

                 (format #t "bnum = ~a measurelength ~a ~%"

                   bnum

                   (ly:context-property context 'measureLength))

                 

                 (ly:context-set-property! context 'measureLength desired-measure-len)

                 (if (= pos-in-list 0)

                     (begin

                      (if (> bnum last-bnum)

                          (ly:context-set-property! context 'whichBar "||"))

                      (set! last-bnum bnum))))))))))

music = {

  \compoundMeter #meter

  \relative c' {c d e2 f g4 a2 b c4 b2 a g4 f2 e d c d e f g a b c d4}

}

\score {

  \new Staff \music

  \layout {

    \context {

      \Score

      \consists #(alternateTiming meter)

    }

    \context {

      \Voice

      \remove Note_heads_engraver

      \remove Rest_engraver

      \consists Completion_heads_engraver

      \consists Completion_rest_engraver

    }

  }

}

%%%%%%%%%%%%

Some notes:

I moved last-bnum into the engraver, as there's no need for it to be a global variable.  Initialize it in the let-block.

The compound meter can be any length (well, there should be a guard against 0, I suppose).

It's easy enough to create the moments you need for measureLength with a function.

HTH,

David