Re: Thanks to David Nalesnik and Jan-Peter Voigt

[Jay Vara]

Hi David,

Thank you very much.  Now I know how to use the listeners! 

With your change it seems to work for the two-staff example with (7 4) (1 4) (2 4) meter. This is the only case of compound metre that I commonly use that has a (1 4) as one of the components. 

Just to be sure, I did check a few other metres, and whenever there is a (1 4) an issue is possible. Typically the problems seem to be in the first few measures. For example, the two staff example with meter = #'((1 4) (2 4)) gives the following.

Best regards

Jay

On Mon, Sep 29, 2014 at 1:37 AM, David Nalesnik <address@hidden> wrote:

Hi Jay,

On Sun, Sep 28, 2014 at 7:24 PM, David Nalesnik <address@hidden> wrote:

Possibly the problem is that the custom engraver is setting measureLength too late for Completion_heads_engraver to use it?

That just might be it.  The Completion_heads_engraver listens for note-events.  So, doing this same with the custom engraver gives us the code below:

 alternateTiming =

#(lambda (sig)

   (lambda (context)

     (let ((last-bnum 0))

       (make-engraver

        (listeners ((note-event engraver event)

                    (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))))

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

                      (format #t "bnum = ~a len ~a pos ~a measurelength ~a completion ~a~%"

                        bnum len pos

                        (ly:context-property context 'measureLength)

                        (ly:context-property context 'completionUnit))

                      (if (= pos-in-list 0)

                          (begin

                           (if (> bnum last-bnum)

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

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

%%%%%%%%%%%

This appears to work with your two-staff example.  How it fares with others, I don't know.  Keep your fingers crossed.

Note: You're using an older syntax for Scheme engravers.  I've adapted this one to use the make-engraver macro that David Kastrup introduced at some point.

Best,

David