What is the proper way of programmatically generating markup?

[Matt Hood]

Hi everyone,

So I’m writing a function that reimplements the ‘\compoundMeter’ command with an Orff-style time signature, whereby the denominator of the signature is a note head (as opposed to a number), e.g. 4/4 = 4/crotchet, 9/8 = 3/dotted-crotchet, 15/16+2/4 = 5/dotted-quaver + 2/crotchet. I’ve been able to implement the first two cases, i.e. no additive signatures,  but I’d like to make the third example work.

**My first question is: does anyone know where can I find the source (scm or otherwise) for \compoundMeter? I can’t find it in the ‘share/scm’ folder. I feel like it would be helpful to reference.**

My attempts to make this work have involved trying to generate the markup using foreach loops, that crawl through a list of lists that might look like:

(  (3 3 (ly:make-duration 3 1))   (4 (ly:make-duration 2))  )

which would be equal to: (9+9/16)+(4/4). All elements except for the last of each loop are numerators, while the last is the denominator.

-----------------

This is the scheme code doing the work (not finished, but the basics should work?). The list-of-lists is referred to as ‘durs':

\version “2.18.2"                

...

(markup

(#:line
  ( for-each
   (lambda (x) 
    (markup "+")
    ( #:center-column 
     

     ;; Numerator Markup. The list supplied to the for-each loop doesn’t contain the duration. [“(cdr (reverse x))”]

     (#:line  
       (for-each 
        (lambda (y) 
         (
          ( markup "+") 
          (#:number (number->string y) )

         )
        )
        (cdr (reverse x))
       )
     )
    

    ;; Denominator markup.

    (#:note-by-number 
     (ly:duration-log (car (reverse x))) 
     (ly:duration-dot-count (car (reverse x))) 
     DOWN
    )
   

   )
  )
  durs
 )
)

)

This haphazard collection of markup needs to somehow fit into:

\override Score.TimeSignature #'text =

which accepts ‘markup’, singular, only. 

This throws errors such as:

warning: type check for `stencil' failed; value `#<unspecified>' must be of type `stencil'

------------------

**So my second question is: How do I programmatically generate markup from information taken from a list, and then put it into a single markup variable?**

Any help at all would be greatly appreciated.

Cheers, Matt.