Snippet: Customizing markFormatter

[Aaron Hill]

Hi folks,

There have been a few mentions of rehearsal marks recently and wanting 
to customize the appearance of \mark \default.  Using \mark \markup 
gives you much freedom at the cost of requiring one to manually manage 
the numbering/naming of these marks.

The (what-I-presume-is-official) solution is instead to \set 
Score.markFormatter to a custom procedure and then simply use \mark 
\default as one would normally.  This new procedure can leverage any 
existing formatting functions as desired.  Consider the following:

%%%%
\version "2.19.82"
\paper { indent = 0 line-width = 4\in ragged-right = ##f }
{
  \set Score.markFormatter = #(lambda (mark context)
    #{ \markup \italic $(format-mark-barnumbers mark context) #} )
  \repeat unfold 3 { \mark \default b'4 4 4 4 | 2 2 | 1 }
}
%%%%

In an attempt to hide the Scheme-ness of the above approach, I put 
together the following music function which replaces placeholder strings 
within the provided markup with the output of the specified formatter 
function:

%%%%
\version "2.19.82"
\paper { indent = 0 line-width = 4\in ragged-right = ##f }

customMarkFormatter = #(define-music-function (markup) (markup?)
  (define (handle-formatter mark context markup)
    (let* ((sym (and (string? markup)
                     (string-prefix? "format-mark" markup)
                     (string->symbol markup)))
           (proc (and sym (defined? sym) (primitive-eval sym))))
      (if (procedure? proc) (proc mark context) markup)))
  (define (markup-fixup mark context markup)
    (if (list? markup)
      (map (lambda (elem) (markup-fixup mark context elem)) markup)
      (handle-formatter mark context markup)))
  #{ \set Score.markFormatter = #(lambda (mark context)
       (markup-fixup mark context markup)) #} )

#(define (format-mark-roman mark context)
  (make-bold-markup (format #f "address@hidden" mark)))

{
  \customMarkFormatter format-mark-roman
  \repeat unfold 3 { \mark \default b'4 4 4 4 | 2 2 | 1 }

  \customMarkFormatter \markup \rotate #30 format-mark-circle-numbers
  \repeat unfold 3 { \mark \default b'4 4 4 4 | 2 2 | 1 }

  \customMarkFormatter \markup
    { format-mark-box-letters \fontsize #-3 format-mark-barnumbers }
  \repeat unfold 3 { \mark \default b'4 4 4 4 | 2 2 | 1 }

  \customMarkFormatter format-mark-undefined
  \mark \default b'4 4 4 4 | 2 2 | 1
}
%%%%

The logic is to look for strings that begin with "format-mark" and then 
attempt to evaluate the procedure.  Since all of the built-in formatting 
functions (as defined in translation-functions.scm) follow this naming 
convention, it made sense to require it to minimize the chance of 
evaluating an incorrect procedure.

The first example is just a trivial equivalent to \set 
Score.markFormatter = #format-mark-roman.  The second and third show 
more customization with markup, where the third in particular 
demonstrates combining the results of two formatting functions.  The 
final example covers the case of an undefined procedure.


-- Aaron Hill

default-mark.1.png
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default-mark.2.png
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