Re: centering text on a measure

[Thomas Morley]

Hi David,

2011/10/3 David Nalesnik <address@hidden>

After your suggestion, I experimented some with creating my own interface and adding it to the interface-list of various grobs.  This creates an interface with a single property ('markers), and then adds it to every grob's description.

#(define add-custom-interface! (ly:add-interface 'grob-marker-interface "Marker for grob" '(markers)))

#(define all-custom-grob-descriptions

   (for-each

     (lambda (x)

       (let ((interfaces

               (ly:assoc-get 'interfaces

                 (ly:assoc-get 'meta

                   (cdr x)))))

         (set! interfaces (append! interfaces '(grob-marker-interface)))))

     all-grob-descriptions))

I don't know enough about the inner workings of LilyPond to understand the benefits of making an interface.  Is it so that, in this case, I could limit which grobs are able to be tagged with the 'markers property?

I'm only a musician and music-teacher without any previous programming-experience, trying to learn scheme and to dive into lilypond-internals deeper and deeper. So excuse me if I remark some moonshine. :)

Regarding the idea of defining custom-properties I thought: What could be done with such a property? After defining a name, the needed type of argument and the description - give it functionality. At first, I thought about rebuilding an existent renamed property. But how?

\version "2.14.2"

#(define (define-grob-custom-property symbol type? description)
  (if (not (equal? (object-property symbol 'backend-doc) #f))
      (ly:error (_ "symbol ~S redefined") symbol))

  (set-object-property! symbol 'backend-type? type?)
  (set-object-property! symbol 'backend-doc description)
  symbol)
  
#(define all-user-grob-custom-properties
  (map
   (lambda (x)
     (apply define-grob-custom-property x))

   `(
     (x-y-offset ,pair? "Rebuild extra-offset")
     )))
     
     \relative c' {
             \override TextScript #'x-y-offset = #'(1 . 1)
    c1-"hello"
     }

This does nothing (of course not)!

Maybe I'm wrong, but I thought adding an interface could be the solution. If not, how to do?

I also don't know if it's possible to limit the grobs to be tagged with the 'markers property when using the 'grob-marker-interface, but probably it could be examinated.

Many thanks for all the fine functions you've created!!

Best,

Harm