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Re: Detect slurred notes in callback function

From: Jakub Pavlík
Subject: Re: Detect slurred notes in callback function
Date: Sun, 14 Feb 2016 11:41:09 +0100

Hi David,

as promised, here is my unsuccessful attempt based on a closure preserving state information between invocations.



\version "2.19.32"

#(define (contains-slur-event-with-direction? lst direction)
   (if (null-list? lst)
       (if (music-is-of-type? (car lst) 'slur-event)
             (eq? (ly:music-property (car lst) 'span-direction) direction)
             (contains-slur-event-with-direction? (cdr lst) direction))))

#(define (notehead-articulations notehead)
   (let ((noteevent (ly:event-property (event-cause notehead) 'music-cause)))
    (ly:music-property noteevent 'articulations)))

#(define (slur-opener? notehead)
   (contains-slur-event-with-direction? (notehead-articulations notehead) 1))

#(define (slur-closer? notehead)
   (contains-slur-event-with-direction? (notehead-articulations notehead) -1))

#(define (make-in-slur-callback inSlur notInSlur)
   (let ((slursOpen 0))
     (display "+++ Factory executed")
     ; this closure will be executed for each NoteHead
     (lambda (grob)
        (display "+++ Closure executed")
        ; to see the order of NoteHead the callback is called for
        (display-scheme-music (ly:event-property (event-cause grob) 'origin))
          ((slur-opener? grob) (set! slursOpen (+ slursOpen 1)))
          ((slur-closer? grob) (set! slursOpen (- slursOpen 1))))
         (if (> slursOpen 0)
             (inSlur grob)
             (notInSlur grob)))

\score {
  \relative c' {
    \override NoteHead #'color = #(make-in-slur-callback
      (lambda (grob) red)
      (lambda (grob) black))

    d e( f) g( a b c)

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