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Re: Problem with r2. in two voices

From: Kieren MacMillan
Subject: Re: Problem with r2. in two voices
Date: Sun, 8 Feb 2015 10:19:06 -0500

Hi Cynthia,

> I guess the only way out is to rewrite the two voices so that one of them 
> issues hidden rests in the score, but the rests in the parts, via tags.

Not at all… I can think of about a half-dozen other ways to make that happen in 

This would be my preference, since it would be applied globally:

\version "2.19.15"

#(define (rest-score r)
  (let ((score 0)
        (yoff (ly:grob-property-data r 'Y-offset))
        (sp (ly:grob-property-data r 'staff-position)))
    (if (number? yoff)
        (set! score (+ score 2))
        (if (eq? yoff 'calculation-in-progress)
            (set! score (- score 3))))
    (and (number? sp)
         (<= 0 2 sp)
         (set! score (+ score 2))
         (set! score (- score (abs (- 1 sp)))))

#(define (merge-rests-on-positioning grob)
  (let* ((can-merge #f)
         (elts (ly:grob-object grob 'elements))
         (num-elts (and (ly:grob-array? elts)
                        (ly:grob-array-length elts)))
         (two-voice? (= num-elts 2)))
    (if two-voice?
        (let* ((v1-grob (ly:grob-array-ref elts 0))
               (v2-grob (ly:grob-array-ref elts 1))
               (v1-rest (ly:grob-object v1-grob 'rest))
               (v2-rest (ly:grob-object v2-grob 'rest)))
           (ly:grob? v1-rest)
           (ly:grob? v2-rest)              
           (let* ((v1-duration-log (ly:grob-property v1-rest 'duration-log))
                  (v2-duration-log (ly:grob-property v2-rest 'duration-log))
                  (v1-dot (ly:grob-object v1-rest 'dot))
                  (v2-dot (ly:grob-object v2-rest 'dot))
                  (v1-dot-count (and (ly:grob? v1-dot)
                                     (ly:grob-property v1-dot 'dot-count -1)))
                  (v2-dot-count (and (ly:grob? v2-dot)
                                     (ly:grob-property v2-dot 'dot-count -1))))
             (set! can-merge
                    (number? v1-duration-log)
                    (number? v2-duration-log)
                    (= v1-duration-log v2-duration-log)
                    (eq? v1-dot-count v2-dot-count)))
             (if can-merge
                 ;; keep the rest that looks best:
                 (let* ((keep-v1? (>= (rest-score v1-rest)
                                      (rest-score v2-rest)))
                        (rest-to-keep (if keep-v1? v1-rest v2-rest))
                        (dot-to-kill (if keep-v1? v2-dot v1-dot)))
                   ;; uncomment if you're curious of which rest was chosen:
                   ;;(ly:grob-set-property! v1-rest 'color green)
                   ;;(ly:grob-set-property! v2-rest 'color blue)
                   (ly:grob-suicide! (if keep-v1? v2-rest v1-rest))
                   (if (ly:grob? dot-to-kill)
                       (ly:grob-suicide! dot-to-kill))
                   (ly:grob-set-property! rest-to-keep 'direction 0)
                   (ly:rest::y-offset-callback rest-to-keep)))))))
    (if can-merge
        (ly:rest-collision::calc-positioning-done grob))))

Aa = \relative c'' { \oneVoice r2. }
Ab = \relative c'' { \oneVoice r2. }

\score {  
  \new Staff \with { \override RestCollision.positioning-done = 
#merge-rests-on-positioning } <<
    \time 3/4
    \new Voice \Aa  \\ 
    \new Voice \Ab 

Hope this helps!

Kieren MacMillan, composer
www:  <>
email:  address@hidden

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