Re: shifting accidentals horizontally

[Valentin Petzel]

Hello Werner,

this Problem is not caused by my solution, but generally by your approach of 
taking the Notes with collision applied (the 8th note bb on the left, the b,e 
on the right) and shifting the bb until it is right of the others. This still 
means that the <b e> will be offcentered.

So this will also happen with your original extra-offset solution. A possible 
solution for this could be to do a similar thing to add certain note columns 
to separate NoteCollision grobs, so they can be spaced independently. However, 
it your case it should suffice to prevent any Collisions to be detected by doing

\once\override Staff.NoteCollision.note-collision-threshold = #-1

(this essentially means a collision is only considered such if the distance is 
under -1, so never).

This will of course mean that you’ll need to use other hshift values, as 
horizontal positioning will then be totally your responsibility. So doing 
something like this should work:

<<
  \new Staff {
    << { \once\override Staff.NoteCollision.note-collision-threshold = #-1 <b'! 
e''!>2. <c'' f''>4 |
         \once\override Staff.NoteCollision.note-collision-threshold = #-1 <b'! 
e''!>2. <c'' f''>4 } \\
       { \once \override NoteColumn.force-hshift = #2
         bes'!8 a' g' f' bes' a' g' f' |
         \once \override NoteColumn.force-hshift = #3
         \once \override Accidental.details.capture = ##t
         bes'!8 a' g' f' bes' a' g' f' } >>
  }
  \new Staff {
    \clef bass
    <a d'>2 q |
    q2 q |
  }
>>

Cheers,
Valentin

Am Dienstag, 13. Juni 2023, 06:37:46 CEST schrieb Werner LEMBERG:
> > @Werner I’ve added a small fix concerning the case when there is no
> > NoteCollision grob (in which case this should not be relevant in the
> > first place).
> 
> 
> Thanks a lot!  I think this would be a great snippet for the
> LSR.
> 
> Note, however, that there are alignment problems with other staves,
> see below.  For this particular case I can fix it by using
> `NoteColumn.X-offset`, but this isn't a sustainable solution.
> 
> 
>     Werner
> 
> 
> ======================================================================
> 
> 
> #(define (which lst)
>    (define (impl lst count)
>      (if (null? lst)
>          #f
>          (if (car lst)
>              count
>              (impl (cdr lst) (1+ count)))))
>    (impl lst 0))
> 
> 
> #(define (custom_accidental_placement_engraver context)
>    (define (grob-array->list x)
>      (if (ly:grob-array? x)
>          (ly:grob-array->list x)
>          '()))
>    (let ((placement #f))
>      (make-engraver
>       (acknowledgers
>        ((accidental-interface engraver grob source-engraver)
>         (if (assoc-get 'capture (ly:grob-property grob 'details) #f)
>             (begin
>               (if (not placement)
>                   (begin
>                    (set! placement (ly:engraver-make-grob engraver
> 'AccidentalPlacement '()))
 (ly:grob-set-parent! placement X
> (ly:grob-parent (ly:grob-parent grob Y) X)) (let ((padding
> (ly:grob-property-data placement 'right-padding))) (ly:grob-set-property!
>                       placement
>                       'right-padding
>                       (lambda (grob)
>                         (let* ((grobs (ly:grob-object placement
> 'accidental-grobs))
 (grobs (apply append (map cdr grobs))) (heads (map
> (lambda (x) (ly:grob-parent x Y)) grobs)) (stems (map (lambda (x)
> (ly:grob-object x 'stem)) heads)) (cols (map (lambda (x) (ly:grob-parent x
> X)) heads)) (collisions (map (lambda (x) (ly:grob-parent x X)) cols))
> (cols2 (apply append
>                                              (map 
>                                               (lambda (x)
>                                                 (grob-array->list
> (ly:grob-object x 'elements)))
 collisions)))
>                                (heads2 (apply append
>                                               (map
>                                                (lambda (x)
>                                                  (grob-array->list
> (ly:grob-object x 'note-heads)))
 cols2)))
>                                (stems2 (map (lambda (x) (ly:grob-object x
> 'stem)) heads))
 (grob-set1 (ly:grob-list->grob-array (append heads
> stems))) (grob-set2 (ly:grob-list->grob-array (append heads stems heads2
> stems2))) (refp (ly:grob-common-refpoint-of-array grob grob-set1 X)) (refp2
> (ly:grob-common-refpoint-of-array grob grob-set2 X)) (ext (ly:grob-extent
> refp refp2 X)) (ext2 (ly:grob-extent refp2 refp2 X)) (offset (car ext))
>                                (offset (- offset (car ext2))))
>                           (- (if (procedure? padding) (padding grob)
> padding) offset)))))))
 (let* ((src-placement (ly:grob-parent grob X))
>                      (grobs (ly:grob-object src-placement
> 'accidental-grobs))
 (has-grob? (map (lambda (pair) (memq grob (cdr pair)))
> grobs)) (pair (list-ref grobs (which has-grob?)))
>                      (notename (car pair))
>                      (groblist (cdr pair))
>                      (new-grobs (ly:grob-object placement
> 'accidental-grobs))
 (new-groblist (assoc-get notename new-grobs '()))
> (groblist (delete grob groblist eq?))
>                      (new-groblist (cons grob new-groblist))
>                      (grobs (assoc-set! grobs notename groblist))
>                      (new-grobs (assoc-set! new-grobs notename
> new-groblist)))
 (ly:grob-set-object! src-placement 'accidental-grobs
> grobs) (ly:grob-set-object! placement 'accidental-grobs new-grobs)
> (ly:grob-set-parent! grob X placement))))))
>       ((finish-timestep engraver)
>        (set! placement #f)))))
> 
> \layout {
>   \context {
>     \Voice
>     \consists #custom_accidental_placement_engraver
>   }
> }
> 
> <<
>   \new Staff {
>     << { <b'! e''!>2. <c'' f''>4 |
>          <b'! e''!>2. <c'' f''>4 } \\
>        { \once \override NoteColumn.force-hshift = #2.4
>          bes'!8 a' g' f' bes' a' g' f' |
>          \once \override NoteColumn.force-hshift = #3.4
>          \once \override Accidental.details.capture = ##t
>          bes'!8 a' g' f' bes' a' g' f' } >>
>   }
>   \new Staff {
>     \clef bass
>     <a d'>2 q |
>     % \once \override NoteColumn.X-offset = #0.8
>     q2 q |
>   }
> 
> >>

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