Re: Horizontal shifting of chords

[Thomas Morley]

Am Mo., 4. Feb. 2019 um 10:35 Uhr schrieb Andrew Bernard
<address@hidden>:
>
> Hi Robert,
>
> You asked to centre the chord, but  then if you add barline offset it's not 
> centred, so I am a bit confused what you mean. although the picture makes it 
> clear.
>
> I just wanted to say that there are often times when you really do want to 
> centre a chord or a rest in a single, especially in Baroque music. To this 
> end, when I asked about this in the past, David Nalesnik and Thomas Morley 
> produced this excellent code. Note that it only works for one thing in a bar, 
> but it's great.
>
> Hope this may help.
>
> One of those things that ought to go in LSR I suppose.
>
>
> Andrew
>
> %====
> % Thanks to David Nalesnik and Thomas Morley.
>
> #(define (sort-by-X-coord sys grob-lst)
>    "Arranges a list of grobs in ascending order by their X-coordinates"
>    (let* ((X-coord (lambda (x) (ly:grob-relative-coordinate x sys X)))
>           (comparator (lambda (p q) (< (X-coord p) (X-coord q)))))
>
>      (sort grob-lst comparator)))
>
> #(define (find-bounding-grobs note-column grob-lst)
>    (let* ((sys (ly:grob-system note-column))
>           (X-coord (lambda (n) (ly:grob-relative-coordinate n sys X)))
>           (note-column-X (X-coord note-column)))
>
>      (define (helper lst)
>        (if (and (< (X-coord (car lst)) note-column-X)
>                 (> (X-coord (cadr lst)) note-column-X))
>            (cons (car lst) (cadr lst))
>            (if (null? (cddr lst))
>                (cons note-column note-column)
>                (helper (cdr lst)))))
>
>      (helper grob-lst)))
>
> #(define (read-out ls1 ls2 ls3 symbol)
>    "Filters all elements of ls1 from ls2 and appends it to ls3"
>    (set! ls3 (append ls3 (filter (lambda (x) (eq? (car ls1) (symbol x))) 
> ls2)))
>    (if (null? (cdr ls1))
>        ls3
>        (read-out (cdr ls1) ls2 ls3 symbol)))
>
> #(define ((center-note-column x-offs) grob)
>    (let* ((sys (ly:grob-system grob))
>           (elements-lst (ly:grob-array->list (ly:grob-object sys 
> 'all-elements)))
>           (grob-name (lambda (x) (assq-ref (ly:grob-property x 'meta) 'name)))
>           (X-extent (lambda (q) (ly:grob-extent q sys X)))
>           ;; NoteColumn
>           (note-column-coord (ly:grob-relative-coordinate grob sys X))
>           (grob-ext (X-extent grob))
>           (grob-length (interval-length grob-ext))
>           ;; NoteHeads
>           (note-heads (ly:grob-object grob 'note-heads))
>           (note-heads-grobs (if (not (null? note-heads))
>                                 (ly:grob-array->list note-heads)
>                                 '()))
>           (one-note-head (if (not (null? note-heads-grobs))
>                              (car note-heads-grobs)
>                              '()))
>           (one-note-head-length (if (not (null? one-note-head))
>                                     (interval-length (X-extent 
> one-note-head)) ;; NB
>                                     0))
>           ;; Stem
>           (stem (ly:grob-object grob 'stem))
>           (stem-dir (ly:grob-property stem 'direction))
>           (stem-length-x (interval-length (X-extent stem))) ;; NB
>           ;; DotColumn
>           (dot-column (ly:note-column-dot-column grob))
>           ;; AccidentalPlacement
>           (accidental-placement (ly:note-column-accidentals grob))
>           ;; Arpeggio
>           (arpeggio (ly:grob-object grob 'arpeggio))
>           ;; Rest
>           (rest (ly:grob-object grob 'rest))
>           ;; Grobs to center between
>           (args (list 'BarLine
>                   'Clef
>                   'KeySignature
>                   'KeyCancellation
>                   'TimeSignature))
>           (grob-lst (read-out args elements-lst '() grob-name))
>           (new-grob-lst (remove (lambda (x) (interval-empty? (X-extent x))) 
> grob-lst))
>           (sorted-grob-lst (sort-by-X-coord sys new-grob-lst))
>           ;; Bounds
>           (bounds (find-bounding-grobs grob sorted-grob-lst))
>           (left (cdr (X-extent (car bounds))))
>           (right (car (X-extent (cdr bounds))))
>
>           ;;(bounds-coord (cons left right)) ;; delete
>
>           (basic-offset
>            (- (average left right)
>              (interval-center (X-extent grob))
>              (* -1 x-offs)))
>           (dir-correction
>            (if (> grob-length one-note-head-length)
>                (* stem-dir (* -2 stem-length-x) grob-length)
>                0))
>
>           ) ;; End of Defs in let*
>
>      ;; Calculation
>      (begin
>       ;;(display "\n\tbounds: \t")(write bounds)
>       (for-each
>        (lambda (x)
>          (cond ((ly:grob? x)
>                 (ly:grob-translate-axis!
>                  x
>                  (- basic-offset dir-correction)
>                  X))))
>        (list
>         (cond ((not (null? note-heads)) grob))
>         dot-column accidental-placement arpeggio rest))
>       )))
>
> centerNoteColumnOn = \override Staff.NoteColumn #'after-line-breaking = 
> #(center-note-column 0)
>
> centerNoteColumnOff = \revert Staff.NoteColumn #'after-line-breaking
>
> onceCenterNoteColumn =
> #(define-music-function (x-offs)(number?)
>    #{
>      \once \override Staff.NoteColumn #'after-line-breaking = 
> #(center-note-column x-offs)
>    #})
>
>
> %====

Iirc, this doesn't work for arpeggio anymore, due to some internal changes.
Its worth some rework anyway.

That said, here a possibility to do things manually:
\override Score.NonMusicalPaperColumn.full-measure-extra-space = 6
\overrideProperty Score.NonMusicalPaperColumn.full-measure-extra-space 6
(adjust the value to taste)

Which one to use depends... and it doesn't work for the first bar of a line.


Cheers,
  Harm