Re: NoteHead X-offset, conflict with ly:grob-relative-coordinate?

[David Nalesnik]

Hi Paul,

On Sat, Dec 8, 2012 at 12:00 PM, Paul Morris <address@hidden> wrote:

[snip]

>>
>> In this case you can make use of the 'stem-attachment property:
>>
>> \override NoteHead #'stem-attachment = #'(-0.8 . 0)
>
> Thanks David,  I hadn't thought of using stem-attachment.  It works for 
> single notes, but unfortunately does not seem to work for repositioning 
> individual noteheads within chords, which is what I want to do.
>
> For example, the snippet below changes stem-attachment to try to reposition 
> every other note (colored green as well just for purposes of illustration).  
> But the notes in a given chord all end up on the same side of the stem rather 
> than some on one side and some on the other.
>
> (I tried using the extra-offset property, and it worked, but it is applied 
> after the spacing has been set, and so could lead to collisions or bad 
> horizontal spacing.  The X-offset property, on the other hand, is applied 
> before spacing is determined.)
>
> -Paul
>
> \version "2.16.1"
>
> note-counter = 1
>
> CustomNoteHeads =
> #(lambda (grob)
>   (let*
>     (
>       (notecol (ly:grob-parent grob 0))
>       (rel-coord (ly:grob-relative-coordinate grob notecol 0))
>     )
>     (cond ((=  0 (modulo note-counter 2))
>       (set! (ly:grob-property grob 'stem-attachment) '(-0.8 . 0))
>       (set! (ly:grob-property grob 'color) green)
>     ))
>     (set! note-counter (+ 1 note-counter))
> ))
>
> \score {
>   \new Staff
>     \with {
>       \override NoteHead #'before-line-breaking = \CustomNoteHeads
>     }
>     {
>         <c'' e''> <d'' f''> <e'' g'' b''> <f'' a'' c'''>
>         <c' e'> <d' f'> <e' g' b'> <f' a' c''>
>         }
>   \layout { }
> }

You posted this question awhile back
(http://www.mail-archive.com/address@hidden/msg70733.html).  Is
the solution I provided there no longer working for you?

I needed to change some values to deal with normal note-shapes, but
this seems to work just fine:

#(define ((shift offsets) grob)
  (let ((note-heads (ly:grob-array->list (ly:grob-object grob 'note-heads))))
    (for-each
      (lambda (p q) (set! (ly:grob-property p 'X-offset) q))
      note-heads offsets)))

displaceHeads =
#(define-music-function (parser location offsets) (list?)
  #{
    \once \override NoteColumn #'before-line-breaking = #(shift offsets)
  #}
)

theMusic = {
  \displaceHeads #'(0 0 1.3)
  <c' e' g' >4

  \displaceHeads #'(0 1.3 1.3)
  <d' f' a'>

  \displaceHeads #'(0 1.3 1.3)
  <d' f' a'>

  \displaceHeads #'(0 0 1.3)
  < c' e' g'>

  \displaceHeads #'(-1.3 -1.3 0)
  < c'' e'' g''>

  \displaceHeads #'(-1.3 -1.3 0)
  < c''' e''' g'''>

  \displaceHeads #'(0 0 1.3)
  < c e g>

  \displaceHeads #'(0 -1.3 0)
  < c'' e'' g''>

  \displaceHeads #'(0 0 -1.3)
  < c'' e'' g''>
}

\new Staff {
  \theMusic
}

-David