Re: Accessing a grob from within a music function

[Thomas Morley]

2017-03-16 22:51 GMT+01:00 Thomas Morley <address@hidden>:
> 2017-03-16 14:23 GMT+01:00 Urs Liska <address@hidden>:
>> Hi,
>>
>> I'm trying to write a function to push a note column like this:
>>
>> pushLeftBroken =
>> #(define-music-function ()()
>>    #{
>>      \once \override NoteColumn.X-offset = 3
>>    #})
>>
>> But I need to make that "3" depend on some characteristics of the actual
>> note column. Basically I need the width of the note column, including
>> attached accidentals.
>>
>> I know how to get to the accidental(s) within a note column, but if I'm
>> not mistaken there's no actual grob inside that.
>>
>> Probably music-function isn't the right approach?
>>
>> What I need is a way to say something like
>>
>> \once \override NoteColumn.X-offset = #(+ 3
>> extent-of-all-accidentals-in-the-note-column)
>>
>> Any ideas?
>> TIA
>> Urs
>
>
>
> Hi Urs,
>
> here my thoughts about the topic so far.
> Although I'm afraid it will not help, because it has to be done
> before-line-breaking.
>
> wanted-value = 20
>
> {
>     c'1( \break
>   \override NoteColumn.before-line-breaking =
>   #(lambda (nc)
>   ;; TODOs
>   ;; add fall-backs if certain grobs are not present, i.e
>   ;; (DotColumn, Arpeggio, AccidentalPlacement)
>     (let* ((dot-col (ly:note-column-dot-column nc))
>            (acc-placement (ly:note-column-accidentals nc))
>            (common-ref
>              (ly:grob-common-refpoint nc acc-placement X))
>            (x-length-of-accs
>              (interval-length
>                (ly:relative-group-extent
>                  (map last (ly:grob-object acc-placement 'accidental-grobs))
>                  common-ref
>                  X))))
>
>        (for-each
>          (lambda (el)
>            (ly:grob-translate-axis!
>              el
>              (+ x-length-of-accs wanted-value)
>              X))
>          (filter
>            (lambda (g) (ly:grob? g))
>            (list
>              acc-placement
>              dot-col
>              nc)))))
>
>
>   <cis'' dis'' fis'' gis''-1\2>2)\arpeggio ^"foo"
> }
>
> Cheers,
>   Harm

Probably:

{
    c'1( \break
  \override NoteColumn.after-line-breaking =
  #(lambda (nc)
     (ly:grob-translate-axis! (ly:grob-parent nc X) 5 X)
     ;; uncomment for viewing
     ;(ly:grob-set-property!
     ;  (ly:grob-parent nc X)
     ;  'stencil
     ;  ly:paper-column::print)
       )


  <cis'' dis'' fis'' gis''-1\2>2)\arpeggio ^"foo"
}

Not tested beyond the above example, though.

Cheers,
  Harm