Hi Urs,
On Tue, Jan 24, 2017 at 7:19 AM, Urs Liska <u...@openlilylib.org> wrote:
> Hi,
>
> how can I find the coordinates of the two note heads a tie or slur is
> attached to?
>
> I need to write a new stencil for these curves and want to hook that not
> to the staff origin but to the actual note heads.
>
> There is some code in
> https://github.com/openlilylib/snippets/blob/master/notation-snippets/shaping-bezier-curves/shapeII.ily
> that does this (esp. in get-extremal-head and in notehead-placement),
> but somehow I have the impression that code is more complicated than
> necessary. Apart from that IIRC this is exactly the part of \shapeII
> that seems to be problematic with current LilyPond.
>
> So, before I start to actually try understanding that code I'd like to
> ask for some pointers how I could better approach the question.
>
Try:
\version "2.19.53"
#(define (get-noteheads grob)
(if (grob::has-interface grob 'note-column-interface)
(ly:grob-array->list (ly:grob-object grob 'note-heads))
(list grob)))
#(define (my-notehead-positions grob)
(let* ((sys (ly:grob-system grob))
(lb (ly:spanner-bound grob LEFT))
(rb (ly:spanner-bound grob RIGHT))
(lb-noteheads (get-noteheads lb))
(rb-noteheads (get-noteheads rb)))
(format #t "~a ~{~a ~}~%"
grob
(map (lambda (nh)
(format #f "(~a, ~a)"
(ly:grob-relative-coordinate nh sys X)
(ly:grob-relative-coordinate nh sys Y)))
(append lb-noteheads rb-noteheads)))))
{
\override Slur.after-line-breaking = #my-notehead-positions
\override Tie.after-line-breaking = #my-notehead-positions
c~ c c( e)
}
%%%%%%%%%%%%%%%%%
The problem with the code above is that querying the Y-coordinate will
mess with vertical spacing. This is clear with more than one staff:
\new PianoStaff <<
\new Staff {
\override Slur.after-line-breaking = #my-notehead-positions
\override Tie.after-line-breaking = #my-notehead-positions
c~ c c( e)
}
\new Staff {
R1
}
>>
%%%%%%%%%%%%%%%%
This, presumably is the problem with \shapeII.
You can get the Y position by 'staff-position of the notes and
calculate the Y from the staff-space, staff-width, etc.
HTH,
David
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