Le vendredi 03 mars 2023 à 08:29 +0100, József Pap a écrit : > Hi all, > Is there a way to print different noteheads to the left and right side of the > stem? I have a custom notehead stencil function already, but I can't seem to > obtain the necessary information (i.e. whether the notehead will go on > left/right side of the stem) from the stencil's scope. I can access the stem > grob and read its direction, but it isn't sufficient, since crowded chords > have noteheads on both sides.
Here is an example:
```
\version "2.24.1"
{
\override NoteHead.stencil =
#(lambda (grob)
(let ((stem (ly:grob-object grob 'stem)))
(ly:grob-property stem 'positioning-done))
(let* ((note-column (ly:grob-parent grob X))
(coord (ly:grob-relative-coordinate grob note-column X))
(is-suspended (< 0.01 (abs coord))))
(grob-interpret-markup
grob
(if is-suspended
#{ \markup "s" #} ; suspended
#{ \markup "n" #} ; normal
))))
\override NoteHead.X-extent = #'(0 . 1.3)
<c' d' e' f' g' a'>
<a' b' c'' d'' e'' f''>
}
```
First, you should trigger the stem's `positioning-done` callback, which is what
shares out the note heads between the two sides of the stem. Then, you can read
the note head's coordinate relative to its note column.
Note that's it's essential to set `X-extent` yourself. Here's I've set it to a
constant, but you could set it to a callback, as long as it does not read the
`stencil` property. Currently, determining which note heads are on the left or
on the right of a chord is not separate from actually placing them (it relates
to [issue #6103](https://gitlab.com/lilypond/lilypond/-/issues/6103)), and
while placing them, LilyPond needs their extents, so you would create a cyclic
dependency if you read `stencil` in `X-extent`.
HTH,
Jean
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