Am So., 7. Nov. 2021 um 14:00 Uhr schrieb Jean Abou Samra <j...@abou-samra.fr>:
> >>> That said,...
> >>> If I always compensate the right ending-point with (pseudo-code)
> >>> (ly:grob-relative-coordinate <Glissando-grob> <System-grob> Y)
> >>> Then the crosses are at those positions Mike's patch promises.
> >> Really System? Isn't this going to create a
> >> cyclic dependency between the stencil and
> >> vertical alignment for non-cross-staff glissandi
> >> via VerticalAxisGroup skylines? Off the top I would
> >> think it should be a matter of correcting
> >> reference points (see above).
> > I compile with recent master, so your added warnings for cyclic
> > dependencies may pop up.
> > They don't.
>
>
> Ah, because vertical alignment works via
> ly:grob-translate-axis! and doesn't mark the
> dependencies. Sigh.
>
> Look at:
>
> <<
> \new Staff {
> c'1
> }
> \new Staff {
> \override Glissando.stencil =
> #(lambda (grob)
> (ly:message "~s"
> (ly:grob-relative-coordinate
> grob
> (ly:grob-system grob)
> Y))
> (ly:line-spanner::print grob))
> c'1\glissando c''1
> }
> >>
>
> It prints "0.0". So there's no cyclic dependency
> warned about, but it's not doing what you intend.
> How could it? The glissando is part of the vertical
> skylines of the VerticalAxisGroup. These are the
> basis for vertical alignment. So you need the glissando's
> stencil before you can take the Y coordinate of the
> glissando relative to the system. Unless you have
> a cross-staff glissando, because these aren't part
> of the skylines -- but even then there is usually no
> reason to take the root system and not just a refpoint
> computed generically for both non-cross-staff
> and cross-staff grobs.
For non-cross-staff Glissando it returns always zero, yes, for
cross-staff a certain value is found:
<<
\new Staff = "top" {
c'1
}
\new Staff {
\override Glissando.stencil =
#(lambda (grob)
(ly:message "~s"
(ly:grob-relative-coordinate
grob
(ly:grob-system grob)
Y))
(ly:line-spanner::print grob))
c'1\glissando \change Staff = "top" c''1
}
>>
-> -12.779
I tend to think: nice, let us always add this value, in any case it
only matters for cross-staff at all.
Why not?
Cheers,
Harm
