Re: DurationLine avoiding RehearsalMarks

[Thomas Morley]

Am Mo., 11. Apr. 2022 um 12:40 Uhr schrieb Jean Abou Samra <jean@abou-samra.fr>:
>
> Le 11/04/2022 à 10:30, Thomas Morley a écrit :
> > Hi Mark,
> > DurationLine is designed not to be printed if breakable items at
> > line-end/start are present, like Clef, KeySignature etc.
> > I wasn't aware RehearsalMark is ofcourse one of them.
> > Currently I'm preparing a patch to disregard RehearsalMark.
> > Is your use-case urgent?
>
>
> Well, the same problem exists for breakable items in another staff
> than the one where the DurationLine is being printed.
>
>
> \version "2.23.7"
>
> \layout {
>    \context {
>      \Voice
>      \consists Duration_line_engraver
>    }
> }
>
> <<
>    \new Staff { c'1\- \break s1 c'1 }
>    \new Staff { s1 \key cis \major s1 s1 }
>  >>

Well, your example prints as I would wish it should.
Alas, there are obviously different opinions. Look at:

\layout {
   \context {
     \Voice
     \consists Duration_line_engraver
   }
}

<<
   \new Staff {
         \override Glissando.breakable = ##t
         c'1(\-\startTextSpan\glissando \break s1 c''1)\stopTextSpan
   }
   \new Staff { s1 \key cis \major s1 s1 }
>>

Not all spanners start/end equal.
Imho, it's a mess which needs design decisions.


> How about adding a Scheme interface for Axis_group_interface::staff_extent
> from lily/axis-group-interface.cc and using it in duration-line::print?

Please remember I don't know C++, thus I don't fully understand what's
done in lily/axis-group-interface.cc, same for the porting to scheme.
Maybe some comments would help.

Obviously grob::has-in-ancestry? is a predicate. It becomes #t if
`potential-ancestor' (the StaffSymbol we're in?) is found.
(Btw, in the recursion "?" is missing)

> It essentially does the same as (untested code):
>
> #(define (grob::has-in-ancestry? grob potential-ancestor axis)
>     (or (eq? grob potential-ancestor)
>         (let ((parent (ly:grob-parent grob axis)))
>           (and (not (null? parent))
>                (grob::has-in-ancestry parent potential-ancestor axis)))))

Though, what's below? I've difficulties with the arguments.
`axis-group' is likely the VerticalAxesGroup: (ly:grob-object grob
'axis-group-parent-Y) ?
`refpoint' is (ly:grob-system grob) ?
`staff' is  (ly:grob-object grob 'staff-symbol) ?
What are `ext-axis' and `parent-axis' meant for?

> #(define (axis-group-interface::staff-extent axis-group refpoint
> ext-axis staff parent-axis)
>     (ly:relative-group-extent
>      (filter
>       (lambda (elt)
>         (grob::has-in-ancestry? elt staff parent-axis))
>       (ly:grob-array->list (ly:grob-object axis-group 'elements)))
>      refpoint
>      ext-axis))

For now I was not able `axis-group-interface::staff-extent' reasonably.

Thanks,
  Harm