Re: DurationLine avoiding RehearsalMarks

[Jean Abou Samra]

Le 12/04/2022 à 11:16, Thomas Morley a écrit :
> Hi Jean,
>
> thanks for all your work and explanations.
> I'll split my answer into different mails.
> This one is about the design
>
> Am Mo., 11. Apr. 2022 um 18:04 Uhr schrieb Jean Abou Samra <jean@abou-samra.fr>:
> > Le 11/04/2022 à 17:20, Thomas Morley a écrit :
> > > 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.
> >
> >
> > Hm. That's right. Let's consider another example:
> >
> > \version "2.23.8"
> >
> > \layout {
> >     \context {
> >       \Voice
> >       \consists Duration_line_engraver
> >     }
> > }
> >
> > \paper {
> >     ragged-right = ##t
> > }
> >
> > <<
> >     \new Staff { c'1\- \break c'1 }
> >     \new Staff { c'1 \breathe c'1 }
> >   >>
> >
> >
> > Well, maybe it doesn't make sense anyway -- I don't think I've
> > ever seen a breathing sign in one staff and not another.
> >
> > Though, if this is something we want to support, I think we'll
> > agree that the duration line in the upper staff should not be
> > affected by the breathing sign, as the breathing sign doesn't
> > apply to that staff.
> I slightly disagree.
>
> In many details DurationLine was tailored after Glissando and
> Glissando _is_ effected by the breathing sign. See:
>
> \layout {
>     \context {
>       \Voice
>       \consists Duration_line_engraver
>     }
> }
>
> \paper {
>     ragged-right = ##t
> }
>
> <<
>     \new Staff {
>            \override Glissando.breakable = ##t
>            \override Glissando.after-line-breaking = ##t
>            \override DurationLine.after-line-breaking = ##t
>            \override Score.RehearsalMark.break-visibility = ##(#t #t #t)
>            c'1\-\glissando
>            %\mark \default
>            \break c''1
>     }
>     \new Staff {
>            c'1
>            \breathe
>            c'1
>     }
>   >>
>
> Thus any design decision should affect both, DurationLine and Glissando, imho.
>
>
> > Making the DurationLine affected only by breakable items in
> > its staff is easy to define (implementation: see below). If
> > we decide that we want different behaviors for different breakable
> > items, like KeySignature vs. BreathingSign, a definition is
> > going to be trickier ...
> If you uncomment \mark above then DurationLine is affected and Glissando not.
> That's the bug at hand, imho.
> I have a fix for it in a local branch, explicitely removing
> RehearsalMark from items to consider.
> Isn't it sufficient here?
>
> If you agree I'll do some polish and probably add a regtest and open a MR.



Well, if the goal is to have DurationLine similar to Glissando,
how about reusing line-spanner-interface code? I haven't reviewed
the code very thoroughly, but I assumed there was a difference
warranting a different code path. If you put
ly:line-spanner::calc-{left,right}-bound-info in
DurationLine.{left,righ}-bound-info, that gives you X values for free
in the bound info properties. Would that solve the problem?

One difference I can foresee is that line-spanner-interface callbacks
fall back to bound-details.left if there is no value in left-broken
(and same at the right) whereas DurationLine does not do this. But
maybe that ought to be uniformized regardless?

If there is a reason to keep DurationLine calculations separate, you
could go for using ly:generic-bound-extent. The line-spanner-interface
uses its C++ equivalent internally.

Best,
Jean