Would there be a way to conditionally include a \pageBreak at top level?
E.g.
\if #(some-predicate) { \pageBreak }
On Fri, May 5, 2023 at 7:58 AM Valentin Petzel <valen...@petzel.at> wrote:
> Hello Eric,
>
> that is understandable. For some context:
>
> when you put \pageBreak at toplevel (or bookpart level) it is first just a
> music stream made up of a single event. Now, when Lilypond encounters
> toplevel
> music objects it usually defaults to truning it into a score, using the
> scheme
> procedure (scorify-music music). But there is some additional logic, which
> is
> done by the scheme procedure (collect-music-aux score-handler music)
> (where
> score-handler is a function that handles the created score). This
> procedure
> has a special path for single event music of type page-marker (which
> something
> like \pageBreak falls under as can be seen in \displayMusic \pageBreak).
>
> Basically instead of a score it creates a Page_marker object, which you
> can
> see if you do
>
> { c }
> \pageBreak
> { c }
> #(display toplevel-scores)
>
> Now, of course in markup this does not work, as first a markup will not
> take
> music, and very importantly markup will not include any page layout events
> of
> any sort. It would be possible to do something like
>
> (collect-music-aux add-score #{ \pageBreak #})
>
> in a markup, scheme or void function, but this would cause some trouble in
> when exactly this is evaluated. Usually we’d expect something like this to
> to
> be placed positionally where the markup is. Let’s say we use a scheme
> function:
>
> pagebreak =
> #(define-void-function () ()
> (collect-music-aux add-score #{ \pageBreak #}))
>
> This is evaluated at the time the expression is parsed (more or less). So
> doing
>
> \markup "a"
> \markup "b"
> \markup{ \pagebreak }
> \markup "c"
>
> will behave as intended, but
>
> \markup "a"
> test = \markup { \pagebreak }
> \markup "b"
> \test
> \markup "c"
>
> will not. If we use a markup function like this
>
> #(define-markup-command (pagebreak layout props) ()
> (collect-music-aux add-score #{ \pageBreak #})
> empty-stencil)
>
> the command is only evaluated when interpreting that markup, at which
> point
> all scores have been added (so we do not get any effect):
>
> \markup "a"
> \markup "b"
> \markup { \pagebreak }
> \markup "c"
>
> So you see there is currently no real way of any kind for getting page
> layout
> commands into a markup. Of course this can be limiting if you want to do
> complex formatting of markups and markuplists, but Lilypond is a music
> engraving software, not a typesetting or text layouting software.
> Lilypond’s
> handling of text is quite primitive, as this is not the main focus of
> development.
>
> Cheers,
> Valentin
>
> Am Freitag, 5. Mai 2023, 01:34:56 CEST schrieb Eric Benson:
> > Well then, sorry for bothering you all! I don't know how I confused
> myself
> > so badly, but I'm just glad to be out of that hole! I think I tried to
> put
> > the \pageBreak inside the \markup, which definitely does not work.
> >
> > On Thu, May 4, 2023 at 4:24 PM Kieren MacMillan
> > <kie...@kierenmacmillan.info>
> > wrote:
> > > Hi Eric,
> > >
> > > > Oh! I think this is new behavior.
> > >
> > > I don’t think so…?
> > > I’ve been using this for many years. :)
> > >
> > > Cheers,
> > > Kieren.
> > > ______________________________________________
> > >
> > > My work day may look different than your work day. Please do not feel
> > > obligated to read or respond to this email outside of your normal
> working
> > > hours.
>
>
