Top level page (no)breaking directives

[Nicolas Sceaux]

Hi,

When dealing with books containing many scores, one may prefer to keep
the score titling and page breaking in the book main file, instead of in
individual score files. Indeed, such directives (between-score page
breaking, titling), are of book scope rather than score scope (alternate
versions of a book using the same scores may have different titling, or
page breaking directives).

In other words, I'd like to write:

  ------- book.ly -------
  \markup \scoreTitle { Score A }
  \toplevelNoPageBreak
  \include "score-A.ly"

  \toplevelPageBreak
  \markup \scoreTitle { Score B }
  \toplevelNoPageBreak
  \include "score-B.ly"
  ------- book.ly -------

with score-A.ly and score-B.ly containing no \header block.

I've been thinking a bit about how to do this, but would like to know if
gurus here have some advice.

The top level page breaking directives may be void music expressions,
with some special music properties set, and caught by
collect-music-for-book. Then:

 - collect-music-for-books adds a new kind of object to toplevel-scores
 (a page breaking marker), which will be used by the page breaker to
 force or forbid a page break.

or:
 - some layout property of the following score is set by
 collect-scores-for-books, which will used by the page breaker (as it
 uses the break-before \header property). Problem: toplevel markups
 don't have this kind of properties.

What do you think?

nicolas