RFC: book parts

[Nicolas Sceaux]

Hi,

When typesetting a book with many scores and with possibly some text
sections, page breaking may become an inextricable issue:

  1) the default, "optimal", page breaker, which gives the best result
wrt line and page breaking when there is no or little text, cannot be
used when the book is very large (say, for an opera conductor score);

  2) the "minimal" page breaker that was added as a workaround, gives
better results for large portions of text, but is not satisfying when it
comes to score pieces. However it is currently the only option for large
books.

Thus, a solution could be to define several parts in a book, where
different page breakers can be used. For instance:

  \paper {
    %% default paper settings, for the whole book
    #(define page-breaking ly:optimal-breaking)
    ...
  }

  \bookpart {
    %% page title, preface, table of contents, etc.
    \paper {
      #(define page-breaking ly:minimal-breaking)
    }
    ...
  }
  \bookpart {
    %% the first act
    ...
  }
  etc

(implicit bookparts would be added around explicit ones when text or
music is found.)

By reducing the page breaking problem to smaller parts, the optimal page
breaker should work (it does not finish when there is too much music).
And the textual parts can be handled by the minimal page breaker.

There may be some extra bonuses with this solution, for instance, easily
defining different page headers for each part. Or changing font size,
margins, landscape/portrait orientation.

What do you think? Are there objections against something like that?

nicolas