[luatex] Interfere with page breaking to balance pages

[Paul Isambert]

Hello Patrick,

Patrick Bergner <mail at patrickbergner.de> a écrit:
> I'm currently working on a project to automate typical manual
> typesetting tasks using LuaTeX. One of these is balancing pages, i.e.,
> making the left and right side of a typical double page in a book equal
> in length.
> 
> Manually this is usually achieved by using a negative value for
> \enlargethispage on the left side of a double page.
> 
> Now I'm trying to replicate this approach with Lua. What I (generally)
> need is the following:
> - Get a callback once TeX has all the material to output a page (or
> double page).
> - Be able to work with the to be placed page content, i.e., getting its
> contents/dimensions _and_ be able to move things around between pages.

[a lot snipped]

Instead of callbacks, I'd recommend kicking in at shipout time with
whatever can do that in LaTeX (e.g. everyshi, I think), and add some
\directlua code manipulating the content of "tex.box.outputbox". Of
course you also need to cancel shipout every other page, since you can't
write a left page to the PDF before it has been compared to the right
one. Unfortunately, I don't know how to do that in LaTeX. I wrote a
paper on the subject, but I'm not sure it will help since it deals
neither with LaTeX nor LuaTeX (I didn't use the former anymore, and I
didn't use the latter yet, when the paper was written), but perhaps
you'll find some ideas: http://tug.org/TUGboat/tb31-1/tb97isambert.pdf

Best,
Paul