Using data from tabulary to typeset columns

Question

While trying to write a better answer to this question, I've made several (probably quite bad) attempts to use the tabulary environment to typeset paragraphs to try to in some way be able to split a paragraph over several pages. As my last attempt incorporating trying to make a parallel environment look like a tabular environment and adjusting this solution gave me a lot of error messages, I've started to think on giving up on this idea..

It seems like the tabulary package typesets the table "twice". Is it possible to use a tabular environment for the first of these typesettings, and then outputting only the calculated column widths, without actually "drawing" the table?

Answer 1

Out of time to implement page breaking but this answers the request for a basic measurement scheme that does a tabulary style (well slightly similar:-) determination of the column widths without setting the table.

The macro measures each of the two arguments and then calculates column width so they have similar height when set. At that point (where the comment is in the code) you can do what you like, for tonight it just sets them in a \vtop (\parbox[t]) of the specified width, so page breaking would not be allowed within the paragraph.

The \ifdim tests prevent either column being set to less than 20% of the textwidth which is an arbitrary amount that could be changed but you need to avoid badly unbalanced input setting silly lengths like 1pt so some cut off is advisable (cf \tymin in tabulary)

Incidentally if you know that the content is all text so the baselines are naturally evenly spaced and matched in each column, it would be much easer to do page breaking rather than if the content can include boxes or as here display math that mean the potential break points in one column do not automatically line up with the break points in the other column.

\documentclass{article}
\usepackage{graphics}
\makeatletter


\long\def\twopara#1#2{%
\@tempdima\dimexpr\textwidth-\columnsep\relax
{\hbadness\@M\raggedright\hsize.5\@tempdima \@tempdima\hsize
\setbox\z@\vbox{{#1\endgraf}}%
\setbox\tw@\vbox{{#2\endgraf}}%
\Gscale@div\tmp{\ht\z@}{\dimexpr\ht\z@+\ht\tw@\relax}%
\global\let\xtmp\tmp}%
\dimen@ \xtmp\@tempdima
\ifdim\dimen@<.2\@tempdima \dimen@.2\@tempdima\fi
\ifdim\dimen@>.8\@tempdima \dimen@.8\@tempdima\fi
\dimen@ii\dimexpr\@tempdima-\dimen@\relax 
% do anything you want with
% #1 \dimen@ wide
% #2 \dimen@ii ide
% \columnsep in between
\hbox{%
\vtop{{\hsize\dimen@ \textwidth\hsize #1\endgraf}}%
\hspace\columnsep
\vtop{{\hsize\dimen@ii \textwidth\hsize #2\endgraf}}%
}}



\makeatletter

\begin{document}

\noindent X\dotfill X

\twopara{
a a a a a a a a a a a a a a a a a a a a a a a a a a 
a a a a a a a a a a a a a a a a a a a a a a a a a a
a a a a a a a a a a a a a a a a a a a a a a a a a a
a a a a a a a a a a a a a a a a a a a a a a a a a a
}
{
b b b b b b b b b b b b b b b b b b b b b b b b b b 
b b b b b b b b b b b b b b b b b b b b b b b b b b 
}

\bigskip

\twopara{
a a a a a a a a a a a a a a a a a a a a a a a a a a 
a a a a a a a a a a a a a a a a a a a a a a a a a a
}
{
b b b b b b b b b b b b b b b b b b b b b b b b b b 
b b b b b b b b b b b b b b b b b b b b b b b b b b 
\[a=b\]
b b b b b b b b b b b b b b b b b b b b b b b b b b 
b b b b b b b b b b b b b b b b b b b b b b b b b b 
b b b b b b b b b b b b b b b b b b b b b b b b b b 

}



\end{document}