% twoblocks.sty %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% defines the command \twoblocks {#1}{#2}
% to position two text blocks side by side
% separated by \colsep horizontal space
% 17.11.1993
% 06.06.1994 % do not read the arguments prematurely: catcodes !
% no warranty whatever
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% (c) Klaus Lagally
%     Institut fuer Informatik
%     Universitaet Stuttgart
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\ifx \twblatcode \undefined \else \expandafter \endinput 
\fi % load only once

\chardef \twblatcode = \catcode`\@  \catcode`\@ = 11

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\newbox \boxa	\newbox \boxb	\newbox \boxc	\newbox \boxd		
\newdimen \htmin	\newdimen \hta		\newdimen \htb
\newdimen \pagerest   	\newdimen \splitheight	\newdimen \totalheight	
\newdimen \colwidth	\newdimen \colsep

\colsep 0.4in % adjust to your preference

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\def \unpackbox #1{% unwrap minipage to get a \vbox only
  \setbox0 \vbox {\unvbox #1\global \setbox1 \lastbox }	% get line
  \setbox0 \hbox {\unhbox1 \unskip \unskip \unpenalty 	% get inner box
  \global \setbox #1 \lastbox }}	% and forget the rest

\def \a@minipagerestore {% modify tabbing and list spacing
  \vskip 0pt plus 12pt \emergencystretch 3cm \hbadness 5000 }

\def \depositboxes {% fill page, recursive
   \nointerlineskip \null \allowbreak	% update page builder parameters
   \pagerest \pagegoal \advance \pagerest -\pagetotal
   \advance \pagerest -\maxdepth
   \advance \pagerest -\baselineskip 	% just to make sure
   \getheights 			% max total height of \boxa and \boxb
\ifdim \totalheight > \pagerest % no more space, split?
   \splitheight \totalheight
   \advance \splitheight -2\baselineskip 	% try to avoid widows
   \ifdim \splitheight > \pagerest \splitheight \pagerest 
   \fi
   \htmin 2\baselineskip 
   \ifdim \splitheight > \htmin 	% try to avoid clubs
	\splitboxes \splitheight	% to \boxc and \boxd, and output
   \else \vfill \eject			% new page
   \fi
   \depositboxes 	% try again
\else \combineboxes 	% output \boxa and \boxb
\fi }

\def \adjustbox #1{% set depth to total height, height zero, full width
  \ifvoid#1 \setbox#1 \null \fi \wd#1 \colwidth
  \dimen0 \ht#1 \advance \dimen0 \dp#1 \ht#1 \z@ \dp#1 \dimen0 }

\def \getheights {% \ht plus \dp of boxes \boxa and \boxb
  \hta \ht \boxa \advance \hta \dp \boxa
  \htb \ht \boxb \advance \htb \dp \boxb
  \ifdim \htb > \hta \totalheight \htb \else \totalheight \hta \fi }

\def \splitboxes #1{% split off #1 from \boxa and \boxb
  \splitmaxdepth \z@ \splittopskip \topskip
  \ifdim #1 > \hta \setbox \boxc \box \boxa
    \else \setbox \boxc \vsplit \boxa to #1 \fi
  \ifdim #1 > \htb \setbox \boxd \box \boxb
    \else \setbox \boxd \vsplit \boxb to #1 \fi
  \outputboxes \boxc \boxd \vfill \eject }

\def \outputboxes #1#2{% hanging from top of \hbox
  \adjustbox #1 \adjustbox #2		% height zero, all depth
  \nointerlineskip
  \hbox to \textwidth {\noindent \box #1\hfill \box #2}\allowbreak }

\def \combineboxes {% output \boxa and \boxb
  \outputboxes \boxa \boxb }

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\def \twoblocks {% two aligned paragraphs
  \bgroup \colwidth \textwidth \advance \colwidth -\colsep 
  \divide \colwidth 2 \let \@minipagerestore \a@minipagerestore
  \setbox \boxa \vbox \bgroup \minipage[t]\colwidth 
  \bgroup \aftergroup \tw@blocks \ignorespaces \let \next }

\def \tw@blocks {% after first block
  \endminipage \egroup \unpackbox \boxa	% unwrap minipage
  \setbox \boxb \vbox \bgroup \minipage[t]\colwidth 
  \bgroup \aftergroup \tw@bl@cks \ignorespaces \let \next }

\def \tw@bl@cks {% after second block
  \endminipage \egroup \unpackbox \boxb	% unwrap minipage
  \depositboxes	\egroup }		% split if necessary

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\catcode `\@ = \twblatcode

\endinput
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
