% Patch LaTeX's output routine to handle marks correctly with two columns.
% Version 1.0
% Joe Pallas <[email protected]>

% Version 1.1
% Corrected by Piet van Oostrum <[email protected]> on Feb 5, 1993
% Originally this file was called "fixhead.sty" which doesn't make sense.
% The original version of this file used a comparison between \firstmark
% and \topmark to check if a mark was given in the first column. However
% this fails in the case that a mark is given that is identical to the one
% on the previous page. Although this can be considered a pathological case
% I didn't want it. The use of the \vsplit should solve this. The only case
% that it doesn't solve is if the user inserts empty marks, but LaTeX marks
% are always of the form {}{}.
% Note: the \topmarks are generally useless in LaTeX because they are
% destroyed by the float mechanism.
% The above comment added Oct 3, 1994.

% Version 1.2
% Oct 5, 1994: replaced \expandafter's by \xdef, which does the same but
% looks less complicated.

% Version 1.3
% Oct 6, 1994: replaced "\global\setbox\@leftcolumn\vsplit\@outputbox
% to\ht\@outputbox" by the two \setbox's below. This ensures that no
% anomalies may occur in pathological cases. These can occur if there are
% large negative glues near the end of the box.
% Oct 6, 1994: save and restore \split*mark just in case someone was going
% to use it and got interrupted by us. The code doesn't make a difference
% between no marks and empty marks, but that difference isn't visible at
% the user level. The strange way to do this is necessary as the marks
% don't obey grouping rules. (Actually also \clearpage processing destroys
% these marks, so the saving/restoring may be of limited value)

% Version 1.4
% Oct 7, 1994: saving of the \split*marks now done by putting them directly
% in a box. Added \vbadness=10000 to get rid of underfull vbox warning.
% Note: we rely on the grouping mechanism to reset various things, as this
% is about the last thing to happen in the output routine.

% Version 1.5
% Oct 11, 1994: suppressed unwanted expansion of the marks. This includes
% undoing the change mentioned in version 1.2.

\def\@outputdblcol{\if@firstcolumn \global\@firstcolumnfalse
% save the left column
    \global\setbox\@leftcolumn\copy\@outputbox
% save the \split*marks
    \setbox\@tempboxa\vbox{
      \toks@\expandafter{\splitfirstmark}
      \mark{\the\toks@}
      \toks@\expandafter{\splitbotmark} % we don't use \splitbotmark but
      \mark{\the\toks@}}                % it gets clobbered by the \vsplit below
% Remember the marks from the first column
    \splitmaxdepth=\maxdimen \vbadness=10000
    \setbox\@outputbox\vsplit\@outputbox to\maxdimen
    \expandafter\gdef\expandafter\@firstcoltopmark\expandafter{\topmark}%
    \expandafter\gdef\expandafter\@firstcolfirstmark
                                \expandafter{\splitfirstmark}%
    \ifx\@firstcolfirstmark\empty\global\let\@setmarks\relax\else
      \gdef\@setmarks{\let\firstmark\@firstcolfirstmark
        \let\topmark\@firstcoltopmark}%
    \fi
% Restore the \split*marks
    \setbox\@tempboxa\vsplit\@tempboxa to 0pt % this resets the \split*marks
% End of change
  \else \global\@firstcolumntrue
    \setbox\@outputbox\vbox{\hbox to\textwidth{\hbox to\columnwidth
      {\box\@leftcolumn \hss}\hfil \vrule width\columnseprule\hfil
       \hbox to\columnwidth{\box\@outputbox \hss}}}\@combinedblfloats
% Override current first and top with those of first column if necessary
       \@setmarks
% End of change
       \@outputpage \begingroup \@dblfloatplacement \@startdblcolumn
       \@whilesw\if@fcolmade \fi{\@outputpage\@startdblcolumn}\endgroup
    \fi}