Revision 2baaae799ffe3be2c7ddafb788831372122243be authored by Joseph Wright on 01 February 2020, 08:09:36 UTC, committed by Joseph Wright on 01 February 2020, 08:09:36 UTC
1 parent fdcaec9
multicol.dtx
% \iffalse meta-comment
%
%
% This file is part of the Standard LaTeX `Tools Bundle'.
% -------------------------------------------------------
%
% It may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in
% https://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions of LaTeX
% version 2005/12/01 or later.
%
% The list of all files belonging to the LaTeX `Tools Bundle' is
% given in the file `manifest.txt'.
%
% \fi
%
% \iffalse This is a METACOMMENT
%
%% Package `multicol' to use with LaTeX2e
%% Copyright 1989-2019 Frank Mittelbach
%%
%% In addition to the terms of LPPL any distributed version
%% (unchanged or modified) of multicol has to keep the statement
%% about the moral obligation for using multicol. In case of major
%% changes where this would not be appropriate the author of the
%% changed version should contact the copyright holder.
%%
%%
%% Moral obligation for using multicol:
%% ------------------------------------
%%
%% Users of multicol who wish to include or use multicol or a modified
%% version in a proprietary and commercially market product are asked
%% under certain conditions (see below) for the payment of a license
%% fee. The size of this fee is to be determined, in each instance,
%% by the commercial user, depending on his/her judgment of the value of
%% multicol for his/her product.
%%
%%
%% The conditions for this are as follows:
%%
%% The producer of a proprietary and commercially market product
%% that involves typesetting using multicol is asked to determine
%% the value of a license fee for using multicol if
%%
%% - the product is a document and the producer has decided to
%% include multicol to typeset (parts of) the document or has
%% directed the author of the document to include multicol (for
%% example, by providing a class file to be used by the author)
%%
%% - the product is a LaTeX class or package that includes multicol
%%
%%
%% There is no moral obligation in case
%%
%% - the product is a document but producer has not directed
%% the author to include multicol (in that case the moral obligation
%% lies with the author of the document)
%%
%% - the product does not involve typesetting, e.g., consists, for
%% example, of distributing multicol and its documentation.
%%
%% - the product is not proprietary, i.e., is made available as free
%% software itself (which doesn't prohibit its commercial marketing)
%%
%% - multicol is used for non-commercial purposes
%%
%%
%% Determining a license fee might result in a license fee of zero
%% (i.e., no payment) in case a producer has determined that the use
%% of multicol has no enhancing effect on the product. This is a
%% plausible scenario, i.e., in the above two cases the producer is
%% only asked to evaluate the value of multicol for the product
%% not for the payment of a license fee per se (which might or might
%% not follow from this evaluation).
%%
%% The license fee, if any, can be payed either to the LaTeX3 fund
%% (see ltx3info.txt in the base LaTeX distribution) or to the author of
%% the program who can be contacted at
%%
%% Frank.Mittelbach@latex-project.org
%%
%<*dtx>
\ProvidesFile{multicol.dtx}
%</dtx>
%<package>\NeedsTeXFormat{LaTeX2e}[2018-04-01]
%<package>
%<package>\providecommand\DeclareRelease[3]{}
%<package>\providecommand\DeclareCurrentRelease[2]{}
%<package>
%<package>\DeclareRelease{}{2017-04-11}{multicol-2017-04-11.sty}
%<package>\DeclareCurrentRelease{}{2018-04-01}
%<package>
%<package>\ProvidesPackage{multicol}
%<driver> \ProvidesFile{multicol.drv}
% \fi
% \ProvidesFile{multicol.dtx}
[2019/12/09 v1.8y multicolumn formatting (FMi)]
%
%
%%
%
% \changes{v1.5n}{1997/06/05}{Applied improvement of documentation,
% kindly done by Robin Fairbairns.}
% \changes{v1.4h}{1992/06/04}{Added mark tracing with
% tracingmulticols$\ge2$}
% \changes{v1.4a}{1992/02/11}{Added support for multicol in inner mode}
% \changes{v1.0d}{1989/05/17}{All lines shortened to 72 or less.}
% \changes{v1.0e}{1989/06/21}{Redefinition of description env. to use
% \cs{descriptionmargin}\quotechar=5pt
% in documentation.}
% \changes{v1.0f}{1989/07/11}{Changed \cs{z@} to 0pt in redefinition of
% description.}
% \changes{v1.1a}{1989/09/20}{\cs{multicolssep} changed to \cs{multicolsep}.}
%
% \def\description{\list{}{\labelwidth 0pt \leftmargin\descriptionmargin
% \itemindent-\leftmargin \let\makelabel\descriptionlabel}}
% \newdimen\descriptionmargin \descriptionmargin=5pt
%
% \DoNotIndex{\@M,\@Mi,\@bsphack,\@cclv,\@colht,\@currlist,\@deferlist}
% \DoNotIndex{\@elt,\@esphack,\@floatplacement}
% \DoNotIndex{\@ifundefined,\@ifnextchar,\@makecol}
% \DoNotIndex{\@ne,\@outputpage,\@scolelt,\@spaces,\@tempb,\@tempcnta}
% \DoNotIndex{\@width}
% \DoNotIndex{\addvspace,\advance,\allowbreak}
% \DoNotIndex{\baselineskip,\begingroup,\box,\columnsep,\copy,\count}
% \DoNotIndex{\count@,\def,\dimen@,\divide,\docdate}
% \DoNotIndex{\edef,\eject,\egroup,\else,\endgroup,\endinput}
% \DoNotIndex{\fi,\fileversion,\filedate}
% \DoNotIndex{\gdef,\global}
% \DoNotIndex{\hbox,\hfil,\hrule,\ht,\hss}
% \DoNotIndex{\ifdim,\ifnum,\ifvoid,\ignorespaces,\insert,\immediate}
% \DoNotIndex{\let,\loop}
% \DoNotIndex{\@maxdepth,\message,\multiply}
% \DoNotIndex{\newbox,\newcount,\newdimen,\newskip,\number,\newpage}
% \DoNotIndex{\outputpenalty,\p@,\penalty}
% \DoNotIndex{\relax,\repeat,\setbox,\skip,\space,\splitmaxdepth}
% \DoNotIndex{\splittopskip,\string,\sixt@@n}
% \DoNotIndex{\the,\thepage,\thr@@,\topskip,\tw@,\typeout}
% \DoNotIndex{\unvbox,\vbox,\vfill,\vsplit,\voidb@x,\vrule}
% \DoNotIndex{\write,\wd}
% \DoNotIndex{\z@}
%
% \MakeShortVerb{\|}
% \newcommand{\mc}{\textsf{multicols}}
% \newcommand{\TUB}{{\sl TUGboat\/}}
% \newcommand{\TB}{{\sl\TeX book\/}}
%
%
% \setcounter{StandardModuleDepth}{2}
% \setcounter{collectmore}{3}
%
% \GetFileInfo{multicol.dtx}
% \title{An environment for multicolumn output\thanks{This file
% has version number \fileversion, last
% revised \filedate.}%
% \thanks{Note: This package is released under terms which affect
% its use in commercial applications. Please see the details at
% the top of the source file.}}
% \author{Frank Mittelbach\\
% {\rm Email:} see top of the source file}
% \date{Printed \today}
%
% \MaintainedByLaTeXTeam{tools}
% \maketitle
%
% \begin{abstract}
% This article describes the use and the implementation of the \mc{}
% environment. This environment allows switching between
% one and multicolumn format on the same page. Footnotes are handled
% correctly (for the most part), but will be placed at the bottom of
% the page and not under each column. \LaTeX{}'s float mechanism,
% however, is partly disabled in this implementation. At the
% moment only page-wide floats (i.e., star-forms) can be used within
% the scope of the environment.
% \end{abstract}
%
% \begin{multicols}{3}[\section*{Preface to version 1.8}]
% The 1.8 release improves on the balancing approach. If due to a
% limited number of break points (e.g., due to large objects) the
% balanced columns exceed the available vertical space, then
% balancing is canceled and a normal page is produced first. Some
% overflow is allowed (controlled by the parameter
% |\maxbalancingoverflow| which defaults to 12pt). This ensures
% that we only cut a normal page if we get enough material carried
% over to next page.
%
% Also added was support for |\enlargethispage|. This means it is
% now possible to request a page to be artificially enlarged or
% shortened. Note that if you enlarge pages by more than one line
% you may have to increase the \textsf{collectmore} counter value to
% ensure that enough material is being picked up.
%
% This command was used on the second page of this manual to shorten
% it by one line, in order to get rid of a number of widow lines on
% the following pages.
%
% There are also some small enhancements to the balancing algorithm
% including a ways to require a minimum number of rows in the result.
%
% Finally, version 1.8 adds the command |\docolaction| to help with
% more complicated actions that depend on the current column. This
% command expects 3 arguments: code that is executed if we are in
% the ``first'' column, code to execute if we end up in any
% ``middle'' column (if there are more than two) and finally code to
% execute if we are in the ``last'' column. Thus
%\begin{verbatim}
% \docolaction{first}
% {middle}{last}
%\end{verbatim}
% would typeset a different word depending the type of column this
% code is executed. Using it like this is probably pointless, but
% you can imagine applications like writing something into the
% nearest margin, etc.
%
% As this feature needs at least two \LaTeX{} runs to produce correct
% results and as it adds to the processing complexity it is only
% made available if one add the option \texttt{colaction} when
% loading the package.
%
% \end{multicols}
%
%
% \begin{multicols}{3}[\section*{Preface to version 1.7
% (right to left support)}]
% The 1.7 release adds support for languages that are typeset
% right-to-left. For those languages the order of the columns on the page
% also need to be reversed---something that wasn't supported before. The next
% paragraph demonstrates the result (as it is typeset as if we are writing
% in a left-to-right language--- so read the rightmost column
% first). The change is initialized via
% |\RLmulticolcolumns| and returning to left-right (default)
% is done via |\LRmulticolcolumns|.
% \end{multicols}
%
% \RLmulticolcolumns
%
% \begin{multicols}{3}
% Right-to-left typesetting will only reverse the column orders. Any
% other support needed will have to be provided by other means,
% e.g., using appropriate fonts and reversing the writing directions
% within the columns. As footnotes are typeset in full measure the
% footnote rule needs to be redefined as if they are below a single
% column, i.e., using |\textwidth| not |\columnwidth|. For example:
%\begin{verbatim}
%\renewcommand \footnoterule{%
% \kern-3pt\hbox to\textwidth
% {\hskip .6\textwidth
% \hrulefill }%
% \kern2.6pt}
%\end{verbatim}
% \end{multicols}
%
% \LRmulticolcolumns
%
% \begin{multicols}{3}[\section*{Preface to version 1.5 + 1.6}]
% \hbadness=10000
% The 1.5 release contains two major changes: \mc{} will now
% support up to 10 columns and two more tuning possibilities have
% been added to the balancing routine. The balancing routine now
% checks the badness
% of the resulting columns and rejects solutions that are larger
% than a certain threshold.
% At the same time \mc{} has been upgraded to run under \LaTeXe{}.
%
% Later changes to 1.5 include |\columnbreak| and |multicols*|.
%
% For version 1.6 micro-spacing around the boxes produced by \mc{}
% has been improved to allow for baseline-grid typesetting.
% \end{multicols}
%
%
% \setcounter{collectmore}{2}
% \begin{multicols}{3}[\section{Introduction}]
% \hbadness=10000
% Switching between two-column and one-column layout is possible in
% \LaTeX{}, but every use of |\twocolumn| or |\onecolumn|
% starts a new page. Moreover, the last page of two-column output
% isn't balanced and this often results in an empty, or nearly
% empty, right column. When I started to write macros for
% \textsf{doc.sty} (see ``The \texttt{doc}--Option'', \TUB\
% volume 10~\#2, pp.~245--273) I thought that it would be nice to
% place the index
% on the same page as the bibliography. And balancing the last page
% would not only look better, it also would save space; provided of
% course that it is also possible to start the next article on the
% same page. Rewriting the index environment was comparatively easy,
% but the next goal, designing an environment which takes care of
% footnotes, floats, etc., was a harder task. It took me a whole
% weekend\footnote{I started with the algorithm given in the \TeX
% book on page 417. Without this help a weekend would not have been
% enough. (This remark was made in the documentation of the initial
% release, since then several hundreds more hours went into
% improving the original code.)} to get together the few lines of
% code below and there is
% still a good chance that I missed something after all.
%
% Try it and, hopefully, enjoy it; and {\em please\/} direct bug
% reports and suggestions back to Mainz.
% \end{multicols}
%
%
% \setcounter{collectmore}{0}
% \begin{multicols}{3}[\section{The User Interface}]
% \hbadness=10000
% To use the environment one simply says\\*[2mm]
% \hspace*{2mm}|\begin{multicols}{|\meta{number}|}|
% \hspace*{12mm}\meta{multicolumn text}\\
% \hspace*{2mm}|\end{multicols}|\\[2mm]
% where \meta{number} is the required number of columns and
%^^A\meta{multicolumn text}
% $\langle${\it multi\-column text\/}$\rangle$ may contain arbitrary
% \LaTeX{} commands, except that floats and marginpars are not
% allowed in the current implementation\footnote{This is dictated by
% lack of time. To implement floats one has to reimplement the
% whole \LaTeX{} output routine.}.
%
% \enlargethispage{-1\baselineskip}
%
% \DescribeMacro\premulticols
% As its first action, the \textsf{multicols} environment measures the
% current page to determine whether there is enough room for some
% portion of multicolumn output. This is controlled by the
% \meta{dimen} variable |\premulticols| which can be changed by
% the user with ordinary \LaTeX{} commands.
% \DescribeMacro\multicolsep
% If the space is less than |\premulticols|, a new page is
% started. Otherwise, a |\vskip| of |\multicolsep| is
% added.\footnote{Actually the added space may be less because we use
% \cs{addvspace} (see the \LaTeX{} manual for further
% information about this command).}
%
% \DescribeMacro\postmulticols
% When the end of the \mc{} environment is encountered, an
% analogous mechanism is employed, but now we test whether there is a
% space larger than |\postmulticols| available. Again we add
% |\multicolsep| or start a new page.
%
% It is often convenient to spread some text over all columns, just
% before the multicolumn output, without any page break in between. To
% achieve this the \mc{} environment has an optional second
% argument which can be used for this purpose. For example, the text
% you are now reading was started with
% \begin{verbatim}
% \begin{multicols}{3}
% [\section{The User
% Interface}] ...
%\end{verbatim}
% If such text is unusually long (or short) the value of
% |\premulticols| might need adjusting to prevent a bad page
% break. We therefore provide a third argument which can be used to
% overwrite the default value of |\premulticols| just for this
% occasion. So if you want to combine some longer single column text
% with a multicols environment you could write
% \begin{verbatim}
% \begin{multicols}{3}
% [\section{Index}
% This index contains ...]
% [6cm]
% ...
%\end{verbatim}
%
%
% \DescribeMacro\columnsep
% The space between columns is controlled by the length parameter
% |\columnsep|. The width for the individual columns is automatically
% calculated from this parameter and the current |\linewidth|. In this
% article a value of \textsf{\the\columnsep} was used.
%
%
% \DescribeMacro\columnseprule
% Separation of columns with vertical rules is achieved by setting the
% parameter |\columnseprule| to some positive value. In this
% article a value of \textsf{.4pt} was used.
%
% \DescribeMacro\columnseprulecolor
% The color of the rules separating the columns can be specified through
% |\columnseprulecolor|. The default value is |\normalcolor|.
%
% \DescribeMacro\multicolbaselineskip
% Since narrow columns tend to need adjustments in interline spacing
% we also provide a \meta{skip} parameter called
% |\multicolbaselineskip| which is added to the
% |\baselineskip| parameter inside the \mc{}
% environment. Please use this parameter with care or leave it alone;
% it is intended only for package file designers since even small
% changes might produce totally unexpected changes to your document.
%
%
% \subsection{Balancing columns}
%
%
% Besides the previously mentioned parameters, some others are
% provided to influence the layout of the columns generated.
%
% Paragraphing in \TeX{} is controlled by several parameters. One of
% the most important is called |\tolerance|: this controls the
% allowed `looseness' (i.e.\ the amount of blank space between words).
% Its default value is 200 (the \LaTeX{} |\fussy|) which is too
% small for narrow columns. On the other hand the |\sloppy|
% declaration (which sets |\tolerance| to $10000=\infty$) is too
% large, allowing really bad spacing.\footnote{Look at the next
% paragraph, it was set with the \cs{sloppy} declaration.}
%
% \begin{sloppypar}
% \DescribeMacro\multicoltolerance \DescribeMacro\multicolpretolerance
% We therefore use a |\multicoltolerance| parameter for the
% |\tolerance| value inside the \mc{} environment. Its default value
% is 9999 which is less than infinity but `bad' enough for most
% paragraphs in a multicolumn environment. Changing its value should
% be done outside the \mc{} environment. Since |\tolerance| is set
% to |\multicoltolerance| at the beginning of every \textsf{multicols}
% environment one can locally overwrite this default by assigning
% \verb*+\tolerance = +\meta{desired value}. There also exists a
% |\multicolpretolerance| parameter holding the value for
% |\pretolerance| within a \mc{} environment. Both parameters are
% usually used only by package designers.
% \end{sloppypar}
%
% Generation of multicolumn output can be divided into two parts. In
% the first part we are collecting material for a page, shipping it
% out, collecting material for the next page, and so on. As a second
% step, balancing will be done when the end of the \mc{} environment
% is reached.
% In the first step \TeX{} might consider more material whilst
% finding the final column content than it actually uses when shipping out the
% page. This might cause a problem if a footnote is encountered in
% the part of the input considered, but not used, on the current page.
% In this case the footnote might show up on the current page, while the
% footnotemark corresponding to this footnote might be set on the next
% one.\footnote{The reason behind this behavior is the asynchronous
% character of the \TeX{} {\it page\_builder}.
% However, this
% could be avoided by defining very complicated output
% routines which don't use \TeX{} primitives like
% \cs{insert} but do everything by hand.
% This is clearly beyond the scope of a weekend problem.}
% Therefore the \mc{} environment gives a warning
% message\footnote{This message will be generated even if there are no
% footnotes in this part of the text.} whenever it is unable to use
% all the material considered so far.
%
% If you don't use footnotes too often the chances of something
% actually going wrong are very slim, but if this happens you can help
% \TeX{} by using a |\pagebreak| command in the final document.
% Another way to influence the behavior of \TeX{} in this respect is
% given by the counter variable `\textsf{collectmore}'. If you use the
% |\setcounter| declaration to set this counter to \meta{number},
% \TeX{} will consider \meta{number} more (or less) lines before
% making its final decision. So a value of $-1$ may solve all your
% problems at the cost of slightly less optimal columns.
%
%
% In the second step (balancing columns) we have other bells and
% whistles. First of all you can say |\raggedcolumns| if you
% don't want the bottom lines to be aligned.
% The default is |\flushcolumns|, so \TeX{} will normally try to
% make both
% the top and bottom baselines of all columns align.
%
% If there is only a small amount of material available for balancing
% then you may end up with very few lines per column. In an extreme
% case there may be only one line which looks distinctly odd. In that
% case it might be better to have more material distributed to the
% earlier columns even if that means that later columns are empty or
% partially empty. This is controlled through the counter
% `\textsf{minrows}' (default 1). If set to a higher value then the
% balancing will have at least that many rows in the first column (and
% also all further columns until it runs outs of material).
%
% Additionally you can set another counter, the `\textsf{unbalance}'
% counter, to some positive \meta{number}. This will make all but the
% right-most column \meta{number} of lines longer than they would
% normally have been. `Lines' in this context refer to normal text
% lines (i.e.\ one |\baselineskip| apart); thus, if your columns
% contain displays,
% for example, you may need a higher \meta{number}
% to shift something from one column into another. A negative value can make sense if
% you have set \textsf{minrows} and want to locally adjust that.
%
% Unlike `\textsf{collectmore},' the `\textsf{unbalance}' counter is reset
% to zero at the end of the environment so it only applies to one
% \mc{} environment.
%
% The two methods may be combined but I suggest using these features
% only when fine tuning important publications.
%
% Two more general tuning possibilities were added with version~1.5.
% \TeX{} allows to measure the badness of a column in terms of an
% integer value, where 0 means optimal and any higher value means a
% certain amount of extra white space. 10000 is considered to be
% infinitely bad (\TeX{} does not distinguish any further). In addition
% the special value 100000 means overfull (i.e., the column contains
% more text than could possibly fit into it).
%
% The new release now measures every generated column and ignores
% solutions where at least one column has a badness being larger than
% the value of the counter \textsf{columnbadness}. The default value for
% this counter is 10000, thus \TeX{} will accept all solutions except
% those being overfull.
% By setting the counter to a smaller value you can force the algorithm
% to search for solutions that do not have columns with a lot of white
% space.
%
% However, if the setting is too low, the algorithm may not find any
% acceptable solution at all and will then finally choose the extreme
% solution of placing all text into the first column.
%
% Often, when columns are balanced, it is impossible to find a solution
% that distributes the text evenly over all columns. If that is the case
% the last column usually has less text than the others. In the earlier
% releases this text was stretched to produce a column with the same
% height as all others, sometimes resulting in really ugly looking
% columns.
%
% In the new release this stretching is only done if the badness of
% the final column is not larger than the value of the counter
% \textsf{finalcolumnbadness}. The default setting is 9999, thus preventing
% the stretching for all columns that \TeX{} would consider infinitely
% bad. In that case the final column is allowed to run short which gives
% a much better result.
%
% And there are two more parameters of some experimental nature, one
% called |\multicolovershoot| the other |\multicolundershoot|. They
% control the amount of space a column within the \mc{} environment is
% allowed to be ``too full'' or ``too short'' without affecting the
% column badness. They are set to 0pt and 2pt, respectively.
%
% Finally, when doing the balancing at the end, columns may become
% higher than the remaining available space. In that case the
% algorithm aborts and instead generates a normal page. However, if the
% amount is not too large, e.g., a line or so, then it might be better to
% keep everything on the same page instead of starting a new page with
% just one line after balancing. So the parameter
% |\maxbalancingoverflow| governs this process: only when the excess
% gets larger than its value balancing is aborted.
%
% \subsection{Not balancing the columns}
%
% Although this package was written to solve the problem of balancing
% columns, I got repeated requests to provide a version where all
% white space is automatically placed in the last column or
% columns. Since version v1.5q this now exists: if you use
% \texttt{multicols*} instead of the usual environment the columns on
% the last page are not balanced. Of course, this environment only
% works on top-level, e.g., inside a box one has to balance to
% determine a column height in absence of a fixed value.
%
%
% \subsection{Manually breaking columns}
%
% Another request often voiced was: ``How do I tell \LaTeX{} that it
% should break the first column after this particular line?''. The
% |\pagebreak| command (which works with the two-column option of
% \LaTeX{}) is of no use here since it would end the collection phase
% of \mc{} and thus all columns on that page. So with version 1.5u
% the |\columnbreak| command was added. If used within a paragraph it
% marks the end of the current line as the desired breakpoint. You can
% observe its effect on
% the previous page where three lines of text have been artificially
% forced into the second column (resulting in some white
% space between paragraphs in the first column).
%
% \subsection{Floats inside a \mc{} environment}
%
% Within the \mc{} environment the usual star float commands are
% available but their function is somewhat different as in the
% two-column mode of standard \LaTeX. Stared floats, e.g.,
% \texttt{figure*}, denote page wide floats that are handled in a similar
% fashion as normal floats outside the \mc{} environment. However,
% they will never show up on the page where they are encountered. In
% other words, one can influence their placement by specifying a
% combination of \texttt{t}, \texttt{b}, and/or \texttt{p} in their optional
% argument, but \texttt{h} doesn't work because the first possible place
% is the top of the next page. One should also note, that this means
% that their placement behavior is determined by the values of
% |\topfraction|, etc.\ rather than by |\dbl...|.
%
%
% \subsection{Support for right-to-left typesetting}
%
% In right-to-left typesetting the order of the columns on the page
% also need to be reversed, i.e., the first column has to appear on the far
% right and the last column on the left. This is supported through the
% commands |\RLmulticolcolumns| (switching to right-to-left typesetting)
% and |\LRmulticolcolumns| (switching to left-to-right typesetting) the
% latter being the default.
%
% \subsection{Warnings}
%
% Under certain circumstances the use of the \mc{} environment may
% result in some
% warnings from \TeX{} or \LaTeX{}. Here is a list
% of the important ones and the possible cause:
% \begin{description}
%
% \item[] {\hspace*{-\labelsep}\tt Underfull \string\hbox\space
% (badness ...)}
%
% As the columns are often very narrow \TeX{} wasn't able to find a
% good way to break the paragraph. Underfull denotes a loose line but
% as long as the badness value is below $10000$ the result is probably
% acceptable.
%
% \item[]
% {\hspace*{-\labelsep}\tt Underfull \string\vbox\space ... while
% \string\output\space is active}
%
% If a column contains a character with an unusual depth, for
% example a `(', in the bottom line then this message may show up. It
% usually has no significance as long as the value is not more than a
% few points.
%
% \item[] {\hspace*{-\labelsep}\tt LaTeX Warning: I moved some lines
% to the next page}
%
% As mentioned above, \mc{} sometimes screws up the footnote
% numbering. As a precaution, whenever there is a footnote on a
% page where \mc{} had to leave a remainder for the following
% page this warning appears. Check the footnote numbering on this
% page. If it turns out that it is wrong, you have to manually break
% the page using |\newpage| or |\pagebreak[..]|.
%
% \item[] {\hspace*{-\labelsep}\tt Floats and marginpars not allowed
% inside `multicols' environment!}
%
% This message appears if you try to use the |\marginpar| command or
% an unstarred version of the \textsf{figure} or \textsf{table} environment.
% Such floats will disappear!
%
% \item[] {\hspace*{-\labelsep}\tt Very deep columns!
% Grid alignment might be broken}
%
% This message can only appear if the option \texttt{grid} was
% chosen. In that case it will show up if a column has a very large
% depth so that \mc{} is unable to back up to its baseline. This
% is only relevant if one tries to produce a document where all
% text lines are aligned at an invisible grid, something that
% requires careful adjustment of many parameters and macros, e.g.,
% heading definitions.
%
% \end{description}
%
%
% \subsection{Tracing the output}
%
% To understand the reasoning behind the decisions \TeX{} makes when
% processing a \mc{} environment, a tracing mechanism is provided.
% If you set the counter `\texttt{tracingmulticols}'
% to a positive \meta{number} you then
% will get some tracing information on the terminal and in the
% transcript file:
% \begin{description}
% \item[$\meta{number}=1$.] \TeX{} will now tell you, whenever it
% enters or leaves a \mc{} environment, the number of columns it
% is working on and its decision about starting a new page before
% or after the environment.
% \item[$\meta{number}=2$.]
% In this case you also get information from the balancing routine:
% the heights tried for the left and right-most columns,
% information about shrinking if the |\raggedcolumns|
% declaration is in force and the value of the `\textsf{unbalance}'
% counter if positive.
% \item[$\meta{number}= 3$.] Setting \meta{number}\pagebreak[2] to
% this value will additionally trace the mark handling
% algorithm. It will show what marks are found, what marks are
% considered, etc. To fully understand this information you will
% probably have to read carefully trough the implementation.
% \item[$\meta{number}\geq 4$.] Setting \meta{number}\pagebreak[2] to
% such a high value will additionally place an |\hrule| into your
% output, separating the part of text which had already been
% considered on the previous page from the rest. Clearly this
% setting should {\em not\/} be used for the final output. It will
% also activate even more debugging code for mark handling.
% \end{description}
%
%
% \end{multicols}
%
% \begin{multicols}{3}[\section{Prefaces to older versions}
% \subsection{Preface to version 1.4}]
% \hbadness=10000
% Beside fixing some bugs as mentioned in the \textsf{multicol.bug} file
% this new release enhances the \mc{} environment by allowing for
% balancing in arbitrary contexts. It is now, for example, possible
% to balance text within a \mc{} or a \textsf{minipage} as shown in
% \ref{tab:newcmds} where a \textsf{multicols} environment within a
% \textsf{quote} environment was used. It is now even possible to nest
% \mc{} environments.
%
% The only restriction to such inner \mc{} environments (nested, or
% within \TeX's internal vertical mode) is that such variants will
% produce a box with the balanced material in it, so that they can
% not be broken across pages or columns.
%
% Additionally I rewrote the algorithm for balancing so that it will
% now produce slightly better results.
%
% I updated the source documentation but like to apologize in
% advance for some `left over' parts that slipped through the
% revision.
%
% A note to people who like to improve the balancing algorithm of
% \mc{}: The balancing routine is now placed into a single macro
% which is called |\balance@columns|. This means that one can easily
% try different balancing routines by rewriting this macro. The
% interface for it is explained in table \ref{tab:balance}. There are
% several improvements possible, one can think of integrating the
% |\badness| function of \TeX3, define a faster algorithm for finding
% the right column height, etc. If somebody thinks he/she has an
% enhancement I would be pleased to learn about it. But please obey
% the copyright notice and don't change \textsf{multicol.dtx} directly!
% \begin{table*}
% \begin{quote}
% \begin{multicols}{2}
% \raggedcolumns
% The macro |\balance@columns| that contains the code for balancing
% gathered material is a macro without parameters. It assumes that
% the material for balancing is stored in the box |\mult@box| which
% is a |\vbox|. It also ``knows'' about all parameters set up by the
% \mc{} environment, like |\col@number|, etc. It can also assume
% that |\@colroom| is the still available space on the current page.
%
% When it finishes it must return the individual columns in boxes
% suitable for further processing with |\page@sofar|. This means
% that the left column should be stored in box register
% |\mult@gfirstbox|, the next
% in register |\mult@firstbox|${}+2$, \ldots,
% only the last one as an exception in
% register |\mult@grightbox|. Furthermore it has to set up
% the two macros
% |\kept@firstmark| and |\kept@botmark| to hold the values for the
% first and bottom mark as found in the individual columns. There
% are some helper functions defined in section \ref{sec:v14} which
% may be used for this. Getting the marks right ``by hand'' is
% non-trivial and it may pay off to first take a look at the
% documentation and implementation of |\balance@columns| below
% before trying anew.
% \end{multicols}
% \end{quote}
% \vspace*{-3ex}
% \vspace*{-0ex}
% \caption{Interface description for \cs{balance@columns}}
% \label{tab:balance}
% \end{table*}
% \end{multicols}
%
% \begin{multicols}{3}[\subsection{Preface to version 1.2}]
% \hbadness=10000
% After the article about the \mc{} environment was published in
% \TUB\ 10\#3, I got numerous requests for these macros. However, I
% also got a changed version of my style file, together with a
% letter asking me if I would include the changes to get better
% paragraphing results in the case of narrow lines. The main
% differences to my original style option were additional parameters
% (like |\multicoladjdemerits| to be used for |\adjdemerits|, etc.)
% which would influence the line breaking algorithm.
%
% But actually resetting such parameters to zero or even worse to a
% negative value won't give better line breaks inside the \mc{}
% environment. \TeX{}s line breaking algorithm will only look at
% those possible line breaks which can be reached without a badness
% higher than the current value of |\tolerance| (or |\pretolerance|
% in the first pass). If this isn't possible, then, as a last
% resort, \TeX{} will produce overfull boxes. All those (and only
% those) possible break points will be considered and finally the
% sequence which results in the fewest demerits will be chosen. This
% means that a value of $-1000$ for |\adjdemerits| instructs \TeX{}
% to prefer visibly incompatible lines instead of producing better
% line breaks.
%
% However, with \TeX{} 3.0 it is possible to get decent line breaks
% even in small columns by setting |\emergencystretch| to an
% appropriate value. I implemented a version which is capable of
% running both in the old and the new \TeX{} (actually it will
% simply ignore the new feature if it is not available). The
% calculation of |\emergencystretch| is probably incorrect. I
% made a few tests but of course one has to have much more experience
% with the new possibilities to achieve the maximum quality.
%
% Version 1.1a had a nice `feature': the penalty for using the
% forbidden floats was their ultimate removal from \LaTeX{}s
% |\@freelist| so that after a few |\marginpar|s inside the \mc{}
% environment floats where disabled forever. (Thanks to Chris
% Rowley for pointing this out.) I removed this misbehavior and at
% the same time decided to allow at least floats spanning all
% columns, e.g., generated by the |figure*| environment. You can
% see the new functionality in table~\ref{tab:newcmds} which was
% inserted at this very point.
% \begin{table*}
% \small
% \setlength{\multicolsep}{0pt}
% \begin{quote}
% \begin{multicols}{2}
% |\setemergencystretch|: This is a hook for people who like
% to play around. It is supposed to set the
% |\emergencystretch| \meta{dimen} register provided in the
% new \TeX{} 3.0. The first argument is the number of columns and
% the second one is the current |\hsize|. At the moment the
% default definition is $4\texttt{pt} \times |#1|$, i.e.\ the
% |\hsize| isn't used at all. But maybe there are better
% formulae.
%
% \setlength{\emergencystretch}{20pt} |\set@floatcmds|: This is
% the hook for the experts who like to implement a full float
% mechanism for the \mc{} environment. The |@| in the name
% should signal that this might not be easy.
% \end{multicols}
% \end{quote}
% \vspace*{-1ex}
% \vspace*{-0ex}
% \caption[]{The new commands of \textsf{multicol.sty} version 1.2.
% Both commands might be removed if good solutions to these
% open problems are found. I hope that these commands will
% prevent that nearly identical style files derived from
% this one are floating around.}
% \label{tab:newcmds}
% \end{table*}
% However single column floats are still forbidden and I don't think
% I will have time to tackle this problem in the near future. As an
% advice for all who want to try: wait for \TeX{} 3.0. It has a few
% features which will make life much easier in multi-column
% surroundings. Nevertheless we are working here at the edge of
% \TeX{}s capabilities, really perfect solutions would need a
% different approach than it was done in \TeX{}s page builder.
%
% The text below is nearly unchanged, I only added documentation at
% places where new code was added.
% \end{multicols}
%
% \changes{v1.5l}{1996/01/13}{Try hard to explain unresolved reference
% that happens if \cs{OnlyDescription} is used}
%
% \StopEventually{\PrintIndex \PrintChanges
% \ifx\Finale\relax
% \typeout{**********************************}
% \typeout{* Info: Typesetting this document with
% \protect\OnlyDescription\space will}
% \typeout{* Info: result in one unresolved
% reference to `sec:v14'.}
% \typeout{* Info: --- tough, it's just not there in this case!}
% \typeout{**********************************}
% \fi
% }
%
%
% \begin{multicols}{2}[\section{The Implementation}
% We are now switching to two-column output to show the
% abilities of this environment (and bad layout decisions).
% \subsection{The documentation driver file}
% ][10\baselineskip]
%
% \hbadness=10000
%
%
% The next bit of code contains the documentation driver file for
% \TeX{}, i.e., the file that will produce the documentation you are
% currently reading. It will be extracted from this file by the \texttt{docstrip} program.
% Since this is the first code in this file one can produce the
% documentation
% simply by running \LaTeX{} on the \texttt{.dtx} file.
% \begin{macrocode}
%<*driver>
\documentclass{ltxdoc}
% \end{macrocode}
% We use the \texttt{balancingshow} option when loading \mc{} so
% that full tracing is produced. This has to be done before the
% \texttt{doc} package is loaded, since \texttt{doc} otherwise
% requires \mc{} without any options.
% \begin{macrocode}
\usepackage{multicol}[1999/05/25]
\usepackage{doc}
% \end{macrocode}
% First we set up the page layout suitable for
% this article.
% \begin{macrocode}
\setlength{\textwidth}{39pc}
\setlength{\textheight}{54pc}
\setlength{\parindent}{1em}
\setlength{\parskip}{0pt plus 1pt}
\setlength{\oddsidemargin}{0pc}
\setlength{\marginparwidth}{0pc}
\setlength{\topmargin}{-2.5pc}
\setlength{\headsep}{20pt}
\setlength{\columnsep}{1.5pc}
% \end{macrocode}
% We want a rule between columns.
% \begin{macrocode}
\setlength\columnseprule{.4pt}
% \end{macrocode}
% We also want to ensure that a new \mc{} environment finds enough
% space at the bottom of the page.
% \begin{macrocode}
\setlength\premulticols{6\baselineskip}
% \end{macrocode}
% When balancing columns we disregard solutions that
% are too bad. Also, if the last column is too bad
% we typeset it without stretch.
% \begin{macrocode}
\setcounter{columnbadness}{7000}
\setcounter{finalcolumnbadness}{7000}
% \end{macrocode}
% The index is supposed to come out in four columns.
% And we don't show macro names in the margin.
% \begin{macrocode}
\setcounter{IndexColumns}{4}
\let\DescribeMacro\SpecialUsageIndex
\let\DescribeEnv\SpecialEnvIndex
\renewcommand\PrintMacroName[1]{}
\CodelineIndex
%\DisableCrossrefs % Partial index
\RecordChanges % Change log
% \end{macrocode}
% Line numbers are very small for this article.
% \begin{macrocode}
\renewcommand{\theCodelineNo}
{\scriptsize\rm\arabic{CodelineNo}}
\settowidth\MacroIndent{\scriptsize\rm 00\ }
\begin{document}
\typeout
{****************************************
^^J* Expect some Under- and overfull boxes.
^^J****************************************}
\DocInput{multicol.dtx}
\end{document}
%</driver>
% \end{macrocode}
%
%
% \end{multicols}
%
% \begin{multicols}{2}[\subsection{Identification and
% option processing}]
%
%
% We start by identifying the package. Since it makes use of features
% only available in \LaTeXe{} we ensure that this format is available.
% (Now this is done earlier in the file.)
% \begin{macrocode}
%<*package>
% \NeedsTeXFormat{LaTeX2e}
% \ProvidesPackage{multicol}[..../../..
% v... multicolumn formatting]
% \end{macrocode}
%
%^^A \subsection{Option processing}
%
% Next we declare options supported by \mc{}. Two-column mode
% and \mc{} do not work together so we warn about possible
% problems. However, since you can revert to |\onecolumn|
% in which case \mc{} does work, we don't make this an error.
% \begin{macrocode}
\DeclareOption{twocolumn}
{\PackageWarning{multicol}{May not work
with the twocolumn option}}
% \end{macrocode}
% Tracing is done using a counter. However
% it is also possible to invoke the tracing
% using the options declared below.
% \begin{macrocode}
\newcount\c@tracingmulticols
\DeclareOption{errorshow}
{\c@tracingmulticols\z@}
\DeclareOption{infoshow}
{\c@tracingmulticols\@ne}
\DeclareOption{balancingshow}
{\c@tracingmulticols\tw@}
\DeclareOption{markshow}
{\c@tracingmulticols\thr@@}
\DeclareOption{debugshow}
{\c@tracingmulticols5\relax}
% \end{macrocode}
% The next option is intended for typesetting on a |\baselineskip|
% grid. Right now it doesn't do anything other than warning if it
% thinks that the grid got lost.
% \changes{v1.6a}{2003/03/15}{New option grid}
% \changes{v1.8x}{2019/10/15}{Use \cs{@maxdepth} not \cs{maxdepth} (gh/190)}
% \begin{macrocode}
\let\mc@gridwarn\maxdimen
\DeclareOption{grid}{\def\mc@gridwarn{\@maxdepth}}
% \end{macrocode}
%
% \changes{v1.8e}{2014/04/23}{Support \cs{docolaction}}
% Next option enables the |\docolaction| command. As this changes
% the \texttt{.aux} file content this is not automatically enabled.
% \begin{macrocode}
\DeclareOption{colaction}{%
\def\mc@col@status@write{%
\protected@write\@auxout{}%
{\string\mc@col@status
{\ifmc@firstcol 1\else 2\fi}}%
\mc@firstcolfalse}%
\def\mc@lastcol@status@write{%
\protected@write\@auxout{}%
{\string\mc@col@status{3}}}%
}
\let\mc@col@status@write\relax
\let\mc@lastcol@status@write\relax
% \end{macrocode}
%
% \begin{macrocode}
\ProcessOptions
% \end{macrocode}
%
%
% \end{multicols}
%
% \begin{multicols}{2}[\subsection{Starting and
% Ending the \mc{} Environment}]
%
% \begin{macro}{\multicols}
% As mentioned before, the \mc{} environment has one mandatory
% argument (the number of columns) and up to two optional ones. We
% start by reading the number of columns into the |\col@number|
% register.
% \begin{macrocode}
\def\multicols#1{\col@number#1\relax
% \end{macrocode}
% If the user forgot the argument, \TeX{} will complain about a
% missing number at this point. The error recovery mechanism will
% then use zero, which isn't a good choice in this case. So we
% should now test whether everything is okay. The minimum is two
% columns at the moment.
% \changes{v1.3b}{1990/10/09}{Minimum of two columns}
% \begin{macrocode}
\ifnum\col@number<\tw@
\PackageWarning{multicol}%
{Using `\number\col@number'
columns doesn't seem a good idea.^^J
I therefore use two columns instead}%
\col@number\tw@ \fi
% \end{macrocode}
% We have only enough box registers for twenty columns, so we need to
% check that the user hasn't asked for more.
% \changes{v1.4k}{1992/06/27}{Maximum of 5 columns (temp)}
% \changes{v1.5a}{1992/11/04}{Allow 10 columns again}
% \changes{v1.8y}{2019/12/09}{Allow for 20 columns (gh/237)}
% \begin{macrocode}
\ifnum\col@number>20
\PackageError{multicol}%
{Too many columns}%
{Current implementation doesn't
support more than 20 columns.%
\MessageBreak
I therefore use 20 columns instead}%
\col@number20 \fi
% \end{macrocode}
% Within the environment we need a special version of the
% kernel |\@footnotetext| command since the original sets the
% the |\hsize| to |\columnwidth| which is not correct in the
% multicol environment. Here |\columnwidth| refers to the width of
% the individual column and the footnote should be in |\textwidth|.
% Since |\@footnotetext| has a different definition inside a
% minipage environment we do not redefine it directly. Instead we
% locally set |\columnwidth| to |\textwidth| and call the original
% (current) definition stored in |\orig@footnotetext|.
% \changes{v1.5p}{1997/12/14}{Redefinition of \cs{@footnotetext}
% only within env pr/2689.}
% \changes{v1.5r}{1998/08/17}{Use \cs{@footnotetext} but with
% local change to \cs{columnwidth}.}
% \changes{v1.5w}{1999/10/21}{Make \cs{@footnotetext} long to allow
% multi-paragraph footnotes.}
% If the \mc{} environment is nested inside another \mc{}
% environment then the redefinition has already happened. So be
% better test for this situation. Otherwise, we will get a \TeX{}
% stack overflow as this would generate a self-referencing definition.
% \changes{v1.6e}{2004/02/14}{Avoid self-referencing definition of
% \cs{@footnotetext} (pr/3618)}.
% \begin{macrocode}
\ifx\@footnotetext\mult@footnotetext\else
\let\orig@footnotetext\@footnotetext
\let\@footnotetext\mult@footnotetext
\fi
% \end{macrocode}
% Now we can safely look for the optional arguments.
% \begin{macrocode}
\@ifnextchar[\mult@cols{\mult@cols[]}}
% \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\mult@footnotetext}
%
% \begin{macrocode}
\long\def\mult@footnotetext#1{\begingroup
\columnwidth\textwidth
\orig@footnotetext{#1}\endgroup}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\mult@cols}
% The |\mult@cols| macro grabs the first optional argument
% (if any) and looks for the second one.
% \begin{macrocode}
\def\mult@cols[#1]{\@ifnextchar[%
% \end{macrocode}
% This argument should be a \meta{dimen} denoting the minimum free
% space needed on the current page to start the environment. If the
% user didn't supply one, we use |\premulticols| as a
% default.
% \begin{macrocode}
{\mult@@cols{#1}}%
{\mult@@cols{#1}[\premulticols]}}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\mult@@cols}
% After removing all arguments from the input we are able
% to start with |\mult@@cols|.
% \begin{macrocode}
\def\mult@@cols#1[#2]{%
% \end{macrocode}
% First thing we do is to decide whether or not this is an
% unbounded multicols environment, i.e. one that may split across
% pages, or one that has to be typeset into a box. If we are in
% \TeX's ``inner'' mode (e.g., inside a box already) then we have a
% boxed version of multicols therefore we set the |@boxedmulticols|
% switch to true. The \mc{} should start in vertical mode. If we
% are not already there we now force it with |\par| since otherwise
% the test for ``inner'' mode wouldn't show if we are in a box.
% \changes{v1.4f}{1992/04/28}{\cs{par} added to allow for correct inner test}
% \begin{macrocode}
\par
\ifinner \@boxedmulticolstrue
% \end{macrocode}
% Otherwise we check |\doublecol@number|. This counter is zero
% outside a multicols environment but positive inside (this happens
% a little later on). In the second case we need to process the
% current multicols also in ``boxed mode'' and so change the switch
% accordingly.
% \begin{macrocode}
\else
\ifnum \doublecol@number>\z@
\@boxedmulticolstrue
\fi
\fi
% \end{macrocode}
% Then we look to see if statistics are requested:
% \begin{macrocode}
\mult@info\z@
{Starting environment with
\the\col@number\space columns%
% \end{macrocode}
% In boxed mode we add some more info.
% \changes{v1.4f}{1992/04/28}{\cs{on@line} added to tracing info}
% \begin{macrocode}
\if@boxedmulticols\MessageBreak
(boxed mode)\fi
}%
% \end{macrocode}
% Then we measure the current page to see whether a useful portion
% of the multicolumn environment can be typeset. This routine
% might start a new page.
% \changes{v1.4a}{1992/02/14}{Forgotten braces added}
% \begin{macrocode}
\enough@room{#2}%
% \end{macrocode}
% Now we output the first argument and produce vertical space
% above the columns. (Note that this argument corresponds to the
% first optional argument of the \textsf{multicols} environment.)
% For many releases this argument was typeset in a group to get
% a similar effect as |\twocolumn[..]| where the argument is
% also implicitly surrounded by braces. However, this conflicts
% with local changes done by things like sectioning commands (which
% account for the majority of commands used in that argument)
% messing up vertical spacing etc.\ later in the document so that
% from version v1.5q on this argument is again typeset at the outer
% level.
% \changes{v1.4e}{1992/03/16}{Typeset optional arg inside group}
% \changes{v1.5q}{1998/01/19}{And removed the group again six years later}
% \begin{macrocode}
#1\par\addvspace\multicolsep
% \end{macrocode}
% When the last line of a paragraph had a positive depth then this
% depth normally taken into account by the baselineskip calculation
% for the next line. However, the columns produced by a following
% \texttt{multicol} are rigid and thus the distance from the
% baseline of a previous text line to the first line in a
% \texttt{multicol} would differ depending on the depth of the
% previous line. To account for this we add a negative space unless
% the depth is \texttt{-1000pt} which signals something special to
% \TeX and is not supposed to be a real depth.
% \changes{v1.5z1}{2003/02/17}{Add a kern to cancel potential depth of
% previous line}
% \begin{macrocode}
\ifdim \prevdepth = -\@m\p@
\else
% \end{macrocode}
% The actual generation of this corrective space is a little bit
% more complicated as it doesn't make sense to always back up to
% the previous baseline (in case an object with a very large depth
% was placed there, e.g., a centered tabular). So we only back up
% to the extend that we are within the |\baselineskip| grid. We
% know that the box produced by \mc{} has |\topskip| at its top so
% that also needs to be taken into account.
% \changes{v1.6a}{2003/03/15}{Adjust spacing}
% \begin{macrocode}
\@tempcnta\prevdepth
\@tempcntb\baselineskip
\divide\@tempcnta\@tempcntb
\advance\@tempcnta\@ne
\dimen@\prevdepth
\advance\dimen@ -\@tempcnta\baselineskip
\advance\dimen@ \topskip
\kern-\dimen@
\fi
% \end{macrocode}
% We start a new grouping level to hide all subsequent changes
% (done in |\prepare@multicols| for example).
% \begin{macrocode}
\begingroup
\prepare@multicols
% \end{macrocode}
% If we are in boxed mode we now open a box to typeset all material
% from the multicols body into it, otherwise we simply go ahead.
% \changes{v1.4g}{1992/05/07}{\cs{global} was probably wrong but at least
% unnecessary}
% \begin{macrocode}
\if@boxedmulticols
\setbox\mult@box\vbox\bgroup
% \end{macrocode}
%
% \changes{v1.8c}{2013/11/03}{Add \cs{color@setgroup} to prevent color leak}
% \begin{macrocode}
\color@setgroup
% \end{macrocode}
% \changes{v1.5?}{1994/?/?}{Penalty moved to later point}
% We may have to reset some parameters at this point,
% perhaps |\@parboxrestore|
% would be the right action but I leave it for the moment.
% \changes{v1.4l}{1992/08/17}{\cs{@totalleftmargin} now in
% \cs{prepare@multicols}}
% \begin{macrocode}
\fi
% \end{macrocode}
% We finish by suppressing initial spaces.
% \begin{macrocode}
\ignorespaces}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\if@boxedmulticols}
% Here is the switch and the box for ``boxed'' multicols code.
% \begin{macrocode}
\newif\if@boxedmulticols
\@boxedmulticolsfalse
\newbox\mult@box
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\enough@room}
% \changes{v1.0c}{1989/05/12}{Penalty 0 added to empty the contribution
% list.}
% The |\enough@room| macro used
% above isn't perfect but works reasonably well in this context. We
% measure the free space on the current page by subtracting
% |\pagetotal| from |\pagegoal|. This isn't entirely
% correct since it doesn't take the `shrinking' (i.e.\
% |\pageshrink|) into account. The `recent contribution list'
% might be nonempty so we start with |\par| and an explicit
% |\penalty|.\footnote{See the documentation of
% \cs{endmulticols} for further details.}
% Actually, we use |\addpenalty| to ensure that a following
% |\addvspace| will `see' the vertical space that might be
% present.
% The use of |\addpenalty| will have the effect that all items from
% the recent contributions will be moved to the main vertical list
% and the |\pagetotal| value will be updated correctly. However,
% the penalty will be placed in front of any dangling glue item
% with the result that the main vertical list may already be
% overfull even if \TeX{} is not invoking the output routine.
% \changes{v1.3b}{1990/10/09}{Do \cs{penalty} with \cs{addpenalty}}
% \changes{v1.4e}{1992/03/16}{But ignore \cs{@nobreak} in \cs{addpenalty}}
% \begin{macrocode}
\def\enough@room#1{%
% \end{macrocode}
% Measuring makes only sense when we are not in ``boxed mode'' so
% the routine does nothing if the switch is true.
% \begin{macrocode}
\if@boxedmulticols\else
\par
% \end{macrocode}
% \label{mac:enoughroom}
% To empty the contribution list the first release contained a
% penalty zero but this had the result that |\addvspace| couldn't
% detect preceding glue. So this was changed to |\addpenalty|. But
% this turned out to be not enough as |\addpenalty| will not add a
% penalty when |@nobreak| is true. Therefore we force this switch
% locally to false. As a result there may be a break between
% preceding text and the start of a multicols environment, but this
% seems acceptable since there is the optional argument for exactly
% this reason.
% \begin{macrocode}
\bgroup\@nobreakfalse\addpenalty\z@\egroup
\page@free \pagegoal
\advance \page@free -\pagetotal
% \end{macrocode}
% To be able to output the value we need to assign it to a register
% first since it might be a register (default) in which case we
% need to use |\the| or it might be a plain value in which case
% |\the| would be wrong.
% \changes{v1.5e}{1994/05/26}{Assign arg to skip register to be able
% to output value}
% \begin{macrocode}
\@tempskipa#1\relax
% \end{macrocode}
% Now we test whether tracing information is required:
% \begin{macrocode}
\mult@info\z@
{Current page:\MessageBreak
height=%
\the\pagegoal: used \the\pagetotal
\space -> free=\the\page@free
\MessageBreak
needed \the\@tempskipa
\space(for #1)}%
% \end{macrocode}
% Our last action is to force a page break if there isn't enough
% room left.
% \begin{macrocode}
\ifdim \page@free <#1\newpage \fi
\fi}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\prepare@multicols}
% When preparing for multicolumn output several things must
% be done.
% \begin{macrocode}
\def\prepare@multicols{%
% \end{macrocode}
% We start saving the current |\@totalleftmargin| and then
% resetting the |\parshape| in case we are inside some list
% environment. The correct indentation for the \mc{} environment in
% such a case will be produced by moving the result to the right by
% |\multicol@leftmargin| later on. If we would use the value of
% |\@totalleftmargin| directly then lists inside the \mc{}
% environment could cause a shift of the output.
% \changes{v1.4l}{1992/08/17}{saved \cs{@totalleftmargin}}
% \begin{macrocode}
\multicol@leftmargin\@totalleftmargin
\@totalleftmargin\z@
\parshape\z@
% \end{macrocode}
% We also set the register |\doublecol@number| for later use. This
% register should contain $2\times |\col@number|$. This is also an
% indicator that we are within a \mc{} environment as mentioned
% above.
% \changes{v1.5a}{1992/11/04}{Add offset to \cs{doublecolnumber}}
% \begin{macrocode}
\doublecol@number\col@number
\multiply\doublecol@number\tw@
\advance\doublecol@number\mult@rightbox
% \end{macrocode}
%
% \begin{macrocode}
\if@boxedmulticols
\let\l@kept@firstmark\kept@firstmark
\let\l@kept@botmark\kept@botmark
\global\let\kept@firstmark\@empty
\global\let\kept@botmark\@empty
\else
% \end{macrocode}
% We add an empty box to the main vertical list to ensure that we
% catch any insertions (held over or inserted at the top of the
% page). Otherwise it might happen that the |\eject| is discarded
% without calling the output routine. Inside the output routine we
% remove this box again. Again this code applies only if we are on
% the main vertical list and not within a box.
% However, it is not enough to turn off interline spacing, we also
% have to clear |\topskip| before adding this box, since |\topskip|
% is always inserted before the first box on a page which would
% leave us with an extra space of |\topskip| if \mc{} start on a
% fresh sheet.
% \changes{v1.3c}{1991/03/03}{\cs{null} inserted and removed in output}
% \changes{v1.4a}{1992/02/11}{Conditional code for boxed mode added.}
% \changes{v1.4o}{1992/11/22}{\cs{topskip} locally zeroed.}
% \begin{macrocode}
\nointerlineskip {\topskip\z@\null}%
\output{%
\global\setbox\partial@page\vbox
{%
% \end{macrocode}
% Now we have to make sure that we catch one special situation which
% may result in loss of text! If the user has a huge amount of
% vertical material within the first optional argument that is larger
% then |\premulticols| and we are near the bottom of the page then it
% can happen that not the |\eject| is triggering this special output
% routine but rather the overfull main vertical list. In that case
% we get another breakpoint through the |\eject| penalty. As a result
% this special output routine would be called twice and the contents
% of |\partial@page|, i.e.\ the material before the \mc{}
% environment gets lost. There are several solutions to avoid this
% problem, but for now we will simply detect this and inform the user
% that he/she has to enlarge the |\premulticols| by using a suitable
% value for the second argument.
% \changes{v1.4a}{1992/02/11}{Checking for text losses.}
% \begin{macrocode}
%<*check>
\ifvoid\partial@page\else
\PackageError{multicol}%
{Error saving partial page}%
{The part of the page before
the multicols environment was
nearly full with^^Jthe result
that starting the environment
will produce an overfull
page. Some^^Jtext may be lost!
Please increase \premulticols
either generally or for this%
^^Jenvironment by specifying a
suitable value in the second
optional argument to^^Jthe
multicols environment.}
\unvbox\partial@page
\box\last@line
\fi
%</check>
\unvbox\@cclv
\global\setbox\last@line\lastbox
}%
% \end{macrocode}
% Finally we need to record the marks that are present within the
% |\partial@page| so that we can construct correct first and bottom
% marks later on. This is done by the following code.
% \changes{v1.4a}{1992/02/14}{kept marks initiated}
% \begin{macrocode}
\prep@keptmarks
% \end{macrocode}
% Finally we have to initialize |\kept@topmark| which should
% ideally be initialized with the mark that is current on ``top''
% of this page. Unfortunately we can't use |\topmark| because this
% register will not always contain what its name promises because
% \LaTeX{} sometimes calls the output routine for float
% management.\footnote{During such a call the \cs{botmark}
% gets globally copied to \cs{topmark} by the \TeX{}
% program.} Therefore we use the second best solution by
% initializing it with |\firstmark|. In fact, for our purpose this
% doesn't matter as we use |\kept@topmark| only to initialize
% |\firstmark| and |\botmark| of a following page if we don't find
% any marks on the current one.
% \changes{v1.4i}{1992/06/18}{\cs{kept@topmark} initialized.}
% \begin{macrocode}
\global\let\kept@topmark\firstmark
}\eject
% \end{macrocode}
% The next thing to do is to assign a new value to |\vsize|.
% \LaTeX{} maintains the free room on the page (i.e.\ the page
% height without the space for already contributed floats) in the
% register |\@colroom|. We must subtract the height of
% |\partial@page| to put the actual free room into this
% variable.
% \begin{macrocode}
\advance\@colroom-\ht\partial@page
% \end{macrocode}
% Then we have to calculate the |\vsize| value to use during column
% assembly. |\set@mult@vsize| takes an argument which allows to
% make the setting local (|\relax|) or global (|\global|). The
% latter variant is used inside the output routine below. At this
% point here we have to make a local change to |\vsize| because we
% want to get the original value for |\vsize| restored in case
% this \mc{} environment ends on the same page where it has started.
% \changes{v1.4p}{1992/11/26}{Use different \cs{vsize} setting}
% \changes{v1.4p}{1992/11/26}{Code moved to \cs{set@mult@vsize}}
% \begin{macrocode}
\set@mult@vsize\relax
% \end{macrocode}
% Now we switch to a new |\output| routine which will be used
% to put the gathered column material together.
% \begin{macrocode}
\output{\multi@column@out}%
% \end{macrocode}
% Finally we handle the footnote insertions. We have to multiply
% the magnification factor and the extra skip by the number of
% columns since each footnote reduces the space for every column
% (remember that we have page-wide footnotes). If, on the other
% hand, footnotes are typeset at the very end of the document, our
% scheme still works since |\count\footins| is zero then, so it
% will not change.
% To allow even further customization the setting of the |\footins|
% parameters is done in a separate macro.
% \changes{v1.5?}{1994/?/?}{Use \cs{init@mult@footins}}
% \begin{macrocode}
\init@mult@footins
% \end{macrocode}
% For the same reason (page-wide footnotes), the \meta{dimen}
% register controlling the maximum space used for footnotes isn't
% changed. Having done this, we must reinsert all the footnotes
% which are already present (i.e.\ those encountered when the
% material saved in |\partial@page| was first processed). This
% will reduce the free space (i.e.\ |\pagetotal|) by the
% appropriate amount since we have changed the magnification
% factor, etc.\ above.
% \begin{macrocode}
\reinsert@footnotes
% \end{macrocode}
% Inside \mc{} a |\clearpage| is fairly useless as we aren't supporting
% floats. In fact, it can cause harm as it doesn't know about the
% |\partial@page| and may therefore result in making columns too long.
% So we change that to behave like |\newpage| but also check if there
% are any deferred floats. If so, perhaps the user tried to place them through
% that |\clearpage| (but that needs to be done before starting the \mc{}
% environment.
% \changes{v1.8q}{2017/04/11}{Make \cs{clearpage} behave like \cs{newpage} (pr/4511)}
% \begin{macrocode}
\def\clearpage{%
\ifx\@deferlist\@empty\else
\PackageError{multicol}%
{Deferred floats not cleared}%
{A \string\clearpage\space inside multicols acts like
\string\newpage\space and doesn't clear floats.\MessageBreak
Move it before the multicols environment if you need it.}%
\fi
\newpage}%
% \end{macrocode}
% All the code above was only necessary for the unrestricted \mc{}
% version, i.e.\ the one that allows page breaks. If we are within
% a box there is no point in setting up special output routines or
% |\vsize|, etc.
% \begin{macrocode}
\fi
% \end{macrocode}
% But now we are coming to code that is necessary in all cases. We
% assign new values to |\vbadness|, |\hbadness| and |\tolerance|
% since it's rather hard for \TeX{} to produce `good' paragraphs
% within narrow columns.
% \changes{v1.2a}{1990/02/05}{\cs{vbadness} 10001 now.}
% \begin{macrocode}
\vbadness\@Mi \hbadness5000
\tolerance\multicoltolerance
% \end{macrocode}
% Since nearly always the first pass will fail we ignore it
% completely telling \TeX{} to hyphenate directly. In fact, we now
% use another register to keep the value for the multicol
% pre-tolerance, so that a designer may allow to use
% |\pretolerance|.
% \changes{v1.2a}{1990/02/05}{\cs{pretolerance} -1 because it nearly never
% succeeds.}
% \changes{v1.4e}{1992/03/20}{Using}
% \begin{macrocode}
\pretolerance\multicolpretolerance
% \end{macrocode}
% For use with the new \TeX{} we set |\emergencystretch| to
% $|\col@number| \times 4pt$. However this is only a guess
% so at the moment this is done in a macro
% |\setemergencystretch| which gets the current |\hsize|
% and the number of columns as arguments. Therefore users are able
% to figure out their own formula.
% \changes{v1.2a}{1990/02/05}{\cs{setemergencystretch} added.}
% \begin{macrocode}
\setemergencystretch\col@number\hsize
% \end{macrocode}
% Another hook to allow people adding their own extensions without
% making a new package is |\set@floatcmds| which handles any
% redefinitions of \LaTeX{}s internal float commands to work with
% the \mc{} environment. At the moment it is only used to redefine
% |\@dblfloat| and |\end@dblfloat|.
% \changes{v1.2a}{1990/02/05}{\cs{set@floatcmds} added.}
% \begin{macrocode}
\set@floatcmds
% \end{macrocode}
% Additionally, we advance |\baselineskip| by
% |\multicolbaselineskip| to allow corrections for narrow
% columns.
% \begin{macrocode}
\advance\baselineskip\multicolbaselineskip
% \end{macrocode}
% \changes{v1.0e}{1989/06/21}{\cs{textwidth} changed to \cs{linewidth}.}
% \changes{v1.0e}{1989/06/21}{So this file will
% work with the `twocolumn' command.}
% The |\hsize| of the columns is given by the formula:
% \[
% { |\linewidth| - (|\col@number|-1)
% \times
% |\columnsep|
% \over
% |\col@number|}
% \]
% The formula above has changed from release to release. We now
% start with the current value of |\linewidth| so that the column
% width is properly calculated when we are inside a minipage or a
% list or some other environment.
% This will be achieved with:
% \begin{macrocode}
\hsize\linewidth \advance\hsize\columnsep
\advance\hsize-\col@number\columnsep
\divide\hsize\col@number
% \end{macrocode}
% We also set |\linewidth| and |\columnwidth| to |\hsize| In the past
% |\columnwidth| was left unchanged. This is inconsistent,
% but |\columnwidth| is used only by floats (which
% aren't allowed in their current implementation) and by the
% |\footnote| macro. Since we want page-wide
% footnotes\footnote{I'm not sure that I really want page-wide
% footnotes. But balancing of the last page can
% only be achieved with this approach or with a
% multi-path algorithm which is complicated and
% slow. But it's a challenge to everybody to
% prove me wrong! Another possibility is to
% reimplement a small part of the {\it
% fire\_up\/} procedure in \TeX{} (the program).
% I think that this is the best solution if you
% are interested in complex page makeup, but it
% has the disadvantage that the resulting
% program cannot be called \TeX{} thereafter.}
% this simple trick saved us from rewriting the |\footnote|
% macros. However, some applications referred to |\columnwidth| as
% the ``width of the current column'' to typeset displays
% (the \texttt{amsmath} package, for example) and to allow the use
% of such applications together with \texttt{multicol} this is now
% changed.
%
% Before we change |\linewidth| to the new value we record its old
% value in some register called |\full@width|. This value is
% used later on when we package all columns together.
% \changes{v1.0e}{1989/06/21}{Setting of \cs{columnwidth} removed.}
% \changes{v1.5o}{1997/11/16}{Setting of \cs{columnwidth} added again
% pr/2664.}
% \begin{macrocode}
\full@width\linewidth
\linewidth\hsize
\columnwidth\hsize
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\init@mult@footins}
% This macro is used to set up the parameters associated
% with footnote floats. It can be redefined by applications that
% require different amount of spaces when typesetting footnotes.
% \begin{macrocode}
\def\init@mult@footins{%
\multiply\count\footins\col@number
\multiply\skip \footins\col@number
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\set@mult@vsize}
%
% Since we have to set |\col@umber| columns on one page,
% each with a height of |\@colroom|, we have to assign
% $
% |\vsize| = |\col@number| \times |\@colroom|
% $
% in order to collect enough material before entering the
% |\output| routine again. In fact we have to add another
% $
% (|\col@number|-1) \times (|\baselineskip|-|\topskip|)
% $
% if you think about it.
% \changes{v1.4p}{1992/11/26}{Macro added.}
% \begin{macrocode}
\def\set@mult@vsize#1{%
\vsize\@colroom
\@tempdima\baselineskip
\advance\@tempdima-\topskip
\advance\vsize\@tempdima
\vsize\col@number\vsize
\advance\vsize-\@tempdima
% \end{macrocode}
% But this might not be enough since we use |\vsplit| later to
% extract the columns from the gathered material. Therefore we add
% some `extra lines,' one for each column plus a corrective action
% depending on the value of the `\texttt{collectmore}' counter.
% The final value is assigned globally if |#1| is |\global| because
% we want to use this macro later inside the output routine too.
% \changes{v1.6c}{2003/04/08}{Collect one line per column more}
% \begin{macrocode}
\advance\vsize\col@number\baselineskip
#1\advance\vsize
\c@collectmore\baselineskip}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\multicol@leftmargin}
% Here is the dimen register we need for saving away the outer
% value of |\@totalleftmargin|.
% \begin{macrocode}
\newdimen\multicol@leftmargin
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@Mvi}
% In versions prior to 1.8r the balancing at the end of the
% environment was done by changing the output routine from
% |\multi@column@out| to |\balance@column@out|. As it turned out
% that this has a couple of issues when the last columns should not
% be balanced after all (for example because they contained several
% |\columnbreak| commands we now stay with one output routine for
% the environment and only signal that we reached the end of the
% environment by marking it with a special penalty that we can check
% for later.
% \changes{v1.8r}{2018/01/28}{Macro added}
% \begin{macrocode}
\mathchardef\@Mvi=10006 % 10005 is \columnbreak
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\endmulticols}
% When the end of the \mc{} environment is sensed we have to
% balance the gathered material. Depending on whether or not we are
% inside a boxed multicol different things must happen. But first
% we end the current paragraph with a |\par| command.
% \begin{macrocode}
\def\endmulticols{\par
\if@boxedmulticols
% \end{macrocode}
% In boxed mode we have to close the box in which we have gathered
% all material for the columns. But before we do this we need to
% remove any space at the end of the box as we don't want to use
% this in balancing. Because of the |\color@endgroup| this can't be
% done later in |\balance@columns| as the color command will hide
% it.
% \changes{v1.8c}{2013/11/03}{Add \cs{color@endgroup} to prevent color leak}
% \changes{v1.8f}{2014/06/19}{Discard spaces before adding \cs{color@endgroup}}
% \begin{macrocode}
\remove@discardable@items\color@endgroup\egroup
% \end{macrocode}
% Now we call |\balance@columns| the routine that balances material
% stored in the box |\mult@box|.
% \changes{v1.5?}{1994/?/?}{Splitting off zero box moved to
% \cs{balance@columns}}
% \begin{macrocode}
\balance@columns
% \end{macrocode}
% After balancing the result has to be returned by the command
% |\page@sofar|. But before we do this we reinsert any marks found
% in box |\mult@box|.
% \begin{macrocode}
\return@nonemptymark{first}%
\kept@firstmark
\return@nonemptymark{bot}%
\kept@botmark
\page@sofar
% \end{macrocode}
%
% \begin{macrocode}
\global\let\kept@firstmark
\l@kept@firstmark
\global\let\kept@botmark
\l@kept@botmark
%<*marktrace>
\mult@info\tw@
{Restore kept marks to\MessageBreak
first: \meaning\kept@firstmark
\MessageBreak bot\space\space:
\meaning\kept@botmark }%
%</marktrace>
% \end{macrocode}
% This finishes the code for the ``boxed'' case.
% \begin{macrocode}
\else
% \end{macrocode}
% If there was a |\columnbreak| on the very last line all material
% will have been moved to the |\colbreak@box|. Thus the galley
% will be empty and no output routine gets called so that the text
% is lost. To avoid this problem (though unlikely) we check if the
% current galley is empty and the |\colbreak@box| contains text and
% if so return that to the galley. If the galley is non-empty any
% material in |\colbreak@box| is added in the output routine since
% it needs to be put in front.
% \changes{v1.6d}{2003/04/17}{Catch problem with \cs{columnbreak} in
% last line}
% \begin{macrocode}
\ifdim\pagegoal=\maxdimen
\ifvoid\colbreak@box\else
\mult@info\@ne{Re-adding forced
break(s) for splitting}%
\unvbox\colbreak@box\fi
\fi
% \end{macrocode}
% If we are in an unrestricted \mc{} environment we end the current
% paragraph above with |\par| but this isn't sufficient since \TeX{}s
% {\it page\_builder} will not totally empty the contribution
% list.\footnote{This once caused a puzzling bug where some of the
% material was balanced twice, resulting in some overprints. The
% reason was the \cs{eject} which was placed at the end of
% the contribution list. Then the {\it page\_builder} was called
% (an explicit \cs{penalty} will empty the contribution
% list), but the line with the \cs{eject} didn't fit onto
% the current page. It was then reconsidered after the output
% routine had ended, causing a second break after one line.}
% Therefore we must also add an explicit |\penalty|. Now the
% contribution list will be emptied and, if its material doesn't
% all fit onto the current page then the output routine will be
% called before we change it.
% \changes{v1.3b}{1990/10/09}{Do \cs{penalty} with \cs{addpenalty}}
% \changes{v1.4e}{1992/03/16}{But ignore \cs{@nobreak} in \cs{addpenalty}}
% \changes{v1.5c}{1993/04/18}{Again use \cs{penalty}}
% At this point we need to use |\penalty| not |\addpenalty| to
% ensure that a) the recent contributions are emptied and b) that
% the very last item on the main vertical list is a valid break
% point so that \TeX{} breaks the page in case it is overfull.
% \begin{macrocode}
\penalty\z@
% \end{macrocode}
% Now it's safe to call the output routine in order to balance
% the columns. We do this by calling it with a special penalty.
% \changes{v1.8r}{2018/01/28}{Use special penalty to signal end of environment}
% \begin{macrocode}
\penalty-\@Mvi
% \end{macrocode}
% If the \mc{} environment body was completely empty or if a
% multi-page \mc{} just ends at a page boundary we have the unusual
% case that the |\eject| will have no effect (since the main
% vertical list is empty)---thus no output routine is called at
% all. As a result the material preceding the \mc{} (stored in
% |\partial@page| will get lost if we don't put this back by hand.
% \changes{v1.4m}{1992/09/04}{Check \cs{partial@page} being emptied}
% \begin{macrocode}
\ifvbox\partial@page
\unvbox\partial@page\fi
% \end{macrocode}
% After the output routine has acted we restore
% the kept marks to their initial value.
% \begin{macrocode}
\global\let\kept@firstmark\@empty
\global\let\kept@botmark\@empty
%<*marktrace>
\mult@info\tw@
{Make kept marks empty}%
%</marktrace>
\fi
% \end{macrocode}
% The output routine above will take care of the |\vsize| and
% reinsert the balanced columns, etc. But it can't reinsert the
% |\footnotes| because we first have to restore the
% |\footins| parameter since we are returning to one column
% mode. This will be done in the next line of code; we simply close
% the group started in |\multicols|.
%
% To fix an obscure bug which is the result of the current
% definition of the |\begin| \ldots\ |\end| macros, we check that
% we are still (logically speaking) in the \mc{} environment. If,
% for example, we forget to close some environment inside the
% \mc{} environment, the following |\endgroup| would be
% incorrectly considered to be the closing of this environment.
% \changes{v1.3c}{1991/03/14}{Check closing env.}
% \begin{macrocode}
\@checkend{multicols}%
\endgroup
% \end{macrocode}
% We also set the `\textsf{unbalance}' counter to its default. This is
% done globally since \LaTeX{} counters are always changed this
% way.\footnote{Actually, we are still in a group started by the
% \cs{begin} macro, so \cs{global} must be used
% anyway.}
% \begin{macrocode}
\global\c@unbalance\z@
% \end{macrocode}
% Now it's time to return any footnotes if we are in unrestricted
% mode. In boxed mode footnotes are kept inside, but in that case
% we have to write another column status into the \texttt{.aux}
% file to support \cs{docolaction} in case we have nested
% environments.
% \changes{v1.8s}{2018/04/20}{Support for \cs{docolaction} (issue/39)}
% \begin{macrocode}
\if@boxedmulticols
\mc@col@status@write
\else
\reinsert@footnotes
% \end{macrocode}
% We also take a look at the amount of free space on the current
% page to see if it's time for a page break. The vertical space
% added thereafter will vanish if |\enough@room| starts a new
% page.
%
% But there is one catch. If the |\end{multicols}| is at the top of
% which can happen if there is a break point just before it (such
% as end ending environment) which was chosen. In that case we
% would do the next page using the internal |\vsize| for multicol
% collection which is a disaster. So we better catch this
% case. Fortunately we can detect it by looking at |\pagegoal|.
% \changes{v1.5x}{2000/05/05}{Detect and fix problem if a multicols
% ends at the top of a page}
% \begin{macrocode}
\ifdim \pagegoal=\maxdimen
\global\vsize\@colroom
\else
\enough@room\postmulticols
\fi
\fi
\addvspace\multicolsep
% \end{macrocode}
% There is one more thing to do: the balanced result of the
% environment is supposed to have a |\prevdepth| of zero as we
% backed up by its real prevdepth within |\page@sofar|. However if
% the balancing happened in the output routine then \TeX{} reverts
% to the |\prevdepth| that was current before the OR once the OR has
% finished. In short |\prevdepth| is something you can't set
% globally it is alway local to the current list being built. Thus
% we need to set it back to zero here to avoid incorrect spacing.
% \changes{v1.8h}{2014/09/12}{Set \cs{prevdepdth} for current vlist
% when returning from multicols environment}
% \begin{macrocode}
\prevdepth\z@
% \end{macrocode}
% If statistics are required we finally report that we have
% finished everything.
% \begin{macrocode}
\mult@info\z@
{Ending environment
\if@boxedmulticols
\space(boxed mode)\fi
}}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\c@unbalance}
% \SpecialMainIndex{\c@collectmore}
% \SpecialMainIndex{\col@number}
% \SpecialMainIndex{\doublecol@number}
% \SpecialMainIndex{\premulticols}
% \SpecialMainIndex{\multicoltolerance}
% \SpecialMainIndex{\multicolpretolerance}
% \SpecialMainIndex{\page@free}
% \SpecialMainIndex{\premulticols}
% \SpecialMainIndex{\postmulticols}
% \SpecialMainIndex{\multicolsep}
% \SpecialMainIndex{\multicolbaselineskip}
% \SpecialMainIndex{\partial@page}
% Let us end this section by allocating all the registers used so
% far.
% \begin{macrocode}
\newcount\c@unbalance
\newcount\c@collectmore
% \end{macrocode}
% In the new \LaTeX{} release |\col@number| is already allocated by
% the kernel, so we don't allocate it again.
% \begin{macrocode}
%\newcount\col@number
\newcount\doublecol@number
\newcount\multicoltolerance
\newcount\multicolpretolerance
\newdimen\full@width
\newdimen\page@free
\newdimen\premulticols
\newdimen\postmulticols
\newskip\multicolsep
\newskip\multicolbaselineskip
\newbox\partial@page
\newbox\last@line
% \end{macrocode}
% And here are their default values:
% \begin{macrocode}
\c@unbalance = 0
\c@collectmore = 0
% \end{macrocode}
% To allow checking whether some macro is used within the \mc{}
% environment the counter |\col@number| gets a default of |1|
% outside the environment.
% \changes{v1.3d}{1991/10/23}{\cs{col@number} set to one}
% \changes{v1.8o}{2016/02/08}{\cs{col@number} already initialized in the
% kernel, so not initializing it in the package
% in case the document is in two-column (pr/4435)}
% \begin{macrocode}
%\col@number = 1
\multicoltolerance = 9999
\multicolpretolerance = -1
\premulticols = 50pt
\postmulticols= 20pt
\multicolsep = 12pt plus 4pt minus 3pt
\multicolbaselineskip=0pt
% \end{macrocode}
% \end{macro}
%
% \end{multicols}
%
% \begin{multicols}{2}[\subsection{The output routines}]
%
% We first start with some simple macros. When typesetting the page we
% save the columns either in the box registers 0, 2, 4,\ldots\
% (locally) or 1, 3, 5,\ldots\ (globally). This is \PlainTeX{} policy
% to avoid an overflow of the save stack.
%
% \begin{macro}{\process@cols}
% Therefore we define a |\process@cols| macro to help us in
% using these registers in the output routines below. It has two
% arguments: the first one is a number; the second one is the
% processing information. It loops starting with |\count@=#1|
% (|\count@| is a scratch register defined in \PlainTeX),
% processes argument |#2|, adds two to |\count@|,
% processes argument |#2| again, etc.\ until |\count@| is
% higher than |\doublecol@number|. It might be easier to
% understand it through an example, so we define it now and
% explain its usage afterwards.
% \begin{macrocode}
\def\process@cols#1#2{\count@#1\relax
\loop
%<*debug>
\typeout{Looking at box \the\count@}
%</debug>
#2%
\advance\count@\tw@
\ifnum\count@<\doublecol@number
\repeat}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\page@sofar}
% We now define |\page@sofar| to give an example of the
% |\process@cols| macro. |\page@sofar| should output everything
% prepared by the balancing routine |\balance@columns|.
% \begin{macrocode}
\def\page@sofar{%
% \end{macrocode}
% |\balance@columns| prepares its output in the even numbered
% scratch box registers.
% Now we output the columns gathered assuming that they are saved
% in the box registers 2 (left column), 4 (second column), \ldots\
% However, the last column (i.e.\ the right-most) should be saved in
% box register 0.\footnote{You will see the reason for this numbering
% when we look at the output routines
% \cs{multi@column@out} and
% \cs{balance@columns@out}.}
% First we ensure that the columns have equal width. We use
% |\process@cols| for this purpose, starting with
% $|\count@|=|\mult@rightbox|$. Therefore |\count@| loops through
% |\mult@rightbox|, $|\mult@rightbox| + 2$,\ldots
% (to |\doublecol@number|).
% \changes{v1.5a}{1992/11/04}{New box mechanism}
% \begin{macrocode}
\process@cols\mult@rightbox
% \end{macrocode}
% We have to check if the box in question is void, because the
% operation |\wd|\meta{number} on a void box will \emph{not} change
% its dimension (sigh).
% \changes{v1.5h}{1994/08/26}{Check for void boxes}
% \changes{v1.5i}{1994/10/02}{But don't remove original code.}
% \begin{macrocode}
{\ifvoid\count@
\setbox\count@\hbox to\hsize{}%
\else
\wd\count@\hsize
\fi}%
% \end{macrocode}
% Now we give some tracing information.
% \changes{v1.4l}{1992/08/17}{use \cs{multicol@leftmargin} instead of
% \cs{@totalleftmargin}}
% \changes{v1.6b}{2003/03/15}{Different info display}
% \begin{macrocode}
\count@\col@number \advance\count@\m@ne
\mult@info\z@
{Column spec: \the\full@width\space = indent
+ columns + sep =\MessageBreak
\the\multicol@leftmargin\space
+ \the\col@number\space
x \the\hsize\space
+ \the\count@\space
x \the\columnsep
}%
% \end{macrocode}
% At this point we should always be in vertical mode.
% \begin{macrocode}
\ifvmode\else\errmessage{Multicol Error}\fi
% \end{macrocode}
% Now we put all columns together in an |\hbox| of width
% |\full@width| (shifting it by |\multicol@leftmargin| to the right
% so that it will be placed correctly if we are within a list
% environment)
% and separating the columns with a rule if desired.
% \changes{v1.5a}{1992/11/04}{New box mechanism}
% \changes{v1.5z}{2000/07/10}{Ensure that column rule has always
% \cs{normalcolor}}
% \changes{v1.6f}{2006/09/19}{Make the color of the rule a hook}
% \changes{v1.4l}{1992/08/17}{use \cs{multicol@leftmargin} instead of
% \cs{@totalleftmargin}}
%
% The box containing the columns has a large height and thus will
% always result in using |\lineskip| if the normal |\baselineskip|
% calculations are used. We therefore better cancel that process.
% \changes{v1.5z1}{2003/02/17}{Suppress interline glue at this point}
% \begin{macrocode}
\nointerlineskip
% \end{macrocode}
% As mentioned earlier we want to have the reference point of the
% box we put on the page being at the baseline of the last line of
% the columns but we also want to ensure that the box has no depth
% so that any following skip is automatically starting from that
% baseline.
% We achieve this by recording the depths of all columns and then
% finally backing up by the maximum. (perhaps a simpler method
% would be to assemble the box in a register and set the depth of
% that box to zero (not checked).
%
% We need a global scratch register for this; using standard \TeX{}
% conventions we choose |\dimen2| and initialize it with the depth
% of the character ``p'' since that is one of the depths that
% compete for the maximum.
% \changes{v1.6a}{2003/03/15}{Preparing for adjusting \cs{prevdepth}}
% \begin{macrocode}
\setbox\z@\hbox{p}\global\dimen\tw@\dp\z@
\moveright\multicol@leftmargin
\hbox to\full@width{%
% \end{macrocode}
% If the document is written in a language that is typeset right-to-left
% then, of course, the multicol columns should be also typeset
% right-to-left. To support this we call |\mc@align@columns| which
% with execute different code depending on the typesetting direction.
% \changes{v1.7b}{2011/12/18}{RL language support fixed}
% \begin{macrocode}
\mc@align@columns
% \end{macrocode}
% The depths of the columns depend on their last lines. To ensure
% that we will always get a similar look as far as the rules are
% concerned we force the depth to be at least the depth of a
% letter~`p' (which is what we set |\dimen2| to above).
% \begin{macrocode}
\rlap{\phantom p}%
}%
% \end{macrocode}
% The processed material might consist of a last line with a
% descender in which case the |\prevdepth| will be
% non-zero. However, this material is getting reformatted now so
% that this value is likely to be wrong. We therefore normalize the
% situation by pretending that the depth is zero. However, if |\page@sofar|
% is being called inside the OR then setting |\prevdepth| here has
% no long-lasting effect, we therefore have to repeat this once we
% return to the main vertical list. Here we set it only for those
% cases where the command is used within a list and then followed by
% something else.
% \changes{v1.8g}{2014/08/24}{Resetting \cs{prevdepth} in the right place}
% \begin{macrocode}
\prevdepth\z@
% \end{macrocode}
% Now after typesetting the box we back up to its baseline by using
% the value stored in |\dimen2| (which will hold the largest depth
% found on any column).
% \changes{v1.8g}{2003/03/15}{Now adjusting \cs{prevdepth}}
% \begin{macrocode}
\kern-\dimen\tw@
% \end{macrocode}
% However, in case one of the columns was unusually deep \TeX{} may
% have tried some corrective actions in which case backing up by
% the saved value will not bring us back to the baseline. A good
% indication for this is a depth of |\@maxdepth| though it is not an
% absolute proof. If the option \texttt{grid} is used
% |\mc@gridwarn| will expand to this, otherwise to |\maxdimen| in
% which case this warning will not show up.
% \changes{v1.8g}{2014/08/24}{Warn if value is exceeded not when equal}
% \begin{macrocode}
\ifdim\dimen\tw@ > \mc@gridwarn
\PackageWarning{multicol}%
{Very deep columns!\MessageBreak
Grid alignment might be broken}%
\fi
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\columnseprulecolor}
% \changes{v1.6f}{2006/09/19}{Make the color of the rule a hook}
% By default the vertical rule between columns will be in |\normalcolor|.
% \begin{macrocode}
\def\columnseprulecolor{\normalcolor}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\reinsert@footnotes}
% Before we tackle the bigger output routines we define just one
% more macro which will help us to find our way through the
% mysteries later. |\reinsert@footnotes| will do what its name
% indicates: it reinserts the footnotes present in
% |\footinbox| so that they will be reprocessed by \TeX{}'s
% {\it page\_builder}.
%
% Instead of actually reinserting the footnotes we insert an empty
% footnote. This will trigger insertion mechanism as well and since
% the old footnotes are still in their box and we are on a fresh page
% |\skip| |footins| should be correctly taken into account.
% \changes{v1.3c}{1990/03/03}{\cs{unbox}ing avoided.}
% \begin{macrocode}
\def\reinsert@footnotes{\ifvoid\footins\else
\insert\footins{}\fi}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\vfilmaxdepth}
% This curious definition is used as the space at the bottom of a
% column if we implement |\raggedcolumns|. Normally one only appends
% |\vfill| in that case but this is actually wrong for columns that
% are more or less full: by adding a glue at the bottom such a
% column doesn't have any depth any more but without it the material
% would be allowed a depth of |\@maxdepth|. So we allow shrinking by
% that amount. This only makes a difference if the box would
% otherwise become overfull and shrinking never exceeds the
% specified value, so we should be fine.
% \changes{v1.8h}{2014/09/12}{Macro added (pr/4395)}
% \changes{v1.8j}{2015/03/07}{Use only `0.0001fil' for stretching}
% \changes{v1.8x}{2019/10/15}{Use \cs{@maxdepth} not \cs{maxdepth} (gh/190)}
% \begin{macrocode}
\def\vfilmaxdepth{\vskip \z@ \@plus .0001fil
\@minus \@maxdepth}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\multi@column@out}
% Now we can't postpone the difficulties any longer. The
% |\multi@column@out| routine will be called in two situations.
% Either the page is full (i.e., we have collected enough material
% to generate all the required columns) or a float or marginpar or
% a |\clearpage| is
% sensed. In the latter case the |\outputpenalty| is less
% than $-10000$, otherwise the penalty which triggered the output
% routine is higher. Therefore it's easy to distinguish both
% cases: we simply test this register.
% \changes{v1.5c}{1993/04/18}{Support \cs{clearpage}}
% \begin{macrocode}
\def\multi@column@out{%
\ifnum\outputpenalty <-\@M
% \end{macrocode}
% If this was a |\clearpage|, a float or a marginpar we call
% |\speci@ls|
% \begin{macrocode}
\speci@ls \else
% \end{macrocode}
% otherwise we construct the final page.
% \changes{v1.5u}{1999/05/25}{Support \cs{columnbreak}}
% \changes{v1.5v}{1999/07/18}{Added debug statements for
% column break support}
% For the next block of code see comments in section~\ref{sec:colbreak}.
% \begin{macrocode}
\ifvoid\colbreak@box\else
\mult@info\@ne{Re-adding forced
break(s) for splitting}%
\setbox\@cclv\vbox{%
\unvbox\colbreak@box
\penalty-\@Mv
\unvbox\@cclv}%
\fi
% \end{macrocode}
% Let us now consider the
% normal case. We have to |\vsplit| the columns from the
% accumulated material in box 255. Therefore we first assign
% appropriate values to |\splittopskip| and |\splitmaxdepth|.
% \begin{macrocode}
\splittopskip\topskip
\splitmaxdepth\@maxdepth
% \end{macrocode}
% We also need to restrict |\boxmaxdepth| so that re-boxing is not
% generating boxes with arbitrary depth.
% \changes{v1.8j}{2015/03/07}{Set \cs{boxmaxdepth}}
% \begin{macrocode}
\boxmaxdepth\@maxdepth
% \end{macrocode}
% Then we calculate the current column height (in |\dimen@|).
% Note that the height of |\partial@page| is already
% subtracted from |\@colroom| so we can use its value as a
% starter.
% \begin{macrocode}
\dimen@\@colroom
% \end{macrocode}
% But we must also subtract the space occupied by footnotes on the
% current page. Note that we first have to reset the skip register
% to its normal value.
% Again, the actual action is carried out in a utility macro, so that
% other applications can modify it.
% \changes{v1.5?}{1994/?/?}{Use \cs{leave@mult@footins}}
% \begin{macrocode}
\divide\skip\footins\col@number
\ifvoid\footins \else
\leave@mult@footins
\fi
% \end{macrocode}
% And there is one more adjustment that we have to make: if the
% user has issue a |\enlargethispage| command then the height the
% |\@kludgeins| box will be the negation of the size by which the
% page should be enlarged. If the star form of this command has
% been used then we also need to shrink the resulting column.
% That local change will be reverted at the end of the output
% routine So for the next page the original state will be
% reestablished. However, in theory there is a possibility to sneak
% in a whole multicols environment into the running header
% definition. If that happens then it will also be affected by this
% change---too bad I think.
% \changes{v1.8a}{2011/12/20}{Support for \cs{enlargethispage}}
% \changes{v1.8v}{2018/12/27}{Removed dead code, the case where this
% can go wrong is too obscure to worry about it (gh/101)}
% \begin{macrocode}
\ifvbox \@kludgeins
\advance \dimen@ -\ht\@kludgeins
% \end{macrocode}
% The star form of |\enlargethispage| makes the width of the box
% greater than zero (sneaky isn't it?).
% \begin{macrocode}
\ifdim \wd\@kludgeins>\z@
\shr@nkingtrue
\fi
\fi
% \end{macrocode}
% Now we are able to |\vsplit| off all but the last column.
% Recall that these columns should be saved in the box registers 2,
% 4,\ldots\ (plus offset).
% \changes{v1.5a}{1992/11/04}{New box mechanism}
% \begin{macrocode}
\process@cols\mult@gfirstbox{%
\setbox\count@
\vsplit\@cclv to\dimen@
% \end{macrocode}
% After splitting we update the kept marks.
% \begin{macrocode}
\set@keptmarks
% \end{macrocode}
% If |\raggedcolumns| is in force we add a |vfill| at the bottom by
% unboxing the split box.
% But we need to unbox anyway to ensure that at the end of the box
% we do not have unwanted space. This can sneak in in certain
% situations, for example, if two lists follow each other and we
% break between them. While such space is usually zero it still has
% an effect because it hides depth of the last line in the column
% and that will result in incorrect placement.
% \changes{v1.3c}{1990/03/03}{\cs{unbox}ing avoided.}
% \changes{v1.8b}{2013/08/28}{And 20odd years later conclude that
% this was wrong and unboxing is always needed.}
% \changes{v1.8b}{2013/08/28}{Remove discardable items at the
% end of split boxes}
% \changes{v1.8h}{2014/09/12}{Use \cs{vfilmaxdepth}}
% \changes{v1.8k}{2015/03/22}{\cs{remove@discardable@items} removed}
% \begin{macrocode}
\setbox\count@
\vbox to\dimen@
{\unvbox\count@
\ifshr@nking\vfilmaxdepth\fi}%
}%
% \end{macrocode}
% Then the last column follows.
% \changes{v1.5a}{1992/11/04}{New box mechanism}
% \changes{v1.8b}{2013/08/28}{Remove discardable items at the
% end of split boxes}
% \changes{v1.8h}{2014/09/12}{Use \cs{vfilmaxdepth}}
% \changes{v1.8k}{2015/03/22}{\cs{remove@discardable@items} removed}
% \begin{macrocode}
\setbox\mult@rightbox
\vsplit\@cclv to\dimen@
\set@keptmarks
\setbox\mult@rightbox\vbox to\dimen@
{\unvbox\mult@rightbox
\ifshr@nking\vfilmaxdepth\fi}%
% \end{macrocode}
% Having done this we hope that box 255 is emptied. If not, we
% reinsert its contents.
% \changes{v1.8a}{2011/12/20}{Only re-add output penalty if it was
% explicitly set}
% \begin{macrocode}
\ifvoid\@cclv \else
\unvbox\@cclv
\ifnum\outputpenalty=\@M
\else
\penalty\outputpenalty
\fi
% \end{macrocode}
% In this case a footnote that happens to fall into the leftover
% bit will be typeset on the wrong page. Therefore we warn the user
% if the current page contains footnotes. The older versions of
% \mc{} produced this warning regardless of whether or not
% footnotes were present, resulting in many unnecessary warnings.
% \changes{v1.3c}{1991/02/17}{Check if footnotes are actually present
% before issuing a warning.}
% \begin{macrocode}
\ifvoid\footins\else
\PackageWarning{multicol}%
{I moved some lines to
the next page.\MessageBreak
Footnotes on page
\thepage\space might be wrong}%
\fi
% \end{macrocode}
% If the `\textsf{tracingmulticols}' counter is 4 or higher we also
% add a rule.
% \begin{macrocode}
\ifnum \c@tracingmulticols>\thr@@
\hrule\allowbreak \fi
\fi
% \end{macrocode}
% To get a correct marks for the current page we have to (locally)
% redefine |\firstmark| and |\botmark|.
% If |\kept@firstmark| is non-empty then |\kept@botmark| must be
% non-empty too so we can use their values. Otherwise we use the
% value of |\kept@topmark| which was first initialized when we
% gathered the |\partical@page| and later on was updated to the
% |\botmark| for the preceding page.
%
% \changes{v1.4a}{1992/02/14}{\cs{botmark} set to \cs{splitbotmark}}
% \begin{macrocode}
\ifx\@empty\kept@firstmark
\let\firstmark\kept@topmark
\let\botmark\kept@topmark
\else
\let\firstmark\kept@firstmark
\let\botmark\kept@botmark
\fi
% \end{macrocode}
% We also initialize |\topmark| with |\kept@topmark|. This will make
% this mark okay for all middle pages of the \mc{} environment.
% \changes{v1.5d}{1993/09/15}{reinit \cs{topmark}}
% \begin{macrocode}
\let\topmark\kept@topmark
%<*marktrace>
\mult@info\tw@
{Use kept top mark:\MessageBreak
\meaning\kept@topmark
\MessageBreak
Use kept first mark:\MessageBreak
\meaning\kept@firstmark
\MessageBreak
Use kept bot mark:\MessageBreak
\meaning\kept@botmark
\MessageBreak
Produce first mark:\MessageBreak
\meaning\firstmark
\MessageBreak
Produce bot mark:\MessageBreak
\meaning\botmark
\@gobbletwo}%
%</marktrace>
% \end{macrocode}
% With a little more effort we could have done better. If we had,
% for example, recorded the shrinkage of the material in
% |\partial@page| it would be now possible to try higher
% values for |\dimen@| (i.e.\ the column height) to overcome
% the problem with the nonempty box 255. But this would make the
% code even more complex so I skipped it in the current
% implementation.
%
% Now we use \LaTeX{}'s standard output
% mechanism.\footnote{This will produce a lot of overhead since both
% output routines are held in memory. The correct
% solution would be to redesign the whole output
% routine used in \LaTeX.}
% Admittedly this is a funny way to do it.
%
% Within the OR |\boxmaxdepth| needs to be unrestricted so we set it back
% now as it was changed above.
% \changes{v1.8p}{2016/04/07}{Reset \cs{boxmaxdepth}}
% \begin{macrocode}
\boxmaxdepth\maxdimen
\setbox\@cclv\vbox{\unvbox\partial@page
\page@sofar}%
% \end{macrocode}
% The macro |\@makecol| adds all floats assigned for the current
% page to this page. |\@outputpage| ships out the resulting box.
% Note that it is just possible that such floats are present even
% if we do not allow any inside a \mc{} environment.
% \begin{macrocode}
\@makecol\@outputpage
% \end{macrocode}
% After the page is shipped out we have to prepare the kept marks
% for the following page. |\kept@firstmark| and |\kept@botmark|
% reinitialized by setting them to |\@empty|. The value of
% |\botmark| is then assigned to |\kept@topmark|.
% \changes{v1.4g}{1992/06/03}{Only change \cs{kept@topmark} if
% \cs{kept@botmark} non-empty}
% \changes{v1.4i}{1992/06/18}{Set \cs{kept@topmark} to \cs{botmark}}
% \begin{macrocode}
\global\let\kept@topmark\botmark
\global\let\kept@firstmark\@empty
\global\let\kept@botmark\@empty
%<*marktrace>
\mult@info\tw@
{(Re)Init top mark:\MessageBreak
\meaning\kept@topmark
\@gobbletwo}%
%</marktrace>
% \end{macrocode}
% Now we reset |\@colroom| to |\@colht| which is \LaTeX's
% saved value of |\textheight|.
% We also have to reset the recorded position of the last
% |\marginpar| as well as the recorded size of in-text floats
% as we are now on a new page.
% \changes{v1.8d}{2014/04/23}{Reset \cs{@mparbottom} after page finishes}
% \changes{v1.8n}{2015/08/19}{Reset \cs{@textfloatsheight} after page finishes}
% \begin{macrocode}
\global\@colroom\@colht
\global \@mparbottom \z@
\global \@textfloatsheight \z@
% \end{macrocode}
% Then we process deferred floats waiting for their chance to be
% placed on the next page.
% \begin{macrocode}
\process@deferreds
\@whilesw\if@fcolmade\fi{\@outputpage
\global\@colroom\@colht
\process@deferreds}%
% \end{macrocode}
% If the user is interested in statistics we inform him about the
% amount of space reserved for floats.
% \begin{macrocode}
\mult@info\@ne
{Colroom:\MessageBreak
\the\@colht\space
after float space removed
= \the\@colroom \@gobble}%
% \end{macrocode}
% Having done all this we must prepare to tackle the next page.
% Therefore we assign a new value to |\vsize|. New, because
% |\partial@page| is now empty and |\@colroom| might be
% reduced by the space reserved for floats.
% \changes{v1.4p}{1992/11/26}{Use different \cs{vsize} setting}
% \begin{macrocode}
\set@mult@vsize \global
% \end{macrocode}
% The |\footins| skip register will be adjusted when the output
% group is closed.
% \changes{v1.3c}{1991/03/03}{Unnecessary code removed}
% \begin{macrocode}
\fi}
% \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\leave@mult@footins}
% This macro is used to subtract the amount of space
% occupied by footnotes for the current space from the
% space available for the current column. The space current column
% is stored in |\dimen@|. See above for the description of the default
% action.
% \changes{v1.5?}{1994/?/?}{Macro added}
% \begin{macrocode}
\def\leave@mult@footins{%
\advance\dimen@-\skip\footins
\advance\dimen@-\ht\footins
}
% \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\speci@ls}
% We left out two macros: |\process@deferreds| and
% |\speci@ls|.
% \changes{v1.5c}{1993/04/18}{Support \cs{clearpage}}
% \begin{macrocode}
\def\speci@ls{%
\ifnum\outputpenalty <-\@Mi
% \end{macrocode}
% If the document ends in the middle of a multicols environment, e.g.,
% if the user forgot the |\end{multicols}|, \TeX{} adds a very
% negative penalty to the end of the galley which is intended to signal
% the output routine that it is time to prepare for shipping out
% everything remaining. Since inside multicols the output routine of
% \LaTeX{} is disabled sometimes we better check for this case: if we
% find a very negative penalty we produce an error message and run
% the default output routine for this case.
% \changes{v1.5s}{1998/09/10}{check for \cs{stop} penalty pr/2873}
% \begin{macrocode}
\ifnum \outputpenalty<-\@MM
\PackageError{multicol}{Document end
inside multicols environment}\@ehd
\@specialoutput
\else
% \end{macrocode}
% \changes{v1.5u}{1999/05/25}{Support \cs{columnbreak}}
% \changes{v1.5v}{1999/07/18}{Added debug statements for
% column break support}
% For the next block of code see comments in section~\ref{sec:colbreak}.
% \begin{macrocode}
\ifnum\outputpenalty = -\@Mv
\mult@info\@ne{Forced column
break seen}%
\global\advance\vsize-\pagetotal
\global\setbox\colbreak@box
\vbox{%
\ifvoid\colbreak@box
\else
\unvbox\colbreak@box
\penalty-\@Mv
\fi
% \end{macrocode}
% As this is the place of a forced break we now remove vertical
% white space just in front of it (or some of it at least) as it is
% quite likely that the break is not exactly in the right place,
% e.g., after a display environment (if LaTeX would break here by
% its own it would break before the space following the display).
%
% Thus we rebox box 255 once (using |\@maxdepth| and calling
% |\remove@discardable@items| inside). The depth of 255 will then
% give us the depth the box would have had if it would have been a
% natural break. We then unbox 255 to get it into the
% |\colbreak@box| and then back up by this depth. This will position
% the bottom of the box at its natural baseline which is useful for
% balancing later on.
% \changes{v1.8k}{2015/03/21}{Remove discardable items just before a
% forced break}
% \changes{v1.8x}{2019/10/15}{Use \cs{@maxdepth} not \cs{maxdepth} (gh/190)}
% \begin{macrocode}
\boxmaxdepth\@maxdepth
\setbox\@cclv\vbox{%
\unvbox\@cclv
\remove@discardable@items}%
\dimen@\dp\@cclv
\unvbox\@cclv
\kern-\dimen@
}%
\reinsert@footnotes
\else
% \end{macrocode}
% Another special case is reaching the end of the \mc{}
% environment which is signaled by |-\@Mvi|.
% \changes{v1.8r}{2018/01/28}{Handling end of env through special penalty}
% \begin{macrocode}
\ifnum\outputpenalty = -\@Mvi
\mult@info\@ne{End penalty of multicols seen}%
% \end{macrocode}
% If we are at this point then we have to run the balancing code
% (which was previously its own output routine). First we pretend
% that we had a normal forced breakpoint and then call
% |\balance@column@out|. The latter may be let to |\multi@column@out|
% if we are inside \texttt{multicols*} in which case we would get a loop
% if the |\outputpenalty| is not changed---this could be cleaned up
% in a better way; basically it is like this, because of the older
% code was using different ORs and I simply reused most of it.
% \begin{macrocode}
\outputpenalty\@M % pretend we had a natural forced break
\balance@columns@out
\else
% \end{macrocode}
% If we encounter a float or a marginpar in the current
% implementation we simply warn the user that this is not allowed.
% Then we reinsert the page and its footnotes.
% \begin{macrocode}
\PackageWarningNoLine{multicol}%
{Floats and marginpars not
allowed inside `multicols'
environment!}%
\unvbox\@cclv\reinsert@footnotes
% \end{macrocode}
% Additionally we empty the |\@currlist| to avoid later error
% messages when the \LaTeX{} output routine is again in force.
% But first we have to place the boxes back onto the
% |\@freelist|. (|\@elt|s default is |\relax| so
% this is possible with |\xdef|.)
% \changes{v1.2a}{1990/02/05}{Float boxes freed.}
% \begin{macrocode}
\xdef\@freelist{\@freelist\@currlist}%
\gdef\@currlist{}%
\fi
\fi
\fi
% \end{macrocode}
% If the penalty is $-10001$ it will come from a |\clearpage| and
% we will execute |\@doclearpage| to get rid of any deferred
% floats.
% \begin{macrocode}
\else \@doclearpage \fi
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\process@deferreds}
% |\process@deferreds| is a simplified version of \LaTeX{}'s
% |\@startpage|. We first call the macro
% |\@floatplacement| to save the current user parameters in
% internal registers. Then we start a new group and save the
% |\@deferlist| temporarily in the macro |\@tempb|.
% \begin{macrocode}
\def\process@deferreds{%
\@floatplacement
\@tryfcolumn\@deferlist
\if@fcolmade\else
\begingroup
\let\@tempb\@deferlist
% \end{macrocode}
% Our next action is to (globally) empty |\@deferlist| and
% assign a new meaning to |\@elt|. Here |\@scolelt| is a
% macro that looks at the boxes in a list to decide whether they
% should be placed on the next page (i.e.\ on |\@toplist| or
% |\@botlist|) or should wait for further processing.
% \begin{macrocode}
\gdef\@deferlist{}%
\let\@elt\@scolelt
% \end{macrocode}
% Now we call |\@tempb| which has the form
% \begin{center}
% |\@elt|\meta{box register}|\@elt|^^A
% \meta{box register}\ldots{}
% \end{center}
% So |\@elt| (i.e.\ |\@scolelt|) will distribute the
% boxes to the three lists.
% \begin{macrocode}
\@tempb \endgroup
\fi}
% \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{ifshr@nking}
% \begin{macro}{\raggedcolumns}
% \begin{macro}{\flushcolumns}
% \changes{v1.1a}{1989/09/20}{\cs{flushedcolumns} renamed to \cs{flushcolumns}.}
% The |\raggedcolumns| and |\flushcolumns|
% declarations are defined with the help of a new |\if...|
% macro.
% \begin{macrocode}
\newif\ifshr@nking
% \end{macrocode}
% The actual definitions are simple: we just switch to \textsf{true}
% or \textsf{false} depending on the desired action. To avoid extra
% spaces in the output we enclose these changes in
% |\@bsphack|\ldots{}\allowbreak|\@esphack|.
% \begin{macrocode}
\def\raggedcolumns{%
\@bsphack\shr@nkingtrue\@esphack}
\def\flushcolumns{%
\@bsphack\shr@nkingfalse\@esphack}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
%
% \begin{macro}{\balance@columns@out}
% Now for the last part of the show: the column balancing output
% routine. Since this code is called with an explicit penalty
% (|\eject|) there is no need to check for something special (eg
% floats). We start by balancing the material gathered.
% \begin{macrocode}
\def\balance@columns@out{%
% \end{macrocode}
% For this we need to put the contents of box 255 into |\mult@box|.
% \changes{v1.5u}{1999/05/25}{Support \cs{columnbreak}}
% \changes{v1.5v}{1999/07/18}{Added debug statements for column break
% support} For the next block of code see also comments in
% section~\ref{sec:colbreak}. All forced breaks except the last are
% inside |\colbreak@box| so all we have to do is to concatenate this
% box with box |\@cclv| and put a penalty in between. Here we test if
% |\colbreak@box| is void so that the message is only generated if
% we really add forced breaks and the penalty.
% \changes{v1.8k}{2015/03/21}{Use \cs{@Mv} and not \cs{break} in case
% this forced break is not used on this page}
% \begin{macrocode}
\setbox\mult@box\vbox{%
\ifvoid\colbreak@box\else
\unvbox\colbreak@box
\penalty-\@Mv
\mult@info\@ne{Re-adding
forced break(s) in balancing}%
\fi
\unvbox\@cclv
% \end{macrocode}
% The last column again is a forced break, so here we discard white
% space as well as that is normally unwanted.
% \changes{v1.8k}{2015/03/21}{Add \cs{remove@discardable@items} at the
% end of the last column when balancing.}
% \begin{macrocode}
\remove@discardable@items
}%
\balance@columns
% \end{macrocode}
% If during balancing the columns got too long the flag
% |\iftoo@bad| is set to true.
% \changes{v1.8a}{2011/12/20}{Balancing concept improved}
% \begin{macrocode}
\iftoo@bad
\mult@info\@ne
{Balancing failed ...
cut a normal page}%
% \end{macrocode}
% In that case we put the material back in box 255 so that we can
% cut a normal page. The curious set of
% |\vskip|s we add is necessary to cancel out the |\splittopskip|
% that got added for balancing.
% \begin{macrocode}
\setbox\@cclv\vbox
{\vskip\topskip
\vskip-\splittopskip
\unvbox\mult@box
% \end{macrocode}
% We also have to re-add the end of environment penalty since after
% this page we may want balance the remaining material.
% \changes{v1.8r}{2018/01/28}{Re-add the final penalty}
% \begin{macrocode}
\penalty-\@Mvi
}%
% \end{macrocode}
% We then call the standard multicol output routine which will
% produce a normal page for us (remember we are still within the
% OR so some part of the code in |\multi@column@out| is actually not
% doing anything---perhaps this should be cleaned up at some point).
% This also means that if there was an |\enlargethispage| present
% it will apply to this page as |\multi@column@out| will look at
% the status of |\@kludgeins|.
% \begin{macrocode}
\multi@column@out
% \end{macrocode}
% Because balancing made the columns too long we are sure that there
% will be some material remaining which was put back onto the main
% vertical list by |\multi@column@out|. This will also put the
% explicit |\eject| penalty back so the current
% |\balance@columns@out| output routine will be called again (so we
% better do not add another penalty or else the OR will be called
% twice and we may get scrambled results).
% \changes{v1.8k}{2015/03/21}{No additional penalty here}
% \begin{macrocode}
\else
% \end{macrocode}
% If the balancing went ok, we are in the position
% to apply |\page@sofar|. But first we have to set |\vsize| to a
% value suitable for one column output.
% \begin{macrocode}
\global\vsize\@colroom
\global\advance\vsize\ht\partial@page
% \end{macrocode}
% We also have to look at |\@kludgeins| and generate a new
% |\insert| in case there was one present due to an
% |\enlargethispage| command.
% \changes{v1.8a}{2011/12/20}{Support for \cs{enlargethispage}}
% \begin{macrocode}
\ifvbox\@kludgeins\insert\@kludgeins
{\unvbox\@kludgeins}\fi
% \end{macrocode}
% Then we |\unvbox| the |\partial@page| (which may be void if we
% are not processing the first page of this \mc{} environment.
% \begin{macrocode}
\unvbox\partial@page
% \end{macrocode}
% Then we return the first and bottom mark and the gathered
% material to the main vertical list.
% \begin{macrocode}
\return@nonemptymark{first}\kept@firstmark
\return@nonemptymark{bot}\kept@botmark
\page@sofar
% \end{macrocode}
% We need to add a penalty at this point which allows to break at
% this point since calling the output routine may have removed the
% only permissible break point thereby ``glueing'' any following
% skip to the balanced box. In case there are any weird settings
% for |\multicolsep| etc. this could produce funny results.
% \changes{v1.5c}{1993/04/18}{added penalty at output routine exit}
% \begin{macrocode}
\penalty\z@
\fi
}
% \end{macrocode}
% As we already know, reinserting of footnotes will be done in the
% macro |\endmulticols|.
% \end{macro}
%
%
% \begin{macro}{\balance@columns}
% This macro now does the actual balancing.
% \begin{macrocode}
\def\balance@columns{%
% \end{macrocode}
% We start by setting the kept marks by updating them with any
% marks from this box. This has to be done \emph{before} we add a
% penalty of $-10000$ to the top of the box, otherwise only an
% empty box will be considered.
% \changes{v1.5h}{1994/08/26}{Get kept marks first}
% \begin{macrocode}
\get@keptmarks\mult@box
% \end{macrocode}
% We then continue by resetting trying to remove any discardable
% stuff at the end of |\mult@box|. This is rather experimental. We
% also add a forced break point at the very beginning, so that we
% can split the box to height zero later on, thereby adding a known
% |\splittopskip| glue at the beginning.
% \changes{v1.8k}{2015/03/21}{\cs{remove@discardable@items} removed}
% \begin{macrocode}
\setbox\mult@box\vbox{%
\penalty-\@M
\unvbox\mult@box
}%
% \end{macrocode}
% Then follow values assignments to get the |\vsplit|ting right.
% We use the natural part of |\topskip| as the natural part for
% |\splittopskip| and allow for a bit of undershoot and overshoot
% by adding some stretch and shrink.
% \changes{v1.5?}{1994/?/?}{Allow columns to come out a bit long or short}
% \changes{v1.8x}{2019/10/15}{Use \cs{@maxdepth} not \cs{maxdepth} (gh/190)}
% \begin{macrocode}
\@tempdima\topskip
\splittopskip\@tempdima
\@plus\multicolundershoot
\@minus\multicolovershoot
\splitmaxdepth\@maxdepth
% \end{macrocode}
% We also have to set |\boxmaxdepth| which normally allows to
% build boxes with arbitrary depth, but as we are building text
% columns we really want to restrict the depth. This is necessary as
% we sometimes rebox the boxes generated by |\vsplit| and then the
% restriction posed by |\splitmaxdepth| gets lost.
% \changes{v1.8h}{2014/09/12}{All column boxes should obey
% \cs{maxdepth} (pr/4395)}
% \changes{v1.8x}{2019/10/15}{Use \cs{@maxdepth} not \cs{maxdepth} (gh/190)}
% \begin{macrocode}
\boxmaxdepth\@maxdepth
% \end{macrocode}
% The next step is a bit tricky: when \TeX{} assembles material in
% a box, the first line isn't preceded by interline glue, i.e.
% there is no parameter like |\boxtopskip| in \TeX{}. This means
% that the baseline of the first line in our box is at some
% unpredictable point depending on the height of the largest
% character in this line. But of course we want all columns to
% align properly at the baselines of their first lines. For this
% reason we have opened |\mult@box| with a |\penalty| \textsf{-10000}.
% This will now allow us to split off from |\mult@box| a tiny bit
% (in fact nothing since the first possible break-point is the
% first item in the box). The result is that |\splittopskip| is
% inserted at the top of |\mult@box| which is exactly what we like
% to achieve.
% \changes{v1.5?}{1994/?/?}{Do splitting to zero here}
% \begin{macrocode}
\setbox\@tempboxa\vsplit\mult@box to\z@
% \end{macrocode}
% Next we try to find a suitable starting point for the calculation
% of the column height. It should be less than the height finally
% chosen, but large enough to reach this final value in only a few
% iterations. The formula which is now implemented will try to
% start with the nearest value which is a multiple of
% |\baselineskip|. The coding is slightly tricky in \TeX{} and
% there are perhaps better ways \ldots
% \changes{v1.4d}{1992/03/04}{New algorithm for start height}
% \begin{macrocode}
\@tempdima\ht\mult@box
\advance\@tempdima\dp\mult@box
\divide\@tempdima\col@number
% \end{macrocode}
% The code above sets |\@tempdima| to the length of a column if we
% simply divide the whole box into equal pieces. To get to the next
% lower multiple of |\baselineskip| we convert this dimen to a
% number (the number of scaled points) then divide this by
% |\baselineskip| (also in scaled points) and then multiply this
% result with |\baselineskip| assigning the result to |\dimen@|.
% This makes |\dimen@| $\leq$ to |\@tempdimena|.
% \begin{macrocode}
\count@\@tempdima
\divide\count@\baselineskip
\dimen@\count@\baselineskip
% \end{macrocode}
% Next step is to correct our result by taking into account the
% difference between |\topskip| and |\baselineskip|. We start by
% adding |\topskip|; if this makes the result too large then we
% have to subtract one |\baselineskip|.
% \begin{macrocode}
\advance\dimen@\topskip
\ifdim \dimen@ >\@tempdima
\advance\dimen@-\baselineskip
\fi
% \end{macrocode}
% As a further restriction we want to see a minimum number of
% rows in the balanced result based on the setting of the counter
% |minrows|. If the starting value is lower we adjust.
% \changes{v1.8w}{2019/03/01}{Provide minrows counter for balancing}
% \begin{macrocode}
\@tempdima\dimexpr
\topskip +\c@minrows\baselineskip-\baselineskip\relax
\ifnum\dimen@<\@tempdima
\mult@info\@ne
{Start value
\the\dimen@ \space ->
\the\@tempdima \space (corrected for minrows)}%
\dimen@\@tempdima
\fi
% \end{macrocode}
% At the user's request we start with a higher value (or lower, but
% this usually only increases the number of tries).
% \begin{macrocode}
\advance\dimen@\c@unbalance\baselineskip
% \end{macrocode}
% We type out statistics if we were asked to do so.
% \changes{v1.4f}{1992/04/28}{\cs{on@line} added to tracing info}
% \begin{macrocode}
\mult@info\@ne
{Balance columns\on@line:
\ifnum\c@unbalance=\z@\else
(off balance=\number\c@unbalance)\fi
\@gobbletwo}%
% \end{macrocode}
% But we don't allow nonsense values for a start.
% \begin{macrocode}
\ifnum\dimen@<\topskip
\mult@info\@ne
{Start value
\the\dimen@ \space ->
\the\topskip \space (corrected)}%
\dimen@\topskip
\fi
% \end{macrocode}
% Now we try to find the final column height. We start by setting
% |\vbadness| to infinity (i.e.\ $10000$) to suppress
% underfull box reports while we are trying to find an acceptable
% solution. We do not need to do it in a group since at the end of
% the output routine everything will be restored. The setting of
% the final columns will nearly always produce underfull boxes with
% badness $10000$ so there is no point in warning the user about
% it.
% \changes{v1.2a}{1990/02/05}{Group around main loop removed.}
% \begin{macrocode}
\vbadness\@M
% \end{macrocode}
% We also allow for overfull boxes while we trying to split the
% columns. They can easily happen if we have objects with unusual depth.
% \changes{v1.8h}{2014/09/12}{Do not report overfull}
% \begin{macrocode}
\vfuzz \maxdimen
% \end{macrocode}
% The variable |\last@try| will hold the dimension used in the
% previous trial splitting. We initialize it with a negative value.
% \changes{v1.5?}{1994/?/?}{Initialize \cs{last@try}}
% \begin{macrocode}
\last@try-\p@
\loop
% \end{macrocode}
% In order not to clutter up \TeX{}'s valuable main memory with
% things that are no longer needed, we empty all globally used box
% registers. This is necessary if we return to this point after an
% unsuccessful trial. We use |\process@cols| for this purpose,
% starting with |\mult@grightbox|. Note the extra braces around
% this macro call. They are needed since \PlainTeX{}'s
% |\loop|\ldots{}\allowbreak|\repeat| mechanism cannot be nested on
% the same level of grouping.
% \changes{v1.5a}{1992/11/04}{New box mechanism}
% \begin{macrocode}
{\process@cols\mult@grightbox
{\global\setbox\count@
\box\voidb@x}}%
% \end{macrocode}
% The contents of box |\mult@box| are now copied globally to
% box~|\mult@grightbox|. (This will be the right-most column, as
% we shall see later.)
% \begin{macrocode}
\global\setbox\mult@grightbox
\copy\mult@box
% \end{macrocode}
% We start with the assumption that the trial will be successful.
% If we end up with a solution that is too bad we set
% |too@bad| to \texttt{true}. We also assume that all forced breaks
% (if any) will be used during balancing. If this is not the case
% we record this in |forcedbreak@leftover|.
% \changes{v1.5b}{1992/11/05}{New badness mechanism}
% \changes{v1.8k}{2015/03/21}{Init \cs{ifforcedbreak@leftover}}
% \begin{macrocode}
%<*badness>
\too@badfalse
\forcedbreak@leftoverfalse
%</badness>
% \end{macrocode}
% Using |\vsplit| we extract the other columns from box register
% |\mult@grightbox|. This leaves box register |\mult@box|
% untouched so that we can start over again if this trial was
% unsuccessful.
% \begin{macrocode}
{\process@cols\mult@firstbox{%
\global\setbox\count@
\vsplit\mult@grightbox to\dimen@
% \end{macrocode}
% After splitting we need to ensure that there isn't any space at
% the bottom, so we rebox once more.
% \changes{v1.8b}{2013/08/28}{Remove discardable items at the
% end of split boxes}
% \changes{v1.8k}{2015/03/21}{Do not use \cs{remove@discardable@items}
% here}
% \begin{macrocode}
\global\setbox\count@
\vbox to\dimen@
{\unvbox\count@}%
% \end{macrocode}
% After every split we check the badness of the resulting column,
% normally the amount of extra white in the column.
% \begin{macrocode}
%<*badness>
\ifnum\c@tracingmulticols>\@ne
\@tempcnta\count@
\advance\@tempcnta-\mult@grightbox
\divide\@tempcnta \tw@
\message{^^JColumn
\number\@tempcnta\space
badness: \the\badness\space}%
\fi
% \end{macrocode}
% If this badness is larger than the allowed column badness
% we reject this solution by setting |too@bad| to \texttt{true}.
% \begin{macrocode}
\ifnum\badness>\c@columnbadness
\ifnum\c@tracingmulticols>\@ne
\message{too bad
(>\the\c@columnbadness)}%
\fi
\too@badtrue
\fi
%</badness>
}}%
% \end{macrocode}
% There is one subtle point here: while all other constructed boxes
% have a depth that is determined by |\splitmaxdepth| and/or
% |\boxmaxdepth| the last box
% will get a natural depth disregarding the original setting and
% the value of |\splitmaxdepth| or |\boxmaxdepth|. This means that
% we may end up with a very large depth in box |\mult@grightbox|
% which would
% make the result of the testing incorrect. So we change the value
% by unboxing the box into itself.
% \begin{macrocode}
\global\setbox\mult@grightbox
\vbox{\unvbox\mult@grightbox}%
% \end{macrocode}
% We also save a copy |\mult@firstbox| at its ``natural'' size
% for later use.
% \begin{macrocode}
\setbox\mult@nat@firstbox
\vbox{\unvcopy\mult@firstbox}%
% \end{macrocode}
% After |\process@cols| has done its job we have the following
% situation:
% \begin{center}
% \begin{tabular}{r@{$\:\:\longleftarrow\:\:$}l}
% box |\mult@rightbox| & all material \\
% box |\mult@gfirstbox| & first column \\
% box |\mult@gfirstbox|${}+2$ & second column \\
% \multicolumn{1}{c}{$\vdots$} &
% \multicolumn{1}{c}{$\vdots$} \\
% box |\mult@grightbox| & last column
% \end{tabular}
% \end{center}
% We report the height of the first column, in brackets
% the natural size is given.
% \changes{v1.5?}{1994/?/?}{Show natural size}
% \begin{macrocode}
\ifnum\c@tracingmulticols>\@ne
\message{^^JFirst column
= \the\dimen@\space
(\the\ht\mult@nat@firstbox)}\fi
% \end{macrocode}
% If |\raggedcolumns| is in force older releases of this file also
% shrank the first column to its natural height at this point.
% This was done so that the first column doesn't run short compared
% to later columns but it is actually producing incorrect results
% (overprinting of text) in boundary cases, so since version v1.5q
% |\raggedcolumns| means allows for all columns to run slightly short.
% \changes{v1.5q}{1998/01/19}{Do not reset \cs{mult@firstbox} (pr2739)}
% \begin{macrocode}
% \ifshr@nking
% \global\setbox\mult@firstbox
% \copy\mult@nat@firstbox
% \fi
% \end{macrocode}
% Then we give information about the last column.\footnote{With
% \TeX{} version 3.141 it is now possible to use \LaTeX's
% \cs{newlinechar} in the \cs{message} command, but
% people with older \TeX{} versions will now get
% \texttt{\string^\string^J} instead of a new line on the screen.}
% \changes{v1.4a}{1992/02/12}{Changed to proper \cs{endlinechar} in\cs{message}}
% \begin{macrocode}
\ifnum\c@tracingmulticols>\@ne
\message{<> last column =
\the\ht\mult@grightbox^^J}%
% \end{macrocode}
% Some tracing code that we don't compile into the production version
% unless asked for. It will produce huge listings of the boxes
% involved in balancing in the transcript file.
% \changes{v1.6f}{2004/07/03}{need to use \cs{mult@grightbox} in the loop}
% \begin{macrocode}
%<*debug>
\ifnum\c@tracingmulticols>4
{\showoutput
\batchmode
\process@cols\mult@grightbox
{\showbox\count@}}%
\errorstopmode
\fi
%</debug>
\fi
% \end{macrocode}
% We check whether our trial was successful. The test used is very
% simple: we merely compare the first and the last column. Thus
% the intermediate columns may be longer than the first if
% |\raggedcolumns| is used. If the right-most column is
% longer than the first then we start over with a larger value for
% |\dimen@|.
% \changes{v1.3c}{1991/03/03}{\cs{global}\cs{advance} left over from older code}
% \begin{macrocode}
\ifdim\ht\mult@grightbox >\dimen@
% \end{macrocode}
% If the height of the last box is too large we mark this trial as
% unsuccessful.
% \changes{v1.5v}{1999/07/18}{Added tracing statements for
% trial unsuccessful}
% \begin{macrocode}
%<*badness>
\too@badtrue
\ifnum\c@tracingmulticols>\@ne
\typeout{Rejected: last
column too large!}%
\fi
\else
% \end{macrocode}
% \changes{v1.5v}{1999/07/18}{Check last column if it contains forced
% break and reject trial if that is the case}
%
% To ensure that there isn't a forced break in the last column we
% try to split off a box of size |\maxdimen| from |\mult@grightbox|
% (or rather from a copy of it). This should result in a void box
% after the split, unless there was a forced break somewhere within
% the column in which case the material after the break would have
% stayed in the box.
% \begin{macrocode}
\setbox\@tempboxa
\copy\mult@grightbox
\setbox\z@\vsplit\@tempboxa to\maxdimen
\ifvoid\@tempboxa
% \end{macrocode}
% Thus if |\@tempboxa| is void we have a valid solution.
% In this case we take a closer
% look at the last column to decide if this column should be made
% as long as all other columns or if it should be allowed to be
% shorter.
% For this we first have to rebox the column into a box of the
% appropriate height. If tracing is enabled we then display the
% badness for this box.
% \begin{macrocode}
\global\setbox\mult@grightbox
\vbox to\dimen@
{\unvbox\mult@grightbox}%
\ifnum\c@tracingmulticols>\@ne
\message{Final badness:
\the\badness}%
\fi
% \end{macrocode}
% We then compare this badness with the allowed badness for the final
% column. If it does not exceed this value we use the box, otherwise
% we rebox it once more and add some glue at the bottom.
% \changes{v1.8h}{2014/09/12}{Use \cs{vfilmaxdepth}}
% \changes{v1.8j}{2015/03/07}{Use \cs{vfil} in this case}
% \begin{macrocode}
\ifnum\badness>\c@finalcolumnbadness
\global\setbox\mult@grightbox
\vbox to\dimen@
{\unvbox\mult@grightbox\vfil}%
\ifnum\c@tracingmulticols>\@ne
\message{ setting natural
(> \the\c@finalcolumnbadness)}%
\fi
\fi
% \end{macrocode}
% If |\@tempboxa| above was not void our trial was unsuccessful and
% we report this fact and try again.
% \changes{v1.6f}{2004/07/03}{\texttt{/colbreak} guard in the wrong position}
% \begin{macrocode}
\else
% \end{macrocode}
% If we have unprocessed forced breaks we normally reiterate with a
% larger column size to fit them in eventually. However, if there
% are simply too many of them (e.g., 3 forced breaks but only 2
% columns to balance) then this will never succeed and we would
% continue growing the columns until we hit the largest possible
% column size. So in addition we check how big the column size is
% compared to available room and if we exceed this by
% |\maxbalancingoverflow| we give up and instead of balancing cut
% another normal page. To be indicate this case we set
% |forcedbreak@leftover| to true.
% \changes{v1.8k}{2015/03/21}{Watch out for columns growing too far in
% case of forced breaks}
% \changes{v1.8l}{2015/03/25}{Added additional tracing if column overflows}
% \begin{macrocode}
\@tempdima\@colroom
\advance\@tempdima \maxbalancingoverflow
\ifdim \dimen@ < \@tempdima
\too@badtrue
\ifnum\c@tracingmulticols>\@ne
\typeout{Rejected: unprocessed
forced break(s) in last column!}%
\fi
\else
\forcedbreak@leftovertrue
\ifnum\c@tracingmulticols>\@ne
\typeout{Failed: columns too large
with unprocessed forced break(s)!}%
\fi
\fi
\fi
\fi
% \end{macrocode}
% If the natural height of the first box is smaller than the
% current trial size but is larger than the previous trial size it
% is likely that we have missed a potentially better
% solution. (This could have happened if for some reason our first
% trial size was too high.) In that case we dismiss this trial and
% restart using the natural height for the next trial.
% \begin{macrocode}
\ifdim\ht\mult@nat@firstbox<\dimen@
\ifdim\ht\mult@nat@firstbox>\last@try
\too@badtrue
\ifnum\c@tracingmulticols>\@ne
\typeout{Retry: using natural
height of first column!}%
\fi
\dimen@\ht\mult@nat@firstbox
\last@try\dimen@
\advance\dimen@-\p@
\fi
\fi
% \end{macrocode}
% Finally the switch |too@bad| is tested. If it was made true
% either earlier on or due to a rightmost column being too large
% we try again with a slightly larger value for |\dimen@|.
% \begin{macrocode}
\iftoo@bad
%</badness>
\advance\dimen@\p@
\repeat
% \end{macrocode}
% If we come out of the loop with the switch |forcedbreak@leftover|
% set to true then balancing has failed and we should cut a normal
% page. We indicate this below with |\too@badtrue| when any of the
% columns get too high, so we set this flag here too in order to
% get the same processing logic.\footnote{Should get cleaned up as
% we now have two different routes to reach this part of the
% processing.}
% \changes{v1.8k}{2015/03/21}{}
% \begin{macrocode}
\ifforcedbreak@leftover
\too@badtrue
\else
% \end{macrocode}
% At that point |\dimen@| holds the height that was determined by
% the balancing loop.
% If that height for the columns turns out to be larger
% than the available space (which is |\@colroom|) we squeeze the
% columns into the space assuming that they will have enough
% shrinkability to allow this.\footnote{This might be wrong, since
% the shrinkability that accounts for the amount of material might
% be present only in some columns. But it is better to try then to
% give up directly.}
% However, this squeezing should only be done if we are balancing
% columns on the main galley and \emph{not} if we are building a
% boxed multicol (in the latter case the current |\@colroom| is
% irrelevant since the produced box might be moved anywhere at a
% later stage).
% \changes{v1.3c}{1991/03/03}{Limit column height to \cs{@colroom}}
% \changes{v1.5q}{1998/01/19}{Removed setting \cs{dimen@} (pr2739)}
% \changes{v1.5y}{2000/06/10}{Limit column height only in unrestricted
% mode (pr/3212)}
% \begin{macrocode}
\if@boxedmulticols\else
\ifdim\dimen@>\@colroom
\dimen@\@colroom
\fi
\fi
% \end{macrocode}
% Then we move the contents of the odd-numbered box registers to
% the even-numbered ones, shrinking them if requested.
% We have to use |\vbox| not |\vtop| (as it was done in
% the first versions) since otherwise the resulting boxes will have
% no height (\TB\/ page 81). This would mean that extra
% |\topskip| is added when the boxes are returned to the
% page-builder via |\page@sofar|.
% \changes{v1.3a}{1990/05/20}{Changed \cs{vtop} to \cs{vbox}.}
% \begin{macrocode}
\process@cols\mult@rightbox
{\@tempcnta\count@
\advance\@tempcnta\@ne
% \end{macrocode}
% when putting the final column together we want overfull
% information:
% \begin{macrocode}
\vfuzz\z@
\setbox\count@\vbox to\dimen@
{%
% \end{macrocode}
%
% \changes{v1.8h}{2014/09/12}{Use \cs{vfilmaxdepth}}
% \begin{macrocode}
\vskip \z@
\@plus-\multicolundershoot
\@minus-\multicolovershoot
\unvbox\@tempcnta
\ifshr@nking\vfilmaxdepth\fi
}%
% \end{macrocode}
% If the resulting box is overfull there was too much material to
% fit into the available space. The question though is how much? If
% it wasn't more than |\maxbalancingoverflow| we accept it still to
% avoid getting very little material for the next page (which we
% would then have difficulties to balance).
% \changes{v1.8a}{2011/12/20}{Balancing concept improved}
% \begin{macrocode}
\ifnum\badness>\@M
\vfuzz\maxdimen % no overfull warning
\setbox\@tempboxa \vbox to\dimen@
{\vskip-\maxbalancingoverflow
\unvcopy\count@}%
\ifnum\badness>\@M
\mult@info\@ne
{Balanced column more than
\the\maxbalancingoverflow\space
too large}%
% \end{macrocode}
% Fail the balancing attempt:
% \begin{macrocode}
\too@badtrue
\else
% \end{macrocode}
% Otherwise report that there is a problem but within the accepted
% boundary.
% \begin{macrocode}
\mult@info\@ne
{Balanced column
too large, but less than
\the\maxbalancingoverflow}%
\fi
\fi
}%
% \end{macrocode}
% Finally end the |\ifforcedbreak@leftover| conditional.
% \changes{v1.8k}{2015/03/21}{Finish the new conditional}
% \begin{macrocode}
\fi
}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\maxbalancingoverflow}
% Amount that balancing is allowed to overflow the available column
% space. We default to 12pt which means about one line in most
% layouts.
% \changes{v1.8a}{2011/12/20}{\cs{maxbalancingoverflow} parameter added}
% \begin{macrocode}
\newdimen\maxbalancingoverflow
\maxbalancingoverflow=12pt
% \end{macrocode}
% \end{macro}
% \end{multicols}
%
% \begin{multicols}{2}[\subsection{The box allocations}]
%
% \begin{macro}{\mult@rightbox}
% \begin{macro}{\mult@grightbox}
% \begin{macro}{\mult@firstbox}
% \begin{macro}{\mult@gfirstbox}
% Early releases of these macros used the first box registers
% 0, 2, 4,\ldots\ for global boxes and 1, 3, 5,\ldots\ for the
% corresponding local boxes. (You might still find some traces
% of this setup in the documentation, sigh.) This produced a problem
% at the moment we had more than 5 columns because then officially
% allocated boxes were overwritten by the algorithm.
% The new release now uses private box registers.
%
% There was in fact a bug in the new implementation because at one
% point \LaTeX{} started to use the extended registers and so
% jumped from below 255 to above omitting the boxes allocated for
% inserts and the output page box.
%
% So nowadays we really have to check if we get the full sequence
% of boxes allocated without holes (i.e., $2\times\textit{max
% cols}+1$) and if not alter the allocation registers to start
% allocating after 255. This is all done quite low-level by looking
% directly at the values of the allocation counters.
% \changes{v1.8y}{2019/12/09}{Allow for 20 columns (gh/237)}
% \begin{macrocode}
\ifnum\numexpr \count20-\count14-1<41 % = 2 * 20 + 1
\count14=\@cclv
\fi
% \end{macrocode}
%
% \begin{macrocode}
\newbox\mult@rightbox
\newbox\mult@grightbox
\newbox\mult@gfirstbox
\newbox\mult@firstbox
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa\newbox\@tempa
\newbox\@tempa
\let\@tempa\relax
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
%
% \end{multicols}
%
%
% \begin{multicols}{2}[\section{New macros and hacks for version 1.2}]
%
% \begin{macro}{\emergencystretch}
% \begin{macro}{\setemergencystretch}
% If we don't use \TeX{} 3.0 |\emergencystretch| is undefined
% so in this case we simply add it as an unused \meta{dimen}
% register.
% \changes{v1.4j}{1992/06/25}{Setting of \cs{emergencystretch} on top
% removed.}
% \begin{macrocode}
\@ifundefined{emergencystretch}
{\newdimen\emergencystretch}{}
% \end{macrocode}
% \changes{v1.2a}{1990/02/05}{Macro added.}
% My tests showed that the following formula worked pretty well.
% Nevertheless the |\setemergencystretch| macro also gets
% |\hsize| as second argument to enable the user to try
% different formulae.
% \begin{macrocode}
\def\setemergencystretch#1#2{%
\emergencystretch 4pt
\multiply\emergencystretch#1}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\set@floatcmds}
% \changes{v1.2a}{1990/02/05}{Macro added.}
% \changes{v1.5g}{1994/06/07}{Updated since floats have changed}
% \changes{v1.5j}{1994/06/07}{Updated since floats have changed again}
% \changes{v1.5l}{1995/10/19}{Added \cs{@largefloatcheck}}
% \changes{v1.6g}{2006/02/23}{Added \cs{@minipagefalse}}
% \changes{v1.6h}{2008/12/05}{Use \cs{@endfloatbox} to better support
% the modifications done by the float package}
% Even if this should be used as a hook we use a |@| in the
% name since it is more for experts.
% \begin{macrocode}
\def\set@floatcmds{%
\let\@dblfloat\@dbflt
\def\end@dblfloat{\@endfloatbox
\@largefloatcheck
\outer@nobreak
% \end{macrocode}
% This is cheap (deferring the floats until after the current page)
% but any other solution would go deep into \LaTeX's output
% routine and I don't like to work on it until I know which parts
% of the output routine have to be reimplemented anyway for
% \LaTeX3.
% \begin{macrocode}
\ifnum\@floatpenalty<\z@
% \end{macrocode}
% We have to add the float to the |\@deferlist| because we assume
% that outside the \mc{} environment we are in one column mode.
% This is not entirely correct, I already used the \mc{}
% environment inside of \LaTeX{}s |\twocolumn| declaration but it
% will do for most applications.
% \begin{macrocode}
\@cons\@deferlist\@currbox
\fi
\ifnum\@floatpenalty=-\@Mii
\@Esphack
\fi}}
% \end{macrocode}
% \end{macro}
%
% \end{multicols}
%
% \begin{multicols}{2}[\subsection{Maintaining the mark registers}]
% \label{sec:v14}
%
% This section contains the routines that set the marks so that they
% will be handled correctly. They have been introduced with version~1.4.
%
% \begin{macro}{\kept@topmark}
% \changes{v1.4h}{1992/06/04}{Init to double brace pair}
% \begin{macro}{\kept@firstmark}
% \begin{macro}{\kept@botmark}
% First thing we do is to reserve three macro names to hold the
% replacement text for \TeX's primitives |\firstmark|, |\botmark| and
% |\topmark|. We initialize the first two to be empty and
% |\kept@topmark| to contain two empty pair of braces. This is
% necessary since |\kept@topmark| is supposed to contain the last
% mark from a preceding page and in \LaTeX{} any ``real'' mark must
% contain two parts representing left and right mark information.
% \begin{macrocode}
\def\kept@topmark{{}{}}
\let\kept@firstmark\@empty
\let\kept@botmark\@empty
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
%
% \begin{macro}{\return@nonemptymark}
% Sometimes we want to return the value of a ``kept'' mark into a
% |\mark| node on the main vertical list. This is done by the
% function |\return@nonemptymark|. As the name suggests it only acts
% if the replacement text of the kept mark is non-empty. This is done
% to avoid adding an empty mark when no mark was actually present. If
% we would nevertheless add such a mark it would be regarded as a
% valid |\firstmark| later on.
% \begin{macrocode}
\def\return@nonemptymark#1#2{%
\ifx#2\@empty
\else
% \end{macrocode}
% For debugging purposes we take a look at the value of the kept mark
% that we are about to return. This code will get stripped out for
% production.
% \begin{macrocode}
%<*marktrace>
\mult@info\tw@
{Returned #1 mark:\MessageBreak
\meaning#2}%
% \nobreak
% \fi
%</marktrace>
% \end{macrocode}
% Since the contents of the mark may be arbitrary \LaTeX{} code we
% better make sure that it doesn't get expanded any further. (Some
% expansion have been done already during the execution of
% |\markright| or |\markboth|.) We therefore use the usual mechanism
% of a toks register to prohibit expansion.\footnote{Due to the
% current definition of \cs{markright} etc.\ it wouldn't
% help to define the \cs{protect} command to prohibit
% expansion as any \cs{protect} has already vanished due to
% earlier expansions.}
% \changes{v1.4n}{1992/09/10}{Make marks robust}
% \changes{v1.5t}{1999/03/22}{re-add \cs{mark} command which was commented out
% by mistake at some point in 1998 (pr/2978)}
% \begin{macrocode}
\toks@\expandafter{#2}%
\mark{\the\toks@}%
% \end{macrocode}
% We don't want any breakpoint between such a returned mark and the
% following material (which is usually just the box where the mark
% came from).
% \begin{macrocode}
\nobreak
\fi}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\get@keptmarks}
% If we have some material in a box register we may want to get the
% first and the last mark out of this box. This can be done with
% |\get@keptmarks| which takes one argument: the box register number
% or its nick name defined by |\newbox|.
% \begin{macrocode}
\def\get@keptmarks#1{%
% \end{macrocode}
% For debugging purposes we take a look at the current dimensions
% of the box since in earlier versions of the code I made some
% mistakes in this area.
% \begin{macrocode}
%<*debug>
\typeout{Mark box #1 before:
ht \the\ht#1, dp \the\dp#1}%
%</debug>
% \end{macrocode}
% Now we open a new group and locally copy the box to itself. As a
% result any operation, i.e.\ |\vsplit|, will only have a local
% effect. Without this trick the box content would get lost up to
% the level where the last assignment to the box register was done.
% \begin{macrocode}
\begingroup
\vbadness\@M
\setbox#1\copy#1%
% \end{macrocode}
% Now we split the box to the maximal possible dimension. This
% should split off the full contents of the box so that effectively
% everything is split off. As a result |\splitfirstmark| and
% |\splitbotmark| will contain the first and last mark in the box
% respectively.
% \begin{macrocode}
\setbox#1\vsplit#1to\maxdimen
% \end{macrocode}
% Therefore we can now set the kept marks which is a global
% operation and afterwards close the group. This will restore the
% original box contents.
% \begin{macrocode}
\set@keptmarks
\endgroup
% \end{macrocode}
% For debugging we take again a look at the box dimension which
% shouldn't have changed.
% \begin{macrocode}
%<*debug>
\typeout{Mark box #1 \space after:
ht \the\ht#1, dp \the\dp#1}%
%</debug>
}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\set@keptmarks}
% The macro |\set@keptmarks| is responsible for setting
% |\kept@firstmark| and |\kept@botmark|, by checking the current
% values for |\splitfirstmark| and |\splitbotmark|.
% \begin{macrocode}
\def\set@keptmarks{%
% \end{macrocode}
% If |\kept@firstmark| is empty we assume that it isn't set. This
% is strictly speaking not correct as we loose the ability to have
% marks that are explicitly empty, but for standard \LaTeX{}
% application it is sufficient. If it is non-empty we don't change
% the value---within the output routines it will then be restored
% to |\@empty|.
% \begin{macrocode}
\ifx\kept@firstmark\@empty
% \end{macrocode}
% We now put the contents of |\splitfirstmark| into
% |\kept@firstmark|. In the case that there wasn't any mark at all
% |\kept@firstmark| will not change by that operation.
% \begin{macrocode}
\expandafter\gdef\expandafter
\kept@firstmark
\expandafter{\splitfirstmark}%
% \end{macrocode}
% When debugging we show the assignment but only when something
% actually happened.
% \begin{macrocode}
%<*marktrace>
\ifx\kept@firstmark\@empty\else
\mult@info\tw@
{Set kept first mark:\MessageBreak
\meaning\kept@firstmark%
\@gobbletwo}%
\fi
%</marktrace>
\fi
% \end{macrocode}
% We always try to set the bottom mark to the |\splitbotmark| but
% of course only when there has been a |\splitbotmark| at all.
% Again, we assume that an empty |\splitbotmark| means that the
% split off box part didn't contain any marks at all.
% \begin{macrocode}
\expandafter\def\expandafter\@tempa
\expandafter{\splitbotmark}%
\ifx\@tempa\@empty\else
\global\let\kept@botmark\@tempa
%<*marktrace>
\mult@info\tw@
{Set kept bot mark:\MessageBreak
\meaning\kept@botmark%
\@gobbletwo}%
%</marktrace>
\fi}%
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\prep@keptmarks}
% The |\prep@keptmarks| function is used to initialize the kept
% marks from the contents of |\partial@page|, i.e.\ the box that
% holds everything from the top of the current page prior to
% starting the \mc{} environment. However, such a box is only
% available if we are not producing a boxed \mc{}.
% \begin{macrocode}
\def\prep@keptmarks{%
\if@boxedmulticols \else
\get@keptmarks\partial@page
\fi}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\remove@discardable@items}
% There are situations when we may have some space at the end of a
% column and this macro here will attempt to get rid of it. The
% typical \LaTeX{} sequence is a series of self-canceling glues so
% if we remove them recursively we are usually fine.
%
% Special care is needed with handling |\vspace*| as that
% corresponds to |\penalty10000|, |\vskip <skip>|, followed by
% |\vskip 0pt|. If we see this sequence going backwards in the
% vertical list we assume that this is a ``desired'' space. We
% therefore stop the recursion and reinsert the spaces.
%
% As the multicol code sometimes add an explicit penalty at the end
% of a column we first attempt to remove it in case it is there.
% \changes{v1.8m}{2015/03/31}{Another rewrite of
% \cs{remove@discardable@items} hopefully okay now}
% \begin{macrocode}
\skip0=0pt
\edef\the@zero@skip{\the\skip0}
\def\remove@discardable@items{%
\unpenalty
% \end{macrocode}
% Save a previous skip (if there) and then remove it, we can't
% really tell the difference between no skip an a skip of zero but
% that's life.
% \begin{macrocode}
\edef\@tempa{\the\lastskip}%
%\typeout{s1=\@tempa}%
\unskip
% \end{macrocode}
% If it was a zero skip (or none) we save the next previous skip
% (if any).
% \begin{macrocode}
\ifx\@tempa\the@zero@skip
\edef\@tempb{\the\lastskip}%
%\typeout{s2=\@tempb}%
% \end{macrocode}
% If this one again was zero (or more likely not there in the first
% place) we stop.
% \begin{macrocode}
\ifx\@tempb\the@zero@skip
\else
% \end{macrocode}
% Otherwise we remove this ``real'' skip. Then we look if it was
% preceded by a penalty of 10000 (i.e., a |\nobreak|)
% \begin{macrocode}
\unskip
%\typeout{p=\lastpenalty}%
\ifnum \lastpenalty=\@M
% \end{macrocode}
% If so this was a |\vspace*| or something equivalent to
% it. Therefore we reintroduce the skips and stop. Otherwise we
% recurse.
% \begin{macrocode}
\vskip\@tempb\vskip\@tempa\relax
\else
\remove@discardable@items
\fi
\fi
\else
% \end{macrocode}
% If the first skip was a non-zero skip we recurse as well.
% \begin{macrocode}
\remove@discardable@items
\fi
}
% \end{macrocode}
% \end{macro}
%
% \begin{macrocode}
%<*badness>
\newif\iftoo@bad
\def\too@badtrue{\global\let\iftoo@bad\iftrue}
\def\too@badfalse{\global\let\iftoo@bad\iffalse}
% \end{macrocode}
%
% \changes{v1.8k}{2015/03/21}{The new switch}
% \begin{macrocode}
\newif\ifforcedbreak@leftover
% \end{macrocode}
%
% \begin{macro}{\c@minrows}
% \changes{v1.8w}{2019/03/01}{Provide minrows counter for balancing}
% \begin{macrocode}
\newcount\c@minrows
\c@minrows=1
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\c@columnbadness}
% \begin{macro}{\c@finalcolumnbadness}
% \begin{macrocode}
\newcount\c@columnbadness
\c@columnbadness=10000
\newcount\c@finalcolumnbadness
\c@finalcolumnbadness=9999
\newdimen\last@try
% \end{macrocode}
%
% \changes{v1.5z1}{2003/02/17}{Change wrong default for
% \cs{multicolovershoot} to zero (pr/3465).}
% \begin{macrocode}
\newdimen\multicolovershoot
\newdimen\multicolundershoot
\multicolovershoot=0pt
\multicolundershoot=2pt
\newbox\mult@nat@firstbox
%</badness>
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\mult@info}
% A helper for producing info messages
% \begin{macrocode}
\def\mult@info#1#2{%
\ifnum\c@tracingmulticols>#1%
\GenericWarning
{(multicol)\@spaces\@spaces}%
{Package multicol: #2}%
\fi
}
% \end{macrocode}
% \end{macro}
%
% \end{multicols}
%
%
% \begin{multicols}{2}[\section{Fixing the
% \cs{columnwidth}}]
%
% \begin{macro}{\@footnotetext}
% \changes{v1.5o}{1997/11/16}{Redefinition added pr/2664.}
% \changes{v1.5r}{1998/08/17}{Use \cs{@footnotetext} but with
% local change to \cs{columnwidth}.}
% \begin{macro}{\mult@footnotetext}
% \changes{v1.5r}{1998/08/17}{Macro removed again.}
% If we store the current column width in |\columnwidth| we have
% to redefine the internal |\@footnotetext| macro to use |\textwidth|
% for the width of the footnotes rather than using the original
% definition.
%
% Starting with version v1.5r this is now done in a way that the original
% definition is still used, except that locally |\columnwidth| is set to
% |\textwidth|.
%
% This solves two problems: first redefinitions of |\@footnotetext|
% done by a class will correctly survive and second if multicols is
% used inside a minipage environment the special definition of
% |\@footnotetext| in that environment will be picked up and not the
% one for the main galley (the latter would result in all footnotes
% getting lost in that case).
%
% See the definition of the |\multicols| command further up for the exact
% code.
% \end{macro}
% \end{macro}
% \end{multicols}
%
%
% \begin{multicols*}{2}[\section{Further extensions}]
%
% This section does contain code for extensions added to this package
% over time. Not all of them may be active, some might sit dormant and
% wait for being activated in some later release.
%
% \subsection{Not balancing the columns}
%
% This is fairly trivial to implement. we just have to disable the
% balancing output routine and replace it by the one that ships out
% the other pages.
%
% \begin{macro}{\multicols*}
% \changes{v1.5q}{1998/01/19}{Macro added}
% The code for this environment was suggested by Matthias Clasen.
% \begin{macrocode}
%<*nobalance>
\@namedef{multicols*}{%
% \end{macrocode}
% If we are not on the main galley, i.e., inside a box of some
% sort, that approach will not work since we don't have a vertical
% size for the box so we better warn that we balance anyway.
% \begin{macrocode}
\ifinner
\PackageWarning{multicol}%
{multicols* inside a box does
not make sense.\MessageBreak
Going to balance anyway}%
\else
% \end{macrocode}
% If we aren't balancing we change the |\balance@columns@out| to
% work like the normal output routine that cuts normal
% pages. However, there is a catch: In case the last page we cut
% (after seeing the end of the environment) is actually larger than
% a page (for example, if it contains more |\columnbreak| commands
% than columns) we end up with some leftover material that is
% returned to the main galley, but now the environment end penalty
% is missing. So we add another one here too. Of course that
% shouldn't be done if there is really only a single final page,
% but fortunately in that case we have just finished a page and any
% penalty on the recent contributions will be discarded, thus the
% extra one is harmless---puh.
% \changes{v1.8t}{2018/06/26}{Re-add end penalty for
% \texttt{multicols*} environment to guard against leftovers (git/53)}
% \begin{macrocode}
\def\balance@columns@out
{\multi@column@out \penalty-\@Mvi }%
\fi
\begin{multicols}
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\endmulticols*}
% When ending the environment we simply end the inner
% \texttt{multicols} environment, except that we better also stick
% in some stretchable vertical glue so that the last column still
% containing text is not vertically stretched out.
%
% We do this as follows: first we ensure that we are back in vertical mode
% and then we cancel out |\lastskip| if it was
% positive (in case of a negative glue we assume that it was
% deliberate, for a deliberate positive glue one needs to use
% |\vspace*|). We can't simply use |\remove@discardable@items| here
% as this only works inside boxes but we are here on the main
% vertical list.
%
% Then we back up by |\prevdepth| but not more than |\boxmaxdepth|
% so that a baseline of the last box is now at the bottom. This way
% the material will align properly in case something like |\vfill|
% spreads it out after all.
% Finally we append |\vfil| to put white space at the bottom of the
% column, but we only do this if we aren't anyway doing |\raggedcolumns|.
% \changes{v1.5q}{1998/01/19}{Macro added}
% \changes{v1.8h}{2014/09/12}{Use \cs{vfilmaxdepth}}
% \changes{v1.8i}{2014/10/28}{Add \cs{null} to hide the final fill and only add
% vertical space if not doing \cs{raggedcolumns}}
% \changes{v1.8j}{2015/03/07}{Redesign the whole approach.}
% \changes{v1.8k}{2015/03/21}{And a bit more redesign because of the
% change in \cs{remove@discardable@items}}
% \changes{v1.8o}{2016/02/08}{Ensure we are back in vmode before using
% \cs{prevdepth} (pr/4448)}
% \begin{macrocode}
\@namedef{endmulticols*}{%
\par
\ifdim\lastskip>\z@ \vskip-\lastskip \fi
\ifdim \prevdepth>\z@
\vskip-\ifdim\prevdepth>\boxmaxdepth
\boxmaxdepth
\else \prevdepth \fi
\fi
\ifshr@nking\else
\vfil
\fi
\end{multicols}}
%</nobalance>
% \end{macrocode}
% \end{macro}
%
%
% \subsection{Manual column breaking} \label{sec:colbreak}
%
% The problem with manual page breaks within \mc{} is the fact that
% during collection of material for all columns a page-forcing penalty
% (i.e. -10000 or higher) would stop the collecting pass which is not
% quite what is desired. On the other hand, using a penalty like -9999
% would mean that there would be occasions where the |\vsplit|ing
% operations within \mc{} would ignore that penalty and still choose a
% different break point.
%
% For this reason the current implementation
% uses a completely different approach. In a nutshell it extends the \LaTeX{}
% output routine handling by introducing an additional penalty flag
% (i.e., a penalty which is forcing but higher than -10000 so that the
% output routine can look at this value and thus knows why it has been
% called).
%
% Inside the output routine we test for this value and if it appears
% we do two things: save the galley up to this point in a special box
% for later use and reduce the |\vsize| by the height of the material
% seen. This way the forcing penalty is now hidden in that box and we
% can restart the collection process for the remaining
% columns. (This is done in |\speci@ls| above.)
%
% In the output routines that do the |\vsplit|ting either for
% balancing or for a full page we simply combine box~255 with the
% saved box thus getting a single box for splitting which now
% contains forcing breaks in the right positions.
%
%
% \begin{macro}{\columnbreak}
% \changes{v1.5u}{1999/05/25}{Macro added}
% |\columnbreak| is modeled after |\pagebreak| except that we
% generate a penalty -10005.
% \begin{macrocode}
\mathchardef\@Mv=10005
\def\columnbreak{%
% \end{macrocode}
% We have to ensure that it is only used within a \mc{}
% environment since if that penalty would be seen by the unmodified
% \LaTeX{} output routine strange things would happen.
% \begin{macrocode}
\ifnum\col@number<\tw@
\PackageError{multicol}%
{\noexpand\columnbreak outside multicols}%
{This command can only be used within
a multicols or multicols* environment.}%
\else
\ifvmode
\penalty -\@Mv\relax
\else
\@bsphack
\vadjust{\penalty -\@Mv\relax}%
\@esphack
\fi
\fi}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\colbreak@box}
% \changes{v1.5u}{1999/05/25}{Macro added}
% Need a box to collect the galley up to the column break.
% \begin{macrocode}
\newbox\colbreak@box
%</package>
% \end{macrocode}
% \end{macro}
%
%
% \subsection{Supporting right-to-left languages} \label{sec:RL}
%
%
% \changes{v1.7a}{2010/10/24}{RL language support added}
% \changes{v1.7b}{2011/12/18}{RL language support fixed}
%
% \begin{macro}{\LR@column@boxes}
% |\LR@column@boxes| is called when we are assembling the columns for left
% to right typesetting. When we start we are inside an |\hbox| of
% full width.
% Left to right typesetting is fairly easy, we basically output
% each column box intermixed with vertical rules and proper
% spacing. As this happens inside a box of a defined width the
% rules and the columns automatically get into the right positions.
% \begin{macrocode}
\def\LR@column@boxes{%
% \end{macrocode}
% We loop through the columns with |\process@cols|
% \begin{macrocode}
\process@cols\mult@gfirstbox{%
% \end{macrocode}
% If the depth of the current box is larger than the maximum found
% so far in |\dimen2| we update that register for later use.
% \changes{v1.6a}{2003/03/15}{Preparing for adjusting \cs{prevdepth}}
% \begin{macrocode}
\ifdim\dp\count@>\dimen\tw@
\global\dimen\tw@\dp\count@ \fi
% \end{macrocode}
% If the \texttt{colaction} option is given we write out status
% information about the current column, otherwise the next command
% does nothing.
% \changes{v1.8e}{2014/04/23}{Support \cs{docolaction}}
% \begin{macrocode}
\mc@col@status@write
% \end{macrocode}
% The typeset box followed by the column rule material
% \begin{macrocode}
\box\count@
\hss{\columnseprulecolor\vrule
\@width\columnseprule}\hss}%
% \end{macrocode}
% As you will have noticed, we started with box register
% |\mult@gfirstbox| (i.e.\
% the left column). So this time |\count@| looped through 2,
% 4,\ldots\ (plus the appropriate offset).
% Finally we add box |\mult@rightbox| and we are done.
% \changes{v1.5a}{1992/11/04}{New box mechanism}
% \changes{v1.6a}{2003/03/15}{Preparing for adjusting \cs{prevdepth}}
% Again we may have to update |\dimen\tw@|.
% \begin{macrocode}
\ifdim\dp\mult@rightbox>\dimen\tw@
\global\dimen\tw@\dp\mult@rightbox \fi
% \end{macrocode}
% If the \texttt{colaction} option is given we write out status
% information about the last column, otherwise the next command
% does nothing.
% \changes{v1.8e}{2014/04/23}{Support \cs{docolaction}}
% \begin{macrocode}
\mc@lastcol@status@write
\box\mult@rightbox
}
% \end{macrocode}
% \end{macro}
% \begin{macro}{\RL@column@boxes}
% Assembling the boxes for right to left typesetting is far more
% complicated. When I first tried to build a solution for this my
% thinking was that all that is necessary to do is to reverse the
% order of the columns. But such an approach produces a subtle bug:
% If we work this way then the first column put on the page will be
% the last column of the text to read. and this means that the
% order in which \TeX{} executes write statements or assembles mark
% material will not happen in the order of the textual flow. So if,
% for example each column contains a section command then these
% sections will appear in reverse order in the table of content.
%
% For this reason some amount of gymnastics is needed to add the
% columns in their natural flow.
% \begin{macrocode}
\def\RL@column@boxes{%
% \end{macrocode}
% First step is to put all rules in the right place (without adding
% the comes which are instead represented by a space of |\hsize|.
% \begin{macrocode}
\process@cols\mult@gfirstbox{%
\hskip\hsize
\hss{\columnseprulecolor\vrule
\@width\columnseprule}\hss
}%
\hskip\hsize
% \end{macrocode}
% At this point in the code our typesetting reference point is at
% the right end of the rightmost column (or rather where that column
% should appear).
%
% We are now typesetting all columns by first backing up by their
% width (which is |\hsize|) then typesetting the box and then
% backing up again, but this time further, i.e., also across the
% column separation. That will then enable us to typeset the next
% column using the same approach until we are done with all but the
% final column.
% \begin{macrocode}
\process@cols\mult@gfirstbox{%
\ifdim\dp\count@>\dimen\tw@
\global\dimen\tw@\dp\count@ \fi
\hskip-\hsize
% \end{macrocode}
%
% \changes{v1.8e}{2014/04/23}{Support \cs{docolaction}}
% \begin{macrocode}
\mc@col@status@write
\box\count@
\hskip-\hsize
\hskip-\columnsep
}%
% \end{macrocode}
% The approach for the final column is similar only that we do not
% have to back up over any column gap.
% \begin{macrocode}
\ifdim\dp\mult@rightbox>\dimen\tw@
\global\dimen\tw@\dp\mult@rightbox \fi
\hskip-\hsize
% \end{macrocode}
%
% \changes{v1.8e}{2014/04/23}{Support \cs{docolaction}}
% \begin{macrocode}
\mc@lastcol@status@write
\box\mult@rightbox
\hskip-\hsize
% \end{macrocode}
% However we do have to move the reference point to its right
% place: to make the rules appear at the expected places, we should
% get the typesetting position to the far right again. As we at the
% moment at the far left we skip to the far right like this:
% \begin{macrocode}
\hskip\full@width
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\RLmulticolcolumns}
% \begin{macro}{\LRmulticolcolumns}
% \begin{macro}{\mc@align@columns}
% Macros to switch between left-right and right-left typesetting. In LR
% typesetting the |\LR@column@boxes| is used to combine
% the columns. When typesetting right to left the |\RL@column@boxes|
% is used instead.
% \begin{macrocode}
\newcommand\RLmulticolcolumns
{\let\mc@align@columns
\RL@column@boxes}
\newcommand\LRmulticolcolumns
{\let\mc@align@columns
\LR@column@boxes}
% \end{macrocode}
% The default is left-to-right:
% \begin{macrocode}
\LRmulticolcolumns
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
%
% \subsection{Supporting \texttt{\textbackslash docolaction}}
%
% \changes{v1.8e}{2014/04/23}{Support \cs{docolaction}}
%
% Whenever we want to do something that depends on the current
% column we execute \verb=\docolaction=. This command takes one
% optional and three mandatory arguments. The mandatory ones denote
% what to do if this is a ``left'', ``middle'', or ``right'' column
% and the optional one is simply there to say what to do if we don't
% know (default is to use the ``left'' column action in that case).
%
% \begin{macro}{\mc@col@check@num}
% We use one counter \verb=\mc@col@check@num= to generate us unique
% label names. Each time we execute \verb=\docolaction= we increment
% this counter to get a new name.
% \begin{macrocode}
\newcount\mc@col@check@num
% \end{macrocode}
% \end{macro}
%
% The generated ``labels'' are named
%\begin{verbatim}
%\mc@col-\the\mc@col@check@num
%\end{verbatim}
% and they hold as values the
% numbers 1, 2, or 3 denoting the current column type.
% \begin{macro}{\docolaction}
%
% The \verb=\docolaction= scans for a star and optional argument
% and 3 mandatory ones, but we do this in chunks (not having xparse
% available).
%
% \changes{v1.8u}{2018/11/09}{Support star with \cs{docolaction}}
% \begin{macrocode}
\newcommand\docolaction{%
% \end{macrocode}
% First check is the support is enabled.
% \begin{macrocode}
\ifx\mc@col@status@write\relax
\PackageError{multicol}%
{Option 'colaction' not selected}%
{\string\docolaction\space
requires the use of the 'colaction'
option on the package}%
\fi
% \end{macrocode}
% Then prepare \verb=\mc@col@type=.
% \begin{macrocode}
\global\advance\mc@col@check@num\@ne
\edef\mc@col@type{\expandafter\ifx
\csname mc@col-\the\mc@col@check@num
\endcsname\relax
0\else
\csname mc@col-\the\mc@col@check@num
\endcsname
\fi}%
% \end{macrocode}
% Finally check for a star, record this information and then call
% \verb=\@docolaction= to do the rest.
% \begin{macrocode}
\@ifstar
{\@docolactionstartrue \@docolaction}%
{\@docolactionstarfalse\@docolaction}%
}
% \end{macrocode}
%
% \begin{macrocode}
\newcommand\@docolaction[4][1]{%
% \end{macrocode}
%
% How does the column number get associated with our label? We
% do this by writing another line into the aux file. Here are the
% preparations.
% \begin{macrocode}
\edef\@docolactioncheck{\write\@auxout
{\string\mc@set@col@status
{mc@col-\the\mc@col@check@num}%
{\mc@col@type}}}%
% \end{macrocode}
% Where we do the actual \verb=\write= depends on the whether or
% not we gave seen a \texttt{*}. If yes, we do it first and then
% execute the code argument, otherwise we execute that code first
% and check at the point after that.
% \begin{macrocode}
\if@docolactionstar \@docolactioncheck \fi
% \end{macrocode}
% We prefix with 0 so that an unknown label (that returns
% \verb=\relax=) will result in case 0
% \begin{macrocode}
\ifcase \mc@col@type\relax
% \end{macrocode}
% If column is unknown we use the default action or the action
% denoted by the optional argument (so that arg can take the value
% 1, 2, 3).
% \begin{macrocode}
\ifcase #1\or #2\or#3\or#4\fi
\or
% \end{macrocode}
% Otherwise we know (or think we know) that this is a first, middle,
% or last column:
% \begin{macrocode}
#2% % 1 First col
\or
#3% % 2 any middle col
\or
#4% % 3 last col
\else
\ERRORwrongdefaultgiven
\fi
% \end{macrocode}
% \begin{macrocode}
\if@docolactionstar \else \@docolactioncheck \fi
}
% \end{macrocode}
% \end{macro}
%
% Here is the if used above:
% \begin{macrocode}
\newif\if@docolactionstar
% \end{macrocode}
%
% Because of extra data writing to the aux file the aux file will
% now contain something like the following after the document is
% processed the first time:
%\begin{verbatim}
%\relax
%\mc@col@status{1}
%\mc@set@col@status{lcol-1}{0}
%\mc@col@status{2}
%\mc@set@col@status{lcol-2}{0}
%\mc@col@status{3}
%\mc@set@col@status{lcol-3}{0}
%\mc@col@status{1}
%\mc@col@status{2}
%\mc@col@status{3}
%\mc@set@col@status{lcol-4}{0}
%\end{verbatim}
% The \verb=\mc@col@status= line denotes the column type and has been
% written out just before corresponding the column box was placed
% onto the page.
% The\verb=\mc@set@col@status= lines have been written out as part
% of shipping the column boxes out, e.g.,
% \verb=\mc@set@col@status{lcol-1}{0}= was therefore somewhere within
% the first column as it appears between \verb=\mc@col@status{1}=
% and \verb=\mc@col@status{2}=
% The second argument in that line is the value used in the previous
% run (or zero if there was no previous run. We can use this to
% determine if a rerun is necessary.
%
% Thus with this knowledge we can set things up to get the labels
% working.
%
%
% \begin{macro}{\mc@col@status}
%
% When the aux file is read in \verb=\mc@col@status= is used to set
% \verb=\mc@curr@col@status=:
% \begin{macrocode}
\def\mc@col@status#1{%
\gdef\mc@curr@col@status{#1}}
% \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\mc@set@col@status}
%
% And when \verb=\mc@set@col@status= is executed we can simply set
% up the label by associating it with the \verb=\mc@curr@col@status=
% and ignore the second argument:
% \begin{macrocode}
\def\mc@set@col@status#1#2{%
\global\expandafter\let\csname #1\endcsname
\mc@curr@col@status}
% \end{macrocode}
% The above definition is being used when the \texttt{.aux} file is
% read in at the beginning. At the end we need a different
% definition to test if another typesetting run is needed. There we
% compare the value used in the current run (stored in the second
% argument) with the value used on the next run. If those two values
% differ we set \verb=@tempswa= to false which will trigger the
% ``Label(s) may have changed'' warning.
% \begin{macrocode}
\AtEndDocument{\def\mc@set@col@status#1#2{%
\ifnum #2=\mc@curr@col@status\else
\@tempswatrue
\fi}%
}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{mc@firstcol}
% Finally, as part of determining in which column we are, we used a
% switch inside |\mc@col@status@write| to determine if we are in the
% first column or not.
% \begin{macrocode}
\newif\ifmc@firstcol
\mc@firstcoltrue
% \end{macrocode}
% \end{macro}
% \end{multicols*}
%
% \Finale
%
\endinput
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