path: root/macros/latex/contrib/bigfoot/bigfoot.dtx

% \iffalse
%%
%% bigfoot is part of the bigfoot bundle for critical typesetting
%% Copyright 2004--2015  David Kastrup <dak@gnu.org>
%%
%% The license notice and corresponding source code for this file are
%% contained in bigfoot.dtx.
%%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation; either version 2 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program; if not, write to the Free Software
% Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
% \fi
% \CheckSum{4580}
% \GetFileInfo{bigfoot.sty}
% \title{The \texttt{bigfoot} package\\version \fileversion}
% \date{\filedate}
% \author{David Kastrup\thanks{dak@gnu.org}}
% \maketitle
% Purpose of this package is to provide a one-stop solution to almost
% all problems related to footnotes.  You can use it as a drop-in
% replacement of the \texttt{manyfoot} package, but without many of
% its shortcomings, and quite a few features of its own.  It uses the
% existing document class layouts for footnotes, so you can usually
% use it without having to worry about the looks.
%
% Features are:
% \begin{itemize}
% \item You can specify and use multiple footnote apparatus.
%   Footnotes for an apparatus lower on the
%   page\footnoteB{like this one} can be anchored in an
%   apparatus\footnote{The plural of ``apparatus'' is actually
%     ``apparatus''\footnoteB{Well, actually ``apparat\=us'' with a
%       long ``u'', but that's just obvious in spoken Latin.}}
%   that is higher on the page.
% \item The last footnote in each apparatus may be broken to the next
%   page.\footnote{This will probably be interesting for footnotes
%     that contain stuff like math equations\footnoteB+{Like
%       \begin{equation}
%         \label{eq:1}
%         \sum_{k=1}^\infty \frac{1}{k^2} = \frac{\pi^2}{6}
%       \end{equation}} or lists\footnoteB+{Like
%       \begin{itemize}
%       \item This, or
%       \item this.
%       \end{itemize}}.}
%   Any subordinate footnote anchors that get moved to the next page
%   will take the corresponding footnote with them.
% \item The order of footnotes in an apparatus is `natural': it starts
%   with any footnote that may have been broken from the next page,
%   followed by footnotes from the current page in the order of the
%   appearance of their footnote
%   marks.\footnoteB{This footnote appears above notes on notes.}
%   Where the order of appearance in the document differs from the
%   order in the source code, you will usually want to use the
%   \cmd{\MakeSorted} command from the |perpage| package to get the
%   numbering fixed appropriately.
% \item Footnotes can be formatted in separate paragraphs, or be run
%   into a single paragraph.  The choice is made per footnote
%   apparatus, but can be overridden for single
%   footnotes.\footnote{I.e., footnotes with display
%     math\footnoteB{We had this already, right?} or list
%     environments\footnoteB{And this looks familiar, too.} have to be
%     done in vertical mode.}
% \item If footnotes are run into one paragraph, a variety of criteria
%   makes sure that this formatting is only chosen when it saves
%   noticeable space and delivers visually attractive results.
% \item Parameters for footnote formatting can be specified globally,
%   or separately for each footnote.
% \item The material in footnotes can contain |\verb|-like material
%   without problems.\footnote{We wrote \verb+|\verb|-like+ above in
%     the main text.\footnoteB{Well, this is not so impressive.  But we
%       wrote \verb/\verb+|\verb|-like+/ in the footnote then.}}
% \item You can use color in footnotes.  If a footnote gets broken
%   across pages, the color at the point of the break will get resumed
%   on the next page.  Actually, the whole color stack will get
%   reinstated.
% \end{itemize}
% As an example of how simple the usage can be, here is the
% documentation driver for this document:
%    \begin{macrocode}
%<*driver>
\documentclass{ltxdoc}
\usepackage{bigfoot}
\usepackage{tabularx}
\usepackage{hyperref}
%    \end{macrocode}
% After loading the packages, we declare two footnote blocks.  One is
% the default footnote block, another block is called~|B| and is
% numbered with letters.  The letters start new on each page.  Both
% footnote blocks default to in-paragraph footnotes.  Since the
% block~|B| can get entries from both the main text as well as the
% default footnote block, the entries are not necessarily generated in
% page order.  So we need to use a sorted counter to fix this (feel
% free to try what happens when using an unsorted counter).
%    \begin{macrocode}
\DeclareNewFootnote[para]{default}
\DeclareNewFootnote[para]{B}[alph]
\MakeSortedPerPage{footnoteB}
%    \end{macrocode}
% In addition, we add an alternate footnote sequence that can be
% interspersed with the normal footnotes by use of the
% \cmd{\footnote'} command which we effectively define here.
%    \begin{macrocode}
\newcounter{footalt}
\def\thefootalt{\fnsymbol{footalt}}
\MakeSortedPerPage[2]{footalt}
\WithSuffix\def\footnotedefault'{\refstepcounter{footalt}%
  \Footnotedefault{\thefootalt}}
%    \end{macrocode}
% Actually, that already was all.  We can now start the document.  The
% following makes sure that we get the full documentation only by
% compiling the separate driver file:
%    \begin{macrocode}
\begin{document}
\OnlyDescription
%<driver> \AlsoImplementation
\DocInput{bigfoot.dtx}
\end{document}
%</driver>
%    \end{macrocode}
% In order to be useful without additional hassle, the normal footnote
% level will be called |default|.  If no such style has been defined
% at the start of the document, it will get defined and used for
% ordinary footnotes, fixing quite a few problems of \LaTeX's own
% footnote placement algorithms.
%
% Apart from that, usage is very much like that of |manyfoot|, so for
% the customization possibilities of |bigfoot| with regards to
% multiple footnote blocks and rules between them, refer to
% |manyfoot|'s documentation.
%
% |bigfoot| contains a lot of bells and whistles for defining your
% footnote formats and can use different formats for different
% footnote blocks.  Those expert options are not documented separately
% yet: look through the code sections to see them explained.
% \StopEventually{}
% \section{The implementation}
% \subsection{Startup code}
% We declare the package and several compatibility options supposed to
% make |bigfoot| a drop-in replacement for |manyfoot|.
%    \begin{macrocode}
%<*style>
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{bigfoot}[2015/08/30 2.1 makes footnotes work]

\DeclareOption{para}{\PackageInfo{bigfoot}{Compatibility option `para'
  has no effect:^^J%
  Spacing will be guessed from `\string\@makefntext' unless^^J%
  `\string\@preparefnhtext' is redefined}}

\DeclareOption{para*}{\PackageInfo{bigfoot}{Compatibility option
    `para*':^^J%
    Redefining `\string\@preparefnhtext'}%
  \def\@preparefnhtext{\ifx\@thefnmark\@empty
    \else\@makefnmark\nobreak\fi}}

\DeclareOption{ruled}{\PassOptionsToPackage{ruled}{manyfoot}}
%    \end{macrocode}
% The normal processing makes footnote text macros allow verbatim and
% similar.  We call this |robust| processing though it is not totally
% accurate.  This is the default.  There is also an option |fragile|
% which will not allow this, but may be required for some definitions
% of \cmd{\@makefntext}.  It turns out that most document classes work
% with the `robust' option, but there might be some that fail, and
% there might be some footnote-modifying packages that also can cause
% failure.
%    \begin{macrocode}
\DeclareOption{robust}{\def\FN@makefncall{\FN@makefnrobust}}
\DeclareOption{fragile}{\def\FN@makefncall{\FN@makefnfragile}}
\ExecuteOptions{robust}
%    \end{macrocode}
% The |verbose| option talks about changed labels at the end of a
% run.  It is for debugging instable configurations that fail to
% converge after a number of \TeX\ runs.  The output is probably
% obscure.
%    \begin{macrocode}
\DeclareOption{verbose}{\AtBeginDocument{%
    \def\@testdef #1#2#3{%
      \def\reserved@a{#3}%
      \expandafter \ifx \csname #1@#2\endcsname
        \reserved@a
      \else \@tempswatrue
        \typeout{Changed label #1/#2:
          \csname #1@#2\endcsname->#3}%
      \fi}}}
%    \end{macrocode}
% The |trace| option is only available if you used |docstrip| while
% explicitly requesting |trace| functionality.  If you set the |trace|
% option, the next option specifies a bit map of trace bits.
%
% The following bits can be set in tracing:
% \begin{tabular}{rl}
%   1&break decisions\\
%   2&horizontal box building\\
%   4&allocation stuff\\
%   8&output routine stuff\\
%  16&retained and kept boxes
% \end{tabular}
%    \begin{macrocode}
%<trace>\DeclareOption{trace}{%
%<trace>\DeclareOption*{\ftflags=\CurrentOption\relax
%<trace>  \DeclareOption*{\OptionNotUsed}}%
%<trace>  \AtEndOfPackage{\RequirePackage{trace}\relax
%<trace>  \errorcontextlines\maxdimen
%<trace>  \showboxdepth4
%<trace>  \showboxbreadth100
%<trace>  \tracingonline=\@ne}%
%<trace>}
%    \end{macrocode}
% The |tracepage| option is followed by another option specifying the
% page to be traced.  If you use it, tracing happens only on the
% specified page.  Only a single page can be specified.
%    \begin{macrocode}
%<trace>\def\FN@tracepage{\c@page}
%<trace>\DeclareOption{tracepage}{%
%<trace>  \DeclareOption*{\edef\FN@tracepage{\CurrentOption}%
%<trace>    \DeclareOption*{\OptionNotUsed}}}
%<trace>\newcount\ftflags
%<trace>\def\foottrace#1{\ifnum\numexpr(\ftflags+(#1))/(2*#1)*(2*#1)%
%<trace>  =\numexpr(\ftflags+3*#1/2)/#1*#1\relax
%<trace>  f\else t\fi\ifnum\FN@tracepage=\c@page t\else n\fi}
\ProcessOptions*
%    \end{macrocode}
% |hyperref|'s footnote support will just cause trouble.  So if
% |hyperref| was already loaded or is going to be loaded, we turn off
% its footnote support.  If you think you know what you are doing, you
% can use \cmd{\hypersetup} to turn it on again before the start of
% the document.  Unfortunately, it appears like \cmd{\hypersetup}
% refuses to be called more than once, so this actually does not work
% unless you load |hyperref| last.
%    \begin{macrocode}
\ifx\hypersetup\@undefined
  \PassOptionsToPackage{hyperfootnotes=false}{hyperref}
\else
  \hypersetup{hyperfootnotes=false}
\fi
%    \end{macrocode}
% We require the |etex| package because
% \begin{enumerate}
% \item We need the facilities of the \eTeX\ engine; and where they
%   are not available, the error messages from not finding the |etex|
%   package or from loading it into the wrong engine make much more
%   sense than what would happen otherwise.
% \item We allocate quite a few registers, and the danger of running
%   out of them is smaller when the extra registers of \eTeX\ are
%   taken into account.  Now unfortunately the LaTeX team has decided
%   in 2015 to do its own extended allocation scheme incompatible with
%   the |etex| package, so we need to guard against this load in case
%   the new LaTeX allocation scheme is detected.
% \end{enumerate}
% We need the |manyfoot| package to build on.  The |suffix| and
% |perpage| package are needed for some small stuff.
%    \begin{macrocode}
\ifx\e@alloc\@undefined
\RequirePackage{etex}
\fi
\RequirePackage{manyfoot}
\RequirePackage{suffix}
\RequirePackage{perpage}
%    \end{macrocode}
% \subsection{Fixes to the \texttt{manyfoot} package}
% While those fixes have been submitted once to the author of
% |manyfoot|, they have not made it into its distribution at the
% current point of time.  In the interest of stability, it would
% probably be best just to incorporate the parts from |manyfoot| that
% get used by |bigfoot|.  This has not yet been done.
%
% \begin{macro}{\MFL@reinsout}
%   We need the appropriate splitting parameters set for the footnote
%   again.  \cmd{\MFL@realinsert} does that, but it has the disadvantage
%   that it uses \cmd{\strutbox}, and that may be set to arbitrary
%   values at the time the output routine is invoked.  |manyfoot|
%   already has this problem with minipages: the split sizes will be
%   those of the font at the end of the minipage instead of those at the
%   time the footnote body was set up.  So we do this here, and see
%   later for more info about how to do this right:
%    \begin{macrocode}
\def\MFL@reinsout#1#2{\ifvoid#2\else
    \ifnum\count\@currbox>\z@
      \advance\@pageht \ht#2%
      \advance\@pageht \skip#2%
      \advance\@pageht \dp#2%
    \fi
    \MFL@realinsert{#2}{\unvbox#2}%
  \fi
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MFL@reins}
%   Actually, I don't get the purpose of the following line in the
%   first place.  But if we do need it for some reason, it is rather
%   certain that we don't want this empty insert to float.  Use
%   \cmd{\MFL@realinsert}, or set the floatingpenalty the hard way.
%    \begin{macrocode}
\def\MFL@reins#1#2{\ifvoid#2\else\insert#2{\floatingpenalty\@MM}\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MFL@mpinsert}
% \begin{macro}{\MFL@minipage}
%   The structure of the \cmd{\MFL@mpinsert} box is overly
%   complicated, and it is a bad idea to unpack the boxes put into it
%   too early: the \cmd{\lastbox} command is pretty inefficient when
%   the list before it is long due to unpacking.  So we just leave
%   everything packed in its own boxes, and unpack only at the moment
%   when we are reinserting.
%    \begin{macrocode}
\long\def\MFL@mpinsert#1#2{%
  \global\setbox#1\vbox{%
    \unvbox#1%
    \nointerlineskip
    \vbox{#2}%
  }%
}

\def\FN@divert{%
  \let\MFL@mpinsertsave\MFL@insert
  \MFL@reinsert \let\MFL@insert\MFL@mpinsert}
\def\FN@enddivert{{\let\@elt\MFL@mpreinsert \MFL@list}}

\def\MFL@minipage{\ifinner\else \FN@divert\fi}
\def\MFL@endminipage{\ifinner\else \FN@enddivert\fi}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\MFL@mpreinsert}
%   When reinserting, we put all but the last insertion into one
%   humongous blob.  This is so that the last insertion can be split
%   by \TeX's paragraph splitting routines.  The footnote types that
%   |bigfoot| supports will never get split by \TeX, anyhow, but it is
%   conceivable that other extension packages for manyfoot work
%   differently.  There is one difference, though: we let a slave mark
%   escape into the main vertical list.
%    \begin{macrocode}
\def\MFL@mpreinsert#1#2{%
  \ifvoid#2\else
    \setbox\@tempboxa\vbox\bgroup\unvbox#2%
      \global\setbox#2\lastbox
      \setbox\z@\lastbox
      \ifvoid\z@
        \egroup
        \setbox\z@\box#2%
      \else
        \MFL@removevboxes \unvbox\z@
        \egroup
        \setbox\z@\box#2%
        \MFL@mpinsertsave#2{\unvbox\@tempboxa}%
      \fi
    \ifvoid\z@\else
      \MFL@mpinsertsave#2{\unvbox\z@}%
    \fi
    \marks\FN@slave{\number\FN@id}%
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MFL@removevboxes}
%   This trick works like \cmd{\removehboxes} in the \TeX book's
%   appendix~D.
%    \begin{macrocode}
\def\MFL@removevboxes{{\setbox\z@\lastbox
    \ifvbox\z@ \MFL@removevboxes \unvbox\z@\fi}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\NCC@makefnmark}
%   This provides the command in case it is not present (some versions
%   did not have it).
%    \begin{macrocode}
\ifx\NCC@makemark\@undefined
  \ifx\NCC@makefnmark\@undefined \else
    \def\NCC@makemark{\NCC@makefnmark}
  \fi
\fi
%    \end{macrocode}
% \end{macro}
%
% While the above operations actually were fixes to |manyfoot|, now we
% actually patch it for our own purposes.  When allocating a new
% footnote, we set its maximum dimension to \cmd{\maxdimen} (since no
% hard limit makes sense, given that we recalculate all respective
% sizes at output time) and allocate a cache box to go with it.  We
% also add the insertion to the list of insertions in
% \cmd{\FN@nestlist}.
% \begin{macro}{\MFL@startplain}
% \begin{macro}{\MFL@startpara}
%    \begin{macrocode}
\def\MFL@startplain#1{\global\dimen#1\maxdimen
  \@cons\FN@nestlist{{}#1}%
  \expandafter\expandafter\expandafter\newbox\FN@cache#1}

\let\MFL@startpara\MFL@startplain
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\RestyleFootnote}
%   This macro gets two arguments: a footnote \meta{type}, and the
%   style to be used for it.  It works by redefining the corresponding
%   |Footnotetext|\meta{type} macro.
%    \begin{macrocode}
\def\RestyleFootnote#1#2{\expandafter\xdef
  \csname Footnotetext#1\endcsname{\expandafter
    \noexpand\csname MFL@fnote#2\endcsname{\csname footins#1\endcsname}}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@stripfootins}
% \begin{macro}{\FN@restylefootnote}
%   We need the same kind of functionality for a footnote specified by
%   its footnote insertion.  So we strip the footnote \meta{type} from
%   the insertion macro name.  Kind of ugly.
%    \begin{macrocode}
\expandafter\def\expandafter\FN@stripfootins\string\footins{}

\def\FN@restylefootnote#1#2{{\edef\next{%
      \noexpand\RestyleFootnote{\expandafter\FN@stripfootins
        \string#1}{#2}}\next}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \subsection{Dealing with footnote-specific code}
% The formatting of footnotes is determined by macros such as
% \cmd{\@makefntext}.  For several blocks of footnotes, we might want
% to have several different ways for formatting them.  Whenever this
% is the case, we call them with
% \begin{quote}
%   |\FN@specific|\marg{insert\#}\marg{macroname}
% \end{quote}
% This will use the default \meta{macroname} unless a special macro has
% been defined with something like
% \begin{quote}
%   |\FootnoteSpecific\marg{type}|\def|\meta{macroname}\dots
% \end{quote}
% A number of other defining commands and constructs are available:
% those are pretty much like the ones for the \cmd{\WithSuffix} command
% implemented by the |suffix| package.
% \begin{macro}{\FN@specific}
%   We use |\romannumeral| here just for the purpose of sustaining
%   expansion.  It expands to nothing when followed by |\z@|
%   eventually.  Thus expanding the expansion of \cmd{\FN@specific}
%   again delivers the (unexpanded) final token to use.
%    \begin{macrocode}
\def\FN@specific#1#2{\romannumeral
  \ifcsname FN\string#2\number#1\endcsname
  \expandafter
    \z@\csname FN\string#2\number#1\expandafter\endcsname
  \else\expandafter\z@
    \expandafter#2\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FootnoteSpecific}
% \begin{macro}{\FN@specific@ii}
%   This is all a bit muddy, but quite similar to what the |suffix|
%   package does, so you might want to look there for the explanation.
%    \begin{macrocode}
\def\FootnoteSpecific#1{\count@\csname footins#1\endcsname\toks@{}%
  \FN@specific@ii}

\long\def\FN@specific@ii#1#2{\toks@\expandafter{\the\toks@#1}%
  \the\expandafter\toks@
  \csname FN\string#2\number\count@\endcsname}

\WithSuffix\def\FN@specific@ii\long{\toks@\expandafter
  {\the\toks@\long}\FN@specific@ii}

\WithSuffix\def\FN@specific@ii\global{\toks@\expandafter
  {\the\toks@\global}\FN@specific@ii}

\WithSuffix\def\FN@specific@ii\expandafter{\expandafter
  \FN@specific@ii\expandafter}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \subsection{Putting footnotes into insertions}
% \subsubsection{Dealing with Ids}
%   Since we have to store additional information for each footnote as
%   long as it is not yet typeset, we allocate and deallocate numeric
%   `id's on an as-needed base, since we do not want to store this
%   sort of information indefinitely, with a large toll on hash space.
%   So we work with indirect ids, where the unique ids are just
%   referenced indirectly.  We do this with `slots'.
% \begin{macro}{\FN@slotxdef}
% \begin{macro}{\FN@slotget}
%   New slots are assigned values with \cmd{\FN@slotxdef}, which can
%   be retrieved again with \cmd{\FN@slotget}.
%    \begin{macrocode}
\def\FN@slotxdef#1{%
  \global\expandafter\xdef\csname FN@slot#1\endcsname}

\def\FN@slotget#1{\csname FN@slot#1\endcsname}
%<trace>\def\FN@slotget#1{%
%<trace>  \expandafter\FN@slotgetii\expandafter
%<trace>     \FN@slotfreelist\expandafter
%<trace>     {\number\number#1}}
%<trace>\def\FN@slotgetii#1#2{%
%<trace>  \ifx#1\@empty \csname FN@slot#2\endcsname\else
%<trace>    \ifnum#1=#2 \errmessage{Use after freed: #1}\else
%<trace>       \expandafter\FN@slotgetii
%<trace>         \csname FN@slot#1\endcsname{#2}\fi\fi}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@slotfreelist}
% \begin{macro}{\FN@nextslot}
%   \cmd{\FN@slotfreelist} point to the first already allocated
%   available id to be reused.  If it is empty, none exist.  In that
%   case, \cmd{FN@nextslot} contains the next slot number to use.
%    \begin{macrocode}
\def\FN@slotfreelist{}
\def\FN@nextslot{1}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@newslot}
%   This allocates a new slot by setting the given macro to a
%   currently unused slot number in decimal form.  If there is
%   something left in the freelist, it is assigned, otherwise a new
%   slot gets allocated.
%    \begin{macrocode}
\def\FN@newslot#1{%
  \ifx\FN@slotfreelist\@empty
    \edef#1{\FN@nextslot}%
    \xdef\FN@nextslot{\number\numexpr \FN@nextslot+\@ne}%
  \else
    \let#1\FN@slotfreelist
    \xdef\FN@slotfreelist{\csname FN@slot\FN@slotfreelist\endcsname}%
  \fi
%<trace>  \if\foottrace4\message{^^JAllocated #1^^J}\fi
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@freeslot}
%   This frees a given slot (by number) again by adding it to the
%   freelist.
%    \begin{macrocode}
\def\FN@freeslot#1{%
%<trace>  \if\foottrace4\message{^^JFreeing #1^^J}\fi
  \global\expandafter\let\csname FN@slot#1\endcsname=\FN@slotfreelist
  \xdef\FN@slotfreelist{#1}}
%    \end{macrocode}
% \end{macro}
%
% \subsubsection{Dealing with footnote stacks}
% Footnote stacks are used for paired footnotes that refer to a text
% range instead of a single text point.  For example, you can use
% something like
% \begin{verbatim}
% Text \var<{was there}is here\var>
% \end{verbatim}
% To have a text variant ``was there'' for the original passage ``is
% here'', and mark it, say, as ``\textsuperscript{a}is
% here\textsuperscript{\textsl{a}}'' by employing the |suffix| package
% suitably.  This would anchor the footnote at the start of the
% passage.  It would also be imaginable to implement the syntax
% \begin{verbatim}
% Text \var<is here\var>{was there}
% \end{verbatim}
% for anchoring it at the end of the given passage.
%    \begin{macrocode}
\global\let\FN@stacklist\@empty
%    \end{macrocode}
% \begin{macro}{\DefineFootnoteStack}
%   This command is used for defining a footnote stack.  It gets a
%   single argument which is the name of the stack and should consist
%   just of ordinary character tokens.
%    \begin{macrocode}
\def\DefineFootnoteStack#1{%
  \global\expandafter\let\csname FN@stack@#1\endcsname\@empty
  \@cons\FN@stacklist{{#1}}%
}
%    \end{macrocode}
% \end{macro}
% At the end of the document, all stacks are checked to make sure they
% have been used up completely.
%    \begin{macrocode}
\AtEndDocument{\FN@checkstacklist}

\def\FN@checkstacklist{{\let\@elt\FN@checkstack
  \FN@stacklist}}

\def\FN@checkstack#1{{\let\@elt\FN@checkstackentry
    \csname FN@stack#1@\endcsname}}

\def\FN@checkstackentry#1#2#3{%
  \PackageError{bigfoot}{Unfinished #1 #2 from line #3}%
  {The specified footnote range is uncomplete}}
%    \end{macrocode}
% \begin{macro}{\PushFootnoteMark}
%   This gets one argument, the name of the footnote stack.  It pushes
%   the current footnote mark name stored in \cmd{\@thefnmark} onto
%   the footnote stack.
%    \begin{macrocode}
\def\PushFootnoteMark#1{{\let\@elt\relax
  \expandafter\unrestored@protected@xdef \csname FN@stack@#1\endcsname
  {\@elt{#1}{\@thefnmark}{\number\inputlineno}\csname
  FN@stack@#1\endcsname}}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\PopFootnoteMark}
%   This gets one argument, the name of the footnote stack.  It pops
%   the value of \cmd{\@thefnmark} from the named footnote stack.
%    \begin{macrocode}
\def\PopFootnoteMark#1{\expandafter
  \ifx\csname FN@stack@#1\endcsname\@empty
    \PackageError{bigfoot}{Empty footnote stack #1}%
    {The specified footnote type has no uncompleted range}%
  \else
  {\let\@elt\FN@firstpop
    \iffalse{\fi\csname FN@stack@#1\endcsname}}\fi}
%    \end{macrocode}
% \end{macro}
%    \begin{macrocode}
\def\FN@firstpop#1#2#3{\protected@xdef\@thefnmark{#2}%
  \let\@elt\relax
  \expandafter\protected@xdef\csname FN@stack@#1\endcsname{%
    \iffalse}\fi}
%    \end{macrocode}
%
% \subsubsection{Continuation marks}
%
% We add a possibility of adding continuation marks.  While the box is
% assembled, immediately before the break, \cmd{\FN@beforebreak} gets
% called, and \cmd{\FN@afterbreak} is called at the top of the
% continuing box.
%    \begin{macrocode}
\ifx\FN@beforebreak\@undefined
  \let\FN@beforebreak\@empty
\fi
\ifx\FN@afterbreak\@undefined
  \let\FN@afterbreak\@empty
\fi
%    \end{macrocode}
%
%
%\subsubsection{The works}
%
% \begin{macro}{\FN@cache}
%   Cacheboxes cache the typeset forms of the insertion boxes for a
%   certain configuration of footnotes.
%    \begin{macrocode}
\def\FN@cache#1{\csname FN@cache\number#1\endcsname}
%    \end{macrocode}
% \end{macro}
% \cmd{\FN@sortlist} takes the current vertical list and sorts the
% contained boxes according to their width (which is supposed to
% contain the sort key).
%
% The algorithm is a pretty straightforward insertion sort with
% $O(n^2)$~steps.  This is the best one can hope for without
% comparisons across non-adjacent list elements.  For presorted lists,
% the performance will be $O(n)$, and that's what we expect to see for
% simple cases (and when there are no sortkeys yet).  Any negative
% width will certainly hang the algorithm.
%
% It also happens that \TeX\ has a hardwired limit for grouping levels
% that hits at 255.  Oops.  We better not have a few hundred footnotes
% in a single block on one page\dots
%    \begin{macrocode}
\def\FN@sortlist{{%
  \setbox\z@\lastbox
  \ifvoid\z@ \else \FN@sortlist\FN@sortlistii \fi}}

\def\FN@sortlistii{%
  \setbox\tw@\lastbox
  \ifvoid\tw@\else
  \ifdim\wd\tw@<\wd\z@ {\FN@sortlistii}%
  \fi\nointerlineskip\box\tw@\fi\nointerlineskip\box\z@}
%    \end{macrocode}
% \begin{macro}{\FN@sortinsert}
%   This function is an \cmd{\@elt} function that will sort the given
%   insertion if it is non-empty and if there is no cache box present
%   (which would imply that the insertion had already been sorted
%   previously).
%    \begin{macrocode}
\def\FN@sortinsert#1#2{\ifvoid\FN@cache#2%
  \ifvoid#2\else\global\setbox#2\vbox{\unvbox#2%
    \FN@sortlist}\fi\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@maybeinvalidatecache}
%   This is called after pulling in additional material from the
%   page.  If the material added an insertion, the cache is junk and
%   must be regenerated.
%    \begin{macrocode}
\def\FN@maybeinvalidatecache#1#2{%
  \ifvoid#2\else\global\setbox\FN@cache#2=\box\voidb@x\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@regeneratecache}
%   This unconditionally regenerates one cache box.  The structure of
%   a cache box is basically a list of vertical boxes.  All but the
%   last such box are packed into a single vertical box which is then
%   followed by the last vertical box.
%    \begin{macrocode}
\def\FN@regeneratecache#1#2{%
   \global\setbox\FN@cache#2=%
   \ifvoid#2%
     \box\voidb@x
   \else
     \vbox{\vbox{\unvcopy#2%
         \setbox\z@\lastbox
         \def\FN@masterinsert{#2}%
         \FN@assembleboxes
         \global\setbox\FN@cache#2\box\z@}%
       \nointerlineskip \box\FN@cache#2}%
    \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@mayberegeneratecache}
%   This regenerates the cache in case the cache box has been voided
%   in order to mark it as invalid.
%    \begin{macrocode}
\def\FN@mayberegeneratecache#1#2{%
  \ifvoid\FN@cache#2%
    \FN@regeneratecache{}#2%
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@cachesize}
%   This calculates the size impact of a cache box on the current page
%   as a term to be added into a \cmd{\glueexpr}-type of expression.
%    \begin{macrocode}
\def\FN@cachesize#1#2{%
  \ifvoid\FN@cache#2%
  \else
    +\skip#2+(\ht\FN@cache#2+\dp\FN@cache#2)*\count#2/\@m
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@clearcache}
%   This just completely voids a cache register.
%    \begin{macrocode}
\def\FN@clearcache#1#2{%
  \global\setbox\FN@cache#2=\box\voidb@x}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@makefnvtext}
%   Ok, this is one of the parts putting together footnotes in para
%   mode.  The footnotes themselves have already been formatted into
%   hboxes (placed there with \cmd{\@preparefnhtext} in order to cater
%   for proper indentation).  \cmd{\@makefnvtext} then formats a
%   single footnote block from horizontal mode pieces (vertical mode
%   pieces are kept as-is).
%   This takes text and typesets it in a single block.  To get correct
%   indentation, it breaks before the first footnote and adjusts the
%   clubpenalties to move them to one line lower effectively.
%   \cmd{\@makefnvtext} is called in vertical mode, and its argument
%   is typeset in horizontal mode right after a break, inside of
%   \cmd{\@makefntext}.
%    \begin{macrocode}
\def\@makefnvtext#1{%
  \FN@specific\FN@masterinsert\@makefntext{%
    \clubpenalties\thr@@\@MM\clubpenalty\z@
    \vadjust{\nobreak\vskip-\baselineskip}\nobreak\hfill\break#1}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\@preparefnhtext}
%   This creates appropriate skips to be put before the horizontal
%   material to make the indentation correct with a breakpoint before
%   the footnote as well as when in run-in text.  This is run once at
%   the start of each horizontal mode footnote when it is first being
%   typeset, in horizontal mode.
%    \begin{macrocode}
\ifx\@preparefnhtext\@undefined
\def\@preparefnhtext{{%
  \setbox\z@\vbox{\FN@specific\FN@masterinsert\@makefntext{%
      \unskip\unpenalty\setbox\z@\lastbox
      \dimen@
        \ifnum\parshape>\z@
          \dimexpr\parshapeindent\tw@-\parshapeindent\@ne\relax
        \else \ifnum\hangafter=\@ne\hangindent \else
          \ifnum\hangafter=\m@ne -\hangindent
          \else \z@ \fi\fi\fi
      \dimen@ii\dimen@
      \ifhbox\z@ \advance\dimen@-\wd\z@
        \setbox\z@\hbox{\unhbox\z@}%
        \advance\dimen@\wd\z@
      \fi
      \xdef\FN@tempinfo{\hskip\the\dimen@
        \vadjust{}\nobreak\hskip-\the\dimen@ii\relax}}}}%
  \FN@tempinfo}
\fi
%    \end{macrocode}
% Now we have in |\FN@tempinfo| the excess width of the label we don't
% want to preserve when doing in-paragraph footnote setting.  A
% sequence of glue before a label now has to consist of stuff that
% vanishes at a breakpoint, followed by stuff that remains.  We have
% to have two behaviors for the contents: behavior one is
% justification at the start of a line, behavior two is justification
% in the line.  When we are at the start of the line, preceding
% interword space disappears swallowed and so the natural criterion
% for distinguishing those cases is this initial line break.  This
% means that we can't avoid articifially adding a line break at the
% start of such a box.  We will back up its height again.  Some
% packages specify a |\hangindent| (I~know of no examples where they
% would actually set |\hangafter| to a value different from its
% default of~1, or set |\hangindent| to a negative value which would
% affect the right margin): due to our artifical line at the top, the
% indent will actually be active for the first line already.  We back
% it out of the actual labels happening at the start of the line.
% Two-line parshapes have the same effect: the first line is not
% actually used, and we put the relevant info for the first line into
% the label.  Different right indentation for the first line is
% something we can't simulate, but again, it should occur rarely.
% When |\parshape| is active, |\hangindent| is ignored.
% \end{macro}
%    \begin{macrocode}
\def\@makefnstartbox{%
  \ifdefined\setspace@singlespace
    \def\baselinestretch{\setspace@singlespace}%
  \fi
  \reset@font\footnotesize
  \hsize\MFL@columnwidth \@parboxrestore
  \interlinepenalty\FN@specific\FN@masterinsert\interfootnotelinepenalty
  \widowpenalty\FN@specific\FN@masterinsert\footnotewidowpenalty
  \clubpenalty\FN@specific\FN@masterinsert\footnoteclubpenalty
  \advance\linepenalty500\relax}

\def\@makefnendbox{%
  \widowpenalty\FN@specific\FN@masterinsert\finalfootnotewidowpenalty}

\newcount\footnotewidowpenalty
\footnotewidowpenalty=250
\newcount\footnoteclubpenalty
\footnoteclubpenalty=250
\newcount\finalfootnotewidowpenalty
\finalfootnotewidowpenalty=4000
%    \end{macrocode}
% \begin{macro}{\@makefnvbox}
%   This is the formatting code for a vertical mode footnote box from
%   already set horizontal material.  It uses \cmd{\@makefnstartbox}
%   for setting up the initial widow/club penalties, and
%   \cmd{\@makefnendbox} for preparing the final end.  It results in a
%   vbox.
%    \begin{macrocode}
\ifx\@makefnvbox\@undefined
  \def\@makefnvbox#1{\vbox{%
      \@makefnstartbox
      \clubpenalties\thr@@\@MM\clubpenalty\z@
      \let\@thefnmark\@empty
      \FN@specific\FN@masterinsert\@makefntext{\rule\z@\footnotesep
        \nobreak
        #1\@finalstrut\strutbox
      \@makefnendbox}}}
\fi
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\hfootfraction}
% \begin{macro}{\vtypefraction}
%   Those parameters govern when a footnote block is going to be set
%   completely in vertical mode.  If a footnote block does not shrink
%   to less than \cmd{\hfootfraction} its size when using in-paragraph
%   notes or has at least \cmd{\vtypefraction} of forcedly vertical
%   footnotes (specified as purely vertical, or vertical because of
%   being large), it is set entirely in vertical mode.
%    \begin{macrocode}
\def\hfootfraction{0.9}
\def\vtypefraction{0.7}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@assembleboxes}
%   This will produce the finished product, by generating all boxes
%   and concatenating them except for the last vbox.  It is assumed
%   that have already set |\box\z@| to |\lastbox| before calling this
%   routine (or, more likely, have already assembled and split the
%   last box).  The last, not yet unpacked |\vbox| is left in
%   |\box\z@| on return.  The original id of the last box of a block
%   is properly transferred to it.
%
%   The last box might have come about by joining several horizontal
%   boxes, so splitting it might separate footnotes.  We deal with
%   that problem at a different point of time by checking the
%   respective Ids when breaking a vbox into pieces: if the split
%   piece does not contain the last footnote beginning, we switch to a
%   slow motion decomposal.  \cmd{\FN@assembleboxes} is supposed to be
%   entered and exited in vertical mode.
%    \begin{macrocode}
\def\FN@assembleboxes{%
%<trace> \ifhmode \PackageError{bigfoot}{Unexpected hmode}{}\fi
  \ifhbox\z@
    \dimen@\dp\z@
%<trace> \MFL@checksinglebox\z@\z@{}{}%
    \dimen@ii\z@
    \setbox\tw@\box\voidb@x
    \loop \advance\dimen@ii\dimexpr\ht\z@+\dp\z@\relax
      \setbox\tw@\hbox{\box\z@\unhbox\tw@}%
      \setbox\z@\lastbox
    \ifhbox\z@
    \repeat
    {\FN@assembleboxes\nointerlineskip\unvbox\z@}%
%    \end{macrocode}
% At this point of time, |\box\tw@| contains a plain hbox with nothing
% but the unadorned hboxes in horizontal mode to be joined into one
% footnote block.  All preceding footnote blocks have been emptied
% into the current vertical list.  We put the |\unvbox| operations in
% a group so that the paragraph shapes will not get reset over the
% break.
%    \begin{macrocode}
    \global\setbox\FN@tempbox\copy\tw@
    \setbox\z@\@makefnvbox{%
      {\unhbox\FN@tempbox}%
      \setbox\z@\lastbox\FN@joinhboxes}%
    \ifcase
      \ifdim\FN@vfound>\dimexpr\vtypefraction\p@*\FN@found\relax \@ne\fi
      \ifdim\dimexpr \ht\z@+\dp\z@>\hfootfraction\dimen@ii \@ne\fi \z@
    \or
      \global\setbox\FN@tempbox\box\tw@
      \setbox\z@\@makefnvbox{\let\@makefnbreak\FN@pseudofillbreak
          {\unhbox\FN@tempbox}\setbox\z@\lastbox\FN@joinhboxes}%
    \fi
    \setbox\tw@\box\voidb@x
    \ht\z@\dimexpr \ht\z@+\dp\z@-\dimen@\relax
    \dp\z@\dimen@
%<trace>  \MFL@checksinglebox\z@\z@{}{}%
  \else
    \ifvbox\z@
%<trace>  \MFL@checksinglebox\z@\z@{}{}%
      {\setbox\z@\lastbox
      \FN@assembleboxes\nointerlineskip\unvbox\z@}%
    \fi
  \fi}
%    \end{macrocode}
% \end{macro}
% Ok, now follow a lot of fuzzy calculation routines.  When we are
% considering truth values, |\p@| (1pt) corresponds to a value of
% ``true'', and |\z@| corresponds to ``false''.
% \begin{macro}{\FN@fuzzyeval}
%   This calculates a ratio, something with which you multiply.  The
%   first two arguments of the function define an interval, and the
%   third argument is a value in that interval.  If |#3| is equal to
%   |#1|, the resulting ratio is~0, if the |#3| is equal to |#2|, the
%   resulting ratio is~1.  Values in between are linearly
%   interpolated.  Values outside of the interval are mapped to 0
%   and~1.  If all three values are equal (hardly useful), 1 is
%   returned.
%    \begin{macrocode}
\def\FN@fuzzyeval#1#2#3{%
  \ifdim\dimexpr(#3)<\dimexpr(#2)\relax
    \ifdim\dimexpr(#3)>\dimexpr(#1)\relax
      *(\dimexpr(#3)-(#1))%
      /(\dimexpr(#2)-(#1))%
    \else *\z@
    \fi
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@fuzzyor}
%   This returns probabilistic \textsc{or}:
%   \[(|#1|+|#2|-|#1|\cdot|#2|)\]
%    \begin{macrocode}
\def\FN@fuzzyor#1#2{(\p@-(\p@-(#1))*(\dimexpr\p@-(#2))/\p@)}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@magicclue}
% Ok, so here is the magic glue calculator.  |#1| and~|#2| give the
% range over which the preceding line changes from `short' to `long'.
% |#3| and |#4| give the range over which the current line changes
% from `short' to `long'.  Both are combined with a probabilistic or
% function, and then a penalty is chosen which ranges from |#5|
% to~|#6| for short to long.
%    \begin{macrocode}
\def\FN@magicglue#1#2#3#4#5#6{%
%<trace> \if\foottrace2\traceon\fi
  \dimen@\dimexpr\p@\FN@fuzzyeval{#1}{#2}\FN@lasthsize\relax
  \dimen@ii\dimexpr\p@\FN@fuzzyeval{#3}{#4}{\ht\z@+\dp\z@}\relax
  \dimen@\dimexpr\FN@fuzzyor\dimen@\dimen@ii
  \count@\numexpr((#6)-(#5))*\dimen@/\p@+(#5)\relax
  \xdef\FN@vfound{\the\dimexpr\FN@vfound+\dimen@}%
  \ifnum\count@>-\@M
    \penalty\count@
    \hskip\glueexpr -\parfillskip+1em minus 0.5em\relax
  \else
    \FN@pseudobreak
  \fi
  \xdef\FN@found{\number\numexpr\FN@found+\@ne}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@pseudobreak}
%   This ends a line, but without introducing parskip and similar.  It
%   also `breaks in' the next line to get proper indentation.  The
%   main difference with regard to \cmd{\break} is that this restarts
%   the reckoning of line numbers for the sake of \cmd{\clubpenalty}
%   calculation.
%    \begin{macrocode}
\def\FN@pseudobreak{%
  {\parskip\z@skip\parfillskip\z@skip\parindent\z@\vadjust{}\par\noindent
    \vadjust{\nobreak\vskip-\baselineskip}\nobreak\hfill\break}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@pseudofillbreak}
%   This is basically just for separating paragraphs by force.
%    \begin{macrocode}
\def\FN@pseudofillbreak{\nobreak\hskip\parfillskip\FN@pseudobreak}
%    \end{macrocode}
%
% \end{macro}
% \begin{macro}{\@makefnbreak}
%   This calculates the glue for the standard horizontal footnotes.
%    \begin{macrocode}
\def\@makefnbreak{\FN@magicglue {\footnotesep+\dp\strutbox}%
  {\footnotesep+\dp\strutbox+\baselineskip}%
  {\footnotesep+\dp\strutbox+0.5\baselineskip}%
  {\footnotesep+\dp\strutbox+2\baselineskip}{-200}{-12000}}
%    \end{macrocode}
% \end{macro}
% \cmd{\FN@joinhboxes} is called with box~0 set to the next box to be
% appended to the current list (all preceding hboxes on the current
% vertical list will have to go in front).  \cmd{\FN@joinhboxes} is
% entered in vertical mode, and will be exited in horizontal mode.
%    \begin{macrocode}
\def\FN@joinhboxes{%
%<trace> \ifvmode \errmessage{Unexpected vertical mode.}\fi
  \begingroup\setbox\z@\lastbox
    \ifhbox\z@ \FN@joinhboxes
%<trace> \ifvmode \errmessage{Unexpected vertical mode.}\fi
      \endgroup
      \nobreak\hskip\parfillskip
      \@makefnbreak
    \else
%<trace> \ifvbox\z@ \errmessage{Unexpected vbox.}\fi
      \endgroup
      \vadjust{\nobreak\vskip-\baselineskip}\nobreak\hfill\break
      \xdef\FN@vfound{\z@}%
      \xdef\FN@found{\z@}%
    \fi
  \xdef\FN@lasthsize{\the\dimexpr \ht\z@ +\dp\z@}%
  \unhbox\z@}
%    \end{macrocode}
% \begin{macro}{\FN@par}
% \begin{macro}{\FN@noindent}
% \begin{macro}{\FN@indent}
%   In-paragraph footnotes are collected in horizontal mode.  So
%   |\par|, \cmd{\noindent} and \cmd{\indent} simply don't work.  We
%   replace them with something having the same effect when the boxes
%   get unhboxed.  Note that this does not admit the tracking of
%   club/widow penalties: in a later version, it should get replaced
%   by something that actually allows for separate paragraphs.  One
%   possibility would be to replace the current single hbox for an
%   in-paragraph footnote by an hbox of hboxes and unbox all of them
%   in separate paragraphs.  But that glosses over the fact that a
%   multi-paragraph footnote does not make sense in anything but
%   vertical mode.  So a saner way would probably be to close off the
%   hbox altogether and reinsert it into a vbox, restarting the whole
%   footnote in vertical mode.  Both of those approaches would require
%   that no groups have been opened since the start of the footnote by
%   the time |\par| gets called.  The below pseudosolution at least
%   has the advantage of not depending on the grouping structure at
%   all.
%    \begin{macrocode}
\def\FN@par{\unskip\nobreak\hskip\parfillskip
  \vadjust{\vskip\parskip}\break\null\kern\parindent\ignorespaces}
\def\FN@noindent{\unkern}
\def\FN@indent{\unkern{\setbox\z@\null\wd\z@\parindent\box\z@}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\MFL@fnoteplain}
% \begin{macro}{\MFL@fnotepara}
%   We redefine |manyfoot|'s basic footnote calls to use our own,
%   versatile variant.
%    \begin{macrocode}
\def\MFL@fnoteplain{\FN@fnotenested{plain}}
\def\MFL@fnotepara{\FN@fnotenested{para}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@fnotenested}
%   This is somewhat contorted: we want |\footnote+| to be in |plain|
%   style and |\footnote-| in |para| style regardless of the current
%   footnote style.  Adding a second |+| or |-| after the first will
%   actually restyle all footnotes coming afterwards appropriately.
%   This should work for all footnote commands getting footnote text.
%    \begin{macrocode}
\def\FN@fnotenested#1#2#3{%
  \edef\reserved@d{#1}%
  \FN@checkvariant{\edef\reserved@d}{%
    \FN@checkvariant{\FN@restylefootnote{#2}}%
    {\csname FN@fnote\reserved@d\endcsname{#2}{#3}}}}

\def\FN@checkvariant#1#2{\def\reserved@a{#1}%
  \def\reserved@b{#2}%
  \futurelet\reserved@c\FN@checkvariantii}

\def\FN@checkvariantii{%
  \ifx\reserved@c+%
    \reserved@a{plain}\expandafter\@firstoftwo
  \else\ifx\reserved@c-%
    \reserved@a{para}\expandafter\expandafter\expandafter
    \@firstoftwo
  \fi\fi
  \reserved@b}
%    \end{macrocode}
% \end{macro}
% In order to be able to sort footnotes according to the order of
% their reference points, we use a sorted counter.
%    \begin{macrocode}
\newcounter{FN@totalid}
\MakeSorted{FN@totalid}
%    \end{macrocode}
% \begin{macro}{\FN@fnoteplain}
% \begin{macro}{\FN@fnotepara}
%   The actual commands are easy enough:
%    \begin{macrocode}
\def\FN@fnoteplain{\FN@fnotecommon\vbox}
\def\FN@fnotepara{\FN@fnotecommon\hbox}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@masterinsert}
%   This contains the insert number of the insert where the footnote
%   mark appears.  If it appears in the main text, 255~will be used.
%    \begin{macrocode}
\def\FN@masterinsert{\@cclv}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@id}
% \begin{macro}{\FN@master}
% \begin{macro}{\FN@slave}
%   Here is the deal with master and slave ids: each footnote has a
%   unique master id.  This master id is larger by one than the last
%   id of its subordinate footnotes.  It is recorded in the mark
%   \cmd{\FN@master} in the footnote box at the start itself, although
%   with an indirection through the \cmd{\FN@newslot} mechanism since
%   the actual id can only become known after all subfootnotes have
%   been typeset.  The same id is recorded in \cmd{\FN@slave} at the
%   ultimate end of the footnote.
%
%   At the point where a \cmd{\FN@master} mark is placed, a default
%   \cmd{\FN@slave} mark is placed also with an id that is one less
%   than the smallest id generated from a footnote that is a
%   `descendent' of the current one.  This makes it possible to
%   distinguish any split off subordinate footnotes.  It must be noted
%   that this sentinel slave id will be the valid id of a completely
%   unrelated footnote!  Since the value is only used for determining
%   one end of an \emph{open} interval of excluded ids, this is no
%   problem.  All subordinate footnotes are numbered sequentially in
%   the order of \emph{completion}, so that any subordinate footnotes
%   have lower ids than their master.
%    \begin{macrocode}
\newcount\FN@id
\FN@id\@ne
\newmarks\FN@master
\newmarks\FN@slave
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@errorstack}
%   This records the history of nested footnotes in order to deliver
%   more useful error messages.
%    \begin{macrocode}
\let\FN@errorstack\@empty
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@fnotecommon}
%   Well, this is the work horse if the footnote macro.  Really bad
%   thing.  We start off by stepping our absolute counter and making a
%   mark.  \cmd{\leavevmode} is required so that the action of
%   |perpage.sty| is done smoothly.
%    \begin{macrocode}
\def\FN@fnotecommon#1#2#3{%
  \leavevmode
  \stepcounter{FN@totalid}%
  \NCC@makemark{#3}%
%    \end{macrocode}
%   It is an error if the footnote insert number of the current
%   footnote does not correspond to a block below the current
%   insertion level.
%    \begin{macrocode}
  \ifnum#2<\FN@masterinsert
    \FN@colorstackbgroup\FN@divert
    \FN@newslot\FN@masterslot
    \count@\FN@id
%    \end{macrocode}
%   \cmd{\dimen@} is here set to a sorting criterion.  This is
%   designed to make the conversion of footnote blocks as reliable as
%   possible.  If we could guarantee convergence, just using
%   \cmd{\c@FN@totalid} would be sufficient for sorting.  It turns out
%   that this is too sensitive to footnotes of different blocks
%   changing pages, so the number of the superior footnote block is
%   allowed to take precedence by multiplying it with 4194304 which is
%   unlikely to get exceeded by \cmd{\c@FN@totalid}.
%    \begin{macrocode}
    \dimen@=\dimexpr64\p@*\FN@masterinsert-\c@FN@totalid sp\relax
    \def\FN@masterinsert{#2}%
    \edef\FN@errorstack{\FN@errorstack^^J%
\FN@masterinsert\space entered in line \number\inputlineno}%
    \let\FN@boxtype=#1%
    \setbox\z@#1\bgroup
%    \end{macrocode}
%   The following is for the likes of PDF\TeX\ which has its own idea
%   about how to restore a color stack.
%    \begin{macrocode}
      \let\current@color\default@color
      \FN@@color@begingroup
      \let\MFL@minipage\relax
      \let\MFL@endminipage\relax
      \@makefnstartbox
%    \end{macrocode}
%   We reset the list parameters in footnotes.  Strictly speaking,
%   this is interfering with \LaTeX's standard operation, but the
%   standard operation does not make sense.
%    \begin{macrocode}
      \let\@listdepth\@mplistdepth \@mplistdepth\z@
      \@itemdepth\z@ \@enumdepth\z@
      \protected@edef\@currentlabel{\csname p@footnote%
         \expandafter\FN@stripfootins\string#2\endcsname\@thefnmark}%
      \ifx\FN@boxtype\vbox \normalcolor\nobreak
      \else \FN@specific{#2}\@preparefnhtext \normalcolor
      \fi
%    \end{macrocode}
%   Ok, now we do the call to \cmd{\@makefntext} which may occur in
%   one of several ways, depending on whether the `robust' or the
%   `fragile' package option got used.
%    \begin{macrocode}
      \expandafter \FN@makefncall
  \else
%    \end{macrocode}
%   We still needed to cater for the error of badly anchored footnotes:
%    \begin{macrocode}
    \PackageError{bigfoot}{#2 forbidden in \FN@masterinsert.}%
    {Higher-placed footnotes can't be anchored in inferior ones.^^J%
    I am not putting this text in a footnote.  History:%
\FN@errorstack}%
    \rule{1em}{\ht\strutbox}%
\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@makefnstart}
% This is called in the start of \cmd{\@makefntext}.
%    \begin{macrocode}
\providecommand{\FN@seitenobreak}{\nobreak}
\def\FN@makefnstart{%
%    \end{macrocode}
%   Record the footnote specific dimensions.  It is assumed that they
%   don't change in the document, at least not before the footnote
%   gets actually placed.
%    \begin{macrocode}
  \expandafter\xdef\csname FN@ht\number\FN@masterinsert\endcsname
    {\the\footnotesep}%
  \expandafter\xdef\csname FN@dp\number\FN@masterinsert\endcsname
    {\the\dp\strutbox}%
  \expandafter\xdef\csname FN@wd\number\FN@masterinsert\endcsname
    {\the\hsize}%
%    \end{macrocode}
%   The footnote gets markers for identifying it and its starting block.
%    \begin{macrocode}
  \marks\FN@master{\FN@masterslot}%
  \marks\FN@slave{\number\FN@id}%
  \nobreak
%    \end{macrocode}
% \cmd{\FN@commonending} will intervene before any tokens that are
% shifted in due to switching back the color stack.  Those will only
% be executed once we completely relinquish control.
%    \begin{macrocode}
  \ifx\FN@boxtype\vbox
    \rule\z@\footnotesep
  \else
    \ifx\FN@par\par\else
      \let\FN@@par\par
      \let\FN@@noindent\noindent
      \let\FN@@indent\indent
    \fi
     \everyvbox\expandafter{\expandafter\everyvbox
       \expandafter{\the\everyvbox}%
       \let\par\FN@@par
       \let\noindent\FN@@noindent
       \let\indent\FN@@indent
       \the\everyvbox}%
     \let\par\FN@par
     \let\noindent\FN@noindent
     \let\indent\FN@indent
  \fi
  \FN@seitenobreak
  \afterassignment\ignorespaces}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@makefnrobust}
%   After preparation, we now do the big bad trick for making
%   footnotes cooperate with \cmd{\verb} and other catcode changing
%   things: we call \cmd{\@makefntext} with an argument of
%   |\iffalse|.  This kills off its expansion right at the point
%   where it would choose to place its argument.
%
%   Furthermore, this swallows the opening brace of the footnote text
%   and then lets the footnote text progress.  The closing group will
%   then trigger the processing via \cmd{\aftergroup}.
%    \begin{macrocode}
\def\FN@makefnrobust#{%
  \FN@specific\FN@masterinsert\@makefntext
  \iffalse\fi
  \bgroup
    \aftergroup\FN@robustending
    \FN@makefnstart
    \let\next}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@robustending}
%   Here we put in the missing part of \cmd{\@makefntext}.
%    \begin{macrocode}
\def\FN@robustending{%
  \expandafter\expandafter\expandafter
  \expandafter\expandafter\expandafter\expandafter
  \iffalse  \FN@specific\FN@masterinsert\@makefntext\fi
  \FN@commonending}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@makefnfragile}
%   This is the escape route when the robust variant does not work.
%   In that case, |\verb| and similar won't work in footnotes.
%    \begin{macrocode}
\long\def\FN@makefnfragile#1{%
  \FN@specific\FN@masterinsert\@makefntext
  {\FN@makefnstart#1\FN@commonending}}
%    \end{macrocode}
%
% \end{macro}
%
% Ok, color handling is a nuisance, to say the least.  Split
% footnotes need to close their color stack on the old page, and reopen
% it on the new one.  So we record the color stack state at each time
% it changes in a marks register.
%    \begin{macrocode}
\newmarks\FN@color
\def\FN@colorstackbgroup{\let\FN@savecolorstack\FN@colorstack
  \global\let\FN@colorstack\@empty
  \bgroup
  \ifdefined\FN@savecolorstack\else
    \let\FN@@set@color\set@color
    \let\FN@@reset@color\reset@color
    \let\FN@@color@begingroup\color@begingroup
  \fi
  \let\set@color\FN@set@color
  \let\reset@color\FN@reset@color
  \let\color@begingroup\FN@color@begingroup}

\def\FN@colorstackegroup{\egroup
  \global\let\FN@colorstack\FN@savecolorstack}

\def\FN@colorstackfinish{\def\@elt##1##2{\FN@@reset@color##2}%
  \FN@colorstack
  \def\@elt##1##2{\noexpand\@elt{}{##2}}%
  \xdef\FN@colorstack{\FN@colorstack}%
  \let\@elt\relax
  \marks\FN@color{}}

\def\FN@reset@color{%
  \bgroup\def\@elt##1##2{\def\FN@next{##1}{\gdef\FN@colorstack{##2}}}%
    \let\FN@next\@empty
    \FN@colorstack
    \ifx\FN@next\@empty
      \FN@colorstackegroup
    \else \egroup
      \FN@@reset@color
      \marks\FN@color{\FN@colorstack}%
  \fi}

\def\FN@color@begingroup{%
  \let\reset@color\FN@@reset@color
  \let\color@begingroup\FN@@color@begingroup
  \let\set@color\FN@@set@color
  \color@begingroup}

\def\FN@set@color{\FN@@set@color
  \xdef\FN@colorstack{\@elt{\current@color}{\FN@colorstack}}%
  \marks\FN@color{\FN@colorstack}}

\def\FN@coloraftersplit#1{%
  \def\@elt##1##2{##2\def\current@color{##1}\set@color}%
  #1%
  \let\@elt\relax}
%    \end{macrocode}
% \begin{macro}{\FN@commonending}
%   We'll eventually arrive here at the end of the footnote.  Now we
%   again call \cmd{\@makefntext}, but this time pass it |\fi| as
%   its argument, and place |\iffalse| before its expansion.  This
%   cuts away the start of the macro.  If this start changes the tail
%   of the macro when executed, the whole trickery will not work.  It
%   turns out that a large sampling of document classes (including the
%   standard ones) happens to work.
%    \begin{macrocode}
\def\FN@commonending{%
  \@makefnendbox
  \ifx\FN@boxtype\vbox\@finalstrut\strutbox \else \unskip \fi
  \FN@colorstackfinish
  \color@endgroup
  \egroup
  \global\advance\FN@id\@ne
  \FN@slotxdef\FN@masterslot{\number\FN@id}%
%    \end{macrocode}
%   Now we want to get an upper estimate of the size.  In case of a
%   horizontal box, we do this by creating a vertical box of it all
%   alone, and measuring that.  Measuring the hbox itself is plain
%   out: \TeX's maximal dimension of something like 5\,m is already
%   busted with about two pages of material.  We put the master slot
%   identification into the depth of the box, and arrange for the
%   total of depth and height of the box to still give the total depth
%   and height of its size on the page.
%    \begin{macrocode}
  \ifhbox\z@
    \global\setbox\FN@tempbox\copy\z@
    \setbox\tw@\@makefnvbox{\unhbox\FN@tempbox}%
    \ht\z@\dimexpr\ht\tw@+\dp\tw@-\FN@masterslot sp\relax
  \else
    \ht\z@\dimexpr\ht\z@+\dp\z@-\FN@masterslot sp\relax
  \fi
%    \end{macrocode}
%   Now we put the sorting criterion into the width of the box, and
%   then put the masterslot id into the depth.
%    \begin{macrocode}
  \wd\z@\dimen@
  \dp\z@\FN@masterslot sp\relax
%<trace>      \ifnum\z@<0\FN@slotget{\FN@masterslot} %
%<trace>      \else \errmessage{Inconsistent
%<trace>        \string\FN@masterslot=\FN@masterslot}\fi
%    \end{macrocode}
%   Now we just need to place the stuff into an insertion and record
%   the possibly changed slave id in order to know what subordinate
%   footnotes belong to this one.
%    \begin{macrocode}
  \MFL@insert\FN@masterinsert{\nointerlineskip\box\z@}%
  \ifdim\lastkern=\z@ \let\FN@next\@empty\else
    \edef\FN@next{\kern\the\lastkern\relax}\unkern
  \fi
  \marks\FN@slave{\number\FN@id}%
  \expandafter\FN@enddivert\expandafter\FN@colorstackegroup
  \FN@next
}
%    \end{macrocode}
% \end{macro}
% A lot of stuff follows.  This should really be cleaned up and
%   documented.
%    \begin{macrocode}
\dimen\footins\maxdimen
\gdef\FN@nestlist{}

\newdimen\FN@outervsize
\newskip\FN@vsize

\newbox\FN@insertions

%<trace>\def\MFL@showone#1#2{\message{Box #2:}\showbox#2%
%<trace>  \MFL@checkconsistency{#2}%
%<trace>  \message{Cachebox #2:}\showbox\FN@cache#2}
%<trace>
%<trace>\def\MFL@checkconsistency#1{{%
%<trace>  \setbox\z@\vbox{\unvcopy#1%
%<trace>    \MFL@checkconsistencyi{#1}}}}
%    \end{macrocode}
% \begin{macro}{\MFL@checksinglebox}
%   Check box~|#1| for consistency.  If it is bad, output box~|#2|.
%   Execute |#3| if it was good, |#4| if it was bad.
%    \begin{macrocode}
%<trace>\def\MFL@checksinglebox#1#2#3#4{%
%<trace>    \ifvoid#1\else
%<trace>      \ifnum\z@<0\FN@slotget{\number\dp#1} %
%<trace>        #3%
%<trace>      \else \errmessage{Inconsistent box #2}%
%<trace>         \showboxdepth4\showboxbreadth100
%<trace>         \showbox#2\relax
%<trace>         #4%
%<trace>      \fi\fi}
%    \end{macrocode}
% \end{macro}
%    \begin{macrocode}
%<trace>\def\MFL@checkconsistencyi#1{%
%<trace>    \unpenalty\unskip\unkern
%<trace>    \setbox\z@\lastbox
%<trace>    \MFL@checksinglebox\z@{#1}{{\MFL@checkconsistencyi{#1}}}{}}
%<trace>
%<trace>\def\MFL@showall{{%
%<trace>    \showboxbreadth=\maxdimen
%<trace>    \showboxdepth=4
%<trace>    \tracingonline=\@ne
%<trace>    \FN@nest@iterate\MFL@showone}}
%    \end{macrocode}
% \begin{macro}{\FN@retaindelayed}
%   This is a complex macro that removes all boxes from the current
%   list that are not to be kept for the next page.  It works on the
%   material from the original insertions, not the cache boxes.
%   The slot specified by \cmd{\count@} is not freed when encountered,
%   all others are freed upon removing the box.  The last box is
%   returned in box~0 if any is retained.  The vertical list might
%   have an unchecked part locked off in front by placing a
%   \cmd{\nobreak} penalty there.  This penalty is removed, and the
%   list before it not touched.
%    \begin{macrocode}
\def\FN@retaindelayed{%
  \setbox\z@\lastbox
  \ifcase
    \ifvoid\z@\m@ne\fi \FN@config\z@
%<trace>  \if\foottrace8\message{^^J\string\FN@retaindelayed:
%<trace>     dropping Id \FN@slotget{\number\dp\z@}}\fi
%<trace>  \if\foottrace{16}{\showboxdepth4 \showboxbreadth400
%<trace>     \tracingonline=\@ne\showbox\z@}\fi
    \ifnum\dp\z@=\count@\else \FN@freeslot{\number\dp\z@}\fi
%<trace> \ifnum\dp\z@<\@ne \errmessage{Unidentified box}\fi
    \expandafter\FN@retaindelayed
  \or
%<trace> \if\foottrace8\message{^^J\string\FN@retaindelayed:
%<trace>    retaining Id \FN@slotget{\number\dp\z@}}\fi
%<trace>  \if\foottrace{16}{\showboxdepth4 \showboxbreadth400
%<trace>     \tracingonline=\@ne\showbox\z@}\fi
    {\FN@retaindelayed \nointerlineskip \box\z@}%
  \else \unpenalty \setbox\z@\lastbox
%<trace>  \ifnum\lastnodetype>\m@ne
%<trace>    \errmessage{Unexpected node \number\lastnodetype}\fi
%<trace>  \ifvoid\z@ \else
%<trace>     \if\foottrace8\message{^^J\string\FN@retaindelayed:
%<trace>        carrying split box \FN@slotget{\number\dp\z@}}\fi
%<trace>     \if\foottrace{16}{\showboxdepth4 \showboxbreadth400
%<trace>        \tracingonline=\@ne\showbox\z@}\fi\fi
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MFL@processplain}
%   This gets called for actually inserting the processed material
%   into the footnote box.  The current state of affairs is that
%   \cmd{\FN@config} contains all footnotes that should get
%   transferred to the next page completely.  The cache boxes contain
%   the collected and typeset footnotes for typesetting on the current
%   page.
%
%   The structure of a cachebox is currently as follows: it is filled
%   with vboxes containing the arranged material, optionally followed
%   by another box to be carried over to the next page flagged with a
%   \cmd{\nobreak} penalty.
%    \begin{macrocode}
\def\MFL@processplain#1{%
%<trace> \MFL@checkconsistency#1%
   \ifvoid\FN@cache#1%
%    \end{macrocode}
% Now if the cache box is void, nothing gets typeset on the current
% page.  What we do, however, is to collect all boxes from the
% original insertion that did not make it on this page and reinsert
% them.  \cmd{\count@} is cleared to zero to retain nothing special.
%    \begin{macrocode}
     \global\setbox\FN@tempbox\vbox\bgroup
       \unvbox#1%
       \count@\z@
       \let\@elt\FN@removecheck \FN@retaindelayed
       \ifvoid\z@ \egroup
       \else \nointerlineskip \box\z@ \egroup
         \MFL@realinsert{#1}{\unvbox\FN@tempbox}%
       \fi
%    \end{macrocode}
% The following stops in the insertion process within the |manyfoot|
% package.
%    \begin{macrocode}
     \expandafter\expandafter
   \fi\iffalse\fi
%    \end{macrocode}
% Ok, this is the case when we have a nonvoid cache box.
%    \begin{macrocode}
   \global\setbox#1\vbox\bgroup%
     \unvbox\FN@cache#1%
     \ifnum\lastpenalty>\z@
       \unpenalty
       \setbox\z@\lastbox
     \else
       \setbox\z@\box\voidb@x
     \fi
%    \end{macrocode}
% Ok, now box zero contains carryover material (if any).  We
% initialize \cmd{\count@} to this so that we will keep this carryover
% material just once.
%    \begin{macrocode}
     \count@\dp\z@
     \global\setbox\FN@tempbox\vbox\bgroup
       \box\z@
       \nobreak
       \unvbox#1%
       \let\@elt\FN@removecheck \FN@retaindelayed
       \ifvoid\z@ \egroup \MFL@removevboxes\egroup
       \else \nointerlineskip \box\z@ \egroup
         \MFL@removevboxes \egroup
         \MFL@realinsert{#1}{\unvbox\FN@tempbox}%
       \fi}

\let\MFL@processpara\MFL@processplain
%    \end{macrocode}
% \end{macro}
% Ok, here is the bit about the caches: whenever we encounter a new
% configuration, we have to first update the caches since we don't
% know the sizes we are dealing with regarding the new configuration
% until we do so.  The caches are kept up to date globally.  When we
% are working at several levels in the recursion, we have a bottom
% active level where we may are looking for a way to find a best break
% and configuration.  We will return at most one configuration once we
% are finished.  While we are working with a returned configuration,
% adding more material on the current list will not require another
% recursion as long as the totals stay underfull: the penalty
% difference between underfull configurations becomes smaller while
% the underfullness decreases, which means that smaller breaks that
% have not been chosen before might become eligible if the penalties
% allow for that.  Only when the badness of underfullness remains
% infinite can't we have any improvement.
%
% Ok, after we recurse for removing an underfull condition, the
% resulting configuration can't actually be used further for breaks
% with less remaining space.  It is, however, clear that if less space
% remains, there is no better break with the same configuration
% leaving \emph{more} space: if there were, it would already have been
% taken.  That means that our goal height for the next break will be
% chosen in order to reach the exact size met on the last recursion.
% No break before that can be chosen on the next try, but a break
% after it might then be taken.
%
% available, or an overfull one.  If a deeper level at any point of
% time returns an overfull configuration, we are finished.  The best
% configuration to be returned is the least underfull.  If there is
% none, the least overfull.  The case of no underfull at all can only
% happen if even splitting this and every subordinate level to minimal
% height and recursing does not yield an underfull.  At every level,
% we need to maintain just a current split, and the previous best
% split at most.
%
% When we change a configuration on recursing, we have to remember the
% configurations for the previous best split.  We can manage that by
% sweeping the current cache values into a local box register
% before recursing with a different configuration: we have to rebuild
% the box registers for a different configuration, anyway.  We don't
% save the configuration from an overfull setting: when we rework the
% list in slow motion mode, we can't help stopping the recursion by
% reaching an overfull setting that is at least as good as the
% initial one.
%
% When we return to a caller, we leave the cache in the configuration
% of the best choice up to now: either we are returning an overfull
% configuration and if it is not the best so far, the caller can
% restore his better choice from his copy, or we are returning an
% underfull configuration in which case the caller might still want to
% improve upon it before returning to its caller in turn.  New: If we
% return an underfull configuration, we also return an ``optimal
% penalty estimate'' that gives the best break point penalty under the
% assumption that additional stretchability is present on the page.
%
% The purpose of this is to offer the possibility of avoiding widows
% and similar by moving more material in some footnotes to the next
% page in exchange for other material.
%
% At the current grouping level we empty out our current cache and
% keep it for working purposes on the vertical list until we return
% (nobody references it while we are working on it).  We always enter
% with an overfull configuration, meaning that \cmd{\FN@vsize} is
% negative.  It is calculated with the current cache\slash config
% setting.
%
% There is a danger of overflow involved with that: if we keep a swept
% complete configuration at each level of recursion, we need $O(n^2)$
% of space here.  The alternative would be to keep the history of how
% the configuration came about.  Since that might involve some
% slow-motion splitting, this is also a speed issue.  Since deep
% recursion with pending best data at each level is not really
% likely, and since we are not going to have that many footnote
% levels to go around, anyway, we just rely on \LaTeX\ having been
% started with sufficient memory.
%
% A workable compromise would be to just store the split boxes
% from a configuration together with the configuration data for
% reconstructing the rest.  After all, we don't need to reconsider
% such a configuration before actually typesetting anything.  And
% whenever we find an acceptable fit (neither underfull\slash
% overfull), we could cut through all the hierarchy without having to
% restore anything.  This has not been implemented yet: at the moment
% we go for the less complicated variation.
%
%
% The algorithm we use here is a bit complicated.  Whenever we
% recurse, we have one of the following situations:
% \begin{enumerate}
% \item An overfull/underfull dilemma: including a minimal amount of
%       material at the current level will cause the page to become
%       overfull.  This can be the case in connection with zero (in
%       case of interline penalties for larger blocks), one or more
%       subordinate footnotes and related footnotes.
% \item A pure overfull dilemma: the page was overfull to start with,
%       we need to reduce it.
% \item an underfull dilemma: some operation in the next level made
%       the page become underfull, only too much so.  We can't make it
%       fuller on the current level, but we can make it even emptier,
%       and let the next level fill it up again.
% \end{enumerate}
%
% In the current implementation, we just ignore the slight probability
% that the optimum choice might lie with case~3.  We don't
% recurse for making the page fuller again.  If we have an
% overfull/underfull dilemma, the recursion will either give us a
% less awful overfull box, or an underfull one.  An overfull box that
% occurs at the highest level of recursion can't be improved on any
% lower level.  So we never need to locally return an overfull box: we
% can compare it to the best overfull box seen before, and if we turn
% out better than that, we overwrite the global best overfull value
% and return the best local underfull if there is such a one.  The
% best local underfull will then be refilled as much as possible on
% the next level without changing the configuration.  Actually, if we
% need to change the configuration, this would also be fine as long as
% we arrive at a better underfull eventually.  But since a change of
% configuration renders our previous split completely useless, as the
% broken paragraph could look disastrously different under a changed
% configuration, we would need to recurse again.  We repeat this
% recursing operation until we don't get an underfull solution
% returned anymore.  We then return the best underfull, if any.  The
% best overfull is stored globally, as mention before.
%
% Does this sound complicated?  Unfortunately, it does.  It also
% sounds somewhat slow.  For that reason, we do a few assumptions that
% will facilitate a good average-case behavior.  The first assumption
% is that we will usually do fine by just splitting in the current
% level (if at all) and not at all in subordinate levels.
%
% We do this assumption on the first pass used for gathering the size
% information and collect the corresponding boxes in nested lists.
% When the recursion tops out, it does so either with an overfull
% page, or an underfull page.  If it does with an underfull page, we
% cache the current configuration for the next pass through the output
% routine, so that we won't need to retypeset and measure assembled
% boxes that have not gathered any new material.  If we top out with an
% overfull page, the previous underfull configuration is still worth
% keeping as well, as it might become the material actually chosen to
% be typeset.
%
% Ok, the current best configuration of the next recursion level is
% gathered on the current vertical list, in a separate box.  We use
% box~2 for this purpose.  A saved configuration consists of the
% complete contents for the current cache box without the trailing
% penalty indicating material from a single split box carried over to
% the next page (boxes that are carried over completely to the next
% page are not maintained here but rather reinserted by
% \cmd{\MFL@processnested}).  This penalty is added in case the box
% is actually disassembled and returned: there is no possibility for
% confusion since we only save such a configuration if indeed there is
% a split present.
%    \begin{macrocode}
\newtoks\FN@output
\FN@output\output

\newbox\FN@tempbox
\newinsert\FN@savebox
\count\FN@savebox\@m
\dimen\FN@savebox\maxdimen
\skip\FN@savebox\z@skip
\global\setbox\FN@savebox\box\voidb@x

\expandafter\expandafter\expandafter\let\FN@cache\FN@savebox=\@cclv

\expandafter\def\csname FN@ht\number\FN@savebox\endcsname{\z@skip}%
\expandafter\def\csname FN@dp\number\FN@savebox\endcsname{\maxdepth}
\expandafter\def\csname FN@wd\number\FN@savebox\endcsname{\columnwidth}

\def\FN@list{\MFL@list\@elt{}\footins}

\def\FN@sweepbox#1#2{\ifvoid#2\else
  \nointerlineskip\box#2\penalty#2\fi}

\def\FN@sweepcachebox#1#2{\nointerlineskip
  \box\FN@cache#2%
  \penalty\FN@cache#2}

\def\FN@copycachebox#1#2{\nointerlineskip
  \copy\FN@cache#2%
  \penalty\FN@cache#2}

\def\FN@restoreboxes{\count@\lastpenalty \unpenalty
  \ifnum\count@>\z@
    \global\setbox\count@\lastbox
    \expandafter\FN@restoreboxes
  \fi}
%    \end{macrocode}
% \begin{macro}{\FN@removecheck}
%   This returns |\@ne| if and only if the current slot master is strictly
%   inside of the specified open interval.  In this case it is not to
%   appear on the current page.
%    \begin{macrocode}
\def\FN@removecheck#1#2{%
  \ifnum#1<\FN@slotget{\number\dp\z@} %
  \ifnum#2>\FN@slotget{\number\dp\z@} %
    \@ne\fi\fi}
%    \end{macrocode}
% \end{macro}
% Parameter recording merely records the relevant value of the
% skip register and sets it to zero.  The purpose is to avoid changes
% of the reserved page space when we collect additional material from
% a page where an insertion of the appropriate kind had already been
% encountered.  This is used for filling up underfull pages.
%    \begin{macrocode}
\def\FN@recordinsertparam#1#2{\ifvoid#2\else
  \global\skip\number#2=\the\skip#2\relax\fi}

\def\FN@clearinsertparam#1#2{\ifvoid#2\else
  \global\skip#2=\z@skip\fi}
%    \end{macrocode}
% \cmd{\FN@insertouterspace} will sum the size of the inserts manually.
%    \begin{macrocode}
\def\FN@insertouterspace#1#2{\ifvoid#2\else
    +\skip#2+(\ht#2+\dp#2)*\count#2/\@m\fi}

\def\FN@list@iterate#1{\let\FN@eltsave\@elt
  \let\@elt#1%
  \FN@list
  \let\@elt\FN@eltsave}

\def\FN@nest@iterate#1{\let\FN@eltsave\@elt
  \let\@elt#1%
  \FN@nestlist
  \let\@elt\FN@eltsave}
%    \end{macrocode}
%
% \subsection{The output routine stuff}
%
% \paragraph{Marks}
% This is used for sweeping all marks up for reinsertion.
% \begin{macro}{\FN@allmarks}
%    \begin{macrocode}
\def\FN@allmarks#1{\@elt{#1}%
  \ifnum#1<\count266
    \expandafter\FN@allmarks\expandafter{\number\numexpr#1+\@ne}%
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@sweeptopmarks}
% \begin{macro}{\FN@topmarkbox}
%   This sweeps the current topmarks and places them into the global box
%   \cmd{\FN@topmarkbox}.
%    \begin{macrocode}
\def\FN@sweeptopmarks{\global\setbox\FN@topmarkbox\vbox{%
    \def\@elt##1{\marks##1{\unexpanded\expandafter{\topmarks##1}}}%
    \FN@allmarks0}}
\newbox\FN@topmarkbox
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\FN@establishmarks}
%   This sets marks from a marks sweep.  The first argument is the
%   mark number, the second is from the first mark on the first scan,
%   the third argument from the bottom mark on the first scan, and the
%   fourth argument from the bottom mark on the second scan (with
%   additional mark entries).  If second and third arguments don't
%   match, no mark gets placed.
%    \begin{macrocode}
\long\def\FN@establishmarks#1#2{\edef\reserved@a{\unexpanded{#2}}%
  \edef\reserved@b{\unexpanded\expandafter{\splitbotmarks#1}}%
  \ifx\reserved@a\reserved@b
    \marks#1{\unexpanded\expandafter{\splitfirstmarks#1}}%
    \marks#1{\unexpanded\expandafter{\reserved@b}}%
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@markspassone}
%   This constitutes the first pass for mark collection.  We do this
%   just to check whether there are any marks in the list.
%    \begin{macrocode}
\def\FN@markspassone#1{\noexpand\FN@establishmarks{#1}%
  {\unexpanded\expandafter{\splitbotmarks#1}}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@insertmarks}
%   This routine transfers first and bottom marks from the current
%   |\box255| to the vertical list in order to get the marks right.
%   This is quite a bother, since we must detect the special case
%   where there are no marks at all in the list, and since we might
%   require the use of several \cmd{\vsplit} commands in a row, since
%   infinite stretch might make the optimal breakpoint lie before the
%   end of the box in spite of its large size.
%
%   So we need to do the splitting in a loop, and do it twice, once
%   with artificial marks at the start.  If those artificial marks
%   make it to \cmd{\splitbotmarks}, we don't place any actual marks.
%    \begin{macrocode}
\def\FN@pseudomarks#1{\marks#1{X}}
\def\FN@insertmarks{%
  {\setbox\z@\copy\@cclv
    \splittopskip-\maxdimen\relax
    \vbadness=\@M
    \vfuzz=\maxdimen
    \loop
    \ifvoid\z@\else
      {\let\@elt\FN@pseudomarks
        \setbox\z@\vbox{\FN@allmarks0\nobreak\unvcopy\z@}%
        \setbox\z@\vsplit\z@ to\maxdimen}%
      \let\@elt\FN@markspassone
      \edef\next{\FN@allmarks0}%
      \setbox\z@\vbox{\nobreak\unvbox\z@}%
      {\setbox\z@\vsplit\z@ to\maxdimen}%
      \next
    \repeat}}
%    \end{macrocode}
% \end{macro}
% \paragraph{Some stuff}
%
% \begin{macro}{\FootnoteMainMinimum}
%   This specifies the minimum amount of main text.  You can make this
%   a complicated expression if you want to, for example by checking
%   the presence of particular footnotes.
%    \begin{macrocode}
\def\FootnoteMinimum{1sp}
\def\FootnoteMainMinimum{0pt}
\expandafter\def\csname\string\FootnoteMinimum\number\FN@savebox
\endcsname{\FootnoteMainMinimum}
%    \end{macrocode}
% \end{macro}
%
%\paragraph{The output routine itself}
%
% This is our own output routine that does all the balancing stuff.
% If we receive a forced penalty here, we must not do any of our
% output processing on our own unless this is the choice of the
% underlying output routine.  We do want to have the `real' output
% routine to have a correct idea about the size that the insertions
% will take up.  So the steps that we \emph{will} actually perform in
% any case are sorting the insertions and calculating their real
% size.  If we have not had a forced penalty, we are free to exit the
% output routine for gathering further material as there are no
% expections of the underlying output routine when it should get
% called.  If we encountered a forced penalty, things are getting more
% complicated.  If the current page happens to be overfull after
% adding the current material, we first need to ship out the material
% for a regular page (after splitting off the necessary material for
% the next page).  We then reinsert the remaining split insertions,
% any possibly split off page material and the penalty.
%
% \TeX\ is rather monotonous in its page break processing.  Increase
% the available page size, and the available page material will also
% increase.  There is a singular exception to that rule, and that are
% split and floating insertions.  However, we notice their presence by
% a non-zero setting of \cmd{\insertpenalties}, and we can just
% measure the material that they have taken up in a forced pass of the
% output routine, adding that much to our request size.  However, this
% operation will change the penalties associated with the page breaks.
%
% Unfortunately, this is not sufficient: the penalty might have been
% inserted with a box immediately preceding it.  In that case the
% penalty would have been guaranteed to eventually turn up in the
% output routine.  If we now reinsert merely all of the above stuff,
% the penalty will just disappear.  If we protect the penalty by
% placing an empty box before it when none of it had been before it
% before, we will get an empty page.  Since we don't know whether the
% penalty was supposed to disappear at the start of an empty page or
% not, we will do the following: if the rest of |\box255| is nonvoid,
% we just reinsert the split insertions followed by the rest of
% \box255 and the penalty and return.  If it is void, we call the
% regular output routine, capturing its output in a |\vbox| of its
% own.  If the regular output routine failed to ship out the prepared
% insertions, we just keep the original data either in their boxes or
% in a reinserted insertion.
%
% It hides the relevant information from the `real' output routine
% until such a time that we have enough material gathered to produce a
% full page.  The exception to this is when we have a special penalty
% that gets passed through to the regular output routine.
%
% If we are on a material collecting spree, \cmd{\FN@savebox} contains
% all boxes from the last output call time.  At the point where we
% enter the output routine, \cmd{\FN@vsize} contains the amount of
% space available for mounting footnotes, after subtracting all
% insertions of footnote variety.  At most times in our output
% routine, the variable will contain the amount of space left after
% everything is put to the page including footnotes.
%    \begin{macrocode}
\savingvdiscards=\@ne
%    \end{macrocode}
% We have the following situations that can cause us to enter the
% output routine:
% \begin{enumerate}
% \item The page has just filled up.
% \item A magic output penalty has been encountered.
% \item We are filling up a previously underfull page.
% \item We are looking for missing insertions that may have floated.
% \end{enumerate}
%
% We are trying to do bookkeeping on the effects of page size for
% insertions that fall into the footnote class.  While we do basic
% bookkeeping for other insertions as well, this can only be
% incomplete since we don't reinsert material.  In consequence,
% multiple material ending up in the same insertion might cause the
% corresponding skip register to be accounted for several times.
% \LaTeX\ does not really reuse insertions in that manner except for
% footnotes, so we are mostly ok here.
%
% |bigfoot| usually does some lookahead in the main list in order to
% obtain optimal breakpoints.  It explicitly undoes the effect this
% has on marks, but insertions are a different matter here.  So floats
% may appear on an earlier page than expected.
%
% If the output routine is invoked with a penalty of $-13750$, then
% the page content is merely used for setting the \cmd{\topmarks}
% array.  In that case, we just clear out the output box and resume.
% We don't fiddle with \cmd{\deadcycles} in order to catch foulups.
%
% Also we don't touch insertion boxes.  There is a particular
% situation where there \emph{are} insertions, namely if we are
% collecting insertions after the last output routine has ended up
% with a non-zero value of \cmd{\insertpenalties}.  In this case, all
% insertions we \emph{do} get are floating insertions, meaning that
% they had a preceding insertion of the same class already on the last
% page, and thus we have zeroed its skip register already.  We are
% assuming that a single pass with such a large \cmd{\vsize} is
% sufficient for pulling all insertions.  If that happens to be
% incorrect, insertions need to get pulled in piecewise, but then we
% are probably in big dodo with regard to page size accounting,
% anyway.
%    \begin{macrocode}
\newcount\FN@outputflag
\FN@outputflag=3158345
\output{%
  \let\@elt\relax
  \ifvoid\@cclv \PackageError{bigfoot}{Empty box 255 in \output}\fi
%<trace> \if\foottrace8%
%<trace>   \message{entering output with
%<trace>      \outputpenalty=\the\outputpenalty:}%
%<trace>   {\showboxdepth4\showboxbreadth\maxdimen\showbox\@cclv}\fi
  \ifnum\outputpenalty=-13750
%<trace>  \if\foottrace8%
%<trace>    \message{Discarding box 255.}%
%<trace>  \fi
    \ifnum\insertpenalties>\z@
      \PackageError{bigfoot}{Too much insertion material}{%
        This error means that the output routine was not able to^^J%
        gather all floating insertions in a single pass.^^J%
        Complain to the author if you consider this a bug}%
    \fi
    \global\advance\FN@outervsize\dimexpr\ht\@cclv-\vsize
    \global\setbox\@cclv\box\voidb@x
  \else
%    \end{macrocode}
% Note that a potential \cmd{\FN@vsadjustlist} will restore the
% previous value of \cmd{\outputpenalty}.  So we need to save it.
%    \begin{macrocode}
  \edef\FN@outputpenalty{\number\outputpenalty}%
  \ifvoid\FN@savebox
    \ifvoid\@holdpg
      \FN@sweeptopmarks
    \fi
    \FN@nest@iterate{\FN@insertouterspace\global\FN@outervsize
      \dimexpr\z@}%
    \global\advance\FN@outervsize\ht\@cclv
    \global\setbox\@cclv\vbox{\unvbox\@cclv\boxmaxdepth\maxdepth}%
    \global\let\FN@vsadjustlist\@empty
%    \end{macrocode}
% \cmd{\FN@outervsize} now contains the value of \cmd{\pagegoal} at
% the time of output.  It should be \cmd{\vsize} adjusted by the
% natural size of insertions.  Note that \cmd{\FN@normaloutput} is not
% required to return with a sensible value of \cmd{\outputpenalty}.
%    \begin{macrocode}
    \FN@normaloutput
  \else
%    \end{macrocode}
% We now are in the situation that we already have collected material
% previously.  We can't be sure that adding a special penalty does not
% take more than one output routine call before delivery.  For that
% reason, we don't rely on special outputs being special and always
% subtract any additionally demanded \cmd{\vspace} from
% \cmd{\FN@outervsize} before calling a special output, so that we can
% afterwards compensate for it.
%    \begin{macrocode}
    \FN@nest@iterate{\FN@insertouterspace\global\advance\FN@outervsize
      \dimexpr\ht\@cclv}%
    \global\setbox\@cclv\vbox{\unvbox\@cclv\boxmaxdepth\maxdepth}%
%    \end{macrocode}
% Now we invalidate the cache boxes for all insertions that had
% changed due to the recent additions to the page (this does
% \emph{not} affect \cmd{\FN@vsize}).
%    \begin{macrocode}
    \FN@nest@iterate\FN@maybeinvalidatecache
%    \end{macrocode}
% We now update all boxes by inserting the previously collected
% material in front of the boxes.
%    \begin{macrocode}
    \vskip\z@skip
    \unvbox\FN@savebox
    \loop
      \count@\lastpenalty
    \ifnum\count@>\z@
      \unpenalty
      \setbox\z@\lastbox
      \global\setbox\count@\vbox{\unvbox\z@\unvbox\count@}%
    \repeat
    \ifcase
      \ifnum\FN@outputpenalty=-13749 \@ne\fi
      \ifnum\FN@outputpenalty=-13751 \@ne\fi \tw@
    \or
%    \end{macrocode}
% \cmd{\outputpenalty} is restored to the original value before the
% total page is glued together.
%    \begin{macrocode}
      \FN@vsadjustlist
%<trace> \if\foottrace8\message{receiving special penalty
%<trace>    \FN@outputpenalty, dissing box 255:}%
%<trace>      {\showboxdepth4 \showboxbreadth400
%<trace>       \tracingonline=\@ne\showbox\@cclv}\fi
%    \end{macrocode}
% This special penalty means that we have been collecting floated
% insertions right now.  So |\box255| is actually empty except for
% filler material.  We restore the old box into it.
%    \begin{macrocode}
      \global\setbox\@cclv\lastbox
      \unskip
%<trace>  \ifnum\lastnodetype>\m@ne
%<trace>    \errmessage{Unexpected node \number\lastnodetype}\fi
      \ifnum\FN@outputpenalty=-13749
        \FN@normaloutput
      \else
        \the\FN@output
        \@pageht-\vsize
        \let\@currbox\footins
        \@reinserts
        \global\vsize-\@pageht
      \fi
    \else
      \dimen@\topskip
      \FN@vsadjustlist
      \setbox\z@\lastbox
      \unskip
%<trace>  \ifnum\lastnodetype>\m@ne
%<trace>    \errmessage{Unexpected node \number\lastnodetype}\fi
%    \end{macrocode}
% Ok, now we reconstruct the box from its parts.  We add the material
% together, taking the previous output penalty and the current page
% discards (if it belongs between those boxes, otherwise we leave it
% on the list) for glueing the stuff together.  The previous output
% penalty then is irrelevant for further purposes and we replace it
% again.  \cmd{\FN@outervsize} has been
% adjusted by the accumulated contributions of insertions to the page
% size.  Fiddling with it would not appear necessary or even prudent.
%    \begin{macrocode}
%<trace>\if\foottrace8
%<trace>   \message{Box 255 before reglue
%<trace>     (outputpenalty=\the\outputpenalty):}%
%<trace>   {\showboxdepth4\showboxbreadth100\showbox\@cclv}\fi
      \global\setbox\@cclv\vbox{%
%    \end{macrocode}
% Now we might have had a \cmd{\topskip} value designed for requesting
% a given number of lines.  We need to remove anything of that kind.
% Splitting again achieves that.  If the current page was empty except
% for insertions, this means that we gain a new breakpoint.  But
% insertions with discardable material before them would be unusual.
%
% The only exception to this may happen if the current page contained
% only insertions: in this case \TeX\ has made a page break before the
% actually inserted \cmd{\topskip} glue (which will then arrive one
% page later).
%
% Note that the pagediscards contain material corresponding to the
% last breakpoint chosen, so they will either start with a penalty
% of~10000 (which is what an actual outputpenalty gets replaced with)
% or will start with discardable material.  We clean it for that
% reason.
%    \begin{macrocode}
        \unvbox\z@
        \global\setbox\@cclv\vbox{\break\unvbox\@cclv}%
        {\splittopskip-\maxdimen \setbox\z@\vsplit\@cclv to\z@}%
        \ifnum\outputpenalty=\@M
          \setbox\z@\vbox{\pagediscards
            \FN@cleanpagepenalty}%
          \unvbox\z@
        \else
          \penalty\outputpenalty
          \pagediscards
        \fi
        \unvbox\@cclv
        \boxmaxdepth\maxdepth}%
%<trace>\if\foottrace8
%<trace>   \message{Box 255 reglued (outputpenalty=\FN@outputpenalty):}%
%<trace>   {\showboxdepth4\showboxbreadth100\showbox\@cclv}\fi
      \global\outputpenalty\FN@outputpenalty\relax
%    \end{macrocode}
% Ok, now if \cmd{\topskip} is actually \emph{positive}, we have been
% collecting material tentatively without having proper marks.  We
% then need to fill in the marks into the list and try again.  Note
% that we are not reinserting anything in order to compensate for
% \cmd{\outputpenalty} being replaced by a nobreak: this is the job of
% \cmd{\FN@normaloutput} when it decides to place material back on the
% page.  That is: when code is written that will make use of
% pagediscards, it has to cater for their proper structure.
%    \begin{macrocode}
      \ifdim\dimen@>\z@
%<trace>  \if\foottrace8
%<trace>    \message{recycling special penalty}
%<trace>  \fi
        \hrule\@height\z@\@depth\z@
        \unvcopy\FN@topmarkbox
        \penalty-13750
        \penalty\FN@outputflag
        \hrule\@height\z@\@depth\z@
        \FN@insertmarks
        \penalty-13749
        \penalty\FN@outputflag
        \FN@prepareoutput
        \global\topskip-\maxdimen
        \global\vsize0.5\maxdimen
        \global\advance\FN@outervsize-\vsize
      \else
        \FN@normaloutput
      \fi
   \fi
  \fi
  \fi}
%    \end{macrocode}
% \begin{macro}{\FN@normaloutput}
%   This is the normal output routine we use.
%   Now we have recovered a sensible state and glued everything together
%   that has been necessary.  All insertion parameters are at their
%   standard values, and any insertions have been collected in the
%   respective boxes.
%    \begin{macrocode}
\def\FN@normaloutput{%
%<trace> \if\foottrace8\message{^^JEntering \string\FN@normaloutput:^^J}\fi
%    \end{macrocode}
% \cmd{\FN@vsize} is now being set to the vertical size taken up by
% the insertions, according to \TeX.  Note that this does not include
% flexibility.  This much amount of space gets available on the
% current page if we remove all insertions.  This figures into
% \cmd{\FN@vsize} as a \emph{positive} quantity since the insertion
% size was taken from \cmd{\pagegoal}, and we reconstitute it in this
% manner.
%    \begin{macrocode}
  \global\FN@vsize\FN@outervsize
  \global\advance\FN@vsize-\ht\@cclv\relax\relax
%    \end{macrocode}
% Now we sort the inserts and regenerate the cache.
%    \begin{macrocode}
  \FN@nest@iterate\FN@sortinsert
  \FN@nest@iterate\FN@clearcache
  \xdef\FN@config{\@elt{\number0\botmarks\FN@slave}%
    {\number\maxdimen}}%
%<trace> \if\foottrace8%
%<trace>    \message{\noexpand\FN@normaloutput start config: \FN@config^^J}%
%<trace> \fi
  \FN@nest@iterate\FN@reconfig
%    \end{macrocode}
% Note that \cmd{\FN@reconfig} subtracts the \emph{actual} size of all
% insertions (after paragraphs have been combined and too early
% insertions moved to the next page) and also subtracts the flexible
% glues associated with the insertions' skip registers, so this
% flexibility is typically negative.  Since the cache registers have
% been explicitly cleared, \cmd{\FN@reconfig} starts from the state
% where indeed no insertions are present.
%    \begin{macrocode}
  \ifcase
    \ifnum\insertpenalties>\z@ \@ne\fi
%    \end{macrocode}
% If we have floating insertions, we need to catch up with them.  This
% is done in case~1 which just places an immediate penalty and
% recurses.
%
% Now here are a few cases that are only checked when we don't have a
% special penalty:
%    \begin{macrocode}
    \ifnum\outputpenalty>-\@M
%    \end{macrocode}
% The first case is if the page is underfull.  We need more material then.
%    \begin{macrocode}
      \ifdim\FN@vsize>-\gluestretch\FN@vsize \tw@ \fi
%    \end{macrocode}
% Second case is when there is not enough vertical minimum material.
%    \begin{macrocode}
      \ifdim\FootnoteMainMinimum>\ht\@cclv \tw@ \fi
    \fi
%    \end{macrocode}
% Case 3 means page is overfull.  If there are no missing insertions,
% try to split.
%    \begin{macrocode}
    \ifdim\FN@vsize<\glueshrink\FN@vsize \thr@@ \fi
%    \end{macrocode}
% page has appropriate size or we have special penalty.  If we have
% come here not the first time, we might have arrived at a non-optimal
% break.  So we attempt a split.
%    \begin{macrocode}
    \ifx\FN@vsadjustlist\@empty \else \thr@@\fi\z@
%    \end{macrocode}
% Ok, now we get the default case in our big routine: case~0.  We just
% pass the result onto the output routine.
%    \begin{macrocode}
    {\vbadness\@M
      \vfuzz\maxdimen
      \global\setbox\@cclv\vbox
      spread\FN@vsize{\unvbox\@cclv\boxmaxdepth\maxdepth}}%
    \the\FN@output
    \let\@currbox\footins
    \@pageht-\vsize
    \@reinserts
    \global\vsize-\@pageht
    \FN@nest@iterate\FN@clearcache
  \or
%    \end{macrocode}
% Case 1: We just pull in remaining insertions and are done.  Note
% that the special penalty here will get turned into an explicit
% nobreak.  So if we have no record of an actual outputpenalty, we
% need to insert an artificial penalty of 0 here.
%    \begin{macrocode}
    \FN@restartoutput
    \penalty -13749
    \penalty \FN@outputflag
  \or
%    \end{macrocode}
% Case 2: Now we want to gather additional material.  This is somewhat
% weird.  We first gather our material with a `normal' setting of
% topskip, and then we'll have another go at the material using proper
% marks.  We can't actually insert anything right now in order not to
% introduce a premature breakpoint.
%    \begin{macrocode}
    \dimen@=\dimexpr\FN@vsize-\glueshrink\FN@vsize\relax
    \FN@prepareoutput
    \global\topskip \normalbaselineskip
    \global\vsize \dimen@
    \global\advance\FN@outervsize-\vsize
    \global\deadcycles\z@
  \else
%    \end{macrocode}
% This is case 3: Fake our output box into something looking like a
% cache box and do the optimal split routine.  The output cache box
% has a few deficiencies: its inner box is \emph{not} depth-extended
% to some default measurement.  That means that where page size
% calculations are involved, one needs to \emph{disregard} its actual
% depth and instead use \cmd{\maxdepth}.  This is somewhat awkward and
% prone to problems.  One alternative might be to mark the box as
% split, extend its depth in the split part and let it be followed by
% nothing as lower part of the split.  But we still would need to
% account for the missing depth at the end.
%    \begin{macrocode}
    \edef\FN@masterid{\number\maxdimen}%
    \def\FN@masterslot{-1}%
    \global\setbox\@cclv\vbox{\box\@cclv}%
    \xdef\FN@config{\noexpand\@elt{\number0\botmarks\FN@slave}%
      {\number\maxdimen}}%
%<trace> \ifvoid\FN@savebox \else \PackageError{bigfoot}{\FN@savebox
%<trace>   \space should be void!}{}\fi
    \global\setbox\FN@savebox\vbox{}%
    \gdef\FN@penalties{0}%
    \edef\FN@defaultpenalty{\ifnum\outputpenalty<\@M
        \number\outputpenalty
      \else
        0\fi}%
    \let\@elt\FN@newlevel
    \@elt{}\FN@savebox\FN@nestlist\FN@mainsplitreturn
    \let\@elt\relax
%<trace> \if\foottrace8{\showboxdepth4\showboxbreadth100\showbox\@cclv}\fi
    \global\setbox\FN@savebox\box\voidb@x
    {%
      \vbadness\@M
      \vfuzz\maxdimen
      \global\setbox\@cclv\vbox spread\FN@vsize{%
        \unvbox\@cclv
        \ifnum\lastpenalty>\z@
          \unpenalty
          \global\setbox\FN@tempbox\lastbox
        \else
          \global\setbox\FN@tempbox\box\voidb@x
        \fi
        \setbox\z@\lastbox
%    \end{macrocode}
% Now if a split has been done, |\box\FN@tempbox| contains the lower
% part of the split.  In either case, |\box\z@| contains the upper
% part of the split (in a prepared form with the splitdiscards in a
% box of their own).  This may be void if there is no main text but
% only footnotes.  If we have carryover material, we add the current
% outputpenalty there and set outputpenalty to a value indicating that
% we have no outputpenalty to add at the end of the current list.
%    \begin{macrocode}
        \ifvoid\z@
          \ifvbox\FN@tempbox
            \ifnum\outputpenalty<\@M
% The output penalty originally from below the split box gets appended
% to the end of the split box.
              \global\setbox\FN@tempbox{\unvbox\FN@tempbox
                \penalty\outputpenalty}%
            \fi
            \global\outputpenalty=\@M
          \fi
        \else
%    \end{macrocode}
% Ok, we have material to go to the next page.  We unpack it and fish
% out the break penalty from the last box.  After checking it, put it in
% box~0.  A prospective current break penalty gets appended to the
% carryover material.  The fished-out break penalty becomes the new
% value of outputpenalty.
%    \begin{macrocode}
          \MFL@removevboxes
          \unvbox\z@
          \edef\FN@defaultpenalty{\number\@M}%
          \FN@getbreakpenalty
          \setbox\z@\lastbox
          \global\setbox\FN@tempbox\vbox\bgroup\unvbox\z@
            \unvbox\FN@tempbox
            \ifnum\lastnodetype<\z@
            \egroup\global\setbox\FN@tempbox\box\voidb@x
            \else
              \ifnum\outputpenalty<\@M
                \penalty\outputpenalty
              \fi
            \egroup
            \global\outputpenalty\FN@breakpenalty
          \fi
        \fi
        \boxmaxdepth\maxdepth}%
    }%
    \setbox\z@\box\FN@tempbox
    \let\@elt\relax
%    \end{macrocode}
% Ok, now we have in box~255 the split off stuff for the current
% output routine, and in box~0 stuff that is going to follow
% afterwards.  If box~0 is not void, we were not able to make use of
% all of box~255.  There is a slight probability that by taking even
% \emph{more} material from the main list, we might get a better
% result (by being able to move footnote material to the next page
% instead), but we don't make use of this possibility here.  In
% general, we assume that if box~0 is nonvoid, we take the resulting
% split.  Otherwise, if the page appears underfull, we pull in more
% material.  If the page is not underfull, we can pass it to the
% output routine.  If box~0 is void, the break was chosen at the
% ultimate end of the vertical list.  If it was not a forced break,
% and if it is not an overfull case already, we pull in more material
% in order to avoid widows in the main text.
%    \begin{macrocode}
    \dimen@=\dimexpr\FN@vsize-\glueshrink\FN@vsize\relax
    \ifcase
      \ifvoid\z@ \ifnum\outputpenalty>-\@M
                    \ifdim\dimen@<\z@ \else \@ne \fi
                 \fi
      \else \thr@@
      \fi
      \ifdim\ht\@cclv<\normalbaselineskip \@ne\fi
      \ifdim\dimen@<\normalbaselineskip \tw@\fi \@ne
    \or
      \FN@prepareoutput
      \global\topskip \normalbaselineskip
      \ifdim\dimen@<\normalbaselineskip \dimen@=2\baselineskip\fi
      \global\vsize \dimen@
      \global\advance\FN@outervsize-\vsize
      \global\deadcycles\z@
    \or
%<trace> \if\foottrace8%
%<trace>   \message{^^JOutput: config is \FN@config...}\fi
      \setbox\tw@\vbox{%
        \the\FN@output
%<trace> \if\foottrace8%
%<trace>   \ifnum\lastnodetype=\m@ne
%<trace>     \message{^^JOutput: end without carryover^^J}%
%<trace>   \else
%<trace>     \message{^^JOutput: end with carryover}}%
%<trace>      {\showboxdepth5 \showboxbreadth400
%<trace>      \tracingonline=\@ne\showbox\tw@
%<trace>   \fi
%<trace> \fi
      }%
      \unvbox\tw@
      \unvbox\z@
      \let\@currbox\footins
      \@pageht-\vsize
      \@reinserts
      \global\vsize-\@pageht
      \FN@nest@iterate\FN@clearcache
    \or
      \FN@restartoutput
      \penalty -13751
      \penalty\FN@outputflag
      \unvbox\z@
      \ifnum\outputpenalty>\@M
      \else \penalty
            \ifnum\outputpenalty=\@M \z@ \else\outputpenalty\fi
      \fi
    \fi
  \fi
%<trace> \if\foottrace8\message{^^JExiting \string\FN@normaloutput^^J}\fi
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@prepareoutput}
%   This is a preparation for gathering more material.  First sweep up
%   all the information about \cmd{\vsize}, \cmd{\topskip} and
%   \cmd{\outputpenalty}.  After that, record the insertion skip
%   parameter of all insertions that have already been started, and
%   reset them to zero so that no additional space gets reserved for
%   them in case more material accumulates.  We don't reset
%   \cmd{\topskip} here since the amount of newly requested material
%   will typically be in total lines, and \cmd{\topskip} might be the
%   only way to figure out the proper request size.  If the current
%   depth and following height would make for a non-standard line
%   distance, we might have a problem here.  There is no obvious way
%   to avoid it, though.
%    \begin{macrocode}
\def\FN@prepareoutput{%
  {\let\@elt\FN@recordinsertparam
   \xdef\FN@vsadjustlist{%
     \global\vsize=\the\vsize
     \global\topskip=\the\topskip
     \global\outputpenalty=\the\outputpenalty\relax
     \FN@list}%
   \let\@elt\FN@clearinsertparam
   \FN@list}%
%    \end{macrocode}
%   Now we collect all boxes in the save box.
%    \begin{macrocode}
%<trace> \ifvoid\FN@savebox \else \PackageError{bigfoot}{\FN@savebox
%<trace>   \space should be void in \string\FN@prepareoutput}{}\fi
  \global\setbox\FN@savebox\vbox{%
    \box\@cclv
    \FN@list@iterate\FN@sweepbox}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@restartoutput}
%   This is for the case where we are requesting additional material
%   and have to cater for sizes.
%    \begin{macrocode}
\def\FN@restartoutput{%
%    \end{macrocode}
% Calculate the remaining size on this page:
%    \begin{macrocode}
  \dimen@=\dimexpr\FN@vsize-\glueshrink\FN@vsize\relax
%    \end{macrocode}
% We just pull in remaining insertions and are done.
%    \begin{macrocode}
%<trace> \if\foottrace8\message{sending special penalty}\fi
  \hrule\@height\z@\@depth\z@
  \unvcopy\FN@topmarkbox
  \penalty -13750
  \penalty\FN@outputflag
  \hrule\@height\z@\@depth\z@
  \FN@insertmarks
  \FN@prepareoutput
  \global\topskip-\maxdimen\relax
  \global\vsize 0.5\maxdimen
  \global\advance\FN@outervsize-\vsize
  \global\deadcycles\z@
}
%    \end{macrocode}
% \end{macro}
%
% Ok, here is the deal.  If the \cmd\FN@truevsize is negative, we have
% an overfull vbox at our hand.  We then start the splitting action.
% We take the first non-split lowest footnote block and split it to
% size, removing subordinate footnotes that we would not be able to
% maintain.  We do this recursively starting by the top footnote
% block.  It must be noted that it would be even better to start with
% the highest-numbered footnote (which corresponds to the latest
% finished footnote in \emph{logical} order, that in the source code),
% but then we get the problem that we might have to remove boxes from
% a footnote block that has already been split, and that is
% troublesome (to put it mildly) in case where the footnote block is
% set in paragraph mode.  It's bad enough backtracking in a fixed
% order across footnote blocks, going back and forward would be pretty
% tough.
%
% So our recursion just walks the footnote blocks once top to bottom,
% splitting and removing boxes that are not needed.  When we recurse,
% we have a dichotomy between current overfull and underfull boxes.
% At each recursion level, we enter with an overfull configuration
% that establishes the breakable section for the footnote block in
% question.
%
% Suppose that we have already established a previous best
% configuration.  When we are recursing, we can only increase the
% badness (a non-broken insertion box contributes nothing to the
% overall badness or penalties, breaking the box causes a badness of
% 10000, minus the break penalty, plus the break badness).  So there
% is no point in recursing if entry badness and break penalty are as
% large as the previous best break penalty or more.
%
% Ok, so we construct the footnote block and try splitting it
% to size.  If this
% gives us a \emph{good} underfull version, we return that (and break
% out of recursion altogether).  Otherwise we remember the underfull
% version before the break and recurse on the overfull version.  If
% this returns an overfull version again, we return the underfull
% version before the break.  If it returns an underfull version, we
% fill up the underfull version as much as possible without a change
% of configuration, then select the best of the last underfull and
% this as new local underfull.  We then take the first overfull
% combination (even allowing a change of configuration), throw away
% the previous split in the next recursion level and recurse on the
% now thoroughly overfull combination again.
%
% When recursion tops out, we compare the current overfull with the
% previous one and record the best.  We prefer keeping an older
% overfull, all other things being equal.
%
% Ok, so what are the data structures we maintain when going through
% all this folderol?
%
% We let the insertion boxes themselves remain untouched: that makes
% it only a bit more complicated to maintain and access the relevant
% boxes, but it might come handy at one time when somebody wants to
% implement recursion that is not strictly top-to-bottom.
%
% Instead we return the relevant information in the cache boxes.  The
% total size of the cache boxes may not correspond to their actual
% contents: in case a split box intended for the next page is stored
% within them, its height is deducted from the total height of the
% cache box (and, consequentially, from \cmd{\FN@vsize}).
%
% \cmd{\FN@vsize}, the amount of free space on the current page, is
% only updated when changing levels of recursion.  Instead we maintain
% score of the accumulated size in the current insertion in
% \cmd{\FN@myvsize}.
%
% What about the penalties and badness we collect?  An unsplit
% footnote block carries a penalty of~0 (so we need not take into
% account unsplit footnote blocks at all during our bookkeeping, as
% they are neutral), a split footnote block is prepenalized with a
% penalty of~10000, plus the badness of the split, plus any penalties
% associated with the split (limited to the $[-10000\ldots10000]$
% range).  This means that no operation on other footnote blocks can
% lower an already accumulated score.  This in turn means that we can
% prune any operations leading to a worse score than the preceding
% best score without having to actually recurse.
%
% This strategy will usually buy us a minimum number of split
% footnotes (since the penalty of~10000 is not easy to compensate)
% and corresponds rather closely to \TeX's own idea of footnote
% splitting.
%
% The following routine will analyze the last box where the results
% from \cmd{\splitdiscards} are stored and return the penalty
% associated with the breakpoint in the macro
% \cmd{\FN@breakpenalty}.
% \begin{macro}{\FN@getbreakpenalty}
%    \begin{macrocode}
\def\FN@getbreakpenalty{{\setbox\z@\lastbox
    \nointerlineskip\copy\z@
    \setbox\z@
      \vbox{\unvbox\z@
        \count@\@M
        \FN@getbreakpenaltyii
        \xdef\FN@tempinfo{\edef\noexpand\FN@breakpenalty{%
            \number\ifnum\count@=\@M \FN@defaultpenalty \else \count@\fi
          }}}}%
  \FN@tempinfo}

\def\FN@getbreakpenaltyii{%
  \ifcase
    \ifnum\lastnodetype<\z@ \m@ne\fi
    \ifnum\lastnodetype<11 \@ne\fi
    \ifnum\lastnodetype>13 \@ne\fi
    \numexpr\lastnodetype-9\relax
  \or
    \PackageError{bigfoot}{Illegal node type}{This can't happen}%
  \or
    \count@\z@ \unskip \expandafter\FN@getbreakpenaltyii
  \or
    \count@\z@ \unkern \expandafter\FN@getbreakpenaltyii
  \or
    \count@\lastpenalty
    \unpenalty \expandafter\FN@getbreakpenaltyii
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@cleanpagepenalty}
%   This is used for removing initial infinite penalties from the
%   pagediscards: those are artifacts of the page break routine.
%    \begin{macrocode}
\def\FN@cleanpagepenalty{%
  \ifcase
    \ifnum\lastnodetype<\z@ \m@ne\fi
    \ifnum\lastnodetype<11 \@ne\fi
    \ifnum\lastnodetype>13 \@ne\fi
    \numexpr\lastnodetype-9\relax
  \or
    \PackageError{bigfoot}{Illegal node type}{This can't happen}%
  \or
    \skip@=\lastskip \unskip
    \expandafter \FN@cleanpagepenalty \expandafter\vskip\the
    \expandafter\skip@
  \or
    \dimen@=\lastkern \unkern
    \expandafter \FN@cleanpagepenalty \expandafter\kern\the
    \expandafter\dimen@
  \or
    \count@\lastpenalty \unpenalty
    \ifnum\count@=\FN@outputflag
      \unpenalty\expandafter\expandafter\expandafter\FN@cleanpagepenalty
    \else
      \expandafter\FN@cleanpagepenalty\expandafter
      \penalty\the\expandafter\expandafter\expandafter\count@
    \fi
  \fi
  \relax}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@mainsplitreturn}
%   This is merely an argument delimiting control sequence to make it
%   possible to figure out which recursion levels still need visiting.
%    \begin{macrocode}
\def\FN@mainsplitreturn{}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@myvsize}
%   This is the size currently taken by this insertion.
%    \begin{macrocode}
\newdimen\FN@myvsize
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\bigfoottolerance}
%   This specifies what footnote arrangement penalty will be accepted
%   without looking for a better solution.
%    \begin{macrocode}
\newcount\bigfoottolerance
\bigfoottolerance=100
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@getbadness}
%   This takes a skip value of remaining space and negative
%   stretchability and shrinkability, and then calculates
%   \cmd{\badness} depending on how good the stretching accommodates
%   the remaining space.
%    \begin{macrocode}
\def\FN@getbadness#1{%
  {\hfuzz\maxdimen\hbadness\@M\setbox\z@\hbox to\z@{\hskip-#1}}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@newlevel}
%   This is the main workhorse of |bigfoot|.  It splits a particular
%   footnote level, recursing if necessary.  The level list is
%   delimited with \cmd{\FN@mainsplitreturn}.  The whole thing is
%   looped through while the splits are being optimized.  While
%   recursing, \cmd{\FN@penalties} contains the accumulated penalities
%   of the current split configuration: a penalty of $10000$ for any
%   split (except the main list), plus the penalty at the split points
%   plus a `hangover' badness for the percentage of material carried
%   over to the following pages.  If nothing is carried over, this
%   is~0, if more is carried over, we get a penalty according to the
%   proportion of carryover material, raised to the third power.
% \begin{macro}{\footnotecarryratio}
%   The fractional variable \cmd{\footnotecarryratio} is used for
%   scaling the leftover material dimensions.  After scaling with
%   \cmd{\footnotecarryratio}, the carried material is treated like
%   missing material in a glue calculation, while the stretchability
%   for this calculation is given by the total size of material before
%   breaking.  So with a setting of~1, there should always be enough
%   stretchability, causing at most a penalty of~100.  That's not very
%   effective, so we scale this up.
%
%   The default value of~2 seems to provide a reasonable penalty for
%   leftover material.  The actual purpose for this component of the
%   scoring is to penalize footnote blocks that seem to carry over
%   disproportionally much material to later pages.
%    \begin{macrocode}
\providecommand\footnotecarryratio{2}
%    \end{macrocode}
% \end{macro}
%   \cmd{\FN@ebadness} is an augmented value, but also counting in the
%   stretch badness for one particular configuration.  Ebadness does
%   not make sense to evaluate more than temporarily: it is not passed
%   through the levels.  Since \cmd{\FN@penalties} is globally
%   tampered with, its value at entry is saved in
%   \cmd{\FN@entrypenalties}.  Whenever we recurse or return,
%   \cmd{\FN@vsize} contains the full information about the available
%   space on the page, even though locally we use \cmd{\FN@myvsize}, a
%   local value, to keep track of the locally reserved space.  The
%   only time when we need to save \cmd{\FN@myvsize} should be when we
%   temporarily leave boxes in order to save the current
%   configuration.
%    \begin{macrocode}
\def\FN@newlevel#1#2#3\FN@mainsplitreturn{%
  \count@\FN@cache#2%
  \ifvoid\count@
%<trace> \if\foottrace1\message{Page=\thepage #2 is empty, recursing with
%<trace>   \the\FN@vsize^^J}%
%<trace>   \message{Config=\unexpanded\expandafter{\FN@config}^^J}\fi
      #3\FN@mainsplitreturn
%<trace> \if\foottrace1%
%<trace>   \message{Page=\thepage #2 was empty,
%<trace>     returning with \the\FN@vsize^^J}%
%<trace>   \message{Config=\unexpanded\expandafter{\FN@config}^^J}\fi
  \else
%<trace> \if\foottrace1\message{Entering #2 with \FN@penalties,
%<trace>   \FN@vsize=\the\FN@vsize,^^J%
%<trace>   Config=\unexpanded\expandafter{\FN@config}^^J}\fi
    {\def\FN@currentinsertion{#2}%
     \def\FN@currentrecursion{#3}%
     \let\FN@entryconfig\FN@config
     \let\FN@entrypenalties\FN@penalties
     \splittopskip\csname FN@ht\number#2\endcsname\relax
     \splitmaxdepth\csname FN@dp\number#2\endcsname\relax
     \hsize\csname FN@wd\number#2\endcsname\relax
     \vbadness=\@M
     \vfuzz\maxdimen
     \let\@elt\relax
     \expandafter\FN@newleveli\expandafter}%
%<trace> \if\foottrace1\message{Exiting #2 with \FN@penalties,
%<trace>   \FN@vsize=\the\FN@vsize,^^J%
%<trace>   Config=\unexpanded\expandafter{\FN@config}^^J}\fi
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@newleveli}
%    \begin{macrocode}
\def\FN@newleveli{%
%    \end{macrocode}
% \cmd{\FN@vsize} already includes the size of the complete unsplit
% insertion.  When we recurse, it has to reflect the correct size at
% the time of recursion.  Rounding error problems don't permit us to
% accumulate any sizes in \cmd{\FN@vsize} from processing our current
% insertion, so we just subtract the whole insertion-related
% content.  We'll add stuff into it when recursing.
%    \begin{macrocode}
    \dimen@\dimexpr\ht\count@
      \ifnum\FN@currentinsertion=\FN@savebox
        +\maxdepth
      \else
        +\dp\count@
      \fi\relax
    \global\advance\FN@vsize\dimexpr \dimen@
      *\count\FN@currentinsertion/\@m\relax\relax
%    \end{macrocode}
% Ok, now we are typesetting and collecting the best box.  Notice
% that we \emph{don't} exit this \cmd{\setbox} command until we have
% found the best possible split.  What we \cmd{\unvbox} here, stays
% dormant except for the last box.  When we collect configurations
% from cache boxes, we don't collect anything from our current box
% that is being assembled.  So the whole action is confined within the
% current list that will replace the cache box after splitting.  The
% meaning of boxes on the various levels are:\par\noindent
% \begin{tabularx}{\linewidth}{ll@{:\hskip\tabcolsep}X}
%   0&box0&where stuff gets collected as tentative material to be
%   unboxed with \cmd{\FN@removevboxes} once the insertion gets readied
%   for shipout\\
%   0&box2&the previous best split that was found\\\hline
%   1&box0&the material that gets worked off, the tail of the split\\
%   1&box2&where the current split is assigned
% \end{tabularx}
% The structure of 0/box2 is the head of the split, followed by
% |\break| penalty, followed by the tail of the split, followed by
% |\penalty\FN@tempbox|, followed by pairs of cache boxes and
% penalties indicating their box number.  That way, the tail can get
% restored immediately into |\FN@tempbox| when using
% |\FN@restoreboxes|.
%    \begin{macrocode}
    \global\setbox\count@\vbox\bgroup\unvbox\count@
%    \end{macrocode}
% We calculate \cmd{\FN@myvsize} as the total space taken up by this
% insertion.  The size of the last box is excluded since it will be
% split now.
%    \begin{macrocode}
      \ifnum\lastpenalty=\z@
        \setbox\tw@\box\voidb@x
        \setbox\z@\lastbox
        \FN@myvsize=\ifnum\lastnodetype<\z@
          \z@
        \else
          \dimexpr\dimen@-\ht\z@-\dp\z@\relax
        \fi
      \else
%    \end{macrocode}
% Now if the box has been split previously, we glue it back together
% again.  Since the lower part of the split has been \emph{subtracted}
% from the total in \cmd{\dimen@}, we need to put it back into the
% equation here.  \cmd{\dimen@} contains the size of the box after
% padding split material has been added.
%    \begin{macrocode}
%<trace> \if\foottrace1\message{Regluing box 2}\fi
        \unpenalty
        \setbox\tw@\lastbox
        \setbox\z@\lastbox
        \FN@myvsize=\dimexpr\dimen@-\ht\z@-\dp\z@\relax
        \dimen@\dp\z@
        \setbox\z@{\unvbox\z@
          \setbox\z@\lastbox
          \unvbox\z@
          \unvbox\tw@}%
        \ht\z@=\dimexpr\ht\z@+\dp\z@-\dimen@\relax
        \dp\z@\dimen@
      \fi
%    \end{macrocode}
% Ok, size is all accounted for.  Go on with optimization.  Note that
% these definitions here are made in \emph{inner} level, so they can't
% make it outside as the result of the optimization.  If we drop out
% of here without superceding them, something's completely rotten.
% ^^A Fixme: Alpha pruning could be implemented by calling with
% ^^A \FN@bestcost already set at entry to the best badness at
% ^^A the respective level.
%    \begin{macrocode}
      \edef\FN@bestcost{\number\maxdimen}%
      \let\FN@bestbadness\FN@bestcost
      \let\FN@bestconfig\@undefined
      \def\FN@bestvsize{-\maxdimen}%
      \let\FN@splitcolors\@empty
%    \end{macrocode}
% Ok, first attempt.  One interesting feature is that we will never
% have to rewind the boxes from a split: we can always just glue the
% box together again.  And apart from tentative splits which we might
% revert if they cause a configuration change, we will not have to
% bother about contributing too much.  What we put in the box here
% can stay.
%
% First we split to the remaining size.  Since we still have all
% subordinate footnotes considered fully, we need at least this split
% size (in case of a configuration change, we will need more).  After
% having done the initial split, we continue splitting until we get
% the necessary mark of the last footnote into our grasp: we can't
% split before that.
%    \begin{macrocode}
      \ifnum\FN@currentinsertion=\FN@savebox
      \else
        \edef\FN@defaultpenalty{\number-\@M}%
        \edef\FN@masterslot{\number\dp\z@}%
        \edef\FN@masterid{\FN@slotget\FN@masterslot}%
      \fi
%    \end{macrocode}
% Now we are building one tentative candidate for returning in
% |\box\z@|.  It will get discarded in case that a better candidate
% was already found before this box completes.
%    \begin{macrocode}
      \setbox\z@
      \vbox\bgroup
%    \end{macrocode}
% Ok, now stuff gets complicated: for the first, tentatively `optimal'
% split, we want to have all available page stretchability properly
% taken into account.  So we take the box, and add the available page
% stretchability at the top.  Note that the stretchability is
% registered negatively.  If we are on the main vertical list, an
% empty page can be an acceptable option, so we add a penalty of zero
% to account for that.  Note that any prospective true penalties will
% already have disappeared into the page break.
%    \begin{macrocode}
        \let\FN@splitcolors\@empty
        \setbox\z@\vbox{\vskip-\glueexpr(\FN@vsize-\dimexpr\FN@vsize
          \relax\@minus\glueshrink\FN@vsize)%
          *\@m/\count\FN@currentinsertion
          \penalty\z@
          \unvbox\z@
          \ifnum\FN@defaultpenalty>-\@M
            \penalty\FN@defaultpenalty\relax\nointerlineskip
            \vbox to\maxdimen{}%
          \fi}%
%    \end{macrocode}
% Ok, now we have pushed the additional available stretch onto the top
% of box~0.  Now we do the actual split to minimal size.  That means
% that we don't consider any of the shrinkability available on the
% page: it might still be better employed in some recursive level.
%    \begin{macrocode}
        \setbox\tw@\vsplit\z@ to%
          \dimexpr\FN@vsize*\@m/\count\FN@currentinsertion
          -\FN@myvsize-\splitmaxdepth
        \relax
        \ifnum\FN@defaultpenalty>-\@M
          \setbox\z@\vbox\bgroup\unvbox\z@\setbox\z@\lastbox
            \unskip
            \unpenalty
            \ifnum\lastnodetype<\z@
              \egroup \setbox\z@\box\voidb@x
            \else
              \egroup
            \fi
        \fi
%    \end{macrocode}
% Ok, now the top of box~2 contains unwanted additional
% stretchability.  The easiest way to get rid of it is by adding its
% negation.
%    \begin{macrocode}
        \setbox\tw@\vbox{%
          \vskip\glueexpr(\FN@vsize-\dimexpr\FN@vsize
          \relax\@minus\glueshrink\FN@vsize)%
          *\@m/\count\FN@currentinsertion
          \unvbox\tw@\boxmaxdepth\splitmaxdepth}%
%    \end{macrocode}
% Ok, now rinse and repeat if we haven't reached the last footnote
% in the block.
%    \begin{macrocode}
        \ifnum\FN@currentinsertion=\FN@savebox
          \edef\FN@slaveid{\splitbotmarks\FN@slave}%
          \FN@contribute@tw@
        \else
          \ifnum0\splitbotmarks\FN@master=\FN@masterslot \else
            \loop
              \FN@contribute@tw@
              \setbox\tw@\vsplit\z@ to\z@
            \ifnum0\splitbotmarks\FN@master=\FN@masterslot
            \else
            \repeat
          \fi
          \let\FN@splitcolors\@empty
          \edef\FN@slaveid{\splitbotmarks\FN@slave}%
          \FN@contribute@tw@
        \fi
%    \end{macrocode}
% All of the above was necessary to ensure that we actually have the
% beginning of the relevant footnote in our material.  From now on,
% we are dealing with legal splits.
% Ok, now we have to check whether the subordinate configuration has
% changed.
%    \begin{macrocode}
        \ifx\FN@slaveid\@empty
%<trace>  \ifnum\FN@currentinsertion=\FN@savebox\else
%<trace>    \errmessage{Missing slaveid in \FN@currentinsertion}\fi
          \edef\FN@slaveid{\number0\topmarks\FN@slave}%
        \fi
        \ifnum\numexpr\FN@slaveid+\@ne<\FN@masterid
          \let\FN@next\FN@slaveid
        \else
          \let\FN@next\@empty
        \fi
%    \end{macrocode}
% At this point of time, we have \cmd{\FN@masterid} set properly for
% our purposes.  It is to be used for returning any \emph{tail} part
% of a box.  \cmd{\FN@slaveid} is by necessity not empty.  If any
% footnote
% has had its mark broken off, its id must be in the open range
% between \cmd{\FN@slaveid} and \cmd{\FN@masterid}.  So a nonempty
% value of \cmd{\FN@next} at this point of time indicates that we have
% to cater for a different configuration rather than the currently
% cached one.
%    \begin{macrocode}
        \FN@splitfurther}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@vsizerecurse}
% This fixes the vertical size up and recurses once.
%    \begin{macrocode}
\def\FN@vsizerecurse{%
    \global\advance\FN@vsize
      -\dimexpr\FN@myvsize*\count\FN@currentinsertion/\@m \relax\relax
    \let\@elt\FN@newlevel
    \FN@currentrecursion\FN@mainsplitreturn
    \let\@elt\relax
    \global\advance\FN@vsize
      \dimexpr\FN@myvsize*\count\FN@currentinsertion/\@m \relax\relax}
%    \end{macrocode}
% \end{macro}
%
% \subsubsection{Main label for reconsideration}
% When we are here, then there is not yet a split in the next footnote
% blocks scheduled.  We might have to restitch stuff together here,
% though.
% \begin{macro}{\FN@splitfurther}
%    \begin{macrocode}
\def\FN@splitfurther{%
  \ifx\FN@next\@empty \else \let \FN@slaveid\FN@next \fi
%    \end{macrocode}
% Ok, if our configuration now differs from the last one for which we
% have cache boxes set up, we have to reconfigure.  It it doesn't, we
% just stitch the boxes together again in order to have correct size
% info.
%    \begin{macrocode}
  \let\FN@next\FN@config
  \xdef\FN@config{%
    \@elt{\FN@slaveid}%
    {\FN@masterid}%
    \FN@entryconfig}%
  \ifx\FN@next\FN@config
    \let\@elt\FN@rejoin
  \else
    \let\@elt\FN@reconfig
  \fi
  \FN@currentrecursion
  \let\@elt\relax
%    \end{macrocode}
% Ok, now we check whether the current configuration is a match for
% the best previous one.  Also we calculate the badness of the current
% situation.
%    \begin{macrocode}
  \xdef\FN@penalties{\number\FN@entrypenalties}%
  \FN@checkcurrent
%    \end{macrocode}
% No point in recursing if we can't beat the current best one.
% However, if we find a forced break, this is considered perfect as
% long as we are not overfull.  Note that recursion can only increase
% the badness if we are still underfull here, so there is no point in
% using \cmd{\FN@penalties} as the deciding factor of whether there may
% be a point in recursing: the current ebadness (which is never less
% than the badness) already is minimal.
%    \begin{macrocode}
  \ifnum
    \ifdim\skip@>\z@ \FN@ebadness \else \FN@penalties \fi
    >\FN@bestcost\relax
%<trace>    \if\foottrace1%
%<trace>    \message{no recursion: \skip@=\the\skip@,
%<trace>      \noexpand\FN@bestvsize=\FN@bestvsize,
%<trace>      \noexpand\FN@ebadness=\FN@ebadness,
%<trace>      \noexpand\FN@penalties=\FN@penalties,
%<trace>      \noexpand\FN@bestcost=\FN@bestcost.}\fi
  \else
%<trace>    \if\foottrace1%
%<trace>    \message{before recursion: \skip@=\the\skip@,
%<trace>      \noexpand\FN@bestvsize=\FN@bestvsize,
%<trace>      \noexpand\FN@ebadness=\FN@ebadness,
%<trace>      \noexpand\FN@penalties=\FN@penalties,
%<trace>      \noexpand\FN@bestcost=\FN@bestcost.^^J
%<trace>      recurse with \noexpand\FN@penalties=\number\FN@entrypenalties.}\fi
    \xdef\FN@penalties{\number\FN@entrypenalties}%
    \FN@vsizerecurse
    \FN@checkcurrent
%<trace>    \if\foottrace1%
%<trace>    \message{after recursion: \skip@=\the\skip@,
%<trace>      \noexpand\FN@bestvsize=\FN@bestvsize,
%<trace>      \noexpand\FN@ebadness=\FN@ebadness,
%<trace>      \noexpand\FN@penalties=\FN@penalties,
%<trace>      \noexpand\FN@bestcost=\FN@bestcost.}\fi
  \fi
%    \end{macrocode}
% Don't look further if we had a forced break or are overfull or are
% at the end of the list.
%    \begin{macrocode}
  \ifcase
    \ifnum\FN@breakpenalty>-\@M \else \@ne \fi
    \ifvoid\z@ \@ne \fi
    \ifnum\badness<\@MM \else \@ne \fi
    \tw@
  \or
    \expandafter \FN@returnbest
  \else
    \FN@mayberecordbest
    \setbox\tw@\vsplit\z@ to\z@
    \edef\FN@next{\splitbotmarks\FN@slave}%
    \FN@contribute@tw@
    \expandafter \FN@splitfurther
  \fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@checkcurrent}
%   Check out the badness of the current configuration.  The last box
%   on the list is the material constituting the discardable material
%   after a split.
%    \begin{macrocode}
\def\FN@checkcurrent{%
  \FN@getbreakpenalty
  \ifnum\FN@breakpenalty<-\@M
    \edef\FN@breakpenalty{\number-\@M}%
  \fi
  \ifnum\FN@currentinsertion=\FN@savebox
  \else
    \ifdim\FN@specific\FN@currentinsertion\footnotecarryratio\p@>\z@
      \skip@
      \ifdim\FN@specific\FN@currentinsertion\footnotecarryratio\p@>\p@
          \dimexpr\ht\z@+\dp\z@\relax
          \@plus-\dimexpr((\FN@myvsize+\ht\z@+\dp\z@)
                          *\p@/\dimexpr
                          \FN@specific\FN@currentinsertion
                          \footnotecarryratio\p@)\relax
      \else
          \FN@specific\FN@currentinsertion
          \footnotecarryratio
          \dimexpr\ht\z@+\dp\z@\relax
          \@plus-\dimexpr\FN@myvsize+\ht\z@+\dp\z@\relax
      \fi
      \relax
      \FN@getbadness\skip@
      \xdef\FN@penalties{\number\numexpr\FN@penalties+\badness}%
    \fi
  \fi
  \skip@\glueexpr\FN@vsize-\FN@myvsize
   *\count\FN@currentinsertion/\@m\relax
  \FN@getbadness\skip@
  \xdef\FN@penalties{\number\numexpr\FN@penalties+%
    \FN@breakpenalty+\@M}%
  \ifnum\badness>\@M
    \edef\FN@ebadness{\number\numexpr\maxdimen-\@ne}%
  \else
    \ifnum\badness=\@M
      \ifdim\skip@<\vsize
        \edef\FN@ebadness{\number\numexpr\maxdimen-\tw@}%
      \else
        \edef\FN@ebadness{\number\numexpr\maxdimen}%
      \fi
    \else
      \edef\FN@ebadness{\number\numexpr
        \FN@penalties+\badness
        \ifdim\FN@specific\FN@currentinsertion\FootnoteMinimum>\FN@myvsize
          1000000
        \fi
        }%
    \fi
  \fi
  \dimen@\glueexpr\FN@bestvsize\relax
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@checkforbest}
%   This generates 2 if the old stored best is better, 1~if the
%   current variation is better.
%    \begin{macrocode}
\def\FN@checkforbest{%
    \ifnum\FN@breakpenalty>-\@M \else
      \ifnum\badness>\@M \else
         \@ne
      \fi
    \fi
%    \end{macrocode}
% Ok, so the split was not as good as to cause us to return
% immediately, and it also was not the last opportunity for a split
% (which again would make us return immediately).
% So we check if it is at least better than the last one, in which
% case we need to replace the previous best.
%    \begin{macrocode}
    \ifnum\FN@bestcost>\FN@ebadness \@ne\fi
    \ifnum\FN@bestcost<\FN@ebadness \tw@\fi
    \ifdim\skip@<\z@
      \ifdim\dimen@<\skip@ \@ne \fi \tw@
    \fi
    \ifdim\dimen@>\skip@ \@ne\fi \tw@}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@mayberecordbest}
%   This checks whether the current configuration is better than a
%   previously saved one.  If it is, the previous configuration gets
%   replaced.  The cache boxes itself are copied, not voided in the
%   process for efficiency reasons.
%    \begin{macrocode}
\def\FN@mayberecordbest{%
%    \end{macrocode}
% If the current break is forced and the page is not overfull, we take
% the break.
%    \begin{macrocode}
  \ifcase
    \FN@checkforbest
  \or
    \xdef\FN@tempinfo{\def\noexpand\FN@bestvsize{\the\skip@}%
      \def\noexpand\FN@bestcost{\FN@ebadness}%
      \def\noexpand\FN@bestbadness{\number\FN@penalties}%
      \def\noexpand\FN@bestconfig{\FN@config}%
      \def\noexpand\FN@bestslaveid{\FN@slaveid}%
      \def\noexpand\FN@bestsplitcolors{\FN@splitcolors}%
      \def\noexpand\FN@breakpenalty{\FN@breakpenalty}%
      \FN@myvsize=\the\FN@myvsize\relax}%
    \global\setbox\FN@tempbox\box\z@
    \egroup
    \FN@tempinfo
    \let\FN@splitcolors\FN@bestsplitcolors
    \let\FN@slaveid\FN@bestslaveid
%    \end{macrocode}
% Now all relevant info has been retrieved, and we collect the best
% box info in |\box\tw@|.  The structure of the information is as
% follows: it starts with the current box in split form, first the
% tail, then the start of the current split box.
% This is then followed by a zero kern, and then by pairs of boxes and
% penalties indicating the swept box.
%    \begin{macrocode}
    \setbox\tw@\vbox{%
%    \end{macrocode}
% We don't need to place master/slave marks here: the necessary
% information is available outside in the \cmd{\FN@masterslot} and
% \cmd{\FN@slaveid} info and gets attached afterwards.
%    \begin{macrocode}
      \copy\z@\break\nointerlineskip
      \copy\FN@tempbox\penalty\FN@tempbox
      \let\@elt\FN@copycachebox
      \FN@currentrecursion}%
    \setbox\z@
    \vbox\bgroup
      \unvbox\z@
      \setbox\z@\box\FN@tempbox
  \fi}
%    \end{macrocode}
% \end{macro}

% \begin{macro}{\FN@returnbest}
%    \begin{macrocode}
\def\FN@returnbest{%
  \ifcase\FN@checkforbest
  \or
    \xdef\FN@tempinfo{\def\noexpand\FN@bestvsize{\the\skip@}%
      \def\noexpand\FN@bestcost{\FN@ebadness}%
      \def\noexpand\FN@bestbadness{\number\FN@penalties}%
      \def\noexpand\FN@bestconfig{\FN@config}%
      \def\noexpand\FN@bestslaveid{\FN@slaveid}%
      \def\noexpand\FN@bestsplitcolors{\FN@splitcolors}%
      \def\noexpand\FN@breakpenalty{\FN@breakpenalty}%
      \FN@myvsize=\the\FN@myvsize\relax}%
    \global\setbox\FN@tempbox\box\z@
    \egroup
    \FN@tempinfo
    \let\FN@splitcolors\FN@bestsplitcolors
    \let\FN@slaveid\FN@bestslaveid
    \global\FN@vsize\FN@bestvsize\relax
%    \end{macrocode}
% Now all relevant info has been retrieved, and we collect the best
% box info in |\box\tw@|.  The structure of the information is as
% follows: it starts with the current box in split form, first the
% tail, then the start of the current split box.
% This is then followed by a zero kern, and then by pairs of boxes and
% penalties indicating the swept box.
%    \begin{macrocode}
  \or
    \global\let\FN@config\FN@bestconfig
    \global\FN@vsize\FN@bestvsize
    \global\let\FN@penalties\FN@bestbadness
    \egroup
%    \end{macrocode}
% Restore the saved configuration.
%    \begin{macrocode}
    \setbox\z@\vbox{\unvbox\tw@ \FN@restoreboxes}%
    \let\FN@splitcolors\FN@bestsplitcolors
    \let\FN@slaveid\FN@bestslaveid
    \unvbox\z@
    \setbox\z@\lastbox
  \fi
%    \end{macrocode}
%    \begin{macrocode}
  \ifnum\FN@currentinsertion=\FN@savebox
  \else
    \setbox\z@\vbox{%
      \prevdepth\dp\z@
      \unvbox\z@
      \ifvoid\FN@tempbox
      \else
        \global\setbox\FN@tempbox\vbox{%
          \marks\FN@master{\FN@masterslot}%
          \marks\FN@slave{\FN@slaveid}%
          \FN@coloraftersplit\FN@splitcolors
          \FN@specific\FN@currentinsertion\FN@afterbreak
          \nobreak
          \unvbox\FN@tempbox}%
        \FN@specific\FN@currentinsertion\FN@beforebreak
        \ht\FN@tempbox
        \dimexpr\ht\FN@tempbox+\dp\FN@tempbox-\FN@masterslot sp\relax
        \dp\FN@tempbox\FN@masterslot sp\relax
        \wd\FN@tempbox\maxdimen
      \fi
    \ifdim\prevdepth<\splitmaxdepth
       \hrule\@height-\prevdepth \@width\z@
             \@depth \splitmaxdepth \relax \fi}%
    \ht\z@=\dimexpr\ht\z@+\dp\z@-\FN@masterslot sp\relax
    \dp\z@=\FN@masterslot sp
  \fi
  \nointerlineskip \box\z@
%    \end{macrocode}
% If nothing is to be carried over, we just finish our assignment to
% the cache box and return.
%    \begin{macrocode}
  \ifvoid\FN@tempbox \egroup
%    \end{macrocode}
% If not, we add the carried-over box to the list, flag it with a
% \cmd{\nobreak}, and subtract its size from the finished box.  Please
% note that the \cmd{\expandafter} chain will expand just
% |\cmd\dimen@|, but everything following it will be evaluated only
% after \cmd{\egroup}, thus using the new height of the box.
%    \begin{macrocode}
  \else
    \dimen@-\dimexpr\ht\FN@tempbox+\dp\FN@tempbox\relax
    \nointerlineskip\box\FN@tempbox
    \nobreak
    \expandafter\egroup
    \expandafter\ht\expandafter\count@\expandafter\dimexpr
    \the\dimen@+\ht\count@\relax
  \fi
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\FN@contribute@tw@}
%   This will go from the state where we have the previous
%   \cmd{\splitdiscards} struttified on the current list some material
%   split off from box~0 in box~2 to a state where box~2 is
%   contributed to the current list.
%    \begin{macrocode}
\def\FN@contribute@tw@{%
%    \end{macrocode}
% First we change the current colors if we have any in our group.  Not
% sure if this is entirely correct.
%    \begin{macrocode}
  \begingroup\edef\FN@next{\splitbotmarks\FN@color}%
  \ifx\FN@next\@empty \endgroup\else \endgroup
    \edef\FN@splitcolors{\splitbotmarks\FN@color}\fi
%    \end{macrocode}
% If the last box is void, there is no previous split to reconstitute.
%    \begin{macrocode}
  \setbox4\lastbox
  \ifvoid4 \setbox4\vbox{\splitdiscards}%
    \setbox\tw@\vbox{\unvbox\tw@\boxmaxdepth\splitmaxdepth}%
  \else
%    \end{macrocode}
% Now the last box is a strut.  We remove its outer dimensions from
% the total account, and then add back its natural dimensions after
% which we pour it back into the current list.
%    \begin{macrocode}
    \advance\FN@myvsize-\dimexpr\ht4+\dp4\relax
    \setbox4\vbox{\unvbox4}%
    \advance\FN@myvsize\dimexpr\ht4+\dp4\relax
    \unvbox4
%    \end{macrocode}
% We want to contribute box~2 back without any topskip glue, so we
% manually remove any such glue by splitting an empty box off.
%    \begin{macrocode}
    \setbox4\vbox{\splitdiscards}%
    \setbox\tw@\vbox{\break\unvbox\tw@}%
    {\splittopskip-\maxdimen \setbox\tw@\vsplit\tw@ to\z@}%
%    \end{macrocode}
% Notice the effect of \TeX's special box scope rules: box~2 assigned
% just right now will be affected by the split.  The result of the
% split will be an empty box that will temporarily overwrite box~2
% within the group, but will be restored back to the split result on
% exit.  In this manner, any topskip glue will have disappeared.
% After the split, box~2 is set to the natural depth and height of
% its contents.
%
% We now add a sort of strut by putting all the discarded material
% inside of a box that creates the proper size.
% If this split is taken, the box is adjusted to have a full depth of
% \cmd{\splitmaxdepth}, and we take this into account.
%    \begin{macrocode}
  \fi
  \ht4-\dp\tw@
  \dp4\ifdim\dp\tw@<\splitmaxdepth \splitmaxdepth \else \dp\tw@ \fi
  \advance\FN@myvsize\dimexpr \ht\tw@+\dp4\relax
  \unvbox\tw@
  \nointerlineskip
  \box4 }
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@uncontribute@tw@}
%   This is just the opposite: after a split, we revert its effects again.
%    \begin{macrocode}
\def\FN@uncontribute@tw@{%
  \ifvoid\tw@ \else
  \setbox\tw@\vbox{\unvbox\tw@\splitdiscards}%
  \setbox\z@\vbox{\break\unvbox\z@}%
  {\splittopskip-\maxdimen \setbox\z@\vsplit\z@ to\z@}%
  \setbox\z@\vbox{\unvbox\tw@\unvbox\z@}\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@reconfig}
%   This reconfigures the insertion cache to contain only the boxes
%   that belong to this page.  If the insertion box is empty, we can
%   skip all the folderol.  If it isn't, we empty the cache box (the
%   number of which we place in \cmd{\count@}) and add its size back
%   to \cmd{\FN@vsize}.
%    \begin{macrocode}
\def\FN@reconfig#1#2{\ifvoid#2%
%<trace> \ifvoid\FN@cache#2\else
%<trace>    \errmessage{\FN@cache#2 should be void}\fi
  \else
  \count@\FN@cache#2%
  \ifvoid\count@\else
    \global\advance\FN@vsize
      \glueexpr(\ht\count@+\dp\count@)*\count#2/\@m+\skip#2\relax
    \global\setbox\count@ \box\voidb@x
  \fi
%    \end{macrocode}
%   Ok, now we have emptied the cache and readjusted the size.  We now
%   fill the cache by first copying the insertion into it.
%    \begin{macrocode}
  \global\setbox\count@\vbox\bgroup\vbox\bgroup\unvcopy#2%
    \let\@elt\FN@removecheck
    \FN@retainkept
%    \end{macrocode}
% Now if nothing was retained, we void the cachebox.
%    \begin{macrocode}
    \ifvoid\z@ \egroup\egroup \global\setbox\count@ \box\voidb@x
%    \end{macrocode}
% Otherwise, we combine all the boxes that remain on the page.
%    \begin{macrocode}
    \else \def\FN@masterinsert{#2}%
      \FN@assembleboxes\global\setbox\count@\box\z@\egroup
      \nointerlineskip\box\count@\egroup
%    \end{macrocode}
% Note that now all footnote boxes are collected into a single vbox,
% followed by the last footnote box as another vbox.
% Now we just need to reduce the available size on the page by the
% height of the assembled material:
%    \begin{macrocode}
    \global\advance\FN@vsize
      -\glueexpr(\ht\count@+\dp\count@)*\count#2/\@m+\skip#2\relax
  \fi\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\FN@rejoin}
%   This glues together cache boxes that have been split, without
%   regenerating them.  This saves a lot of time as compared to
%   \cmd{\FN@reconfig}.
%    \begin{macrocode}
\def\FN@rejoin#1#2{{%
%<trace> \if\foottrace1\message{^^JRejoining #2}\fi
  \count@\FN@cache#2%
  \ifvoid\count@\else
    \global\advance\FN@vsize\dimexpr
       (\ht\count@+\dp\count@)*\count#2/\@m\relax
    \global\setbox\count@\vbox{%
      \unvbox\count@
      \ifnum\lastpenalty>\z@
        \unpenalty
        \setbox\tw@\lastbox
        \setbox\z@\lastbox
        \dimen@\dp\z@
        \setbox\z@\vbox{%
          \unvbox\z@
          \setbox\z@\lastbox
          \unvbox\z@
          \unvbox\tw@}%
        \ht\z@=\dimexpr\ht\z@+\dp\z@-\dimen@\relax
        \dp\z@=\dimen@
        \nointerlineskip
        \box\z@
      \fi}%
    \global\advance\FN@vsize-\dimexpr
        (\ht\count@+\dp\count@)*\count#2/\@m\relax
  \fi}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\FN@retainkept}
%  This relies on \cmd{\@elt} being set to \cmd{\FN@removecheck} which
%  expands to \cmd{\@ne} if |\box0| is strictly between the two values
%  from an entry of \cmd{\FN@config}, which means that it is material
%  that should get moved to the next page.  In that case, we recurse
%  while dropping the box in question.  Otherwise we keep it.
%  Recursion bottoms out when there are no boxes left.  The function
%  leaves the last retained box in box~0; if there are no boxes to be
%  retained, this will be void.
%    \begin{macrocode}
\def\FN@retainkept{%
  \setbox\z@\lastbox
  \ifcase
    \ifvoid\z@\m@ne\fi \FN@config\z@
%<trace>  \if\foottrace8\message{^^J\string\FN@retainkept:
%<trace>     retaining Id \FN@slotget{\number\dp\z@}}\fi
%<trace>  \if\foottrace{16}{\showboxdepth4 \showboxbreadth400
%<trace>     \tracingonline=\@ne\showbox\z@}\fi
    {\FN@retainkept \nointerlineskip \box\z@}%
  \or
%<trace>  \if\foottrace8\message{^^J\string\FN@retainkept:
%<trace>     dropping Id \FN@slotget{\number\dp\z@}}\fi
%<trace>  \if\foottrace{16}{\showboxdepth4 \showboxbreadth400
%<trace>     \tracingonline=\@ne\showbox\z@}\fi
    \FN@retainkept
%<trace>  \else
%<trace>  \ifnum\lastnodetype>\m@ne
%<trace>    \errmessage{Unexpected node \number\lastnodetype}\fi
  \fi}
%    \end{macrocode}
% \end{macro}
% Well, as the last measure, we change the output routine to our new
% routine.
%    \begin{macrocode}
\let\output\FN@output
%    \end{macrocode}
% Ok, here is debugging code intercepting all calls of the regular
% output routine and reporting its entry and exit states.
%    \begin{macrocode}
%<trace> \newtoks\FN@tr@output
%<trace> \FN@tr@output\output
%<trace> \output{\if\foottrace8{%
%<trace>   \setbox\z@\vbox{%
%<trace>     \message{Calling regular output with
%<trace>       \outputpenalty=\the\outputpenalty, box255 as}%
%<trace>     \showbox\@cclv
%<trace>     \the\FN@tr@output
%<trace>     \message{Returning from regular output with
%<trace>     \ifnum\lastnodetype<\z@
%<trace>       empty vertical list.\else vlist:}}%
%<trace>   \showbox\z@
%<trace>   \unvbox\z@{{\fi}}}\else\the\FN@tr@output\fi}
%<trace> \let\output\FN@tr@output
%    \end{macrocode}
% If the footnote type ``default'' has not been declared by the time
% the document starts, we do so at the start of the document.
% Unfortunately, by this time the initialization code in |manyfoot|'s
% own \cmd{\AtBeginDocument} hook has already run, so we manually run
% the initialization hook just for the command we inserted ourselves.
%    \begin{macrocode}
\def\FN@maybestart#1#2#3{\ifx#3\relax
  \csname MFL@start#1\endcsname{#2}\fi#3}
\@onlypreamble\FN@maybestart
\AtBeginDocument{\@ifundefined{footinsdefault}%
  {\newfootnote[plain]{default}%
    {\let\@elt\FN@maybestart
      \MFL@list\relax}%
  }{}%
%    \end{macrocode}
% And since LaTeX's macros are inferior to our own (and would probably
% not match too well), we reroot them to the default footnote style.
%    \begin{macrocode}
  \def\@footnotetext{\Footnotetextdefault{}}%
  \def\p@footnotedefault{\p@footnote}%
}
%</style>
%    \end{macrocode}
%
% \section{Various driver files}
% The installer, in case it is missing.  If it is to be used via
% |make|, we don't specify an installation path, since
% \begin{quote}
%   |make install|
% \end{quote}
% is supposed to cater for the installation itself.
%    \begin{macrocode}
%<installer> \input docstrip
%<installer&make> \askforoverwritefalse \nopreamble
%<installer> \generate{
%<installer>    \file{bigfoot.drv}{\from{bigfoot.dtx}{driver}}
%<installer>    \file{perpage.drv}{\from{perpage.dtx}{driver}}
%<installer>    \file{suffix.drv}{\from{suffix.dtx}{driver}}
%<installer&!make>    \usedir{tex/latex/bigfoot}
%<installer>    \file{bigfoot.sty}{\from{bigfoot.dtx}{style}}
%<installer>    \file{perpage.sty}{\from{perpage.dtx}{style}}
%<installer>    \file{suffix.sty}{\from{suffix.dtx}{style}}
%<installer> }
%<installer> \endbatchfile
%    \end{macrocode}
% \Finale
% \endinput
% Local Variables:
% mode: doctex
% TeX-master: "bigfoot.drv"
% End: