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%% floatflt.dtx  (with options: `gammalkod')
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%% Copyright (c) 1994-1996 by Mats Dahlgren <matsd@physchem.kth.se>. 
%% All rights reserved. See the file `floatflt.ins' for information 
%% on how you may (re-)distribute the `floatflt' package files. 
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 \documentclass[11pt]{article}
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 \textheight=1.1\textheight
 \textwidth=1.15\textwidth
 \oddsidemargin=0pt
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 \begin{document}
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 \title{\LaTeX-Paragraphs Floating around Figures}
 \author{{\it Thomas Kneser}\\{\footnotesize
 Gesellschaft f\"ur wissenschaftliche Datenverarbeitung
  mbH G\"ottingen, FRG}}
 \date{August 20, 1990}
 \maketitle
 %
 \begin{abstract}
 %
 \noindent Frequently figures do not fill the full pagewidth.
 If the width of such figures is only half of the
 pagewidth or even less,
 textlines should be set beside the figures,
 or -- from another point of view -- figures should `float'
 in paragraphs.
 This article presents the \LaTeX{} style option {\tt FLOATFIG}
 which can be used to set such Floating Figures as easily
 as \LaTeX's standard figures.
 \end{abstract}
 %
 \section{The name of the game}
 The macros which make up the {\tt FLOATFIG} style option
 are based on PLAIN-\TeX\ macros developed by Thomas Reid
 (TUGBoat Vol. 8 \# 3 page 315), who pointed out
 how to set figures
 {\bf right justified} with paragraphs floating around them.
 For such objects
 Th. Reid has chosen the term `Floating Figures'.

 This choice might cause some confusion,
 when we adapt these macros for \LaTeX,
 since Leslie Lamport uses the term `float' for objects
 which are realized as \TeX-\verb+\inserts+.
 While L. Lamports floats are floating in `main vertical list',
 floats introduced by Th. Reid
 are floating in paragraphs.
 For the following we adopt the latter meaning.
 \section{How to use it}
 The Floating Figures style option is fully compatible with
 \LaTeX's standard figure facility:
 \begin{enumerate}
 \item Floating Figures and standard figures may be requested
       in any sequence,
 \item Floating Figures can be captioned like standard figures,
 \item captioned Floating Figures are inserted in the list of figures
       which may be printed by the standard
       \verb+\listoffigures+ command.
 \end{enumerate}
 A Floating Figure may be requested as follows:
 \begin{verbatim}
   \documentstyle[floatfig]{article}
   \begin{document}
   \initfloatingfigs
           .
           .
   \begin{floatingfigure}{5.6cm}
   \vspace{6.cm}
   \caption{Intermolecular potential K-Xe}% optional !
   \end{floatingfigure}
           .
           .
   \end{document}
 \end{verbatim}
 where {\tt 5.6cm} specifies the width of the figure space.
 A Floating Figure may only be requested in vertical mode, that is
 between paragraphs.

 A Floating Figure will be set as soon as possible after its request
 has be encountered by \TeX.
 That means,
 it will be tested if there is enough vertical space
 on the current page;
 otherwise the figure moves to the next page.

 Floating Figures are set {\bf alternating},
 that is on the right hand side on odd and
 on the left hand side on even numbered pages.
 %
 \subsection{Restrictions}
 \begin{enumerate}
 \item The {\tt FLOATFIG} style option may not be combined with the
 {\tt TWOCOLUMN} style option,
 \item a Floating Figure will never appear in a paragraph
 which begins on top of a page.
 \end{enumerate}
 %
 \section{About the internals}
 %
 We have extended the macros designed by Th.~Reid with regard to:
 \begin{enumerate}
 \item implantation into the \LaTeX{} context,
 \item alternating setting of Floating Figures as explained above,
 \item generation of warning messages for `collisions' of
       two Floating Figures.
 \end{enumerate}
 %
 \subsection{Implantation into the \LaTeX{} context}
 The PLAIN-\TeX{} implementation by Th.~Reid
 is based on a redefined \verb+\output+ routine:
 %
 \begin{verbatim}
   \edef\oldoutput{\the\output}%
   \output={\the\outputpretest\ifoutput\oldoutput\fi}
   \outputpretest={\outputtrue}
 \end{verbatim}
 %
 If a Floating Figure is requested,
 the content of the
 \verb+\outputpretest+ token register is prepared to decide:
 \begin{enumerate}
 \item if there is enough vertical space to set the Floating Figure,
 \item if setting of a Floating Figure is in progress or
 \item if indeed the current page has to be sent to the DVI file.
 \end{enumerate}
 %
 In general, \TeX{} has to deal with more than one paragraph until
 a Floating Figure will be completely processed.
 During this process
 the redefined \verb+\output+ routine is
 called at the begin of {\bf every} paragraph;
 this is done indirectly
 by expanding the control sequence \verb+\tryfig+.
 Therefore, the \verb+\everypar+ token
 list is prepared by the following command sequence:
 \begin{verbatim}
   \edef\oldeverypar{\the\everypar}
   \everypar={\tryfig\oldeverypar}
 \end{verbatim}
 Now \verb+\tryfig+ triggers the (modified)
 \verb+\output+ routine, which then does the decisions
 and actions mentioned above.

 Adopting this concept when using the macros in the \LaTeX{} context,
 we are faced with the following problems:
 \begin{enumerate}
 \item At the time \hbox{\tt FLOATFIG.STY} is read in,
       the \verb+\output+ routine is still undefined;
       its definition is retarded until
       \verb+\begin{document}+ will be expanded;
       so the redefinition of the \verb+\output+ routine has to be
       done after \verb+\begin{document}+
       by the command \verb+\initfloatingfigs+
       (see section `Known Problems' below).
 \item There are situations where
       \LaTeX{} decides to redefine the \verb+\everypar+ token list
       without saving of the former content;
       this occurs for instance when expanding
       a \verb+\section+ control sequence.
       We overcome this by redefining \verb+\everypar+ whenever
       the \verb+\floatingfigure+ environment is entered.
 %
       Hence to avoid problems, a Floating Figure should be requested
       early enough before any sectioning control sequence
       (see also subsection `Misleading collision warnings').\hfil\break
 %
       Furthermore, the concurrent definitions of
       \verb+\everypar+ are the reason why
       Floating Figures cannot move across section boundaries.
 \end{enumerate}
 %
 \subsection{Alternating figure setting}
 The problem to be solved
 is to decide if a certain figure has to be set
 left- or rightjustified.
 This decision has to made according to
 the value of the pagecount (left if even, right if odd).
 That is we are dealing with the wellknown problem
 to associate a certain part of input text with the number
 of the page on which it will be set finally.

 As pointed out by D.E. Knuth in `The {\TeX}book' this association
 is done not before \verb+\output+ routine time.
 But the problem is not so hard to solve,
 since in Th.~Reid's version there is already a modified
 \verb+\output+ routine which decides if a certain figure will
 fit on the current page.
 As a by-product of this decision one easily gains
 the information `odd' or `even' for the pagecount
 of the current page.
 So our problem reduces to the following simple decision:
 \begin{verbatim}
   \ifodd\count0 %
      \hbox to \hsize{\hss\copy\figbox}%
      \global\oddpagestrue
    \else% leftsetting
      \hbox to \hsize{\copy\figbox\hss}%
      \global\oddpagesfalse
    \fi% \ifodd\count0
 \end{verbatim}
 %
 \subsection{Collisions of Floating Figures}
 We define a collision as a situation where:
 \begin{enumerate}
 \item a Floating Figure is requested before the predecessor
       has been finished,
 \item some sectioning is requested before a Floating Figure has been
       finished.
 \end{enumerate}

 While the {\tt FLOATFIG} style option cannot avoid such collisions,
 it will recognize them.
 For diagnostic purposes we have therefore defined
 the switch \verb+\iffigprocessing+ and another count register called
 \verb+\ffigcount+.
 This count register is used to attach
 a sequence number to each Floating Figure,
 so they can be identified uniquely within collision warning messages.
 These sequence numbers are not to be confused
 with the figure count maintained by standard \LaTeX.
 %
 \section{Known Problems}
 \subsection{Need of Initialization}
 The present version of the style option needs to be initialized
 by control sequence
 {\tt\verb+\initfloatingfigs+} as mentioned above.\footnote{%
 This is not needed with \LaTeXe{}. /MD}

 We hope a later version will initialize itself,
 when the first request to a Floating Figure is encountered.
 One problem with such an automatic initialization seems
 to be,
 that we are grouped down
 since we are inside a \LaTeX{} environment.
 Our first attempt failed
 to make the respective settings \verb+\global+.
 %
 \subsection{Misleading collision warnings}
 As mentioned above, Floating Figures do not move
 across section boundaries.
 If a Floating Figure is requested near a section end,
 the figure will be truncated,
 if it does not fit in the current section.

 If this occurs for instance with floating figure number~4,
 a collision will be reported when the request for
 floating figure number~5 is encountered;
 so the respective warning message may be substantially retarded.
 In fact, the message will tell us that there is a problem with figure~4,
 but there will be no further hint.
 So one has to analyze `by hand' that the problem is {\bf not} caused
 by collision with figure~5 but with a section heading;
 even worse: if there is no floating figure~5, one gets no warning message
 at all.

 Furthermore, warning messages will be generated if a Floating Figure
 ends in paragraph $n$ and the next one begins with paragraph $n+1$.
 These warning messages are to be ignored; they are due to some retardation
 caused by the \verb+\everypar+ mechanism.
 %
 \section{Conclusions}
 Working on \texttt{FLOATFIG.STY} we had some unexpected problems
 which were caused
 by \LaTeX's somewhat unsafe assignments to the \verb+\everypar+ token list.
 This is due to the fact that the use
 of this token list is fundamental
 to the algorithm designed by Th.~Reid.
 On the other hand we did expect problems to couple
 the Floating Figures with \LaTeX's figure caption adminstration,
 that is to achieve a single figure caption numbering for
 the standard figures and the Floating Figures and to get both types
 listed by the \verb+\listoffigures+ control sequence.
 %
 But these problems could easily be solved
 by the following local definiton within the {\tt FLOATFIG} environment:
 \begin{verbatim}
   \def\@captype{figure}
 \end{verbatim}
 Obviously this is due to the fact
 that \LaTeX's caption apparatus is thoroughly parameterized.

 The \verb+FLOATFIG.STY+ file is stored in the
 {\tt EARN/BITNET} listserver
 in Heidelberg; \hfil\break
 {\tt VM/CMS} users should enter the commands:
 \begin{verbatim}
   TELL LISTSERV AT DHDURZ1 GET LATEXSTY INDEX
   TELL LISTSERV AT DHDURZ1 GET LATEXSTY README
   TELL LISTSERV AT DHDURZ1 GET LATEXSTY FILELIST
   TELL LISTSERV AT DHDURZ1 GET FLOATFIG ZOOUUE LATEXSTY
 \end{verbatim}
 to obtain information about how to obtain the style option file.
\subsection{Note by Mats Dahlgren}
Several features described in this document still apply to the
\LaTeXe\ \texttt{floatflt} package, whereas others do not.  Please
run \LaTeX{} on \texttt{floatflt.dtx} twice and read the resulting
documentation before you use the package.
(This note was added on October 20, 1994; changed on December 27,
1994.)

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