% \iffalse
%%    The preview style for extracting previews from LaTeX documents.
%%    Developed as part of AUCTeX <URL:https://www.gnu.org/software/auctex/>.
%
%     Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006,
%                   2010, 2017-2024 Free Software Foundation
%
%     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 3 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{1770}
% \GetFileInfo{preview.sty}
% \date{\filedate}
% \author{David Kastrup\thanks{\texttt{bug-auctex@gnu.org}}}
% \title{The \texttt{preview} Package for \LaTeX\\Version \fileversion}
% \maketitle
% \section{Introduction}
% The main purpose of this package is the extraction of certain
% environments (most notably displayed formulas) from \LaTeX\ sources
% as graphics.  This works with DVI files postprocessed by either
% Dvips and Ghostscript or dvipng, but it also works when you are
% using PDF\TeX\ for generating PDF files (usually also postprocessed
% by Ghostscript).
%
% Current uses of the package include the \previewlatex\ package for
% WYSIWYG functionality in the AUC\TeX\ editing environment,
% generation of previews in LyX, as part of the operation of the
% pst-pdf package, the tbook XML system and some other tools.
% 
% Producing EPS files with Dvips and its derivatives using the
% \texttt{-E} option is not a good alternative: People make do by
% fiddling around with |\thispagestyle{empty}| and hoping for the best
% (namely, that the specified contents will indeed fit on single
% pages), and then trying to guess the baseline of the resulting code
% and stuff, but this is at best dissatisfactory.  The preview package
% provides an easy way to ensure that exactly one page per request
% gets shipped, with a well-defined baseline and no page decorations.
% While you still can use the preview package with the `classic'
% \begin{quote}
% |dvips -E -i|
% \end{quote}
% invocation, there are better ways available that don't rely on Dvips
% not getting confused by PostScript specials.
% 
% For most applications, you'll want to make use of the |tightpage|
% option.  This will embed the page dimensions into the PostScript or
% PDF code, obliterating the need to use the |-E -i| options to Dvips.
% You can then produce all image files with a single run of
% Ghostscript from a single PDF or PostScript (as opposed to EPS)
% file.
% 
% Various options exist that will pass \TeX\ dimensions and other
% information about the respective shipped out material (including
% descender size) into the log file, where external applications might
% make use of it.
% 
% The possibility for generating a whole set of graphics with a single
% run of Ghostscript (whether from \LaTeX\ or PDF\LaTeX) increases
% both speed and robustness of applications.  It is also feasible to
% use dvipng on a DVI file with the options
% \begin{quote}
%   |-picky -noghostscript|
% \end{quote}
% to omit generating any image file that requires Ghostscript, then
% let a script generate all missing files using Dvips/Ghostscript.
% This will usually speed up the process significantly.
% 
% \section{Package options}
% The package is included with the customary
% \begin{quote}
% |\usepackage|\oarg{options}|{preview}|
% \end{quote}
% You should usually load this package as the last one, since it
% redefines several things that other packages may also provide.
% 
% The following options are available:
% \begin{description}
% \item[|active|] is the most essential option.  If this option is not
%   specified, the |preview| package will be inactive and the document
%   will be typeset as if the |preview| package were not loaded,
%   except that all declarations and environments defined by the
%   package are still legal but have no effect.  This allows defining
%   previewing characteristics in your document, and only activating
%   them by calling \LaTeX\ as
% \begin{quote}
% \raggedright
% |latex '\PassOptionsToPackage{active}{preview}| |\input|\marg{filename}|'|
% \end{quote}
% \item[|noconfig|] Usually the file |prdefault.cfg| gets loaded
%   whenever the |preview| package gets activated.  |prdefault.cfg| is
%   supposed to contain definitions that can cater for otherwise bad
%   results, for example, if a certain document class would otherwise
%   lead to trouble.  It also can be used to override any settings
%   made in this package, since it is loaded at the very end of it.
%   In addition, there may be configuration files specific for certain
%   |preview| options like |auctex| which have more immediate needs.
%   The |noconfig| option suppresses loading of those option files,
%   too.
% \item[|psfixbb|] Dvips determines the bounding boxes from the
%   material in the DVI file it understands.  Lots of PostScript
%   specials are not part of that.  Since the \TeX\ boxes do not make
%   it into the DVI file, but merely characters, rules and specials
%   do, Dvips might include far too small areas.  The option |psfixbb|
%   will include |/dev/null| as a graphic file in the ultimate upper
%   left and lower right corner of the previewed box.  This will make
%   Dvips generate an appropriate bounding box.
% \item[|dvips|] If this option is specified as a class option or to
%   other packages, several packages pass things like page size
%   information to Dvips, or cause crop marks or draft messages
%   written on pages.  This seriously hampers the usability of
%   previews.  If this option is specified, the changes will be undone
%   if possible.
% \item[|pdftex|] If this option is set, PDF\TeX\ is assumed as the
%   output driver.  This mainly affects the |tightpage| option.
% \item[|xetex|] If this option is set, Xe\TeX\ is assumed as the
%   output driver.  This mainly affects the |tightpage| option.
% \item[|displaymath|] will make all displayed math environments
%   subject to preview processing.  This will typically be the most
%   desired option.
% \item[|floats|] will make all float objects subject to preview
%   processing.  If you want to be more selective about what floats to
%   pass through to a preview, you should instead use the
%   \cmd{\PreviewSnarfEnvironment} command on the floats you want to
%   have previewed.
% \item[|textmath|] will make all text math subject to previews.
%   Since math mode is used throughly inside of \LaTeX\ even for other
%   purposes, this works by redefining \cmd\(, \cmd\)
%   and |$| and the |math| environment (apparently some people use ^^A$
%   that).  Only occurences of these text math delimiters in later
%   loaded packages and in the main document will thus be affected.
% \item[|graphics|] will subject all \cmd{\includegraphics} commands
%   to a preview.
% \item[|sections|] will subject all section headers to a preview.
% \item[|delayed|] will delay all activations and redefinitions the
%   |preview| package makes until |\||begin{document}|.  The purpose
%   of this is to cater for documents which should be subjected to the
%   |preview| package without having been prepared for it.  You can
%   process such documents with
%   \begin{quote}
%     |latex '\RequirePackage[active,delayed,|\meta{options}|]{preview}|
%     |\input|\marg{filename}|'|
%   \end{quote}
%   This relaxes the requirement to be loading the |preview| package
%   as last package.
% \item[\meta{driver}] loads a special driver file
%   |pr|\meta{driver}|.def|.  The remaining options are implemented
%   through the use of driver files.
% \item[|auctex|] This driver will produce fake error messages at the
%   start and end of every preview environment that enable the Emacs
%   package \previewlatex\ in connection with AUC\TeX\ to pinpoint
%   the exact source location where the previews have originated.
%   Unfortunately, there is no other reliable means of passing the
%   current \TeX\ input position \emph{in} a line to external
%   programs.  In order to make the parsing more robust, this option
%   also switches off quite a few diagnostics that could be
%   misinterpreted.
% 
%   You should not specify this option manually, since it will only be
%   needed by automated runs that want to parse the pseudo error
%   messages.  Those runs will then use \cmd{\PassOptionsToPackage} in
%   order to effect the desired behaviour.  In addition,
%   |prauctex.cfg| will get loaded unless inhibited by the |noconfig|
%   option.  This caters for the most frequently encountered
%   problematic commands.
% \item[|showlabels|] During the editing process, some people like to
%   see the label names in their equations, figures and the like.  Now
%   if you are using Emacs for editing, and in particular
%   \previewlatex, I'd strongly recommend that you check out the
%   Ref\TeX\ package which pretty much obliterates the need for this
%   kind of functionality.  If you still want it, standard \LaTeX\
%   provides it with the |showkeys| package, and there is also the
%   less encompassing |showlabels| package.  Unfortunately, since
%   those go to some pain not to change the page layout and spacing,
%   they also don't change |preview|'s idea of the \TeX\ dimensions of
%   the involved boxes.  So if you are using |preview| for determing
%   bounding boxes, those packages are mostly useless.  The option
%   |showlabels| offers a substitute for them.
% \item[|tightpage|] It is not uncommon to want to use the results of
%   |preview| as graphic images for some other application.  One
%   possibility is to generate a flurry of EPS files with
%   \begin{quote}
%     |dvips -E -i -Pwww -o| \meta{outputfile}|.000| \meta{inputfile}
%   \end{quote}
%   However, in case those are to be processed further into graphic
%   image files by Ghostscript, this process is inefficient since all
%   of those files need to be processed one by one.  In addition, it
%   is necessary to extract the bounding box comments from the EPS
%   files and convert them into page dimension parameters for
%   Ghostscript in order to avoid full-page graphics.  This is not
%   even possible if you wanted to use Ghostscript in a~\emph{single}
%   run for generating the files from a single PostScript file, since
%   Dvips will in that case leave no bounding box information
%   anywhere.
% 
%   The solution is to use the |tightpage| option.  That way a single
%   command line like
%   \begin{quote}
%     \raggedright
%     \texttt{gs -sDEVICE=png16m -dTextAlphaBits=4 -r300
%       -dGraphicsAlphaBits=4 -dSAFER -q -dNOPAUSE
%       -sOutputFile=\meta{outputfile}\%d.png \meta{inputfile}.ps}
%   \end{quote}
%   will be able to produce tight graphics from a single PostScript
%   file generated with Dvips \emph{without} use of the options
%   |-E -i|, in a single run.
%
%   The |tightpage| option actually also works when using the |pdftex|
%   option and generating PDF files with PDF\TeX.  The resulting PDF
%   file has separate page dimensions for every page and can directly
%   be converted with one run of Ghostscript into image files.
%
%   If neither |dvips| or |pdftex| have been specified, the
%   corresponding option will get autodetected and invoked.
%
%   If you need this in a batch environment where you don't want to
%   use |preview|'s automatic extraction facilities, no problem: just
%   don't use any of the extraction options, and wrap everything to be
%   previewed into |preview| environments.  This is how LyX does its
%   math previews.
% 
%   If the pages under the |tightpage| option are just too tight, you
%   can adjust by setting the length |\PreviewBorder| to a different
%   value by using \cmd{\setlength}.  The default value is
%   |0.50001bp|, which is half of a usual PostScript point, rounded
%   up.  If you go below this value, the resulting page size may drop
%   below |1bp|, and Ghostscript does not seem to like that.  If you
%   need finer control, you can adjust the bounding box dimensions
%   individually by changing the macro |\PreviewBbAdjust| with the
%   help of |\renewcommand|.  Its default value is
%   \begin{quote}
%     \raggedright
%     |\newcommand| |\PreviewBbAdjust|
%       |{-\PreviewBorder| |-\PreviewBorder|
%       |\PreviewBorder|  |\PreviewBorder}|
%   \end{quote}
%   This adjusts the left, lower, right and upper borders by the given
%   amount.  The macro must contain 4~\TeX\ dimensions after another,
%   and you may not omit the units if you specify them explicitly
%   instead of by register.  PostScript points have the unit~|bp|.
% \item[|lyx|] This option is for the sake of LyX developers.  It will
%   output a few diagnostics relevant for the sake of LyX' preview
%   functionality (at the time of writing, mostly implemented for math
%   insets, in versions of LyX starting with 1.3.0).
% \item[|counters|] This writes out diagnostics at the start and the
%   end of previews.  Only the counters changed since the last output
%   get written, and if no counters changed, nothing gets written at
%   all.  The list consists of counter name and value, both enclosed
%   in |{}| braces, followed by a space.  The last such pair is
%   followed by a colon (|:|) if it is at the start of the preview
%   snippet, and by a period (|.|) if it is at the end.  The order of
%   different diagnostics like this being issued depends on the order
%   of the specification of the options when calling the package.
% 
%   Systems like \previewlatex\ use this for keeping counters accurate
%   when single previews are regenerated.
% \item[|footnotes|] This makes footnotes render as previews, and only
%   as their footnote symbol.  A convenient editing feature inside of
%   Emacs.
% \end{description}
% The following options are just for debugging purposes of the package
% and similar to the corresponding \TeX\ commands they allude to:
% \begin{description}
% \item[|tracingall|] causes lots of diagnostic output to appear in
%   the log file during the preview collecting phases of \TeX's
%   operation.  In contrast to the similarly named \TeX\ command, it
%   will not switch to |\errorstopmode|, nor will it change the
%   setting of |\tracingonline|.
% \item[|showbox|] This option will show the contents of the boxes
%   shipped out to the DVI files.  It also sets |\showboxbreadth| and
%   |\showboxdepth| to their maximum values at the end of loading this
%   package, but you may reset them if you don't like that.
% \end{description}
% \section{Provided Commands}
% \DescribeEnv{preview} The |preview| environment causes its contents
% to be set as a single preview image.  Insertions like figures and
% footnotes (except those included in minipages) will typically lead
% to error messages or be lost.  In case the |preview| package has not
% been activated, the contents of this environment will be typeset
% normally.
% 
% \DescribeEnv{nopreview} The |nopreview| environment will cause its
% contents not to undergo any special treatment by the |preview|
% package.  When |preview| is active, the contents will be discarded
% like all main text that does not trigger the |preview| hooks.  When
% |preview| is not active, the contents will be typeset just like the
% main text.
% 
% Note that both of these environments typeset things as usual when
% preview is not active.  If you need something typeset conditionally,
% use the \cmd{\ifPreview} conditional for it.
% 
% \DescribeMacro{\PreviewMacro} If you want to make a macro like
% \cmd{\includegraphics} (actually, this is what is done by the
% |graphics| option to |preview|) produce a preview image, you put a
% declaration like
% \begin{quote}
% |\PreviewMacro[*[[!]{\includegraphics}|
% \end{quote}
% or, more readable,
% \begin{quote}
% |\PreviewMacro[{*[][]{}}]{\includegraphics}|
% \end{quote}
% into your preamble.  The optional argument to \cmd{\PreviewMacro}
% specifies the arguments \cmd{\includegraphics} accepts, since this
% is necessary information for properly ending the preview box.  Note
% that if you are using the more readable form, you have to enclose
% the argument in a |[{| and |}]| pair.  The inner braces are
% necessary to stop any included |[]| pairs from prematurely ending
% the optional argument, and to make a single |{}|
% denoting an optional argument not get stripped away by \TeX's
% argument parsing.
% 
% The letters simply mean
% \begin{description}
% \item[|*|] indicates an optional |*| modifier, as in
%   |\includegraphics*|.
% \item[|[|]^^A]
%   indicates an optional argument in brackets.  This syntax
%   is somewhat baroque, but brief.
% \item[{|[]|}] also indicates an optional argument in brackets.  Be
%   sure to have encluded the entire optional argument specification
%   in an additional pair of braces as described above.
% \item[|!|] indicates a mandatory argument.
% \item[|\char`{\char`}|] indicates the same.  Again, be sure to have
%   that additional level of braces around the whole argument
%   specification.
% \item[|?|\meta{delimiter}\marg{true case}\marg{false case}] is a
%   conditional.  The next character is checked against being equal to
%   \meta{delimiter}.  If it is, the specification \meta{true case} is
%   used for the further parsing, otherwise \meta{false case} will be
%   employed.  In neither case is something consumed from the input,
%   so \marg{true case} will still have to deal with the upcoming
%   delimiter.
% \item[|@|\marg{literal sequence}] will insert the given sequence
%   literally into the executed call of the command.
% \item[|-|] will just drop the next token.  It will probably be most
%   often used in the true branch of a |?| specification.
% \item[|\#|\marg{argument}\marg{replacement}] is a transformation
%   rule that calls a macro with the given argument and replacement
%   text on the rest of the argument list.  The replacement is used in
%   the executed call of the command.  This can be used for parsing
%   arbitrary constructs.  For example, the |[]| option could manually
%   be implemented with the option string |?[{#{[#1]}{[{#1}]}}{}|.
%   PStricks users might enjoy this sort of flexibility.
% \item[|:|\marg{argument}\marg{replacement}] is again a
%   transformation rule.  As opposed to |#|, however, the result of
%   the transformation is parsed again.  You'll rarely need this.
% \end{description}
% 
% There is a second optional argument in brackets that can be used to
% declare any default action to be taken instead.  This is mostly for
% the sake of macros that influence numbering: you would want to keep
% their effects in that respect.  The default action should use |#1|
% for referring to the original (not the patched) command with the
% parsed options appended.  Not specifying a second optional argument
% here is equivalent to specifying~|[#1]|.
% 
% \DescribeMacro{\PreviewMacro*} A similar invocation
% \cmd{\PreviewMacro*} simply throws the macro and all of its
% arguments declared in the manner above away.  This is mostly useful
% for having things like \cmd{\footnote} not do their magic on their
% arguments.  More often than not, you don't want to declare any
% arguments to scan to \cmd{\PreviewMacro*} since you would want the
% remaining arguments to be treated as usual text and typeset in that
% manner instead of being thrown away.  An exception might be, say,
% sort keys for \cmd{\cite}.
% 
% A second optional argument in brackets can be used to declare any
% default action to be taken instead.  This is for the sake of macros
% that influence numbering: you would want to keep their effects in
% that respect.  The default action might use |#1| for referring to
% the original (not the patched) command with the parsed options
% appended.  Not specifying a second optional argument here is
% equivalent to specifying~|[]| since the command usually gets thrown
% away.
% 
% As an example for using this argument, you might want to specify
% \begin{quote}
%   |\PreviewMacro*[{[]}][#1{}]{\footnote}|
% \end{quote}
% This will replace a footnote by an empty footnote, but taking any
% optional parameter into account, since an optional paramter changes
% the numbering scheme.  That way the real argument for the footnote
% remains for processing by \previewlatex.
% 
% \DescribeMacro{\PreviewEnvironment} The macro
% \cmd{\PreviewEnvironment} works just as \cmd{\PreviewMacro} does,
% only for environments.  \DescribeMacro{\PreviewEnvironment*} And the
% same goes for \cmd{\PreviewEnvironment*} as compared to
% \cmd{\PreviewMacro*}.
% 
% \DescribeMacro{\PreviewSnarfEnvironment} This macro does not typeset
% the original environment inside of a preview box, but instead
% typesets just the contents of the original environment inside of the
% preview box, leaving nothing for the original environment.  This has
% to be used for figures, for example, since they would
% \begin{enumerate}
% \item produce insertion material that cannot be extracted to the
%   preview properly,
% \item complain with an error message about not being in outer par
%   mode.
% \end{enumerate}
% 
% \DescribeMacro{\PreviewOpen}
% \DescribeMacro{\PreviewClose}
% Those Macros form a matched preview pair.  This is for macros that
% behave similar as \cmd{\begin} and \cmd{\end} of an environment.  It
% is essential for the operation of \cmd{\PreviewOpen} that the macro
% treated with it will open an additional group even when the preview
% falls inside of another preview or inside of a |nopreview|
% environment.  Similarly, the macro treated with \cmd{\PreviewClose}
% will close an environment even when inactive.
% 
% \DescribeMacro{\ifPreview} In case you need to know whether
% |preview| is active, you can use the conditional \cmd{\ifPreview}
% together with |\else| and |\fi|.
%
% \StopEventually{}
% \section{The Implementation}
% We provide version and date manually.  This should really be done at
% docstrip time instead.  Takers?
% \begin{macro}{\pr@version}
% \begin{macro}{\pr@date}
%    \begin{macrocode}
%<*style>
%<*!active>
\NeedsTeXFormat{LaTeX2e}
\def\pr@version{14.0.6}
\def\pr@date{2024/06/30}
\ProvidesPackage{preview}[\pr@date\space \pr@version\space (AUCTeX/preview-latex)]
%    \end{macrocode}
% \end{macro}
% \end{macro}
% Since many parts here will not be needed as long as the package is
% inactive, we will include them enclosed with |<*active>| and
% |</active>| guards.  That way, we can append all of this stuff at a
% place where it does not get loaded if not necessary.
%
%\begin{macro}{\ifPreview}
%  Setting the \cmd{\ifPreview} command should not be done by the
%  user, so we don't use \cmd{\newif} here.  As a consequence, there
%  are no \cmd{\Previewtrue} and \cmd{\Previewfalse} commands.
%    \begin{macrocode}
\let\ifPreview\iffalse
%</!active>
%    \end{macrocode}
%\end{macro}
%\begin{macro}{\ifpr@outer}
%  We don't allow previews inside of previews.  The macro
%  \cmd{\ifpr@outer} can be used for checking whether we are outside
%  of any preview code.
%    \begin{macrocode}
%<*active>
\newif\ifpr@outer
\pr@outertrue
%</active>
%    \end{macrocode}
%\end{macro}
%
%\begin{macro}{\preview@delay}
%  The usual meaning of \cmd{\preview@delay} is to just echo its
%  argument in normal |preview| operation.  If |preview| is inactive,
%  it swallows its argument.  If the |delayed| option is active, the
%  contents will be passed to the \cmd{\AtBeginDocument} hook.
%\begin{macro}{\pr@advise}
%  The core macro for modifying commands is \cmd{\pr@advise}.  You
%  pass it the original command name as first argument and what should
%  be executed before the saved original command as second argument.
%\begin{macro}{\pr@advise@ship}
%  The most often used macro for modifying commands is
%  \cmd{\pr@advise@ship}.  It receives three arguments.  The first is
%  the macro to modify, the second specifies some actions to be done
%  inside of a box to be created before the original macro gets
%  executed, the third one specifies actions after the original macro
%  got executed.
%\begin{macro}{\pr@loadcfg}
%  The macro \cmd{\pr@loadcfg} is used for loading in configuration
%  files, unless disabled by the |noconfig| option.  After discussion
%  with maintainer of pst-pdf package Rolf Niepraschk (Thanks!), we
%  add here a check for existence of |luatex85.sty| and load it if
%  available.  With this, |preview| will also work with newer |luatex|
%  versions.
%    \begin{macrocode}
%<*!active>
\let\preview@delay=\@gobble
\let\pr@advise=\@gobbletwo
\long\def\pr@advise@ship#1#2#3{}
\def\pr@loadcfg#1{\InputIfFileExists{#1.cfg}{}{}}
\IfFileExists{luatex85.sty}{\RequirePackage{luatex85}}{}
\DeclareOption{noconfig}{\let\pr@loadcfg=\@gobble}
%    \end{macrocode}
%\begin{macro}{\pr@addto@front}
%  This adds code globally to the front of a macro.
%    \begin{macrocode}
\long\def\pr@addto@front#1#2{%
  \toks@{#2}\toks@\expandafter{\the\expandafter\toks@#1}%
  \xdef#1{\the\toks@}}
%    \end{macrocode}
% \end{macro}
% These commands get more interesting when |preview| is active:
%    \begin{macrocode}
\DeclareOption{active}{%
  \let\ifPreview\iftrue
  \def\pr@advise#1{%
    \expandafter\pr@adviseii\csname pr@\string#1\endcsname#1}%
  \long\def\pr@advise@ship#1#2#3{\pr@advise#1{\pr@protect@ship{#2}{#3}}}%
  \let\preview@delay\@firstofone}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% 
% \begin{macro}{\pr@adviseii}
%   Now \cmd{\pr@advise} needs its helper macro.  In order to avoid
%   recursive definitions, we advise only macros that are not yet
%   advised.  Or, more exactly, we throw away the old advice and only
%   take the new one.  We use e\TeX's \cmd{\protected} where available
%   for some extra robustness.
%    \begin{macrocode}
\long\def\pr@adviseii#1#2#3{\preview@delay{%
  \ifx#1\relax \let#1#2\fi
  \toks@{#3#1}%
  \ifx\@undefined\protected \else \protected\fi
  \long\edef#2{\the\toks@}}}
%    \end{macrocode}
%\end{macro}
%
% The |delayed| option is easy to implement: this is \emph{not} done
% with \cmd{\let} since at the course of document processing, \LaTeX\
% redefines \cmd{\AtBeginDocument} and we want to follow that
% redefinition.
%    \begin{macrocode}
\DeclareOption{delayed}{%
  \ifPreview \def\preview@delay{\AtBeginDocument}\fi
}
%    \end{macrocode}
%
%\begin{macro}{\ifpr@fixbb}
%  Another conditional.  \cmd{\ifpr@fixbb} tells us whether we want to
%  surround the typeset materials with invisible rules so that Dvips
%  gets the bounding boxes right for, say, pure PostScript inclusions.
%
%  If you are installing this on an operating system different from
%  the one |preview| has been developed on, you might want to redefine
%  |\pr@markerbox| in your |prdefault.cfg| file to use a file known to
%  be empty, like |/dev/null| is under Unix.  Make this redefinition
%  depend on \cmd{\ifpr@fixbb} since only then |\pr@markerbox| will be
%  defined.
%    \begin{macrocode}
\newif\ifpr@fixbb
\pr@fixbbfalse
\DeclareOption{psfixbb}{\ifPreview%
  \pr@fixbbtrue
  \newbox\pr@markerbox
  \setbox\pr@markerbox\hbox{\special{psfile=/dev/null}}\fi
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@graphicstype}
%   The |dvips| option redefines the |bop-hook| to reset the page
%   size.
%    \begin{macrocode}
\let\pr@graphicstype=\z@
\DeclareOption{dvips}{%
  \let\pr@graphicstype\@ne
  \preview@delay{\AtBeginDvi{%
      \special{!/preview@version(\pr@version)def}
      \special{!userdict begin/preview-bop-level 0 def%
      /bop-hook{/preview-bop-level dup load dup 0 le{/isls false def%
          /vsize 792 def/hsize 612 def}if 1 add store}bind def%
      /eop-hook{/preview-bop-level dup load dup 0 gt{1 sub}if
        store}bind def end}}}}
%    \end{macrocode}
% The |pdftex| option just sets \cmd{\pr@graphicstype}.
%    \begin{macrocode}
\DeclareOption{pdftex}{%
  \let\pr@graphicstype\tw@}
%    \end{macrocode}
% And so does the |xetex| option.
%    \begin{macrocode}
\DeclareOption{xetex}{%
  \let\pr@graphicstype\thr@@}
%</!active>
%    \end{macrocode}
% \end{macro}
% \subsection{The internals}
%
% Those are only needed if |preview| is active.
%    \begin{macrocode}
%<*active>
%    \end{macrocode}
% \begin{macro}{\pr@snippet}
%   \cmd{\pr@snippet} is the current snippet number.  We need a
%   separate counter to \cmd{\c@page} since several other commands
%   might fiddle with the page number.
%    \begin{macrocode}
\newcount\pr@snippet
\global\pr@snippet=1
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@protect}
%   This macro gets one argument which is unpacked and executed in
%   typesetting situations where we are not yet inside of a preview.
%    \begin{macrocode}
\def\pr@protect{\ifx\protect\@typeset@protect
  \ifpr@outer \expandafter\expandafter\expandafter
     \@secondoftwo\fi\fi\@gobble}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@protect@ship}
%   Now for the above mentioned \cmd{\pr@protect@ship}.  This gets
%   three arguments.  The first is what to do at the beginning of the
%   preview, the second what to do at the end, the third is the macro
%   where we stored the original definition.
%
%   In case we are not in a typesetting situation,
%   \cmd{\pr@protect@ship} leaves the stored macro to fend for its
%   own.  No better or worse protection than the original.  And we
%   only do anything different when \cmd{\ifpr@outer} turns out to be
%   true.
%    \begin{macrocode}
\def\pr@protect@ship{\pr@protect{\@firstoftwo\pr@startbox}%
   \@gobbletwo}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@insert}
% \begin{macro}{\pr@mark}
% \begin{macro}{\pr@marks}
%   We don't want insertions to end up on our lists.  So we disable
%   them right now by replacing them with the following:
%    \begin{macrocode}
\def\pr@insert{\begingroup\afterassignment\pr@insertii\count@}
\def\pr@insertii{\endgroup\setbox\pr@box\vbox}
%    \end{macrocode}
% Similar things hold for marks.
%    \begin{macrocode}
\def\pr@mark{{\afterassignment}\toks@}
\def\pr@marks{{\aftergroup\pr@mark\afterassignment}\count@}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@box}
% \begin{macro}{\pr@startbox}
%   Previews will be stored in \cmd{\box}\cmd{\pr@box}.
%   \cmd{\pr@startbox} gets two arguments: code to execute immediately
%   before the following stuff, code to execute afterwards.  You have
%   to cater for \cmd{\pr@endbox} being called at the right time
%   yourself.  We will use a \cmd{\vsplit} on the box later in order
%   to remove any leading glues, penalties and similar stuff.  For
%   this reason we start off the box with an optimal break point.
%    \begin{macrocode}
\newbox\pr@box
\long\def\pr@startbox#1#2{%
  \ifpr@outer
    \toks@{#2}%
    \edef\pr@cleanup{\the\toks@}%
    \setbox\pr@box\vbox\bgroup
    \break
    \pr@outerfalse\@arrayparboxrestore
    \let\insert\pr@insert
    \let\mark\pr@mark
    \let\marks\pr@marks
    \expandafter\expandafter\expandafter
    \pr@ship@start
    \expandafter\@firstofone
  \else
     \expandafter \@gobble
  \fi{#1}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@endbox}
%   Cleaning up also is straightforward.  If we have to watch the
%   bounding \TeX\ box, we want to remove spurious skips.  We also
%   want to unwrap a possible single line paragraph, so that the box
%   is not full line length.  We use \cmd{\vsplit} to clean up leading
%   glue and stuff, and we make some attempt of removing trailing
%   ones.  After that, we wrap up the box including possible material
%   from \cmd{\AtBeginDvi}.  If the |psfixbb| option is active, we
%   adorn the upper left and lower right corners with copies of
%   \cmd{\pr@markerbox}.  The first few lines cater for \LaTeX\ hiding
%   things like like the code for \cmd{\paragraph} in \cmd{\everypar}.
%    \begin{macrocode}
\def\pr@endbox{%
   \let\reserved@a\relax
   \ifvmode \edef\reserved@a{\the\everypar}%
      \ifx\reserved@a\@empty\else
            \dimen@\prevdepth
            \noindent\par
            \setbox\z@\lastbox\unskip\unpenalty
            \prevdepth\dimen@
            \setbox\z@\hbox\bgroup\penalty-\maxdimen\unhbox\z@
              \ifnum\lastpenalty=-\maxdimen\egroup
              \else\egroup\box\z@ \fi\fi\fi
   \ifhmode \par\unskip\setbox\z@\lastbox
     \nointerlineskip\hbox{\unhbox\z@\/}%
   \else \unskip\unpenalty\unskip \fi
   \egroup
   \setbox\pr@box\vbox{%
       \baselineskip\z@skip \lineskip\z@skip \lineskiplimit\z@
       \@begindvi
       \nointerlineskip
       \splittopskip\z@skip\setbox\z@\vsplit\pr@box to\z@
       \unvbox\z@
       \nointerlineskip
       %\color@setgroup
       \box\pr@box
       %\color@endgroup
     }%
%    \end{macrocode}
% \begin{macro}{\pr@ship@end}
%   \label{sec:prshipend}At this point, \cmd{\pr@ship@end} gets
%   called.  You must not under any circumstances change |\box\pr@box|
%   in any way that would add typeset material at the front of it,
%   except for PostScript header specials, since the front of
%   |\box\pr@box| may contain stuff from \cmd{\AtBeginDvi}.
%   \cmd{\pr@ship@end} contains two types of code additions: stuff
%   that adds to |\box\pr@box|, like the |labels| option does, and
%   stuff that measures out things or otherwise takes a look at the
%   finished |\box\pr@box|, like the |auctex| or |showbox| option do.
%   The former should use \cmd{pr@addto@front} for adding to this
%   hook, the latter use \cmd{g@addto@macro} for adding at the end of
%   this hook.
%
%   Note that we shift the output box up by its height via
%   \cmd{\voffset}.  This has three reasons: first we make sure that
%   no package-inflicted non-zero value of \cmd{\voffset} or
%   \cmd{\hoffset} will have any influence on the positioning of our
%   box.  Second we shift the box such that its basepoint will exactly
%   be at the (1in,1in)~mark defined by \TeX.  That way we can
%   properly take ascenders into account.  And the third reason is
%   that \TeX\ treats a \cmd{\hbox} and a \cmd{\vbox} differently with
%   regard to the treating of its depth.  Shifting \cmd{\voffset} and
%   \cmd{\hoffset} can be inhibited by setting |\pr@offset@override|.
%    \begin{macrocode}
   \pr@ship@end
   {\let\protect\noexpand
   \ifx\pr@offset@override\@undefined
     \voffset=-\ht\pr@box
     \hoffset=\z@
   \fi
   \c@page=\pr@snippet
   \pr@shipout
   \ifpr@fixbb\hbox{%
     \dimen@\wd\pr@box
     \@tempdima\ht\pr@box
     \@tempdimb\dp\pr@box
     \box\pr@box
     \llap{\raise\@tempdima\copy\pr@markerbox\kern\dimen@}%
     \lower\@tempdimb\copy\pr@markerbox}%
   \else \box\pr@box \fi}%
   \global\advance\pr@snippet\@ne
   \pr@cleanup
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% Oh, and we kill off the usual meaning of \cmd{\shipout} in case
% somebody makes a special output routine.  The following test is
% pretty much the same as in |everyshi.sty|.  One of its implications
% is that if someone does a \cmd{\shipout} of a \emph{void} box,
% things will go horribly wrong.
% \begin{macro}{\pr@@shipout}
%    \begin{macrocode}
\def\pr@@shipout{\deadcycles\z@\bgroup\setbox\z@\box\voidb@x
  \afterassignment\pr@shipoutegroup\setbox\z@}
\def\pr@shipoutegroup{\ifvoid\z@ \expandafter\aftergroup\fi \egroup}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@shipout}
%   We now need to check which command we are replacing.  Before
%   things got sophisticated in 2020 or 2021, this had been
%   \cmd{\shipout} but now it could be \cmd{\tex\_shipout:D}.  \LaTeX\
%   got a hook mechanism for managing output routines, but it doesn't
%   really work well for wholesale replacement of the \cmd{\shipout}
%   command like |preview| does.
%    \begin{macrocode}
\ifx\shipout\@undefined
  \begingroup
  \catcode`\:=10
  \catcode`\_=10
  \ifx\tex_shipout:D\@undefined
    \PackageError{preview}{Cannot find \protect\shipout\space primitive}%
    {preview needs to replace the \protect\shipout\space primitive with
      its own routine to do its work.  Due to packages or formats
      interfering, it cannot be identified.  Please report this.}
  \else
    \global\let\pr@shipout=\tex_shipout:D
    \global\let\tex_shipout:D=\pr@@shipout
  \fi
  \endgroup
\else
  \let\pr@shipout=\shipout
  \let\shipout=\pr@@shipout
\fi
%    \end{macrocode}
% \end{macro}
% \subsection{Parsing commands}
% \begin{macro}{\pr@parseit}
% \begin{macro}{\pr@endparse}
% \begin{macro}{\pr@callafter}
%   The following stuff is for parsing the arguments of commands we
%   want to somehow surround with stuff.  Usage is
%   \begin{quote}
%     \cmd{\pr@callafter}\meta{aftertoken}\meta{parsestring}\cmd{\pr@endparse}\\
%     \qquad\meta{macro}\meta{parameters}
%   \end{quote}
%   \meta{aftertoken} is stored away and gets executed once parsing
%   completes, with its first argument being the parsed material.
%   \meta{parsestring} would be, for example for the
%   \cmd{\includegraphics} macro, |*[[!|, an optional |*| argument
%   followed by two optional arguments enclosed in |[]|, followed by
%   one mandatory argument.
%
%   For the sake of a somewhat more intuitive syntax, we now support
%   also the syntax |{*[]{}}| in the optional argument.  Since \TeX\
%   strips redundant braces, we have to write |[{{}}]| in this syntax
%   for a single mandatory argument.  Hard to avoid.  We use an
%   unusual character for ending the parsing.  The implementation is
%   rather trivial.
%    \begin{macrocode}
\def\pr@parseit#1{\csname pr@parse#1\endcsname}
\let\pr@endparse=\@percentchar
\def\next#1{%
\def\pr@callafter{%
  \afterassignment\pr@parseit
  \let#1= }}
\expandafter\next\csname pr@parse\pr@endparse\endcsname
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@parse*}
%   Straightforward, same mechanism \LaTeX\ itself employs.  We take
%   some care not to pass potential |#| tokens unprotected through
%   macros.
%    \begin{macrocode}
\long\expandafter\def\csname pr@parse*\endcsname#1\pr@endparse#2{%
  \begingroup\toks@{#1\pr@endparse{#2}}%
  \edef\next##1{\endgroup##1\the\toks@}%
  \@ifstar{\next{\pr@parse@*}}{\next\pr@parseit}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@parse[}
% \begin{macro}{\pr@brace}
%   Copies optional parameters in brackets if present.  The additional
%   level of braces is necessary to ensure that braces the user might
%   have put to hide a~|]| bracket in an optional argument don't get
%   lost.  There will be no harm if such braces were not there at the
%   start.
%    \begin{macrocode}
\long\expandafter\def\csname pr@parse[\endcsname#1\pr@endparse#2{%
  \begingroup\toks@{#1\pr@endparse{#2}}%
  \edef\next##1{\endgroup##1\the\toks@}%
  \@ifnextchar[{\next\pr@bracket}{\next\pr@parseit}}
\long\def\pr@bracket#1\pr@endparse#2[#3]{%
   \pr@parseit#1\pr@endparse{#2[{#3}]}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@parse]}
%   This is basically a do-nothing, so that we may use the syntax
%   |{*[][]!}| in the optional argument instead of the more concise
%   but ugly |*[[!| which confuses the brace matchers of editors.
%    \begin{macrocode}
\expandafter\let\csname pr@parse]\endcsname=\pr@parseit
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@parse}
% \begin{macro}{\pr@parse!}
%   Mandatory arguments are perhaps easiest to parse.
%    \begin{macrocode}
\long\def\pr@parse#1\pr@endparse#2#3{%
  \pr@parseit#1\pr@endparse{#2{#3}}}
\expandafter\let\csname pr@parse!\endcsname=\pr@parse
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@parse?}
% \begin{macro}{\pr@parsecond}
%   This does an explicit call of |\@ifnextchar| and forks into the
%   given two alternatives as a result.
%    \begin{macrocode}
\long\expandafter\def\csname pr@parse?\endcsname#1#2\pr@endparse#3{%
  \begingroup\toks@{#2\pr@endparse{#3}}%
  \@ifnextchar#1{\pr@parsecond\@firstoftwo}%
                {\pr@parsecond\@secondoftwo}}
\def\pr@parsecond#1{\expandafter\endgroup
  \expandafter\expandafter\expandafter\pr@parseit
  \expandafter#1\the\toks@}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@parse@}
%   This makes it possible to insert literal material into the
%   argument list.
%    \begin{macrocode}
 \long\def\pr@parse@#1#2\pr@endparse#3{%
   \pr@parseit #2\pr@endparse{#3#1}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@parse-}
%   This will just drop the next token.
%    \begin{macrocode}
\long\expandafter\def\csname pr@parse-\endcsname
  #1\pr@endparse#2{\begingroup
  \toks@{\endgroup\pr@parseit #1\pr@endparse{#2}}%
  {\aftergroup\the\aftergroup\toks@ \afterassignment}%
  \let\next= }
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@parse:}
%   The following is a transform rule.  A macro is being defined with
%   the given argument list and replacement, and the transformed
%   version replaces the original.  The result of the transform is
%   still subject to being parsed.
%    \begin{macrocode}
\long\expandafter\def\csname pr@parse:\endcsname
  #1#2#3\pr@endparse#4{\begingroup
    \toks@{\endgroup \pr@parseit#3\pr@endparse{#4}}%
    \long\def\next#1{#2}%
    \the\expandafter\toks@\next}
%    \end{macrocode}
% \end{macro}
% \edef\next{\noexpand\begin{macro}{\noexpand
%    \pr@parse\string#}}
% \next
%   Another transform rule, but this passes the transformed material
%   into the token list.
%    \begin{macrocode}
\long\expandafter\def\csname pr@parse#\endcsname
  #1#2#3\pr@endparse#4{\begingroup
    \toks@{#4}%
    \long\edef\next##1{\toks@{\the\toks@##1}}%
    \toks@{\endgroup \pr@parseit#3\pr@endparse}%
    \long\def\reserved@a#1{{#2}}%
    \the\expandafter\next\reserved@a}
%</active>
%    \end{macrocode}
% \end{macro}
%
% \subsection{Selection options}
% The |displaymath| option.  The |equation| environments in AMS\LaTeX\
% already do too much before our hook gets to interfere, so we hook
% earlier.  Some juggling is involved to ensure we get the original
% |\everydisplay| tokens only once and where appropriate.
%
% The incredible hack with |\dt@ptrue| is necessary for working around
% bug `amslatex/3425'.
%    \begin{macrocode}
%<*!active>
\begingroup
\catcode`\*=11
\@firstofone{\endgroup
\DeclareOption{displaymath}{%
  \preview@delay{\toks@{%
      \pr@startbox{\noindent$$%
        \aftergroup\pr@endbox\@gobbletwo}{$$}\@firstofone}%
    \everydisplay\expandafter{\the\expandafter\toks@
      \expandafter{\the\everydisplay}}}%
  \pr@advise@ship\equation{\begingroup\aftergroup\pr@endbox
    \def\dt@ptrue{\m@ne=\m@ne}\noindent}%
    {\endgroup}%
  \pr@advise@ship\equation*{\begingroup\aftergroup\pr@endbox
    \def\dt@ptrue{\m@ne=\m@ne}\noindent}%
    {\endgroup}%
  \PreviewOpen[][\def\dt@ptrue{\m@ne=\m@ne}\noindent#1]\[%
  \PreviewClose\]%
  \PreviewEnvironment[][\noindent#1]{eqnarray}%
  \PreviewEnvironment[][\noindent#1]{eqnarray*}%
  \PreviewEnvironment{displaymath}%
}}
%    \end{macrocode}
%
% The |textmath| option.  Some folderol in order to define the active
% |$|
% math mode delimiter.  \cmd\pr@textmathcheck is used for checking
% whether we have a single |$| or double |$$|.
% In the latter case, we enter display math (this sort of display math
% is not allowed inside of \LaTeX\ because of inconsistent spacing,
% but surprisingly many people use it nevertheless).  Strictly
% speaking, this is incorrect, since not every
% |$$| actually means display math.  For example, |\hbox{$$}| will
% because of restricted horizontal mode rather yield an empty text
% math formula.  Since our implementation moved the sequence inside of
% a |\vbox|, the interpretation will change.  People should just not
% enter rubbish like that.
%    \begin{macrocode}
\begingroup
\def\next#1#2{%
  \endgroup
  \DeclareOption{textmath}{%
    \PreviewEnvironment{math}%
    \preview@delay{\ifx#1\@undefined \let#1=$%$
      \fi\catcode`\$=\active
      \ifx\xyreuncatcodes\@undefined\else
        \edef\next{\catcode`@=\the\catcode`@\relax}%
        \makeatother\expandafter\xyreuncatcodes\next\fi}%
    \pr@advise@ship\(\pr@endaftergroup{}% \)
    \pr@advise@ship#1{\@firstoftwo{\let#1=#2%
        \futurelet\reserved@a\pr@textmathcheck}}{}}%
  \def\pr@textmathcheck{\expandafter\pr@endaftergroup
    \ifx\reserved@a#1{#2#2}\expandafter\@gobbletwo\fi#2}}
\lccode`\~=`\$
\lowercase{\expandafter\next\expandafter~}%
  \csname pr@\string$%$
  \endcsname
%</!active>
%    \end{macrocode}
% \begin{macro}{\pr@endaftergroup}
%   This justs ends the box after the group opened by |#1| is closed
%   again.
%    \begin{macrocode}
%<*active>
\def\pr@endaftergroup#1{#1\aftergroup\pr@endbox}
%</active>
%    \end{macrocode}
% \end{macro}
%
% The |graphics| option.
%    \begin{macrocode}
%<*!active>
\DeclareOption{graphics}{%
  \PreviewMacro[*[[!]{\includegraphics}%]]
}
%    \end{macrocode}
% The |floats| option.  The complications here are merely to spare us
% bug reports about broken document classes that use |\let| on
% |\endfigure| and similar.  Notable culprits that have not been
% changed in years in spite of reports are |elsart.cls| and
% |IEEEtran.cls|.  Complain when you are concerned.
%    \begin{macrocode}
\def\pr@floatfix#1#2{\ifx#1#2%
  \ifx#1\@undefined\else
  \PackageWarningNoLine{preview}{%
Your document class has a bad definition^^J
of \string#1, most likely^^J
\string\let\string#1=\string#2^^J
which has now been changed to^^J
\string\def\string#1{\string#2}^^J
because otherwise subsequent changes to \string#2^^J
(like done by several packages changing float behaviour)^^J
can't take effect on \string#1.^^J
Please complain to your document class author}%
  \def#1{#2}\fi\fi}
\begingroup
\def\next#1#2{\endgroup
  \DeclareOption{floats}{%
    \pr@floatfix\endfigure\end@float
    \pr@floatfix\endtable\end@float
    \pr@floatfix#1\end@dblfloat
    \pr@floatfix#2\end@dblfloat
    \PreviewSnarfEnvironment[![]{@float}%]
    \PreviewSnarfEnvironment[![]{@dblfloat}%]
  }}
\expandafter\next\csname endfigure*\expandafter\endcsname
  \csname endtable*\endcsname
%    \end{macrocode}
%  The |sections| option.  Two optional parameters might occur in
%  |memoir.cls|.
%    \begin{macrocode}
\DeclareOption{sections}{%
  \PreviewMacro[!!!!!!*[[!]{\@startsection}%]]
  \PreviewMacro[*[[!]{\chapter}%]]
}
%    \end{macrocode}
% We now interpret any further options as driver files we load.  Note
% that these driver files are loaded even when |preview| is not
% active.  The reason is that they might define commands (like
% \cmd{\PreviewCommand}) that should be available even in case of an
% inactive package.  Large parts of the |preview| package will not
% have been loaded in this case: you have to cater for that.
%    \begin{macrocode}
\DeclareOption*
   {\InputIfFileExists{pr\CurrentOption.def}{}{\OptionNotUsed}}
%    \end{macrocode}
%
% \subsection{Preview attaching commands}
% \begin{macro}{\PreviewMacro}
%   As explained above. Detect possible |*| and call appropriate
%   macro.
%    \begin{macrocode}
\def\PreviewMacro{\@ifstar\pr@starmacro\pr@macro}
%    \end{macrocode}
% The version without |*| is now rather straightforward.
% \begin{macro}{\pr@macro}
% \begin{macro}{\pr@domacro}
% \begin{macro}{\pr@macroii}
% \begin{macro}{\pr@endmacro}
%    \begin{macrocode}
\long\def\pr@domacro#1#2{%
   \long\def\next##1{#2}%
   \pr@callafter\next#1]\pr@endparse}
\newcommand\pr@macro[1][]{%
   \toks@{\pr@domacro{#1}}%
   \long\edef\next[##1]##2{%
    \noexpand\pr@advise@ship{##2}{\the\toks@{##1\noexpand\pr@endbox}}{}}%
   \@ifnextchar[\next\pr@macroii}
\def\pr@macroii{\next[##1]}
\long\def\pr@endmacro#1{#1\pr@endbox}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{PreviewMacro*}
% \begin{macro}{\pr@protect@domacro}
% \begin{macro}{\pr@starmacro}
%   The version with |*| has to parse the arguments, then throw them
%   away.  Some internal macros first, then the interface call.
%    \begin{macrocode}
\long\def\pr@protect@domacro#1#2{\pr@protect{%
    \long\def\next##1{#2}%
    \pr@callafter\next#1]\pr@endparse}}
\newcommand\pr@starmacro[1][]{\toks@{\pr@protect@domacro{#1}}%
    \long\edef\next[##1]##2{%
      \noexpand\pr@advise##2{\the\toks@{##1}}}%
    \@ifnextchar[\next{\next[]}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\PreviewOpen}
%   As explained above. Detect possible |*| and call appropriate macro.
%    \begin{macrocode}
\def\PreviewOpen{\@ifstar\pr@starmacro\pr@open}
%    \end{macrocode}
% The version without |*| is now rather straightforward.
% \begin{macro}{\pr@open}
%    \begin{macrocode}
\newcommand\pr@open[1][]{%
   \toks@{\pr@domacro{#1}}%
   \long\edef\next[##1]##2{%
     \noexpand\pr@advise##2{\begingroup
     \noexpand\pr@protect@ship
        {\the\toks@{\begingroup\aftergroup\noexpand\pr@endbox##1}}%
        {\endgroup}}}%
   \@ifnextchar[\next\pr@macroii}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\PreviewClose}
%   As explained above. Detect possible |*| and call appropriate
%   macro.
%    \begin{macrocode}
\def\PreviewClose{\@ifstar\pr@starmacro\pr@close}
%    \end{macrocode}
% The version without |*| is now rather straightforward.
% \begin{macro}{\pr@close}
%    \begin{macrocode}
\newcommand\pr@close[1][]{%
  \toks@{\pr@domacro{#1}}%
  \long\edef\next[##1]##2{%
   \noexpand\pr@advise{##2}{\the\toks@{##1\endgroup}}}%
   \@ifnextchar[\next\pr@macroii}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\PreviewEnvironment}
%   Actually, this ignores any syntax argument.  But don't tell
%   anybody.  Except for the |*|~variant, it respects (actually
%   ignores) any argument!  Of course, we'll need to deactivate
%   |\end{|\meta{environment}|}| as well.
%    \begin{macrocode}
\def\PreviewEnvironment{\@ifstar\pr@starenv\pr@env}
\newcommand\pr@starenv[1][]{\toks@{\pr@starmacro[{#1}]}%
  \long\edef\next##1##2{%
    \the\toks@[{##2}]##1}%
  \begingroup\pr@starenvii}
\newcommand\pr@starenvii[2][]{\endgroup
  \expandafter\next\csname#2\endcsname{#1}%
  \expandafter\pr@starmacro\csname end#2\endcsname}
\newcommand\pr@env[1][]{%
   \toks@{\pr@domacro{#1}}%
   \long\edef\next[##1]##2{%
   \noexpand\expandafter\noexpand\pr@advise@ship
     \noexpand\csname##2\noexpand\endcsname{\the\toks@
      {\begingroup\aftergroup\noexpand\pr@endbox##1}}{\endgroup}}%
   \@ifnextchar[\next\pr@macroii %]
 }
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\PreviewSnarfEnvironment}
%   This is a nuisance since we have to advise \emph{both} the
%   environment and its end.
%    \begin{macrocode}
\newcommand{\PreviewSnarfEnvironment}[2][]{%
  \expandafter\pr@advise
   \csname #2\endcsname{\pr@snarfafter{#1}}%
 \expandafter\pr@advise
   \csname end#2\endcsname{\pr@endsnarf}}
%</!active>
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@snarfafter}
% \begin{macro}{\pr@startsnarf}
% \begin{macro}{\pr@endsnarf}
%   Ok, this looks complicated, but we have to start a group in order
%   to be able to hook \cmd{\pr@endbox} into the game only when
%   \cmd{\ifpr@outer} has triggered the start.  And we need to get our
%   start messages out before parsing the arguments.
%    \begin{macrocode}
%<*active>
\let\pr@endsnarf\relax
\long\def\pr@snarfafter#1{\ifpr@outer
     \pr@ship@start
     \let\pr@ship@start\relax
     \let\pr@endsnarf\endgroup
   \else
     \let\pr@endsnarf\relax
   \fi
  \pr@protect{\pr@callafter\pr@startsnarf#1]\pr@endparse}}
\def\pr@startsnarf#1{#1\begingroup
   \pr@startbox{\begingroup\aftergroup\pr@endbox}{\endgroup}%
   \ignorespaces}
%</active>
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\pr@ship@start}
% \begin{macro}{\pr@ship@end}
%   The hooks \cmd{\pr@ship@start} and \cmd{\pr@ship@end} can be added
%   to by option files by the help of the \cmd{\g@addto@macro} command
%   from \LaTeX, and by the \cmd{\pr@addto@front} command from
%   |preview.sty| itself.  They are called just before starting to
%   process some preview, and just after it.  Here is the policy for
%   adding to them: \cmd{\pr@ship@start} is called inside of the vbox
%   |\pr@box| before typeset material gets produced.  It is, however,
%   preceded by a break command that is intended for usage in
%   \cmd{\vsplit}, so that any following glue might disappear.  In
%   case you want to add any material on the list, you have to precede
%   it with \cmd{\unpenalty} and have to follow it with \cmd{\break}.
%   You have make sure that under no circumstances any other legal
%   breakpoints appear before that, and your material should
%   contribute no nonzero dimensions to the page.  For the policies of
%   the \cmd{\pr@ship@end} hook, see the description on
%   page~\pageref{sec:prshipend}.
%    \begin{macrocode}
%<*!active>
\let\pr@ship@start\@empty
\let\pr@ship@end\@empty
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{environment}{preview}
% \begin{environment}{nopreview}
%   First we write the definitions of these environments when
%   |preview| is inactive.  We will redefine them if |preview| gets
%   activated.
%    \begin{macrocode}
\newenvironment{preview}{\ignorespaces}{\ifhmode\unskip\fi}
\newenvironment{nopreview}{\ignorespaces}{\ifhmode\unskip\fi}
%    \end{macrocode}
% \end{environment}
% \end{environment}
%
% We now process the options and finish in case we are not active.
%    \begin{macrocode}
\ProcessOptions\relax
\ifPreview\else\expandafter\endinput\fi
%</!active>
%    \end{macrocode}
% Now for the redefinition of the |preview| and |endpreview|
% environments:
%    \begin{macrocode}
%<*active>
\renewenvironment{preview}{\begingroup
   \pr@startbox{\begingroup\aftergroup\pr@endbox}%
               {\endgroup}%
   \ignorespaces}%
   {\ifhmode\unskip\fi\endgroup}
\renewenvironment{nopreview}{\pr@outerfalse\ignorespaces}%
  {\ifhmode\unskip\fi}
%    \end{macrocode}
% We use the normal output routine, but hijack it a bit for our
% purposes to preserve \cmd{\AtBeginDvi} hooks and not get previews
% while in output: that could become rather ugly.
%
% The main work of disabling normal output relies on a \cmd{\shipout}
% redefinition.
% \begin{macro}{\pr@output}
%    \begin{macrocode}
\newtoks\pr@output
\pr@output\output
\output{%
  \pr@outerfalse
  \let\@begindvi\@empty
  \the\pr@output}
\let\output\pr@output
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@typeinfos}
%   Then we have some document info that style files might want to
%   output.
%    \begin{macrocode}
\def\pr@typeinfos{\typeout{Preview: Fontsize \f@size pt}%
  \ifnum\mag=\@m\else\typeout{Preview: Magnification \number\mag}\fi
  \ifx\pdfoutput\@undefined
    \ifx\XeTeXversion\@undefined \else
      % FIXME: The message should not be emitted if XeTeX does not produce
      % PDF.  There does not seem to be a primitive for that, though.
      \typeout{Preview: PDFoutput 1}%
    \fi
  \else
    \ifx\pdfoutput\relax \else
      \ifnum\pdfoutput>\z@
        \typeout{Preview: PDFoutput 1}%
      \fi
    \fi
  \fi
}
\AtBeginDocument{\pr@typeinfos}
%    \end{macrocode}
% \end{macro}
% And at the end we load the default configuration file, so that it
% may override settings from this package:
%    \begin{macrocode}
\pr@loadcfg{prdefault}
%</active>
%</style>
%    \end{macrocode}
%
% \section{The option files}
% \subsection{The \texttt{auctex} option}
% The AUC\TeX\ option will cause error messages to spew.  We want them
% on the terminal, but we don't want \LaTeX\ to stop its automated
% run.  We delay \cmd{\nonstopmode} in case the user has any
% pseudo-interactive folderol like reading in of file names in his
% preamble.  Because we are so good-hearted, we will not break this as
% long as the document has not started, but after that we need the
% error message mechanism operative.
%
% The |\nofiles| command here tries to avoid clobbering input files
% used for references and similar.  It will come too late if you call
% the package with \cmd{\AtBeginDocument}, so you'll need to issue
% |\nofiles| yourself in that case.  Previously, this was done
% unconditionally in the main style file, but since we don't know what
% the package may be used for, this was inappropriate.
%
% So here is the contents of the |prauctex.def| file:
%    \begin{macrocode}
%<auctex>\ifPreview\else\expandafter\endinput\fi
%<auctex>\nofiles
%<auctex>\preview@delay{\nonstopmode}
%    \end{macrocode}
% Ok, here comes creative error message formatting.  It turns out a
% sizable portion of the runtime is spent in I/O.  Making the error
% messages short is an advantage.  It is not possible to convince
% \TeX\ to make shorter error messages than this: \TeX\ always wants
% to include context.  This is about the shortest \ae sthetic one we
% can muster.
%    \begin{macrocode}
%<auctex>\begingroup
%<auctex>\lccode`\~=`\-
%<auctex>\lccode`\{=`\<
%<auctex>\lccode`\}=`\>
%<auctex>\lowercase{\endgroup
%<auctex>  \def\pr@msgi{{~}}}
%<auctex>\def\pr@msgii{Preview:
%<auctex>   Snippet \number\pr@snippet\space}
%<auctex>\begingroup
%<auctex>\catcode`\-=13
%<auctex>\catcode`\<=13
%<auctex>\@firstofone{\endgroup
%<auctex>\def\pr@msg#1{{%
%<auctex>   \let<\pr@msgi
%<auctex>   \def-{\pr@msgii#1}%
%<auctex>   \errhelp{Not a real error.}%
%<auctex>   \errmessage<}}}
%<auctex>\g@addto@macro\pr@ship@start{\pr@msg{started}}
%<auctex>\g@addto@macro\pr@ship@end{\pr@msg{ended.%
%<auctex>  (\number\ht\pr@box+\number\dp\pr@box x\number\wd\pr@box)}}
%    \end{macrocode}
% This looks pretty baffling, but it produces something short and
% semi-graphical, namely |<-><->|.  That is a macro |<| that expands
% into |<->|, where |<| and |>| are the braces around an
% \cmd{\errmessage} argument and |-| is a macro expanding to the full
% text of the error message.  Cough cough.  You did not really want to
% know, did you?
%
% Since over/underfull boxes are about the messiest things to parse,
% we disable them by setting the appropriate badness limits and making
% the variables point to junk.  We also disable other stuff.  While we
% set \cmd{\showboxbreadth} and \cmd{\showboxdepth} to indicate as
% little diagnostic output as possible, we keep them operative, so
% that the user retains the option of debugging using this stuff.  The
% other variables concerning the generation of warnings and
% daignostics, however, are more often set by commonly employed
% packages and macros such as \cmd{\sloppy}.  So we kill them off for
% good.
%    \begin{macrocode}
%<auctex>\hbadness=\maxdimen
%<auctex>\newcount\hbadness
%<auctex>\vbadness=\maxdimen
%<auctex>\let\vbadness=\hbadness
%<auctex>\hfuzz=\maxdimen
%<auctex>\newdimen\hfuzz
%<auctex>\vfuzz=\maxdimen
%<auctex>\let\vfuzz=\hfuzz
%<auctex>\showboxdepth=-1
%<auctex>\showboxbreadth=-1
%    \end{macrocode}
% Ok, now we load a possible configuration file.
%    \begin{macrocode}
%<auctex>\pr@loadcfg{prauctex}
%    \end{macrocode}
% And here we cater for several frequently used commands in
% |prauctex.cfg|:
%    \begin{macrocode}
%<auccfg>\PreviewMacro*[[][#1{}]\footnote
%<auccfg>\PreviewMacro*[?[{@{[]}}{}][#1]\item
%<auccfg>\PreviewMacro*\emph
%<auccfg>\PreviewMacro*\textrm
%<auccfg>\PreviewMacro*\textbf
%<auccfg>\PreviewMacro*\textit
%<auccfg>\PreviewMacro*\textsc
%<auccfg>\PreviewMacro*\textsf
%<auccfg>\PreviewMacro*\textsl
%<auccfg>\PreviewMacro*\texttt
%<auccfg>\PreviewMacro*\textulc
%<auccfg>\PreviewMacro*\textmd
%<auccfg>\PreviewMacro*\textnormal
%<auccfg>\PreviewMacro*\textup
%<auccfg>\PreviewMacro*\textsw
%<auccfg>\PreviewMacro*\textcolor
%<auccfg>\PreviewMacro*\mbox
%<auccfg>\PreviewMacro*[][#1{}]\author
%<auccfg>\PreviewMacro*[][#1{}]\title
%<auccfg>\PreviewMacro*\and
%<auccfg>\PreviewMacro*\thanks
%<auccfg>\PreviewMacro*[][#1{}]\caption
%<auccfg>\preview@delay{\@ifundefined{pr@\string\@startsection}{%
%<auccfg>  \PreviewMacro*[!!!!!!*][#1{}]\@startsection}{}}
%<auccfg>\preview@delay{\@ifundefined{pr@\string\chapter}{%
%<auccfg>  \PreviewMacro*[*][#1{}]\chapter}{}}
%<auccfg>\PreviewMacro*\index
%    \end{macrocode}
%
% \subsection{The \texttt{lyx} option}
% The following is the option providing LyX with info for its preview
% implementation.
%    \begin{macrocode}
%<lyx>\ifPreview\else\expandafter\endinput\fi
%<lyx>\pr@loadcfg{prlyx}
%<lyx>\g@addto@macro\pr@ship@end{\typeout{Preview:
%<lyx>  Snippet \number\pr@snippet\space
%<lyx>  \number\ht\pr@box\space \number\dp\pr@box \space\number\wd\pr@box}}
%    \end{macrocode}
%
% \subsection{The \texttt{counters} option}
% This outputs a checkpoint.  We do this by saving all counter
% registers in backup macros starting with |\pr@c@| in their name.  A
% checkpoint first writes out all changed counters (previously
% unchecked counters are not written out unless different from zero),
% then saves all involved counter values.  \LaTeX\ tracks its counters
% in the global variable \cmd{\cl@ckpt}.
%    \begin{macrocode}
%<counters>\ifPreview\else\expandafter\endinput\fi
%<counters>\def\pr@eltprint#1{\expandafter\@gobble\ifnum\value{#1}=0%
%<counters>  \csname pr@c@#1\endcsname\else\relax
%<counters>  \space{#1}{\arabic{#1}}\fi}
%<counters>\def\pr@eltdef#1{\expandafter\xdef
%<counters>  \csname pr@c@#1\endcsname{\arabic{#1}}}
%<counters>\def\pr@ckpt#1{{\let\@elt\pr@eltprint\edef\next{\cl@@ckpt}%
%<counters>  \ifx\next\@empty\else\typeout{Preview: Counters\next#1}%
%<counters>  \let\@elt\pr@eltdef\cl@@ckpt\fi}}
%<counters>\pr@addto@front\pr@ship@start{\pr@ckpt:}
%<counters>\pr@addto@front\pr@ship@end{\pr@ckpt.}
%    \end{macrocode}
%
% \subsection{Debugging options}
% Those are for debugging the operation of |preview|, and thus are
% mostly of interest for people that want to use |preview| for their
% own purposes.  Since debugging output is potentially confusing to
% the error message parsing from AUC\TeX, you should not turn on
% |\tracingonline| or switch from |\nonstopmode| unless you are
% certain your package will never be used with \previewlatex.
%
% \paragraph{The \texttt{showbox} option} will generate diagnostic
% output for every produced box.  It does not delay the resetting of
% the |\showboxbreadth| and |\showboxdepth| parameters so that you can
% still change them after the loading of the package.  It does,
% however, move them to the end of the package loading, so that they
% will not be affected by the |auctex| option.
%    \begin{macrocode}
%<showbox>\ifPreview\else\expandafter\endinput\fi
%<showbox>\AtEndOfPackage{%
%<showbox>  \showboxbreadth\maxdimen
%<showbox>  \showboxdepth\maxdimen}
%<showbox>\g@addto@macro\pr@ship@end{\showbox\pr@box}
%    \end{macrocode}
%
% \paragraph{The \texttt{tracingall} option} is for the really heavy
% diagnostic stuff.  For the reasons mentioned above, we do not want
% to change the setting of the interaction mode, nor of the
% |tracingonline| flag.  If the user wants them different, he should
% set them outside of the preview boxes.
%    \begin{macrocode}
%<tracingall>\ifPreview\else\expandafter\endinput\fi
%<tracingall>\pr@addto@front\pr@ship@start{\let\tracingonline\count@
%<tracingall>  \let\errorstopmode\@empty\tracingall}
%    \end{macrocode}
%
% \subsection{Supporting conversions}
% It is not uncommon to want to use the results of |preview| as
% images.  One possibility is to generate a flurry of EPS files with
% \begin{quote}
%   |dvips -E -i -Ppdf -o| \meta{outputfile}|.000| \meta{inputfile}
% \end{quote}
% However, in case those are to be processed further into graphic
% image files by Ghostscript, this process is inefficient.  One cannot
% use Ghostscript in a single run for generating the files, however,
% since one needs to set the page size (or full size pages will be
% produced).  The |tightpage| option will set the page dimensions at
% the start of each PostScript page so that the output will be sized
% appropriately.  That way, a single pass of Dvips followed by a
% single pass of Ghostscript will be sufficient for generating all
% images.
%
% You will have to specify the output driver to be used, either
% |dvips| or |pdftex|.
%
% \begin{macro}{\PreviewBorder}
% \begin{macro}{\PreviewBbAdjust}
%   We start this off with the user tunable parameters which get
%   defined even in the case of an inactive package, so that
%   redefinitions and assignments to them will always work:
%    \begin{macrocode}
%<tightpage>\ifx\PreviewBorder\@undefined
%<tightpage>  \newdimen\PreviewBorder
%<tightpage>  \PreviewBorder=0.50001bp
%<tightpage>\fi
%<tightpage>\ifx\PreviewBbAdjust\@undefined
%<tightpage>  \def\PreviewBbAdjust{-\PreviewBorder -\PreviewBorder
%<tightpage>    \PreviewBorder \PreviewBorder}
%<tightpage>\fi
%    \end{macrocode}
% \end{macro}
% \end{macro}
% Here is stuff used for parsing this:
%    \begin{macrocode}
%<tightpage>\ifPreview\else\expandafter\endinput\fi
%<tightpage>\def\pr@nextbb{\edef\next{\next\space\number\dimen@}%
%<tightpage>  \expandafter\xdef\csname pr@bb@%
%<tightpage>    \romannumeral\count@\endcsname{\the\dimen@}%
%<tightpage>  \advance\count@\@ne\ifnum\count@<5
%<tightpage>  \afterassignment\pr@nextbb\dimen@=\fi}
%    \end{macrocode}
% And here is the stuff that we fudge into our hook.  Of course, we
% have to do it in a box, and we start this box off with our special.
% There is one small consideration here: it might come before any
% |\AtBeginDvi| stuff containing header specials.  It turns out Dvips
% rearranges this amicably: header code specials get transferred to
% the appropriate header section, anyhow, so this ensures that we come
% right after the bop section.  We insert the 7~numbers here: the
% 4~bounding box adjustments, and the 3~\TeX\ box dimensions.  In case
% the box adjustments have changed since the last time, we write them
% out to the console.
%    \begin{macrocode}
%<tightpage>\ifnum\pr@graphicstype=\z@
%<tightpage>  \ifcase
%<tightpage>    \ifx\XeTeXversion\@undefined
%<tightpage>      \ifx\pdfoutput\@undefined \@ne\fi
%<tightpage>      \ifx\pdfoutput\relax \@ne\fi
%<tightpage>      \ifnum\pdfoutput>\z@ \tw@\fi \@ne
%<tightpage>    \else \thr@@\fi
%<tightpage>  \or \ExecuteOptions{dvips}\relax
%<tightpage>  \or \ExecuteOptions{pdftex}\relax
%<tightpage>  \or \ExecuteOptions{xetex}\relax\fi\fi
%<tightpage>\global\let\pr@bbadjust\@empty
%<tightpage>\pr@addto@front\pr@ship@end{\begingroup
%<tightpage>  \let\next\@gobble
%<tightpage>  \count@\@ne\afterassignment\pr@nextbb
%<tightpage>  \dimen@\PreviewBbAdjust
%<tightpage>  \ifx\pr@bbadjust\next
%<tightpage>  \else \global\let\pr@bbadjust\next
%<tightpage>  \typeout{Preview: Tightpage \pr@bbadjust}%
%<tightpage>  \fi\endgroup}
%<tightpage>\ifcase\pr@graphicstype
%<tightpage>\or
%<tightpage>  \g@addto@macro\pr@ship@end{\setbox\pr@box\hbox{%
%<tightpage>    \special{ps::\pr@bbadjust\space
%<tightpage>      \number\ifdim\ht\pr@box>\z@ \ht\pr@box
%<tightpage>             \else \z@
%<tightpage>             \fi \space
%<tightpage>      \number\ifdim\dp\pr@box>\z@ \dp\pr@box
%<tightpage>             \else \z@
%<tightpage>             \fi \space
%<tightpage>      \number\ifdim\wd\pr@box>\z@ \wd\pr@box
%<tightpage>             \else \z@
%<tightpage>             \fi}\box\pr@box}}
%<tightpage>\or
%<tightpage>  \g@addto@macro\pr@ship@end{{\dimen@\ht\pr@box
%<tightpage>    \ifdim\dimen@<\z@ \dimen@\z@\fi
%<tightpage>    \advance\dimen@\pr@bb@iv
%<tightpage>    \dimen@ii=\dimen@
%<tightpage>    \global\pdfvorigin\dimen@
%<tightpage>    \dimen@\dp\pr@box
%<tightpage>    \ifdim\dimen@<\z@ \dimen@\z@\fi
%<tightpage>    \advance\dimen@-\pr@bb@ii
%<tightpage>    \advance\dimen@\dimen@ii
%<tightpage>    \global\pdfpageheight\dimen@
%<tightpage>    \dimen@\wd\pr@box
%<tightpage>    \ifdim\dimen@<\z@ \dimen@=\z@\fi
%<tightpage>    \advance\dimen@-\pr@bb@i
%<tightpage>    \advance\dimen@\pr@bb@iii
%<tightpage>    \global\pdfpagewidth\dimen@
%<tightpage>    \global\pdfhorigin-\pr@bb@i}}
%<tightpage>\or
%<tightpage>  \g@addto@macro\pr@ship@end{\dimen@\ht\pr@box
%<tightpage>    \ifdim\dimen@<\z@ \dimen@\z@\fi
%<tightpage>    \advance\dimen@\pr@bb@iv
%<tightpage>    \dimen@ii=\dimen@
%<tightpage>    \voffset=-1in
%<tightpage>    \advance\voffset\dimen@
%<tightpage>    \advance\voffset-\ht\pr@box
%<tightpage>    \dimen@\dp\pr@box
%<tightpage>    \ifdim\dimen@<\z@ \dimen@\z@\fi
%<tightpage>    \advance\dimen@-\pr@bb@ii
%<tightpage>    \advance\dimen@\dimen@ii
%<tightpage>    \global\pdfpageheight\dimen@
%<tightpage>    \global\paperheight\dimen@
%<tightpage>    \dimen@\wd\pr@box
%<tightpage>    \ifdim\dimen@<\z@ \dimen@=\z@\fi
%<tightpage>    \advance\dimen@-\pr@bb@i
%<tightpage>    \advance\dimen@\pr@bb@iii
%<tightpage>    \global\pdfpagewidth\dimen@
%<tightpage>    \hoffset=-1in
%<tightpage>    \advance\hoffset-\pr@bb@i
%<tightpage>    \let\pr@offset@override\@empty}
%<tightpage>\fi
%    \end{macrocode}
% Ok, here comes the beef.  First we fish the 7~numbers from the file
% with |token| and convert them from \TeX~|sp| to PostScript points.
%    \begin{macrocode}
%<tightpage>\ifnum\pr@graphicstype=\@ne
%<tightpage>\preview@delay{\AtBeginDvi{%
%    \end{macrocode}
% Backwards-compatibility. Once we are certain that dvipng-1.6 or
% later is widely used, the three following specials can be exchanged
% for the simple |\special{!/preview@tightpage true def}|
%    \begin{macrocode}
%<tightpage>  \special{!/preview@tightpage true def (%
%<tightpage>     compatibility PostScript comment for dvipng<=1.5 }
%<tightpage>  \special{!userdict begin/bop-hook{%
%<tightpage>     7{currentfile token not{stop}if 
%<tightpage>       65781.76 div DVImag mul}repeat
%<tightpage>       72 add 72 2 copy gt{exch}if 4 2 roll
%<tightpage>       neg 2 copy lt{exch}if dup 0 gt{pop 0 exch}%
%<tightpage>       {exch dup 0 lt{pop 0}if}ifelse 720 add exch 720 add
%<tightpage>       3 1 roll
%<tightpage>       4{5 -1 roll add 4 1 roll}repeat 
%<tightpage>     <</PageSize[5 -1 roll 6 index sub 5 -1 roll 5 index sub]%
%<tightpage>       /PageOffset[7 -2 roll [1 1 dtransform exch]%
%<tightpage>       {0 ge{neg}if exch}forall]>>setpagedevice%
%<tightpage>       //bop-hook exec}bind def end}
%<tightpage>  \special{!userdict (some extra code to avoid 
%<tightpage>     dvipng>=1.6 unknown special:
%<tightpage>       7{currentfile token not{stop}if 65781.76 div })) pop}
%    \end{macrocode}
% The ``userdict'' at the start of the last special is also there to
% avoid an unknown special in dvipng$<=1.6$. This is the end of the
% backwards-compatibility code.
%    \begin{macrocode}
%<tightpage>  \special{!userdict begin/bop-hook{%
%<tightpage>  preview-bop-level 0 le{%
%<tightpage>     7{currentfile token not{stop}if
%<tightpage>       65781.76 div DVImag mul}repeat
%    \end{macrocode}
% Next we produce the horizontal part of the bounding box as
% \[ (1\mathrm{in},1\mathrm{in}) +
% \bigl(\min(|\wd\pr@box|,0),\max(|\wd\pr@box|,0)\bigr) \]
% and roll it to the bottom of the stack:
%    \begin{macrocode}
%<tightpage>     72 add 72 2 copy gt{exch}if 4 2 roll
%    \end{macrocode}
% Next is the vertical part of the bounding box.  Depth counts in
% negatively, and we again take $\min$ and $\max$ of possible extents
% in the vertical direction, limited by 0.  720 corresponds to
% $10\,\mathrm{in}$ and is the famous $1\,\mathrm{in}$ distance away
% from the edge of letterpaper.
%    \begin{macrocode}
%<tightpage>     neg 2 copy lt{exch}if dup 0 gt{pop 0 exch}%
%<tightpage>     {exch dup 0 lt{pop 0}if}ifelse 720 add exch 720 add
%<tightpage>     3 1 roll
%    \end{macrocode}
% Ok, we now have the bounding box on the stack in the proper order
% llx, lly, urx, ury.  We add the adjustments:
%    \begin{macrocode}
%<tightpage>    4{5 -1 roll add 4 1 roll}repeat
%    \end{macrocode}
% The page size is calculated as the appropriate differences, the page
% offset consists of the coordinates of the lower left corner, with
% those coordinates negated that would be reckoned positive in the
% device coordinate system.
%    \begin{macrocode}
%<tightpage>     <</PageSize[5 -1 roll 6 index sub 5 -1 roll 5 index sub]%
%<tightpage>       /PageOffset[7 -2 roll [1 1 dtransform exch]%
%<tightpage>       {0 ge{neg}if exch}forall]>>setpagedevice}if%
%    \end{macrocode}
% So we now bind the old definition of |bop-hook| into our new
% definition and finish it.
%    \begin{macrocode}
%<tightpage>     //bop-hook exec}bind def end}}}
%<tightpage>\fi
%    \end{macrocode}
%
% \subsection{The \texttt{showlabels} option}
% During the editing process, some people like to see the label names
% in their equations, figures and the like.  Now if you are using
% Emacs for editing, and in particular \previewlatex, I'd strongly
% recommend that you check out the Ref\TeX\ package which pretty much
% obliterates the need for this kind of functionality.  If you still
% want it, standard \LaTeX\ provides it with the |showkeys| package,
% and there is also the less encompassing |showlabels| package.
% Unfortunately, since those go to some pain not to change the page
% layout and spacing, they also don't change |preview|'s idea of the
% \TeX\ dimensions of the involved boxes.
%
% So those packages are mostly useless.  So we present here an
% alternative hack that will get the labels through.
% \begin{macro}{\pr@labelbox}
%   This works by collecting them into a separate box which we then
%   tack to the right of the previews.
%    \begin{macrocode}
%<showlabels>\ifPreview\else\expandafter\endinput\fi
%<showlabels>\newbox\pr@labelbox
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@label}
%   We follow up with our own definition of the \cmd{\label} macro
%   which will be active only in previews.  The original definition is
%   stored in |\pr@@label|.  |\pr@lastlabel| contains the last typeset
%   label in order to avoid duplication in certain environments, and
%   we keep the stuff in |\pr@labelbox|.
%    \begin{macrocode}
%<showlabels>\def\pr@label#1{\pr@@label{#1}%
%    \end{macrocode}
%   Ok, now we generate the box, by placing the label below any existing
%   stuff.
%    \begin{macrocode}
%<showlabels>   \ifpr@setbox\z@{#1}%
%<showlabels>     \global\setbox\pr@labelbox\vbox{\unvbox\pr@labelbox
%<showlabels>      \box\z@}\egroup\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\ifpr@setbox}
%   |\ifpr@setbox| receives two arguments, |#1| is the box into which
%   to set a label, |#2| is the label text itself.  If a label needs
%   to be set (if it is not a duplicate in the current box, and is
%   nonempty, and we are in the course of typesetting and so on), we
%   are left in a true conditional and an open group with the preset
%   box.  If nothing should be set, no group is opened, and we get
%   into skipping to the closing of the conditional.  Since
%   |\ifpr@setbox| is a macro, you should not place the call to it
%   into conditional text, since it will not pair up with |\fi| until
%   being expanded.
%
%   We have some trickery involved here.  |\romannumeral\z@| expands
%   to empty, and will also remove everything between the two of them
%   that also expands to empty, like a chain of |\fi|.
%    \begin{macrocode}
%<showlabels>\def\ifpr@setbox#1#2{%
%<showlabels>  \romannumeral%
%<showlabels>  \ifx\protect\@typeset@protect\ifpr@outer\else
%    \end{macrocode}
%   Ignore empty labels\dots
%    \begin{macrocode}
%<showlabels>   \z@\bgroup
%<showlabels>   \protected@edef\next{#2}\@onelevel@sanitize\next
%<showlabels>   \ifx\next\@empty\egroup\romannumeral\else
%    \end{macrocode}
%   and labels equal to the last one.
%    \begin{macrocode}
%<showlabels>   \ifx\next\pr@lastlabel\egroup\romannumeral\else
%<showlabels>   \global\let\pr@lastlabel\next
%<showlabels>   \setbox#1\pr@boxlabel\pr@lastlabel
%<showlabels>   \expandafter\expandafter\romannumeral\fi\fi\fi\fi
%<showlabels>   \z@\iffalse\iftrue\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@boxlabel}
%   Now the actual typesetting of a label box is done.  We use a small
%   typewriter font inside of a framed box (the default frame/box
%   separating distance is a bit large).
%    \begin{macrocode}
%<showlabels>\def\pr@boxlabel#1{\hbox{\normalfont
%<showlabels>   \footnotesize\ttfamily\fboxsep0.4ex\relax\fbox{#1}}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@maketag}
%   And here is a version for |amsmath| equations.  They look better
%   when the label is right beside the tag, so we place it there, but
%   augment |\box\pr@labelbox| with an appropriate placeholder.
%    \begin{macrocode}
%<showlabels>\def\pr@maketag#1{\pr@@maketag{#1}%
%<showlabels>  \ifpr@setbox\z@{\df@label}%
%<showlabels>      \global\setbox\pr@labelbox\vbox{%
%<showlabels>         \hrule\@width\wd\z@\@height\z@
%<showlabels>         \unvbox\pr@labelbox}%
%    \end{macrocode}
%   Set the width of the box to empty so that the label placement gets
%   not disturbed, then append it.
%    \begin{macrocode}
%<showlabels>        \wd\z@\z@\box\z@ \egroup\fi}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\pr@lastlabel}
%   Ok, here is how we activate this: we clear out box and label info
%    \begin{macrocode}
%<showlabels>\g@addto@macro\pr@ship@start{%
%<showlabels>  \global\setbox\pr@labelbox\box\voidb@x
%<showlabels>  \xdef\pr@lastlabel{}%
%    \end{macrocode}
%   The definitions above are global because we might be in any amount
%   of nesting.  We then reassign the appropriate labelling macros:
%    \begin{macrocode}
%<showlabels>  \global\let\pr@@label\label \let\label\pr@label
%<showlabels>  \global\let\pr@@maketag\maketag@@@
%<showlabels>  \let\maketag@@@\pr@maketag
%<showlabels>}
%    \end{macrocode}
% \end{macro}
% Now all we have to do is to add the stuff to the box in question.
% The stuff at the front works around a bug in |ntheorem.sty|.
%    \begin{macrocode}
%<showlabels>\pr@addto@front\pr@ship@end{%
%<showlabels>   \ifx \label\pr@label \global\let\label\pr@@label \fi
%<showlabels>   \ifx \maketag@@@\pr@maketag
%<showlabels>        \global\let\maketag@@@\pr@@maketag \fi
%<showlabels>   \ifvoid\pr@labelbox
%<showlabels>   \else \setbox\pr@box\hbox{%
%<showlabels>         \box\pr@box\,\box\pr@labelbox}%
%<showlabels>   \fi}
%    \end{macrocode}
% \subsection{The \texttt{footnotes} option}
% This is rather simplistic right now.  It overrides the default
% footnote action (which is to disable footnotes altogether for better
% visibility).
%    \begin{macrocode}
%<footnotes>\PreviewMacro[[!]\footnote %]
%    \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
%<installer> \generate{
%<installer>    \file{preview.drv}{\from{preview.dtx}{driver}}
%<installer&!make>    \usedir{tex/latex/preview}
%<installer>    \file{preview.sty}{\from{preview.dtx}{style}
%<installer>                       \from{preview.dtx}{style,active}}
%<installer>    \file{prauctex.def}{\from{preview.dtx}{auctex}}
%<installer>    \file{prauctex.cfg}{\from{preview.dtx}{auccfg}}
%<installer>    \file{prshowbox.def}{\from{preview.dtx}{showbox}}
%<installer>    \file{prshowlabels.def}{\from{preview.dtx}{showlabels}}
%<installer>    \file{prtracingall.def}{\from{preview.dtx}{tracingall}}
%<installer>    \file{prtightpage.def}{\from{preview.dtx}{tightpage}}
%<installer>    \file{prlyx.def}{\from{preview.dtx}{lyx}}
%<installer>    \file{prcounters.def}{\from{preview.dtx}{counters}}
%<installer>    \file{prfootnotes.def}{\from{preview.dtx}{footnotes}}
%<installer> }
%<installer> \endbatchfile
%    \end{macrocode}
% And here comes the documentation driver.
%    \begin{macrocode}
%<driver> \documentclass{ltxdoc}
%<driver> \usepackage{preview}
%<driver> \let\ifPreview\relax
%<driver> \newcommand\previewlatex{\texttt{preview-latex}}
%<driver> \begin{document}
%<driver> \DocInput{preview.dtx}
%<driver> \end{document}
%    \end{macrocode}
% \Finale{}
% \iffalse
% Local Variables: 
% mode: docTeX
% TeX-master: "preview.drv"
% End: 
% \fi
