preview.dtx.svn-base

moses开源的机器翻译系统

   \@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 contains 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.
%    \begin{macrocode}
   \pr@ship@end
   {\let\protect\noexpand
   \voffset=-\ht\pr@box
   \hoffset=\z@
   \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 is rather
% ugly, but should do the trick most of the time since \cmd{\shipout}
% is most often called in a local group by \cmd{\output}.
% \begin{macro}{\shipout}
%    \begin{macrocode}
\let\pr@shipout=\shipout
\def\shipout{\deadcycles\z@\setbox\z@\box\voidb@x\setbox\z@}
%    \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}%