% \iffalse meta-comment
% pbox.dtx - DocStrip source code for the pbox package
% Copyright (C) 2003  Simon Law
% 
%   This program is free software; you can redistribute it and/or modify
%   it under the terms of the GNU General Public License as published by
%   the Free Software Foundation; either version 2 of the License, or
%   (at your option) any later version.
% 
%   This program is distributed in the hope that it will be useful,
%   but WITHOUT ANY WARRANTY; without even the implied warranty of
%   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%   GNU General Public License for more details.
% 
%   You should have received a copy of the GNU General Public License
%   along with this program; if not, write to the Free Software
%   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
%
% \fi
% \iffalse
%<style>\NeedsTeXFormat{LaTeX2e}
%<style>\ProvidesPackage{pbox}[2003/04/06 v1.0 Dynamic parboxes]
%<*driver>
\NeedsTeXFormat{LaTeX2e}[1995/12/01]
\documentclass{ltxdoc}
\usepackage{pbox}
\usepackage{url}
\usepackage{textcomp}
\usepackage{fancyvrb}
\newlength{\ExampleWidth}
\setlength{\ExampleWidth}{3.5cm}
\fvset{gobble=6,numbersep=3pt,frame=single,
       numbers=left,xleftmargin=5mm,xrightmargin=0pt}
\fvset{xrightmargin=\ExampleWidth}
\EnableCrossrefs
 %\DisableCrossrefs     % Say \DisableCrossrefs if index is ready
\CodelineIndex
\RecordChanges          % Gather update information
 %\OnlyDescription      % comment out for implementation details
 \OldMakeindex           % use if your MakeIndex is pre-v2.9
 %\setlength\hfuzz{15pt}  % don't make so many
 %\hbadness=7000          % over and under full box warnings
\begin{document}
  \DocInput{pbox.dtx}
\end{document}
%</driver>
% \fi
%
% \StopEventually{\PrintIndex \PrintChanges}
% \CheckSum{77}
%
% \DoNotIndex{\begin}
% \DoNotIndex{\columnwidth}
% \DoNotIndex{\DeclareRobustCommand,\def}
% \DoNotIndex{\end,\equal}
% \DoNotIndex{\ifthenelse}
% \DoNotIndex{\lengthtest}
% \DoNotIndex{\makebox}
% \DoNotIndex{\newcommand,\newlength}
% \DoNotIndex{\parbox}
% \DoNotIndex{\relax,\RequirePackage}
% \DoNotIndex{\setlength,\settowidth}
% \setcounter{IndexColumns}{2}
%
% \CharacterTable
%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
%   Digits        \0\1\2\3\4\5\6\7\8\9
%   Exclamation   \!     Double quote  \"     Hash (number) \#
%   Dollar        \$     Percent       \%     Ampersand     \&
%   Acute accent  \'     Left paren    \(     Right paren   \)
%   Asterisk      \*     Plus          \+     Comma         \,
%   Minus         \-     Point         \.     Solidus       \/
%   Colon         \:     Semicolon     \;     Less than     \<
%   Equals        \=     Greater than  \>     Question mark \?
%   Commercial at \@     Left bracket  \[     Backslash     \\
%   Right bracket \]     Circumflex    \^     Underscore    \_
%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%   Right brace   \}     Tilde         \~}
%
% \changes{v1.0}{2003/03/19}{Initial release.}
%
% \GetFileInfo{pbox.sty}
%
% \title{The \textsf{pbox} package\thanks{Version \fileversion, 
%                                         last revised \filedate}}
% \author{Simon Law \\ \url{sfllaw@engmail.uwaterloo.ca}}
% \maketitle
%^^A \tableofcontents
%
% \section{Introduction}
%
% Most skilled \LaTeX{} users are familiar with the various box 
% commands.  These commands include |\makebox|, |\framebox|, |\savebox|,
% and |\parbox|.  These boxes takes a parameter that specifies the 
% width of box to create.  To simplify matters, there are the |\mbox|, 
% |\fbox|, and |\sbox| commands that fit the box created to the size of
% its contents.  Conspicuously absent, however, is a |\pbox| command.
%
% \section{A variable-width \texttt{\textbackslash parbox}}
%
% At first glance, it seems quite inappropriate to create a |\pbox|
% command.  After all, the size of a multi-line box will most likely be
% limited by the |\textwidth| or |\columnwidth| of the text it encloses.
% When a line of text is too long, it will be wrapped by \TeX{}'s own 
% line-breaking algorithms.  However, there are certain circumstances 
% where one would want a variable-width |\parbox|.
%
% For example, you may want to align the top and bottom lines of 
% multi-line boxes.  The simplest way to do this is with |parbox| 
% commands with an arbitrary width.
% \makeatletter
% \begingroup\center
% \begin{minipage}[c]{\ExampleWidth-5mm}
%     \parbox[b]{2cm}{Hello\\World!}^^A
%     \parbox[t]{2cm}{Bonjour\\monde!}
% \end{minipage}
% \begin{minipage}{\textwidth-\ExampleWidth}
%   \fvset{xrightmargin=0pt}
%   \begin{Verbatim}
%     \parbox[b]{2cm}{Hello\\World!}%
%     \parbox[t]{2cm}{Bonjour\\monde!}
%   \end{Verbatim}
% \end{minipage}
% \endcenter\endgroup
% \makeatother
%
% \begin{DescribeMacro}{\pbox}
% However, this is not convenient.  It may take several attempts to 
% guess the correct width; and if there was ever a need to change the 
% contents of the boxes, then the hard-coded widths must be changed as 
% well.  It would ideal to have a box that would collapse to the 
% minimal required width.
% \makeatletter
% \begingroup\center
% \begin{minipage}[c]{\ExampleWidth-5mm}
%     \pbox[b]{0.5\textwidth}{Hello\\World!}^^A
%     \pbox[t]{0.5\textwidth}{Bonjour\\monde!}
% \end{minipage}
% \begin{minipage}{\textwidth-\ExampleWidth}
%   \fvset{xrightmargin=0pt}
%   \begin{Verbatim}
%     \pbox[b]{0.5\textwidth}{Hello\\World!}%
%     \pbox[t]{0.5\textwidth}{Bonjour\\monde!}
%   \end{Verbatim}
% \end{minipage}
% \endcenter\endgroup
% \makeatother
% \end{DescribeMacro}
% Notice how the exclaimation mark and the capital B have no extra 
% space between each other, implying that |\pbox| creates minimal-width
% boxes.
%
% \section{Determining minimum widths}
%
% This is all well and good, but how does one measure the width of one
% of these boxes?  Well, a rather painful way would be to use
% |\settowidth| in conjunction with a |\parbox|.  But it is far easier
% to do it with the new width commands.
%
% \begin{DescribeMacro}{\settominwidth}
% The |\settominwidth| command works very similarly to the standard 
% |\settowidth| command.  
% \begin{description}
% \item
% |\settowidth[|\textit{max\_width}|]{|\textit{cmd}|}{|\textit{text}|}|
% sets the value of the a length command \textit{cmd} equal to the width 
% of the multi-line \textit{text}.  The optional argument
% \textit{max\_width} allows you to specify the maximum width that will
% be returned; it defaults to |\columnwidth|.
% \end{description}
% \end{DescribeMacro}
%
% \begin{DescribeMacro}{\widthofpbox}
% To provide completeness for the \textsf{calc} package, the
% |\widthofpbox| command was implemented to complement the |\widthof| 
% command.
% \begin{description}
% \item
% |\widthofpbox{|\textit{text}|}| returns the width of the multi-line 
% \textit{text}.  
% \end{description}
% Here is an example:
% \makeatletter
% \begingroup\center
% \begin{minipage}[c]{\ExampleWidth-5mm}
%     I\\
%     need\\
%     support\\
%     \rule{\widthofpbox{I\\need\\support}}{0.4pt}
% \end{minipage}
% \begin{minipage}{\textwidth-\ExampleWidth}
%   \fvset{xrightmargin=0pt}
%   \begin{Verbatim}
%     I\\
%     need\\
%     support\\
%     \rule{\widthofpbox{I\\need\\support}}{0.4pt}
%   \end{Verbatim}
% \end{minipage}
% \endcenter\endgroup
% \makeatother
% \end{DescribeMacro}
%
% \section{Limitations}
%
% Unfortunately, there are some limitations in this package.  One of the
% intrinsic limitations is that you cannot do anything in a |\pbox| that
% you could not do in a |\parbox|.  This seems quite reasonable, so
% it should not be a hardship.
%
% Since |\pbox| is implemented using the \textbf{tabular} environment,
% there are some things that cannot, and should not be used.  You should 
% note that errant |&| characters within a |\pbox| do not generate 
% meaningful error messages.  As well, it is unfortunate that
% |\linebreak| and |\newline| do not work as expected.
%
% Since it is a box, you cannot use the \textbf{verbatim} environment
% within.  I recommend that you use the \textsf{fancyvrb} package which
% contains the \textbf{BVerbatim} and \textbf{LVerbatim} environments
% for typesetting boxed verbatim text.
%
% Alas, I have also discovered that certain uses of |\widthof| and
% |\widthofpbox| do not work within the \textsf{docstrip} environment.
%
% \section{Implementation}
% \iffalse
%<*style>
% \fi
%
% I use the standard \textsf{calc} package for general math.  As well, 
% I wish % to support a |\widthofpbox| command, so I will demand that the
% |\widthof| command exists as well.
%    \begin{macrocode}
\RequirePackage{calc}
%    \end{macrocode}
%
% In order to perform |\lengthtest|s and |\equal|ity tests, I need to
% include the standard \textsf{ifthen} package.  This also provides me
% with simple conditionals.
%    \begin{macrocode}
\RequirePackage{ifthen}
%    \end{macrocode}
%
% \begin{macro}{\settominwidth}
% The minimum length is determined by the clever use of the
% \textbf{tabular} environment.  It knows how to calculate the minimum
% requisite width for a column, and the way determines the end of a
% column is with its end of row command |\\| .
% This command is conveniently similar to the command typically used to
% break lines.
%
% As you can see, |#1| defaults to the width of a column.  This will
% either be |\textwidth| or the width defined by the \textbf{twocolumn}
% option, or even the \textsf{multicol} package.
%    \begin{macrocode}
\newcommand{\settominwidth}[3][\columnwidth]{%
%    \end{macrocode}
% Here, I set the length command |#2|.  Notice the argument to the
% \textbf{tabular} environment.  I use |@{}| to eliminate any horizontal
% padding, and use the |l| alignment to grab the width of the text in
% |#3|.
%    \begin{macrocode}
  \settowidth{#2}{\begin{tabular}{@{}l@{}}#3\end{tabular}}%
%    \end{macrocode}
% Finally, I wish to make sure that the length I have set in |#2| is
% not larger than the maximum stored in |#1|.
%    \begin{macrocode}
  \ifthenelse{\lengthtest{#1<#2}}{\setlength{#2}{#1}}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\widthofpbox}
% In order to find the width of a |\pbox|, I use the same
% \textbf{tabular} trick from |\settominwidth|.  I use the |\widthof|
% command in order to preserve its semantics instead of trying to
% emulate them using my |\settominwidth| command.
%
% I do \emph{not} check against a maximum length here.  Restricting this
% command to a maximum length would mean that I throw away length
% information if the text is too long.
%    \begin{macrocode}
\newcommand{\widthofpbox}[1]{%
  \widthof{\begin{tabular}{@{}l@{}}#1\end{tabular}}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\pbox}
% \begin{macro}{\pb@xi}
% \begin{macro}{\pb@xii}
% It is not possible to implement |\pbox| in a simple way.  The command
% definition commands in \LaTeX{} don't afford you more than one
% optional parameter; however, |\parbox| has three.
%
% In order to faithfully simulate the three optional arguments, I must
% trick \LaTeX{} in to catching three optional
% arguments~\cite{fto:optargs}.  Therefore |\pbox|,
% |\pb@xi|, and |\pb@xii| are used to capture the optional arguments in
% the |\pb@xargi|, |\pb@xargii|, and |\pb@xargiii| commands.  These are
% then passsed to |\pb@xiii| for actual processing.
%    \begin{macrocode}
\DeclareRobustCommand*{\pbox}[1][]{%
  \def\pb@xargi{#1}%
  \pb@xi}
\DeclareRobustCommand*{\pb@xi}[1][]{%
  \def\pb@xargii{#1}%
  \pb@xii}
\DeclareRobustCommand*{\pb@xii}[1][]{%
  \def\pb@xargiii{#1}%
  \pb@xiii}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\pb@xiii}
% In order to create the final paragraph box, I parse out the two
% manditory arguments.  I then use the provided maximal length |#1| to
% determine the actual width of the |\parbox|.
%    \begin{macrocode}
\newlength{\pb@xlen}
\DeclareRobustCommand{\pb@xiii}[2]{%
  \settominwidth[#1]{\pb@xlen}{#2}%
%    \end{macrocode}
%
% Since the default optional arguments are all empty, I should be able
% to just pass them to |\parbox|.  However, |\parbox| interprets empty
% optional values differently than just non-existant optional values.
% So, I must make complicated decisions; if an optional argument is
% empty, then I will just skip it..
%    \begin{macrocode}
  \ifthenelse{\equal{\pb@xargi}{}}
    {\parbox{\pb@xlen}{#2}}
    {\ifthenelse{\equal{\pb@xargii}{}}
      {\ifthenelse{\equal{\pb@xargiii}{}}
        {\parbox[\pb@xargi]{\pb@xlen}{#2}}
        {\parbox[\pb@xargi][][\pb@xargiii]{\pb@xlen}{#2}}}
      {\ifthenelse{\equal{\pb@xargiii}{}}
        {\parbox[\pb@xargi][\pb@xargii]{\pb@xlen}{#2}}
        {\parbox[\pb@xargi][\pb@xargii][\pb@xargiii]{\pb@xlen}{#2}}}}%
%    \end{macrocode}
%
% Finally, I must clean up the optional arguments and remove their
% special meaning.  As well, I will terminate the |\parbox| I have
% created with an empty |\makebox| in order to prevent the
% |\def\pb@x...\relax| commands from interfering with other commands
% that expect |\pbox| to solely consist of a box.
%    \begin{macrocode}
  \def\pb@xargi\relax
  \def\pb@xargii\relax
  \def\pb@xargiii\relax
  \makebox[0pt]{}}
%    \end{macrocode}
% \end{macro}
% \iffalse
%</style>
% \fi
% \begin{thebibliography}{99}
% \bibitem{fto:optargs} Robin Fairbanks.
% ``A command with two optional arguments.''
% \emph{\TeX{} Frequently Asked Questions.}
% \url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=twooptarg}
% (current 6 April 2003.)
% \end{thebibliography}
% \Finale
\endinput