% \iffalse meta-comment
%
% Copyright (C) 2004 by Scott Pakin <scott+dash@pakin.org>
% -------------------------------------------------------
%
% This file may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in:
%
%    http://www.latex-project.org/lppl.txt
%
% and version 1.3c or later is part of all distributions of LaTeX
% version 2006/05/20 or later.
%
% \fi
%
% \iffalse
%<*driver>
\ProvidesFile{dashrule.dtx}
%</driver>
%<package>\NeedsTeXFormat{LaTeX2e}[1999/12/01]
%<package>\ProvidesPackage{dashrule}
%<*package>
    [2008/04/27 v1.1 Dashed rules]
%</package>
%
%<*driver>
\documentclass{ltxdoc}
\usepackage{dashrule}[2008/04/27]
\usepackage{titlesec}
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
  \DocInput{dashrule.dtx}
  \PrintChanges
  \PrintIndex
\end{document}
%</driver>
% \fi
%
% \CheckSum{62}
%
% \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}{2001/04/23}{Initial version}
%
% \GetFileInfo{dashrule.dtx}
%
% \DoNotIndex{\addtocounter,\csname,\DeclareRobustCommand,\def,\else,\empty}
% \DoNotIndex{\endcsname,\expandafter,\fi,\hbox,\hskip,\hspace,\ifodd,\ifx}
% \DoNotIndex{\let,\mbox,\newcounter,\relax,\setcounter}
%
% ^^A  Precede every section title with a dashed rule.
% \titleformat{\section}
%   {\unskip\vskip 2.3ex plus 0.2ex
%    \vbox{\noindent\hdashrule[0pt][x]{\fill}{1pt}{5pt}\rule{5pt}{1pt}}
%    \vskip 2.3ex plus 0.2ex}
%   {\normalfont\Large\bfseries\thesection}
%   {1em}
%   {\normalfont\Large\bfseries}
%
%
% \title{The \textsf{dashrule} package\thanks{This document
%   corresponds to \textsf{dashrule}~\fileversion, dated \filedate.}}
% \author{Scott Pakin \\ \texttt{scott+dash@pakin.org}}
%
% \maketitle
%
% \begin{abstract}
%   The \textsf{dashrule} package makes it easy to draw a huge variety
%   of dashed rules (i.e., lines) in \LaTeX.  \textsf{dashrule} provides
%   a command, |\hdashrule|, which is a cross between \LaTeX's |\rule|
%   and PostScript's |setdash| command.  |\hdashrule| draws horizontally
%   dashed rules using the same syntax as |\rule| but with an
%   additional, |setdash|-like parameter that specifies the pattern of
%   dash segments and the space between those segments.  Because
%   \textsf{dashrule}'s rules are constructed internally using |\rule|
%   (as opposed to, e.g., PostScript |\special|s) they are fully
%   compatible with every \LaTeX{} back-end processor.
% \end{abstract}
%
%
% \section{Usage}
%
% \DescribeMacro{\hdashrule}
% \LaTeX's |\rule| command draws a rectangular blob of ink with a given
% width, height, and distance above the baseline.  The
% \textsf{dashrule} package introduces an analogous command,
% |\hdashrule|, which draws the same blob of ink, but horizontally
% dashed.  |\hdashrule| takes five parameters, two of which are
% optional:
%
% \bigskip
% \noindent\hspace{-\leftmargini}%
% \fbox{\texttt{\string\hdashrule}
%       \oarg{raise} \oarg{leader} \marg{width} \marg{height} \marg{dash}}
% \bigskip
%
% The \meta{raise}, \meta{width}, and \meta{height} parameters have the
% same meaning as in \LaTeX's |\rule| macro: the distance to raise the
% rule above the baseline and the width and height of the rule.
%
% Because |\hdashrule| is implemented in terms of \TeX's primitive
% leader commands (|\leaders|, |\cleaders|, and |\xleaders|), the dash
% pattern must be repeated an integral number of times.  \meta{leader}
% specifies what to do with the extra whitespace (always less than the
% width of the dash pattern) that this requirement introduces.  The
% default, which corresponds to \TeX's |\leaders| command, adds space to
% both ends of the rule so the dash patterns from multiple |\hdashrule|s
% line up.  If \meta{leader} is~|c|, which corresponds to \TeX's
% |\cleaders| command, an equal amount of whitespace is added to both
% ends of the rule.  If \meta{leader} is~|x|, which corresponds to
% \TeX's |\xleaders| command, the whitespace is divided up, and the same
% amount of whitespace separates each repetition of the dash pattern.
%
% The \meta{dash} argument specifies the dash pattern and is analogous
% to the \textit{array} argument to PostScript's |setdash| function.
% That is, it is a list of space-separated \meta{dimen}s that alternate
% ``on'' and ``off'' distances.  For instance, ``|2pt 1pt|'' means a
% 2\,pt.\ rule, followed by a 1\,pt.\ gap, followed by a 2\,pt.\ rule,
% followed by a 1\,pt.\ gap, and so forth.  An odd number of
% \meta{dimen}s is no different; ``|2pt|'' alternates 2\,pt.\ rules and
% 2\,pt.\ gaps, and ``|1pt 2pt 3pt|'' repeats ``1\,pt.\ rule, 2\,pt.\
% gap, 3\,pt.\ rule, 1\,pt.\ gap, 2\,pt.\ rule, 3\,pt.\ gap.''
%
%
% \section{Examples}
%
% The following are some typical ways to use |\hdashrule|.  Each example
% changes from the previous in only one parameter.  For clarity,
% underlines are used to indicate modified text, and the rule is
% bracketed by an upper- and lowercase~``X''.
%
% \begin{center}
% \renewcommand{\arraystretch}{1.5}
% \newcommand{\chg}[1]{\underbar{\texttt{#1}}}
% \begin{tabular}{l@{\qquad}l}
%   |\hdashrule{2cm}{1pt}{1pt}| &
%   X\hdashrule{2cm}{1pt}{1pt}x \\
%
%   |\hdashrule{|\chg{4cm}|}{1pt}{1pt}| &
%   X\hdashrule{4cm}{1pt}{1pt}x \\
%
%   |\hdashrule|\chg{[0.5ex]}|{4cm}{1pt}{1pt}| &
%   X\hdashrule[0.5ex]{4cm}{1pt}{1pt}x \\
%
%   |\hdashrule[0.5ex]{4cm}{1pt}{|\chg{3mm}|}| &
%   X\hdashrule[0.5ex]{4cm}{1pt}{3mm}x \\
%
%   |\hdashrule[0.5ex]{4cm}{|\chg{1mm}|}{3mm}| &
%   X\hdashrule[0.5ex]{4cm}{1mm}{3mm}x \\
%
%   |\hdashrule[0.5ex]{4cm}{1mm}{3mm |\chg{3pt}|}| &
%   X\hdashrule[0.5ex]{4cm}{1mm}{3mm 3pt}x \\
%
%   |\hdashrule[0.5ex]{4cm}{1mm}{%| \\[-1.5ex]
%   |  3mm 3pt |\chg{1mm 2pt}|}| &
%   X\hdashrule[0.5ex]{4cm}{1mm}{3mm 3pt 1mm 2pt}x \\
% \end{tabular}
% \end{center}
%
% \bigskip
% \noindent
% These next examples show the effect of using different leader types.
% Each leader is used with both a 4\,cm~wide rule and a 3\,cm~wide rule.
%
% \begin{center}
% \renewcommand{\arraystretch}{1.25}
% \begin{tabular}{l@{\qquad}l}
%   |\hdashrule[0.5ex]{4cm}{1mm}{8mm 2pt}| &
%   X\hdashrule[0.5ex]{4cm}{1mm}{8mm 2pt}x \\
%
%   |\hdashrule[0.5ex]{3cm}{1mm}{8mm 2pt}| &
%   X\hdashrule[0.5ex]{3cm}{1mm}{8mm 2pt}x \\[2ex]
%
%   |\hdashrule[0.5ex][c]{4cm}{1mm}{8mm 2pt}| &
%   X\hdashrule[0.5ex][c]{4cm}{1mm}{8mm 2pt}x \\
%
%   |\hdashrule[0.5ex][c]{3cm}{1mm}{8mm 2pt}| &
%   X\hdashrule[0.5ex][c]{3cm}{1mm}{8mm 2pt}x \\[2ex]
%
%   |\hdashrule[0.5ex][x]{4cm}{1mm}{8mm 2pt}| &
%   X\hdashrule[0.5ex][x]{4cm}{1mm}{8mm 2pt}x \\
%
%   |\hdashrule[0.5ex][x]{3cm}{1mm}{8mm 2pt}| &
%   X\hdashrule[0.5ex][x]{3cm}{1mm}{8mm 2pt}x \\
% \end{tabular}
% \end{center}
%
% \noindent
% Notice how the dashes in the first pair of |\hdashrule|s line up; the
% rules in the second pair each have an equal amount of whitespace on
% either side of the rule; and the rules in the third pair have extra
% spaces within the dash pattern itself instead of around it.  The
% |x|~qualifier is rarely useful for dashed rules because it alters the
% pattern itself.  However, |x| does enable rules with long dashes to
% better fill a comparatively small width, as in the following example:
%
% \begin{center}
% \renewcommand{\arraystretch}{1.25}
% \begin{tabular}{l@{\qquad}l}
%   |\hdashrule[0.5ex][x]{3in}{2pt}{2cm 0pt}| \\
%   X\hdashrule[0.5ex][x]{3in}{2pt}{2cm 0pt}x
% \end{tabular}
% \end{center}
%
% \noindent
% The gaps in the above are clearly wider than~|0pt|, but they \emph{are}
% evenly spaced.
%
%
% \section{Differences from \texttt{setdash}}
%
% |\hdashrule| is different from PostScript's |setdash| command in the
% following ways:
%
% \begin{itemize}
%   \item |setdash| takes on/off values in terms of PostScript points
%   (\TeX{} ``big points'' or~``|bp|''), while |\hdashrule| requires
%   explicit units.
%
%   \item There is no equivalent of |setdash|'s \textit{offset}
%   parameter to specify a starting offset into the pattern.  If you're
%   desperate you can fake \textit{offset} with a leading |\rule| and
%   |\hspace|.
%
%   \item Unlike |setdash|, |\hdashrule| can't draw a solid line.  Use
%   |\rule| for solid lines.
% \end{itemize}
%
%
% \StopEventually{^^A
%   \section{Future Work}
%
%   \textsf{dashrule} \fileversion{} supports only horizontally dashed
%   rules.  Future versions (if any) may support vertically dashed rules
%   as well.  For the time being, the \textsf{graphicx} package's
%   \texttt{\string\rotatebox} can be used to define a
%   \texttt{\string\vdashrule} in terms of a rotated
%   \texttt{\string\hdashrule}.
%
%   The next logical step after adding a \texttt{\string\vdashrule} is
%   to support dashed rectangles, which would be composed of
%   \texttt{\string\hdashrule}s and \texttt{\string\vdashrule}s.  Other
%   possible enhancements would be a way of drawing dotted lines,
%   presumably composed from the limited set of circle characters
%   available in \LaTeX's fonts.
% }
%
%
% \section{Implementation}
%
%    \begin{macrocode}
%<*package>
%    \end{macrocode}
%
% \begin{macro}{\hdr@do@rule}
% This macro is exactly like \LaTeX's |\rule| except that the optional
% argument is required, and it has the side effect of pointing
% |\hdr@do@something| to |\hdr@do@skip|.
%    \begin{macrocode}
\def\hdr@do@rule[#1]#2#3{%
  \rule[#1]{#2}{#3}%
  \let\hdr@do@something=\hdr@do@skip
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\hdr@do@skip}
% This macro takes the same arguments as |\hdr@do@rule|, but instead of
% drawing a rule, it inserts an equivalent amount of horizontal
% whitespace.  Additionally, it points |\hdr@do@something| to
% |\hdr@do@rule| as a side effect.
%    \begin{macrocode}
\def\hdr@do@skip[#1]#2#3{%
  \hspace*{#2}%
  \let\hdr@do@something=\hdr@do@rule
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\c@hdr@segments}
% \begin{macro}{\hdr@tally@segments}
% Dash patterns containing an odd number of segments are treated
% differently from dash patterns containing an even number of segments.
% We therefore define a macro, |\hdr@tally@segments|, which counts the
% number of space-separated segments in a dash pattern and stores the
% tally in the |hdr@segments| counter.  Note that |hdr@segments| should
% be initialized to~|0| before invoking |\hdr@tally@segments|.
%    \begin{macrocode}
\newcounter{hdr@segments}
\def\hdr@tally@segments#1 {%
  \ifx#1!%
  \else
    \addtocounter{hdr@segments}{1}%
    \expandafter\hdr@tally@segments
  \fi
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\hdashrule}
% This is the only macro in \textsf{dashrule}'s external interface.
% (|\hdashrule@ii| does most of the work for |\hdashrule|, though.)  All
% |\hdashrule| itself does is invoke |\hdashrule@i| with its first
% optional argument or~|0.0pt| if none was provided.  |\hdashrule@i|, in
% turn, invokes |\hdashrule@ii| with the two optional arguments,
% supplying |\empty| as the default value of the second optional
% argument.
% \changes{v1.1}{2008/04/27}{Preceded the invocation of
%   \texttt{\string\string\string\@testopt} with an empty box so that
%   \texttt{\string\string\string\hdashrule} can now begin a paragraph}
%    \begin{macrocode}
\DeclareRobustCommand{\hdashrule}{\mbox{}\@testopt{\hdashrule@i}{0pt}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\hdashrule@i}
% Supply |\empty| as the default second argument and call
% |\hdashrule@ii|.
%    \begin{macrocode}
\def\hdashrule@i[#1]{\@testopt{\hdashrule@ii[#1]}\empty}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\hdashrule@ii}
% Now we can do the real work for |\hdashrule|.  |\hdashrule@ii| takes
% the following parameters:
%
% \begin{center}
% \begin{tabular}{ccccc}
%   |#1| & |#2| & |#3| & |#4| & |#5| \\
%   \oarg{raise} & \oarg{leader} & \marg{width} & \marg{height} & \marg{dash}
% \end{tabular}
% \end{center}
%
% \noindent
% The \meta{raise}, \meta{width}, and \meta{height} parameters have the
% same meaning as in \LaTeX's |\rule| macro.  \meta{leader} specifies
% the \TeX\ leader function to use to fill \meta{width} amount of
% space.  It should be |c| for |\cleaders|, |x| for |\xleaders|, or
% nothing for ordinary |\leaders|.  The \meta{dash} argument specifies
% the dash pattern and is analogous to the \textit{array} argument to
% PostScript's |setdash| function.  That is, it is a list of
% space-separated \meta{dimen}s that alternate ``on'' and ``off''
% distances.
%    \begin{macrocode}
\def\hdashrule@ii[#1][#2]#3#4#5{%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\hdr@do@something}
% The |\hdr@do@something| alias alternates between |\hdr@do@rule|
% and |\hdr@do@skip|, starting with |\hdr@do@rule|.
%    \begin{macrocode}
  \let\hdr@do@something=\hdr@do@rule
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\hdr@parse@dash}
% For every space-separated \meta{dimen} in \meta{dash}, we invoke
% |\hdr@do@something| to draw a rule or a space, as appropriate.  We
% define |\hdr@parse@dash| within |\hdashrule@ii| so we don't have to
% pass in |\hdashrule@ii|'s~|#1| and~|#4| on every invocation.
%    \begin{macrocode}
  \def\hdr@parse@dash##1 {%
    \ifx##1!%
    \else
      \hdr@do@something[#1]{##1}{#4}%
      \expandafter\hdr@parse@dash
    \fi
  }%
%    \end{macrocode}
% We now count the number of segments in the dash pattern so we can
% determine if we have an even or odd number of them.
%    \begin{macrocode}
  \setcounter{hdr@segments}{0}%
  \hdr@tally@segments#5 !
%    \end{macrocode}
% Finally, we invoke |\leaders|, |\cleaders|, or |\xleaders| to draw the
% dashed line, repeating the pattern until \meta{width} space is filled.
% The trick here is that odd-lengthed pattern descriptions must be
% repeated to yield the complete pattern.  For instance, the pattern
% ``|1pt|'' is actually short for ``1\,pt.\ rule, 1\,pt.\ space,'' and
% ``|2pt 4pt 6pt|'' is an abridged version of ``2\,pt.\ rule, 4\,pt.\
% space, 6\,pt.\ rule, 2\,pt.\ space, 4\,pt.\ rule, 6\,pt.\ space.''
% Although it is valid to repeat even-lengthed patterns as well---an
% earlier draft of |\hdashrule@ii| did just that---this produces
% inferior results because \TeX's various leader commands do not split
% boxes.  The longer the pattern, the less likely it will fit snugly
% into the given width.
%    \begin{macrocode}
  \ifodd\c@hdr@segments
    \csname#2leaders\endcsname
      \hbox{\hdr@parse@dash#5 #5 ! }%
      \hskip#3\relax
  \else
    \csname#2leaders\endcsname
      \hbox{\hdr@parse@dash#5 ! }%
      \hskip#3\relax
  \fi
}
%    \end{macrocode}
% \end{macro}
%
% \Finale
\endinput