% \iffalse meta-comment
%
% Copyright (C) 2005,2006,2007,2008,2009 by Vilar Camara Neto.
%
% This file may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either
% version 1.2 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 1.2 or later is part of all distributions of
% LaTeX version 1999/12/01 or later.
%
% Currently this work has the LPPL maintenance status "maintained".
%
% The Current Maintainer of this work is Vilar Camara Neto.
%
% This work consists of the files breakurl.dtx and
% breakurl.ins and the derived file breakurl.sty.
%
% \fi
%
% \iffalse
%<*driver>
\ProvidesFile{breakurl.dtx}
%</driver>
%<package>\NeedsTeXFormat{LaTeX2e}[1999/12/01]
%<package>\ProvidesPackage{breakurl}
%<*package>
    [2009/01/24 v1.30 Breakable hyperref URLs]
%</package>
%<*driver>
\documentclass{ltxdoc}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
\DocInput{breakurl.dtx}
\end{document}
%</driver>
% \fi

% \CheckSum{391}


% \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{v1.30}{2009/01/24}{Breaks are now allowed before percent signs}
% \changes{v1.23}{2008/07/15}{\string\hypersetup can now be used anywhere}
% \changes{v1.22}{2008/04/05}{Corrected a misuse of \string\leavevmode which
%   generated blank lines inside tables}
% \changes{v1.21}{2007/06/20}{\string\burlalt and \string\urlalt now work under
%   pdflatex; also bug fixes from Heiko Oberdiek}
% \changes{v1.20}{2006/08/26}{Changes to reflect update of hyperref package}
% \changes{v1.10}{2005/09/23}{Added the command \string\urlalt, allowing one to
%   specify different values for displayed and actual link}
% \changes{v1.01}{2005/09/22}{Fixed a bug when a page break occurs in the
%   middle of a link}
% \changes{v1.00}{2005/07/10}{Support for \string\UrlLeft and \string\UrlRight
%   macros}
% \changes{v0.04}{2005/04/24}{hyperref's `colorlinks' and `urlcolor' options
%   are now working}
% \changes{v0.03}{2005/03/23}{New `vertfit' option; compatibility with pdfeTeX
%   engine}
% \changes{v0.02}{2005/03/20}{Smarter (not segmented) links, optionally allows
%   breaks after hyphens}
% \changes{v0.01}{2005/03/05}{Initial version (first draft)}
%
% \GetFileInfo{breakurl.dtx}
%
% \newcommand{\pkg}[1]{\textsf{#1}}
%
% \title{The \pkg{breakurl} package\thanks{This document corresponds to
% \textsf{breakurl}~\fileversion, dated~\filedate.}}
% \author{Vilar Camara Neto \\
% \texttt{neto@dcc.ufmg.br}}
% \date{January 24, 2009}
%
% \maketitle
%
% \StopEventually
%
% \sloppy
%
% \section{Introduction}
%
% The \pkg{hyperref} package brings a lot of interesting tools to ``boost''
% documents produced by \LaTeX. For instance, a PDF file can have clickable
% links to references, section headings, URLs, etc.
%
% Generating a link to a URL may be a concern if it stands near the end of a
% line of text. When one uses pdf\LaTeX{} to directly generate a PDF document,
% there's no problem: the driver can break a link across more than one line.
% However, the |dvips| driver (used when one prefers the \LaTeX{} $\rightarrow$
% DVI $\rightarrow$ PostScript $\rightarrow$ PDF path), because of internal
% reasons, can't issue line breaks in the middle of a link. Sometimes this
% turns into a serious aesthetic problem, generating largely underfull/overfull
% paragraphs; sometimes the final effect is so bad that the link can't even fit
% inside the physical page limits.
%
% To overcome that |dvips| limitation, the \pkg{breakurl} package was designed
% with a simple solution: it provides a command called |\burl| (it stands for
% ``breakable URL''). Instead of generating one long, atomic link, this command
% breaks it into small pieces, allowing line breaks between them. Each sequence
% of pieces that stand together in one line are converted to a hot (clickable)
% link in the PDF document. Also, by default the |\url| command is turned into
% a synonym of |\burl|, so there's no need to do a search-replace operation to
% immediately start using the package.
%
%
% \section{How to use it}
% \label{sec:howtouse}
%
% At the preamble, just put |\usepackage{breakurl}| somewhere \emph{after}
% |\usepackage{hyperref}|. The |\burl| command is defined and, by default, the
% package also turns the |\url| command into a synonym of |\burl|. This might
% come in handy, for example, if you use Bib\TeX{}, your |.bib|-file has lots
% of |\url| commands and you don't want to replace them by |\burl|. If, for
% some reason, you want to preserve the original behavior of |\url| (i.e., it
% creates an unbreakable link), you must supply the |preserveurlmacro| option
% to the package (see Section \ref{sec:pkgoptions}).
%
% In the middle of the document, the syntax of |\burl| (and its synonym |\url|)
% is the same as the original |\url|: |\burl|\marg{URL}, where \meta{URL} is,
% of course, the address to point to. You don't need to care (escape) about
% special characters like \texttt{\%}, \texttt{\&}, \texttt{\_}, and so on.
%
% Another handy command is |\burlalt|\marg{ActualURL}\marg{DisplayedURL}, where
% \meta{ActualURL} is the actual link and \meta{DisplayedURL} is the link text
% to be displayed in the document. For consistency, |\urlalt| is a synonym of
% |\burlalt|, unless the |preserveurlmacro| package option is
% specified.\footnote{The \texttt{\string\burlalt} command resembles
% \texttt{\string\hyperref}'s \texttt{\string\href}, but since it works in a
% different manner I decided not to call it ``\texttt{\string\bhref}''.}
%
% The default behavior of the package is to break the link after any sequence
% of these characters:
% \begin{center}
% \begin{tabular}{lll}
%   `|:|' (colon) &
%   `|/|' (slash) &
%   `|.|' (dot) \\
%   `|?|' (question mark) &
%   `|#|' (hash) &
%   `|&|' (ampersand) \\
%   `|_|' (underline) &
%   `|,|' (comma) &
%   `|;|' (semicolon) \\
%   `|!|' (exclamation mark)
% \end{tabular}
% \end{center}
% and before occurrences of any of these:
% \begin{center}
% \begin{tabular}{l}
%   `|%|' (percent sign)
% \end{tabular}
% \end{center}
%
% Remember that (with exception of percent sign) breaks are only allowed
% \emph{after} a sequence of these characters, so a link starting with
% |http://| will never break before the second slash.
%
% Also note that I decided not to include the `|-|' (hyphen) character in the
% default lists. It's to avoid a possible confusion when someone encounters a
% break after a hyphen, e.g.:
%
% \begin{quote}
% Please visit the page at |http://internet-|\\
% |page.com|, which shows\ldots
% \end{quote}
%
% Here comes the doubt: The author is pointing to |http://internet-page.com| or
% to |http://internetpage.com|? The \pkg{breakurl} package \emph{never} adds a
% hyphen when a link is broken across lines --- so, the first choice would be
% the right one ---, but we can't assume that the reader knows this rule; so, I
% decided to disallow breaks after hyphens. Nevertheless, if you want to
% overcome my decision, use the |hyphenbreaks| option:
%
% \begin{quote}
%   |\usepackage[hyphenbreaks]{breakurl}|
% \end{quote}
%
%
% \subsection{Package options}
% \label{sec:pkgoptions}
%
% \newcommand{\defmark}{$\triangleright$}
% \newcommand{\sep}{$\mid$}
%
% When using the |\usepackage| command, you can give some options to customize
% the package behavior. Possible options are explained below:
%
% \begin{itemize}
% \item |hyphenbreaks|\par
%   Instructs the package to allow line breaks after hyphens.
%
% \item |preserveurlmacro|\par
%   Instructs the package to leave the |\url| command exactly as it was before
%   the package inclusion. Also, |\urlalt| isn't defined as a synonym of
%   |\burlalt|. In either case (i.e., using |preserveurlmacro| or not), the
%   breakable link is available via the |\burl| command.
%
% \item |vertfit=|\meta{criterion}\par
%   Estabilishes how the link rectangle's height (and depth) will behave
%   against the corresponding URL text's vertical range. There are three
%   options for \meta{criterion}: |local| makes each rectangle fit tightly to
%   its text's vertical range. This means that each line of a link broken
%   across lines can have a rectangle with different vertical sizes. |global|
%   first calculates the height (and depth) to enclose the entire link and
%   preserves the measures, so the link maintains the vertical size across
%   lines. |strut| goes even further and ensures that the rectangle's vertical
%   range corresponds to |\strut|. With this option, rectangles in adjacent
%   lines can overlap. The default is |vertfit=local|.
% \end{itemize}
%
%
% \subsection{Additional comments}
%
% As stated in the introduction, the \pkg{breakurl} is designed for those
% compiling documents via \LaTeX{}, not pdf\LaTeX. In the latter case, the
% package doesn't (re)define the |\url| command: it only defines |\burl| to be
% a synonym of whatever |\url| is defined (e.g., via \pkg{url} or
% \pkg{hyperref} packages). Of course, |\burl| may behave differently compared
% to (non-pdf)\LaTeX, because then the system will use other rules to make line
% breaks, spacing, etc.
%
% Also, this package was not designed to nor tested against other drivers: it's
% compatible with dvips only.
%
%
% \subsection{Changelog}
%
% (presented in reverse chronological order)
%
% \begin{description}
%
% \item[v1.30] Breaks are now allowed before percent sign (|%|).
%
% \item[v1.23] |\hypersetup| now works anywhere.
%
% \item[v1.22] Corrected blank lines appearing inside tables.
%
% \item[v1.21] |\burlalt| and the synonym |\urlalt| now work with pdflatex.
%   Also, there are a couple of bug fixes (thank you again, Heiko).
%
% \item[v1.20] An update was needed because \pkg{hyperref}'s internals were
%   changed. (Thanks Heiko for sending the correction patch.) Troubleshooting
%   now includes a note about |\sloppy|.
%
% \item[v1.10] A new command, |\burlalt| (and the synonym |\urlalt|), allows
%   one to specify different values for actual and displayed link.
%
% \item[v1.01] Fixed a bug that was happening when a link is split across
%   pages.
%
% \item[v1.00] The |\UrlLeft| and |\UrlRight| (defined and explained in the
%   |url| package) are now partially supported. By ``partially'' I mean:
%   although the original (|url.sty|'s) documentation allows defining
%   |\UrlLeft| as a command with one argument (things such
%   \texttt{\string\def\string\UrlLeft\#1\string\UrlRight\{}\emph{do things
%   with \#1}\texttt{\}}, this isn't expected to work with \pkg{breakurl}.
%   Please use only the basic definition, e.g.: |\def\UrlLeft{<url:\ }|
%   |\def\UrlRight{>}|.
%
% \item[v0.04] Corrected a bug that prevented URLs to be in color, in despite
%   of \pkg{hyperref}'s |colorlinks| and |urlcolor| options. Added an error
%   message if |vertfit| parameter is invalid.
%
% \item[v0.03] The package was tested against |pdfeTeX| engine (which may be
%   the default for some |teTeX| distributions). Introduced a new package
%   option, |vertfit|.
%
% \item[v0.02] The main issue of the initial release --- the odd-looking
%   sequence of small links in the same line, if one uses \pkg{hyperref}'s link
%   borders --- was resolved: now the package generates only one rectangle per
%   line. Also, breaks after hyphens, which weren't allowed in the previous
%   release, are now a users' option. Finally, the package can be used with
%   pdf\LaTeX{} (in this case, |\burl| is defined to be a synonym of the
%   original |\url| command).
%
% \item[v0.01] Initial release.
%
% \end{description}
%
%
% \subsection{Troubleshooting}
%
% Here comes a few notes about known issues:
%
% \begin{itemize}
%
% \item I received some comments saying that in some cases \pkg{breakurl}
%   destroys the formatting of the document: the left/right margins aren't
%   respected, justification becomes weird, etc. In all these cases, the
%   problems were corrected when other packages were upgraded, notabily
%   |xkeyval|.
%
% \item If your compilation issues the following error:
%   \begin{quote}
%     |! Undefined control sequence.|\\
%     |<argument> \headerps@out| \ldots
%   \end{quote}
%   then you need to specify the |dvips| driver as an option to the
%   \pkg{hyperref} package, e.g.:
%   \begin{quote}
%   |\usepackage[dvips]{hyperref}|
%   \end{quote}
%
%   However, this is related to old versions of \pkg{hyperref}: the package is
%   able to automatically determine the driver in current versions. It's
%   probabily better to update your \LaTeX{} system.
%
% \item If everything compiles but sometimes URLs still don't respect the right
%   margin, don't blame the package yet :-) . Roughly speaking, by default the
%   right margin is a limit to be respected ``only if word spacing is okay'',
%   so it may be ignored even when URLs aren't used. Check the following
%   paragraph:
%
%   \fussy
%
%   Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Proin
%   zzzzzzzzzzzzzzzzzzzzzzz\ldots
%
%   \sloppy
%
%   To overcome this (and make right margins a hard limit) use the command
%   |\sloppy|, preferably before |\begin{document}|. This makes the previous
%   paragraph look like:
%
%   Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Proin
%   zzzzzzzzzzzzzzzzzzzzzzz\ldots
%
%   As a drawback word spacing becomes terrible, but now the text is kept
%   inside designed margins. You should decide what looks better.
%
% \end{itemize}
%
% \subsection{Acknowledgments}
%
% Thanks to Hendri Adriaens, Donald Arseneau, Michael Friendly, Morten Høgholm,
% David Le Kim, Damian Menscher, Tristan Miller, Heiko Oberdiek, Christoph
% Schiller, Xiaotian Sun, Michael Toews, David Tulloh, Adrian Vogel, Yu Zhang,
% and Jinsong Zhao for suggestions, bug reports, comments, and corrections. A
% special thanks to the participants of |comp.text.tex| newsgroups for their
% constant effort to help thousands of people in the beautiful world of \TeX{}
% and \LaTeX.
%
%
% \section{Source code}
%
% This section describes the |breakurl.sty| source code.
%
% The \pkg{breakurl} requires some packages, so let's include them:
%
%    \begin{macrocode}
\RequirePackage{xkeyval}
\RequirePackage{ifpdf}
%    \end{macrocode}

% Is the document being processed by pdf\LaTeX? (Actually, is there a PDF file
% being directly generated?) Then, well, this package doesn't apply: let's just
% define |\burl| to call the default |\url|.
%
%    \begin{macrocode}
\ifpdf
  % Dummy package options
  \DeclareOptionX{preserveurlmacro}{}
  \DeclareOptionX{hyphenbreaks}{}
  \DeclareOptionX{vertfit}{}
  \ProcessOptionsX\relax

  \PackageWarning{breakurl}{%
  You are using breakurl while processing via pdflatex.\MessageBreak
  \string\burl\space will be just a synonym of \string\url.\MessageBreak}
  \DeclareRobustCommand{\burl}{\url}
  \DeclareRobustCommand*{\burlalt}{\hyper@normalise\burl@alt}
  \def\burl@alt#1#2{\hyper@linkurl{\Hurl{#1}}{#2}}
  \expandafter\endinput
\fi
%    \end{macrocode}

% Since \pkg{breakurl} is an extension to \pkg{hyperref}, let's complain loudly
% if the latter was not yet loaded:
%
%    \begin{macrocode}
\@ifpackageloaded{hyperref}{}{%
  \PackageError{breakurl}{The breakurl depends on hyperref package}%
  {I can't do anything. Please type X <return>, edit the source file%
  \MessageBreak
  and add \string\usepackage\string{hyperref\string} before
  \string\usepackage\string{breakurl\string}.}
  \endinput
}
%    \end{macrocode}

% The package options are handled by |\newif|s, which are declared and
% initialised:
%
%    \begin{macrocode}
\newif\if@preserveurlmacro\@preserveurlmacrofalse
\newif\if@burl@fitstrut\@burl@fitstrutfalse
\newif\if@burl@fitglobal\@burl@fitglobalfalse
%    \end{macrocode}

% \DescribeMacro{\burl@toks}
% The \pkg{breakurl} package uses a token list to store characters and tokens
% until a break point is reached:
%
%    \begin{macrocode}
\newtoks\burl@toks
%    \end{macrocode}

% \DescribeMacro{\burl@charlistbefore}
% \DescribeMacro{\burl@charlistafter}
% \DescribeMacro{\burl@defifstructure}
% The following support routines are designed to build the conditional
% structure that is the kernel of |\burl|: comparing each incoming character
% with the list of ``breakable'' characters and taking decisions on that. This
% conditional structure is built by |\burl@defifstructure| --- which is called
% only at the end of package loading, because the character list (stored in
% |\burl@charlistbefore|) can be modified by the |hyphenbreaks| option.
%
%    \begin{macrocode}
\let\burl@charlistbefore\empty
\let\burl@charlistafter\empty

\def\burl@addtocharlistbefore{\g@addto@macro\burl@charlistbefore}
\def\burl@addtocharlistafter{\g@addto@macro\burl@charlistafter}

\bgroup
  \catcode`\&=12\relax
  \hyper@normalise\burl@addtocharlistbefore{%}
  \hyper@normalise\burl@addtocharlistafter{:/.?#&_,;!}
\egroup

\def\burl@growmif#1#2{%
  \g@addto@macro\burl@mif{\def\burl@ttt{#1}\ifx\burl@ttt\@nextchar#2\else}%
}
\def\burl@growmfi{%
  \g@addto@macro\burl@mfi{\fi}%
}
\def\burl@defifstructure{%
  \let\burl@mif\empty
  \let\burl@mfi\empty
  \expandafter\@tfor\expandafter\@nextchar\expandafter:\expandafter=%
    \burl@charlistbefore\do{%
    \expandafter\burl@growmif\@nextchar\@burl@breakbeforetrue
    \burl@growmfi
  }%
  \expandafter\@tfor\expandafter\@nextchar\expandafter:\expandafter=%
    \burl@charlistafter\do{%
    \expandafter\burl@growmif\@nextchar\@burl@breakaftertrue
    \burl@growmfi
  }%
}

\AtEndOfPackage{\burl@defifstructure}
%    \end{macrocode}

% The package options are declared and handled as follows:
%
%    \begin{macrocode}
\def\burl@setvertfit#1{%
  \lowercase{\def\burl@temp{#1}}%
  \def\burl@opt{local}\ifx\burl@temp\burl@opt
    \@burl@fitstrutfalse\@burl@fitglobalfalse
  \else\def\burl@opt{strut}\ifx\burl@temp\burl@opt
    \@burl@fitstruttrue\@burl@fitglobalfalse
  \else\def\burl@opt{global}\ifx\burl@temp\burl@opt
    \@burl@fitstrutfalse\@burl@fitglobaltrue
  \else
    \PackageWarning{breakurl}{Unrecognized vertfit option `\burl@temp'.%
    \MessageBreak
    Adopting default `local'}
    \@burl@fitstrutfalse\@burl@fitglobalfalse
  \fi\fi\fi
}

\DeclareOptionX{preserveurlmacro}{\@preserveurlmacrotrue}
\DeclareOptionX{hyphenbreaks}{%
  \bgroup
    \catcode`\&=12\relax
    \hyper@normalise\burl@addtocharlistafter{-}%
  \egroup
}
\DeclareOptionX{vertfit}[local]{\burl@setvertfit{#1}}

\ProcessOptionsX\relax
%    \end{macrocode}

% These supporting routines are modified versions of those found in the
% \pkg{hyperref} package. They were adapted to allow a link to be progressively
% built, i.e., when we say ``put a link rectangle here'', the package will
% decide if this will be made.
%
%    \begin{macrocode}
\def\burl@hyper@linkurl#1#2{%
  \begingroup
    \hyper@chars
    \burl@condpdflink{#1}%
  \endgroup
}

\def\burl@condpdflink#1{%
  \literalps@out{
    /burl@bordercolor {\@urlbordercolor} def
    /burl@border {\@pdfborder} def
  }%
  \if@burl@fitstrut
    \sbox\pdf@box{#1\strut}%
  \else\if@burl@fitglobal
    \sbox\pdf@box{\burl@url}%
  \else
    \sbox\pdf@box{#1}%
  \fi\fi
  \dimen@\ht\pdf@box\dimen@ii\dp\pdf@box
  \sbox\pdf@box{#1}%
  \ifdim\dimen@ii=\z@
    \literalps@out{BU.SS}%
  \else
    \lower\dimen@ii\hbox{\literalps@out{BU.SS}}%
  \fi
  \ifHy@breaklinks\unhbox\else\box\fi\pdf@box
  \ifdim\dimen@=\z@
    \literalps@out{BU.SE}%
  \else
    \raise\dimen@\hbox{\literalps@out{BU.SE}}%
  \fi
  \pdf@addtoksx{H.B}%
}
%    \end{macrocode}

% \DescribeMacro{\burl}
% |\burl| prepares the catcodes (via |\hyper@normalise|) and calls the |\burl@|
% macro, which does the actual work.
%
%    \begin{macrocode}
\DeclareRobustCommand*{\burl}{%
  \leavevmode
  \begingroup
  \let\hyper@linkurl=\burl@hyper@linkurl
  \catcode`\&=12\relax
  \hyper@normalise\burl@
}
%    \end{macrocode}

% \DescribeMacro{\burlalt}
% |\burlalt| does the same as |\burl|, but calls another macro (|\burl@alt|)
% to read two following arguments instead of only one.
%
%    \begin{macrocode}
\DeclareRobustCommand*{\burlalt}{%
  \begingroup
  \let\hyper@linkurl=\burl@hyper@linkurl
  \catcode`\&=12\relax
  \hyper@normalise\burl@alt
}
%    \end{macrocode}

% \DescribeMacro{\burl@}
% \DescribeMacro{\burl@alt}
% \DescribeMacro{\burl@@alt}
% |\burl@| \marg{URL} just eats the next argument to define the URL address and
% the link to be displayed. Both are used by |\burl@doit|.
%
% |\burl@alt| \marg{ActualURL} and |\burl@@alt| \marg{DisplayedURL} work
% together to eat the two arguments (the actual URL to point to and the link
% text to be displayed). Again, both are used by |\burl@doit|.
%
%    \begin{macrocode}
\newif\if@burl@breakbefore
\newif\if@burl@breakafter
\newif\if@burl@prevbreakafter

\bgroup
\catcode`\&=12\relax
\gdef\burl@#1{%
  \def\burl@url{#1}%
  \def\burl@urltext{#1}%
  \burl@doit
}

\gdef\burl@alt#1{%
  \def\burl@url{#1}%
  \hyper@normalise\burl@@alt
}
\gdef\burl@@alt#1{%
  \def\burl@urltext{#1}%
  \burl@doit
}
%    \end{macrocode}

% \DescribeMacro{\burl@doit}
% |\burl@doit| works much like hyperref's |\url@| macro (actually, this code
% macro was borrowed and adapted from the original |\url@|): it builds a series
% of links, allowing line breaks between them. The characters are accumulated
% and eventually flushed via the |\burl@flush| macro.
%
% Support for |\UrlLeft|/|\UrlRight|: The |\UrlRight| is emptied until the very
% last flush (when it is restored). The |\UrlLeft| is emptied after the first
% flush. So, any string defined in those macros are meant to be displayed only
% before the first piece and after the last one, which (of course) is what we
% expect to happen. Unfortunately, breaking doesn't happen inside those
% strings, since they're not rendered verbatim (and so they aren't processed
% inside the breaking mechanism).
%
%    \begin{macrocode}
\gdef\burl@doit{%
  \burl@toks{}%
  \let\burl@UrlRight\UrlRight
  \let\UrlRight\empty
  \@burl@prevbreakafterfalse
  \@ifundefined{@urlcolor}{\Hy@colorlink\@linkcolor}{\Hy@colorlink\@urlcolor}%
  \expandafter\@tfor\expandafter\@nextchar\expandafter:\expandafter=%
    \burl@urltext\do{%
    \if@burl@breakafter\@burl@prevbreakaftertrue
      \else\@burl@prevbreakafterfalse\fi
    \@burl@breakbeforefalse
    \@burl@breakafterfalse
    \expandafter\burl@mif\burl@mfi
    \if@burl@breakbefore
      % Breakable if the current char is in the `can break before' list
      \burl@flush\linebreak[0]%
    \else
      \if@burl@prevbreakafter
        \if@burl@breakafter\else
          % Breakable if the current char is not in any of the `can break'
          % lists, but the previous is in the `can break after' list.
          % This mechanism accounts for sequences of `break after' characters,
          % where a break is allowed only after the last one
          \burl@flush\linebreak[0]%
        \fi
      \fi
    \fi
    \expandafter\expandafter\expandafter\burl@toks
      \expandafter\expandafter\expandafter{%
      \expandafter\the\expandafter\burl@toks\@nextchar}%
  }%
  \let\UrlRight\burl@UrlRight
  \burl@flush
  \literalps@out{BU.E}%
  \Hy@endcolorlink
  \endgroup
}
\egroup
%    \end{macrocode}

% \DescribeMacro{\burl@flush}
% This macro flushes the characters accumulated during the |\burl@| processing,
% creating a link to the URL.
%
%    \begin{macrocode}
\def\the@burl@toks{\the\burl@toks}

\def\burl@flush{%
  \expandafter\def\expandafter\burl@toks@def\expandafter{\the\burl@toks}%
  \literalps@out{/BU.L (\burl@url) def}%
  \hyper@linkurl{\expandafter\Hurl\expandafter{\burl@toks@def}}{\burl@url}%
  \global\burl@toks{}%
  \let\UrlLeft\empty
}%
%    \end{macrocode}

% Now the synonyms |\url| and |\urlalt| are (re)defined, unless the
% |preserveurlmacro| option is given.
%
%    \begin{macrocode}
\if@preserveurlmacro\else\let\url\burl\let\urlalt\burlalt\fi
%    \end{macrocode}

% Internally, the package works as follows: each link segment (i.e., a list of
% non-breakable characters followed by breakable characters) ends with a PDF
% command that checks if the line ends here. If this check is true, then (and
% only then) the PDF link rectangle is built, embracing all link segments of
% this line.
%
% To make that work, we need some code to work at the PostScript processing
% level. The supporting routines to do so are introduced in the PS dictionary
% initialization block via specials. Each routine is explained below.
%
% The variables used here are: |burl@stx| and |burl@endx|, which defines the
% link's horizontal range; |burl@boty| and |burl@topy|, which defines the
% link's vertical range; |burl@llx|, |burl@lly|, |burl@urx|, and |burl@ury|,
% which define the bounding box of the current link segment (they resemble the
% \pkg{hyperref}'s |pdf@llx|--|pdf@ury| counterparts); and |BU.L|, which holds
% the target URL.
%
%    \begin{macrocode}
\AtBeginDvi{%
  \headerps@out{%
    /burl@stx null def
%    \end{macrocode}
%
% |BU.S| is called whenever a link begins:
%
%    \begin{macrocode}
    /BU.S {
      /burl@stx null def
    } def
%    \end{macrocode}
%
% |BU.SS| is called whenever a link segment begins:
%
%    \begin{macrocode}
    /BU.SS {
      currentpoint
      /burl@lly exch def
      /burl@llx exch def
      burl@stx null ne {burl@endx burl@llx ne {BU.FL BU.S} if} if
      burl@stx null eq {
        burl@llx dup /burl@stx exch def /burl@endx exch def
        burl@lly dup /burl@boty exch def /burl@topy exch def
      } if
      burl@lly burl@boty gt {/burl@boty burl@lly def} if
    } def
%    \end{macrocode}
%
% |BU.SE| is called whenever a link segment ends:
%
%    \begin{macrocode}
    /BU.SE {
      currentpoint
      /burl@ury exch def
      dup /burl@urx exch def /burl@endx exch def
      burl@ury burl@topy lt {/burl@topy burl@ury def} if
    } def
%    \end{macrocode}
%
% |BU.SE| is called whenever the entire link ends:
%
%    \begin{macrocode}
    /BU.E {
      BU.FL
    } def
%    \end{macrocode}
%
% |BU.FL| is called to conditionally flush the group of link segments that we
% have so far. This is meant to be called at each line break:
%
%    \begin{macrocode}
    /BU.FL {
      burl@stx null ne {BU.DF} if
    } def
%    \end{macrocode}
%
% |BU.DF| is the routine to actually put the link rectangle in the PDF file:
%
%    \begin{macrocode}
    /BU.DF {
      BU.BB
      [ /H /I /Border [burl@border] /Color [burl@bordercolor]
      /Action << /Subtype /URI /URI BU.L >> /Subtype /Link BU.B /ANN pdfmark
      /burl@stx null def
    } def
%    \end{macrocode}
%
% |BU.FF| adds margins to the calculated tight rectangle:
%
%    \begin{macrocode}
    /BU.BB {
      burl@stx HyperBorder sub /burl@stx exch def
      burl@endx HyperBorder add /burl@endx exch def
      burl@boty HyperBorder add /burl@boty exch def
      burl@topy HyperBorder sub /burl@topy exch def
    } def
%    \end{macrocode}
%
% |BU.B| converts the coordinates into a rectangle:
%
%    \begin{macrocode}
    /BU.B {
      /Rect[burl@stx burl@boty burl@endx burl@topy]
    } def
%    \end{macrocode}
%
% Finally, we must redefine |eop|, which is called just when the page ends, to
% handle links that are split across pages. (|eop-hook| isn't the right place
% to do so, since this hook is called after the dictionaries were reverted to a
% previous state, vanishing the rectangle coordinates.)
%
%    \begin{macrocode}
    /eop where {
      begin
      /@ldeopburl /eop load def
      /eop { SDict begin BU.FL end @ldeopburl } def
      end
    } {
      /eop { SDict begin BU.FL end } def
    } ifelse
  }%
}
%    \end{macrocode}
%
% \Finale
