%D \module [
%D         file=t-letterspace,
%D      version=2011-03-15T12:59:48+0100 or later,
%D        title=\CONTEXT\ User Module,
%D     subtitle=Letterspacing commands,
%D       author=Philipp Gesang,
%D         date=\currentdate,
%D    copyright=Philipp Gesang,
%D      license=2-clause BSD,
%D ]

\writestatus{loading}{ConTeXt User Module / Letterspace}

\startmodule [letterspace]

\startinterface all
  \setinterfacevariable {letterspace} {letterspace}
\stopinterface

\unprotect

\definenamespace [\v!letterspace] [
  command=yes,
  comment=Letterspace module,
  name=\v!letterspace,
  \s!parent=\v!letterspace,
  setup=list,
  style=no,
  type=module,
  version=hg,
]

%D \macros
%D    {letterspace}
%D
%D \useURL [wschuster] [https://bitbucket.org/wolfs/] [] [Wolfgang Schuster]
%D \from[wschuster]’s {\em fancybreak} and {\em annotation}
%D modules served as the primary source for the following code.
%D You’ll have to thank him if it works and blame me if it doesn’t.

\appendtoks
  \setuevalue{\currentletterspace}{\doletterspace [\currentletterspace]}%
  \setuevalue{\e!start\currentletterspace}{\dostartletterspace[\currentletterspace]}%
  \setuevalue{\e!stop \currentletterspace}{\dostopletterspace}%
\to \everydefineletterspace

\definecharacterkerning [letterspace:current]

\unexpanded\def\doletterspace[#1]{%
  \edef\currentletterspace{#1}%
  \dosingleempty\dodoletterspace%
}

\def\dodoletterspace[#1]{%
  \iffirstargument
    \doifassignment{#1}{%
      \setupletterspace[\currentletterspace][#1]%
    }%
  \fi
  \dododoletterspace%
}

\def\dododoletterspace#1{%
  \def\currentobject{#1}%
  \dontleavehmode
  \setupcharacterkerning[letterspace:current][factor=\letterspaceparameter{spacefactor}]%
  \def\letterspace_setstuff{%
    \setcharacterkerning[letterspace:current]%
    \advance \spaceskip  \letterspaceparameter{textskip}%
    \advance \xspaceskip \letterspaceparameter{textskip}%
  }%
  \ifhmode\ifnum\lastnodetype=\@@gluenode
      \unskip{\letterspace_setstuff\ }%
    \fi
  \fi%
  {\letterspace_setstuff\currentobject}%
  \doifnextspace{%
    {\letterspace_setstuff\ }%
    \gobblespacetokens%
  }%
}

%D This is a partial ripoff of a couple of macros from
%D \type{syst-aux.mkiv}.
%D \useURL [flet] [http://www.tug.org/TUGboat/Articles/tb09-3/tb22bechtolsheim.pdf] [] [\type{futurelet}]
%D Very helpful for further understanding of what’s exactly going
%D on: Stephan von Bechtolsheim’s tutorial on \from[flet].

\def\doifnextspace#1{%
  \def\!!string{#1}%
  \futurelet\nexttoken\inspectnexttoken%
}

\def\inspectnexttoken{%
  \ifx\nexttoken\blankspace
    \@EA\!!string
  \fi%
}

%D \macros
%D    {startletterspace,stopletterspace}
%D
%D These rely even more shamelessly on \from[wschuster]’s code
%D from the {\em fancybreak} module.

\unexpanded\def\dostartletterspace[#1]{%
  \edef\currentletterspace{#1}%
  \dosingleempty\dodostartletterspace%
}

\def\dodostartletterspace[#1]{%
  \iffirstargument
    \setupletterspace[\currentletterspace][#1]%
  \fi
  \dododoletterspace\bgroup%
}

\let\dostopletterspace\egroup

%D \macros
%D    {setupletterspace}
%D
%D Initial setup.
%D Setting the normal inline letterspacing factor
%D \type{textfactor} and a separate factor for capital spacing
%D \type{capfactor}.


\setupletterspace [%
  capfactor=.05,
  capskip=.33em,
  textfactor=.125,
  textskip=.33em,
  shortcommands=false, % “true” | “yes” | “yep” -- defaults to “false”
]

\defineletterspace[\v!letterspace]

\def\letterspace_truestrings{true,yep,yes}

\def\letterspace_define_shortcommands{%
  \doifinset{\letterspaceparameter{shortcommands}}{\letterspace_truestrings}{%
    \writestatus{letterspace}{enabling short commands}%
    %\global\let\CS\capitalspace%
    \global\let\LS\letterspace%
  }%
}

\appendtoks \letterspace_define_shortcommands \to \everystarttext

\protect \stopmodule \endinput

% vim:ft=context:sw=2:ts=2