%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

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

\unprotect

%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”
]

%D Defining two letterspace settings.

\definecharacterkerning [textspace]
\definecharacterkerning [capspace]

\setupcharacterkerning [textspace] [factor=\letterspaceparameter{textfactor}]
\setupcharacterkerning  [capspace] [factor=\letterspaceparameter{capfactor}]

\unexpanded\def\letterspace_letterspace#1{%
  \letterspace_do_letterspace{l}{#1}%
}

\unexpanded\def\letterspace_capitalspace#1{%
  \letterspace_do_letterspace{c}{#1}%
}

\let \letterspace\letterspace_letterspace
\let\capitalspace\letterspace_capitalspace

\def\letterspace_do_letterspace#1#2{%
  \doif{#1}{l}{%
    \let\currentletterspacecmd\letterspace_dodo_letterspace%
  }%
  \doif{#1}{c}{%
    \let\currentletterspacecmd\letterspace_dodo_capitalspace%
  }%
  \ifhmode\ifnum\lastnodetype=\@@gluenode
      \unskip{\currentletterspacecmd\ }%
    \fi
  \fi%
  {\currentletterspacecmd#2}%
  \doifnextspace{%
    {\currentletterspacecmd\ }%
    \gobblespacetokens%
  }%
}

\def\letterspace_dodo_letterspace{%
  \dontleavehmode \setcharacterkerning[textspace]%
  \advance \spaceskip  \letterspaceparameter{textskip}%
  \advance \xspaceskip \letterspaceparameter{textskip}%
}%

\def\letterspace_dodo_capitalspace{%
  \dontleavehmode \setcharacterkerning[capspace]%
  \advance \spaceskip  \letterspaceparameter{capskip}%
  \advance \xspaceskip \letterspaceparameter{capskip}%
}%

%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%
}

\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