%D \module
%D   [       file=typo-krn,
%D        version=2009.03.27, % code moved from core-spa.mkiv
%D          title=\CONTEXT\ Typesetting Macros,
%D       subtitle=Spacing,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright=\PRAGMA]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

\writestatus{loading}{ConTeXt Typesetting Macros / Kerning}

\unprotect

\registerctxluafile{typo-krn}{1.001}

\definesystemattribute[kern]

% more
%
% {\setcharacterkerning[extrakerning]\input davis\relax}

\newcount \maxcharacterkerningid

\def\definecharacterkerning
  {\dosingleargument\dodefinecharacterkerning}

\def\dodefinecharacterkerning[#1]%
  {\ifcsname\??ck#1\endcsname \else
     \global\advance\maxcharacterkerningid\plusone
     \setxvalue{\??ck:#1}{\the\maxcharacterkerningid}%
   \fi}

\def\setupcharacterkerning
  {\dodoubleargument\dosetupcharacterkerning}

\def\dosetupcharacterkerning[#1][#2]%
  {\ifcsname\??ck:#1\endcsname
     \begingroup
     \getparameters[\??ck][\c!factor=0,#2]%
     \ctxlua{kerns.setspacing(\getvalue{\??ck:#1},\@@ckfactor)}%
     \endgroup
   \fi}

\def\setcharacterkerning
  {\ctxlua{kerns.enabled=true}%
   \gdef\setcharacterkerning[##1]{\dosetattribute{kern}{\csname\??ck:##1\endcsname}}%
   \setcharacterkerning}

\letvalue{\??ck:\s!reset}\attributeunsetvalue

\definecharacterkerning[extrakerning]

\setupcharacterkerning[extrakerning][\c!factor=.125]

\protect \endinput