%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][public]

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

\unexpanded\def\definecharacterkerning
  {\dodoubleargument\dodefinecharacterkerning}

\def\dodefinecharacterkerning[#1][#2]%
  {\getparameters[\??ck#1][\c!factor=0.125,#2]%
   \setuvalue{\??ck:#1}{\dosetcharacterkerning{#1}}}

\unexpanded\def\setupcharacterkerning
  {\dodoubleargument\dosetupcharacterkerning}

\def\dosetupcharacterkerning[#1][#2]%
  {\ifcsname\??ck:#1\endcsname
     \getparameters[\??ck#1][#2]%
   \else
     \dodefinecharacterkerning[#1][#2]% bonus
   \fi}

\unexpanded\def\dosetcharacterkerning#1%
  {\ctxlua{typesetters.kerns.set(\csname\??ck#1\c!factor\endcsname)}}

\unexpanded\def\setcharacterkerning[#1]%
  {\csname\??ck:#1\endcsname}

\unexpanded\def\resetcharacterkerning % fast one
  {\attribute\kernattribute\attributeunsetvalue}

\letvalue{\??ck\s!reset\c!factor}\attributeunsetvalue % trick

\appendtoks
    \resetcharacterkerning
\to \everyresettypesetting

\definecharacterkerning [extrakerning] [\c!factor=.125] % used in manuals

%D Added after discussion on list (posted by WS, adapted abit by HH)
%D \unknown\ this needs to be interfaced (\type {\v!kerncharacters}).
%D
%D \starttyping
%D \setuphead[section][style=\sca,textstyle={\kerncharacters[.5]}] \section{Section}
%D \stoptyping
%D
%D We could combine this with the previous definition command but
%D then we alwasy would get a command defined which is not beforehand
%D a good idea.

\def\v!kerncharacters{kerncharacters} % no time now for translations

\definecharacterkerning [\v!kerncharacters] [\c!factor=.125]

\unexpanded\def\kerncharacters
  {\dosingleempty\dokerncharacters}

\def\dokerncharacters[#1]%
  {\groupedcommand{\dodokerncharacters{#1}}\donothing}

\def\dodokerncharacters#1%
  {\iffirstargument
     \setupcharacterkerning[\v!kerncharacters][\c!factor=#1]%
   \fi
   \setcharacterkerning[\v!kerncharacters]}

\protect \endinput