%D \module
%D   [      file=s-system-units.mkxl,
%D        version=2023.08.16,
%D          title=\CONTEXT\ Style File,
%D       subtitle=System Units,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

% \definepalet
%   [unitclasses]
%   [1=darkred,    % tex
%    2=darkblue,   % pdftex
%    3=darkgreen,  % luametatex
%    4=darkgray]   % user

\unprotect

\newdimension \unitsmapwidth

\permanent\tolerant\protected\def\showunitsmap[#1]%
  {\vpack\bgroup \forgetall
   \ttx \setupinterlinespace
   \global\unitsmapwidth40\emwidth
   \hpack to \unitsmapwidth\bgroup
     \kern\emwidth
     \localcontrolledloop\alowercaseasciicode\zlowercaseasciicode \plusone
       {\hss\char\currentloopiterator\hss}%
   \egroup
   \ifcstok{#1}\v!tight\globaldonefalse\else\globaldonetrue\fi
   \localcontrolledloop\alowercaseasciicode\zlowercaseasciicode\plusone
     {\ifglobaldone\globalfoundtrue\else\globalfoundfalse\fi
      \setbox\scratchbox\hpack to \unitsmapwidth\bgroup
      \char\currentloopiterator
      \bf
      \hss
      \localcontrolledloop\alowercaseasciicode\zlowercaseasciicode\plusone
        {\scratchcounter\associateunit\numexpr
           (\previousloopiterator\plusone-\alowercaseasciicode)*26+%
           (\currentloopiterator         -\alowercaseasciicode)%
         \relax
         \hss
         \ifzeronum\scratchcounter
           \kern\emwidth
         \else
           \begingroup
           \ifcase\scratchcounter\or\darkred\or\darkblue\or\darkgreen\else\darkgray\fi
           \char\previousloopiterator\plusone
           \char\currentloopiterator
           \endgroup
           \globalfoundtrue
         \fi
         \hss}%
      \egroup
      \ifglobalfound
        \box\scratchbox
      \fi}%
   \egroup}

\permanent\protected\def\showunitsmaplegend
  {\hpack\bgroup
     \ttx\setstrut\white
     \unitsmapwidth.25\unitsmapwidth
     \backgroundline[darkred]  {\strut\hbox to \unitsmapwidth{\hss        tex\hss}}%
     \backgroundline[darkblue] {\strut\hbox to \unitsmapwidth{\hss     pdftex\hss}}%
     \backgroundline[darkgreen]{\strut\hbox to \unitsmapwidth{\hss luametatex\hss}}%
     \backgroundline[darkgray] {\strut\hbox to \unitsmapwidth{\hss    context\hss}}%
   \egroup}

\protect

\continueifinputfile{s-system-units.mkxl}

\starttext

\startTEXpage[offset=1ts]
    \showunitsmap
    \showunitsmaplegend
\stopTEXpage

\startTEXpage[offset=1ts]
    \showunitsmap[tight]
    \showunitsmaplegend
\stopTEXpage

\stoptext

