colo-ext.mkiv / last modification: 2020-01-30 14:16
%D \module
%D   [       file=colo-ext, % mostof thsi code used to be in colo-ini.tex
%D        version=1997.04.01,
%D          title=\CONTEXT\ Color Macros,
%D       subtitle=Extras,
%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.

\writestatus{loading}{ConTeXt Color Macros / Extras}

\unprotect

%D \macros
%D   {negatecolorcomponent, negativecolorbox}
%D
%D Sometimes, especially when we deal with typesetting
%D devices, we want to reverse the color scheme. Instead of
%D recalculating all those colors, we use a quick and dirty
%D approach:
%D
%D \starttyping
%D \negativecolorbox0
%D \stoptyping
%D
%D will negate the colors in box zero.

\unexpanded\def\negatecolorbox#1% or just set attr of #1
  {\setbox#1\hpack to \wd#1%
     {\scratchdimen\wd#1\relax
      \startnegative % might change
      \blackrule[\c!color=\s!white,\c!height=\ht#1,\c!depth=\dp#1,\c!width=\scratchdimen]%
      \hskip-\scratchdimen
      \leaders\box#1\hfill% this triggers application to the box .. a real dirty hack!
      \stopnegative}}

%D There are in principle two ways to handle overprint: bound to colors
%D or independent. For the moment we only support independent overprint
%D handling. Here we deal with a per-document setting.

%D We can move the stack and attribute setting to the \LUA\ end.

\installcorenamespace{colorintent}

\unexpanded\def\registercolorintent#1#2% \relax is needed !
  {\setevalue{\??colorintent#1}{\attribute\colorintentattribute\clf_registercolorintent{#2}\relax}}

\unexpanded\def\colo_intents_set
  {\clf_enablecolorintents
   \unexpanded\gdef\colo_intents_set##1{\csname\??colorintent##1\endcsname}%
   \colo_intents_set}

\registercolorintent{knockout} {knockout}
\registercolorintent{overprint}{overprint}

\installattributestack\colorintentattribute

\setevalue{\??colorintent\v!none}{\attribute\colorintentattribute\attributeunsetvalue} % or reset? used at all?

\unexpanded\def\startcolorintent[#1]%
  {\pushattribute\colorintentattribute
   \colo_intents_set{#1}}

\unexpanded\def\stopcolorintent
  {\popattribute\colorintentattribute}

\unexpanded\def\startoverprint{\startcolorintent[\v!overprint]}
\unexpanded\def\startknockout {\startcolorintent[\v!knockout ]}

\let\stopoverprint\stopcolorintent
\let\stopknockout \stopcolorintent

\let\starttextcolorintent\relax
\let\stoptextcolorintent \relax

\appendtoks
    \colo_intents_set_text
\to \everysetupcolors

\let\p_colo_intent\empty

\def\colo_intents_set_text
  {\edef\p_colo_intent{\colorsparameter\c!intent}%
   \ifx\p_colo_intent\v!none \else
     \unexpanded\xdef\starttextcolorintent{\colo_intents_set{\p_colo_intent}}%
     \glet\colo_intents_set_text\relax
     \colo_intents_set\p_colo_intent
   \fi}

\appendtoks \starttextcolorintent \to \everystarttextproperties
\appendtoks \stoptextcolorintent  \to \everystoptextproperties

\setupcolors
  [\c!intent=\v!none]

\protect \endinput