%D \module
%D   [       file=attr-alt,
%D        version=2007.06.06,
%D          title=\CONTEXT\ Attribute Macros,
%D       subtitle=Alternates,
%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 Attribute Macros / Alternates}

\registerctxluafile{attr-alt}{autosuffix}

%D The main reason for providing this is that we need to make sure we have no
%D dangling end markers when we cross a page. Public viewers don't seem to support
%D actual text at all and acrobat has some funny selection issues.
%D
%D \starttyping
%D test
%D     \startalternate[text={A}]
%D         \dorecurse{10}{A }
%D         \startalternate[text={B}]
%D             \dorecurse{10}{B }
%D         \stopalternate
%D         \dorecurse{10}{A }
%D     \stopalternate
%D test \par
%D \stoptyping
%D
%D \starttyping
%D test \startalternate[text={e=mc^2}]!$e=mc^2$\stopalternate\par
%D test \alternate{e=mc^2}{copy:}\nbsp$e=mc^2$\par
%D \stoptyping

\unprotect

\permanent\protected\def\startalternate[#S#1]% maybe better/also: [text={...}]
  {\begingroup
   \getdummyparameters[\c!text=,#1]%
   \clf_setalternate text {\dummyparameter\c!text}\relax}

\permanent\protected\def\stopalternate
  {\endgroup}

\permanent\protected\def\alternate#1%
  {\groupedcommand{\clf_setalternate text {#1}\relax}{}}

\permanent\protected\def\setalternate  #1{\clf_setalternate text {#1}\relax}
\permanent\protected\def\resetalternate  {\clf_resetalternate}

\protect \endinput