%D \module
%D   [       file=prop-lay,
%D        version=2003.04.20,
%D          title=\CONTEXT\ Property Macros,
%D       subtitle=Layers,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
%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 Property Macros / Layers}

%D Highly experimental, will probably change/evolve. Also, quite certainly
%D we will no longer share code between mkii and mkiv.

% test, nesting is somewhat special with layers
%
% \defineproperty[hans][layer]
% \defineproperty[ton] [layer]
% \setupheadertexts[no layer]
% 1\startproperty[hans]2\startproperty[ton]3\stopproperty4\stopproperty5

\unprotect

% will be redone ... no longer using property mechanism (less clashes)

\let\currentviewerlayer\empty

\appendtoks
    \let\currentviewerlayer\empty
\to \everypagebody

\unexpanded\def\startlayerproperty
  {\pushmacro\currentviewerlayer % grouped (used in interaction)
   \let\currentlayerproperty\currentproperty % can be cross group
   \dotriggerviewerlayer\currentlayerproperty}

\unexpanded\def\stoplayerproperty
  {\popmacro\currentviewerlayer % grouped (used in interaction)
   \let\currentlayerproperty\previousproperty % can be cross group
   \dotriggerviewerlayer\currentlayerproperty}

\def\checklayerproperty % could be made more clever
  {\registerviewerlayer\currentproperty\currentproperty
   \ctxlua{backends.codeinjections.defineviewerlayer{
     tag       = "\currentproperty",
     title     = "\checkedpropertyparameter\c!title\currentproperty",
     visible   = "\checkedpropertyparameter\c!state\v!start",
     kind      = 0, % 1 == frozen
     printable = "\checkedpropertyparameter\v!printable\v!yes"  % v! looks wrong
   }}}

%D \starttext
%D
%D \setuppapersize[S4][S4]
%D \setuplayout[middle]
%D \setupcolors[state=start]
%D \setupinteraction[state=start,color=,contrastcolor=]
%D
%D \defineproperty [L1] [layer] [title=layer 1]
%D \defineproperty [L2] [layer] [title=layer 2]
%D
%D \button{HIDE   L1}[HideLayer{L1}]
%D \button{VIDE   L1}[VideLayer{L1}]
%D \button{TOGGLE L1}[ToggleLayer{L1}]
%D
%D \button{HIDE L2}[HideLayer{L2}]
%D \button{VIDE L2}[VideLayer{L2}]
%D \button{TOGGLE L2}[ToggleLayer{L2}]
%D
%D \noheaderandfooterlines \centerbox{\startoverlay
%D   {\definedfont[Mono at 150pt]%
%D    \startproperty[L1]\red   TEST\stopproperty}
%D   {\definedfont[Mono at 150pt]%
%D    \startproperty[L2]\green TEST\stopproperty}
%D \stopoverlay} \page
%D
%D \noheaderandfooterlines \centerbox{\startoverlay
%D   {\definedfont[Mono at 15pt]%
%D    \goto{\startproperty[L1]\red   TEST\stopproperty}[CloseDocument]}
%D   {\definedfont[Mono at 15pt]%
%D    \goto{\startproperty[L2]\green TEST\stopproperty}[CloseDocument]}
%D \stopoverlay} \page
%D
%D \startproperty[L1]
%D   level 1 \startproperty[L2]level 2 \stopproperty level 1
%D \stopproperty
%D
%D \startproperty[L1]
%D   level 1 \page \startproperty[L2]level 2 \stopproperty level 1
%D \stopproperty
%D
%D \stoptext

\def\doinitializelayoutcomponent#1#2%
  {\ctxlua{backends.codeinjections.defineviewerlayer{% this will move to the lua end i.e be merged with register
     tag       = "#1:#2",
     title     = "#1 #2",
     visible   = "\v!start",
     kind      = 0, % 1 == frozen
     printable = "\v!yes"
   }}%
   \edef\layoutcomponentboxattribute{attr \viewerlayerattribute \ctxlua{tex.write(viewerlayers.register('#1:#2',true))}\relax}%
   \expandafter\glet\csname\??ly>#1:#2\endcsname\layoutcomponentboxattribute}

\def\dosetlayoutcomponentattribute#1#2% make this faster
  {\expandafter\let\expandafter\layoutcomponentboxattribute\csname\??ly>#1:#2\endcsname
   \ifx\layoutcomponentboxattribute\relax
     \doinitializelayoutcomponent{#1}{#2}% get rid of { }
   \fi}

\def\doresetlayoutcomponentattribute
  {\let\layoutcomponentboxattribute\empty}

\let\setlayoutcomponentattribute  \gobbletwoarguments
\let\resetlayoutcomponentattribute\relax
\let\layoutcomponentboxattribute  \empty

\def\showlayoutcomponents
  {\ctxlua{viewerlayers.enable()}%
   \let\setlayoutcomponentattribute  \dosetlayoutcomponentattribute
   \let\resetlayoutcomponentattribute\doresetlayoutcomponentattribute}

\protect \endinput

% \starttext
% \showlayoutcomponents
% \setupinteraction[state=start]
% \setupheadertexts[{\goto{page 1}[page(2)]}]
% test \setlayoutcomponentattribute{test}{aap}\hbox \layoutcomponentboxattribute \bgroup aap
%     \setlayoutcomponentattribute{test}{noot}\hbox \layoutcomponentboxattribute \bgroup noot
%     \setlayoutcomponentattribute{test}{mies}\hbox \layoutcomponentboxattribute \bgroup mies
%     \egroup noot \egroup aap \egroup
% test \setlayoutcomponentattribute{test}{hans}\hbox \layoutcomponentboxattribute \bgroup aap \hbox{!} aap\egroup
% test \page test \page
% \stoptext