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

%D Currently there is a limitation in mixed inline usage. This has to do with the fact
%D that we have a stacked model but cannot determine where to revert to (as we can
%D have AABBCCAA ranges). Maybe I'll solve that one day. It only affects nested inline
%D layers and these make not much sense anyway. We'd have to store the complete nesting
%D stack in the attribute in order to be able to cross pages and that demands a new
%D mechanism.

\unprotect

\registerctxluafile{attr-lay}{autosuffix}

% needs to work over stopitemize grouping etc

\installcorenamespace{viewerlayer}

\installcommandhandler \??viewerlayer {viewerlayer} \??viewerlayer

\setupviewerlayer
  [\c!state=\v!start,
   \c!title=,
   \c!export=\v!yes, % exportable is ugly
   \c!printable=\v!yes,
   \c!scope=\v!local, % maybe global but needs checking with layout
   \c!method=\v!none]

\permanent\def\attr_layoutcomponent_whatever#1%
  {#1%
    tag       {\currentviewerlayer}%
    title     {\viewerlayerparameter\c!title}%
    visible   {\viewerlayerparameter\c!state}%
    editable  {\v!yes}%
    export    {\viewerlayerparameter\c!export}%
    printable {\viewerlayerparameter\c!printable}%
    scope     {\viewerlayerparameter\c!scope}%
  \relax}

\appendtoks
  \attr_layoutcomponent_whatever\clf_defineviewerlayer
  \ifcstok{\viewerlayerparameter\c!method}\v!command
    \protected\frozen\instance\xdefcsname\e!start\currentviewerlayer\endcsname{\startviewerlayer[\currentviewerlayer]}%
  \else
    \protected\frozen\instance\xdefcsname\e!stop \currentviewerlayer\endcsname{\stopviewerlayer}%
  \fi
\to \everydefineviewerlayer

\appendtoks
  \attr_layoutcomponent_whatever\clf_setupviewerlayer
\to \everysetupviewerlayer

% \startviewerlayer[#1] % defined at lua end
% \stopviewerlayer      % defined at lua end

\permanent\protected\def\viewerlayer[#1]%
  {\groupedcommand{\startviewerlayer[#1]}{\stopviewerlayer}}

% some day we will keep this at the lua end as the info is only needed there

\newtoks\currentviewerlayertoks % soon we can set macros at the lua end

\def\currentviewerlayer{\the\currentviewerlayertoks}

\appendtoks
    \lettonothing\currentviewerlayer
\to \everybeforepagebody

% layout components are implemented rather directly (speed)

\installcorenamespace{layoutcomponentattribute}

\mutable\lettonothing\layoutcomponentboxattribute

\permanent\def\attr_layoutcomponent_initialize#1%
  {\edef\layoutcomponentboxattribute{\clf_definedlayoutcomponent{#1}}%
   \edef\layoutcomponentboxattribute{attr \viewerlayerattribute \layoutcomponentboxattribute\relax}%
   \gletcsname\??layoutcomponentattribute#1\endcsname\layoutcomponentboxattribute}

\permanent\def\attr_layoutcomponent_set#1% make this faster
  {\expandafter\let\expandafter\layoutcomponentboxattribute\csname\??layoutcomponentattribute#1\endcsname
   \ifrelax\layoutcomponentboxattribute
     \attr_layoutcomponent_initialize{#1}% get rid of { }
   \fi}

\permanent\def\attr_layoutcomponent_reset
  {\lettonothing\layoutcomponentboxattribute}

\permanent\let         \setlayoutcomponentattribute  \gobbleoneargument
\permanent\let         \resetlayoutcomponentattribute\relax
          \lettonothing\layoutcomponentboxattribute

\permanent\protected\def\showlayoutcomponents
  {\enforced\let\setlayoutcomponentattribute  \attr_layoutcomponent_set
   \enforced\let\resetlayoutcomponentattribute\attr_layoutcomponent_reset}

\protected\def\attr_layoutcomponent_cleanup
  {\clf_cleanuplayers}

\appendtoks
    \attr_layoutcomponent_cleanup
\to \everyshipout

\protect \endinput