%D \module
%D   [       file=scrn-int,
%D        version=2011.02.27, % moved from scrn-int
%D          title=\CONTEXT\ Core Macros,
%D       subtitle=Widgets,
%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 Interaction Macros / Widgets}

\registerctxluafile{scrn-wid}{1.001}

% todo: expansion in comments (default is expanded)

\unprotect

%D Attachments (mkiv upgraded):
%D
%D As usual in \CONTEXT\ we separate the general definition (frontend)
%D and the rendering (backend).

% old but stil valid method:
%
% \useattachment[test.tex]
% \useattachment[whatever][test.tex]
% \useattachment[whatever][newname][test.tex]
% \useattachment[whatever][title][newname][test.tex]
%
% new method:
%
% \registerattachment[sometag][specification] % name file author title subtitle
%
% \attachment[sometag][extra specs]
% \attachment[test.tex]
% \attachment[file=test.tex]
% \attachment[file=test.tex,method=hidden]
% \attachment[name=newname,file=test.tex]
% \attachment[title=mytitle,name=newname,file=test.tex]
%
% indirect
%
% \defineattachment[whatever5][file=test.tex] \attachment[whatever5][method=hidden]
% \defineattachment[whatever5][file=test.tex,method=hidden] \attachment[whatever5]
%
% direct (no definitions)
%
% \attachment[test][file=oeps.tex,title=Oeps,author=Hans,subtitle=TeX File,method=hidden]
% \attachment[label=test,file=oeps.tex,title=Oeps,author=Hans,subtitle=TeX File,method=hidden]
%
% autolabel:
%
% \attachment[file=oeps.tex,title=Oeps,author=Hans,subtitle=TeX File,method=hidden]
%
% % \setupattachments[\c!symbol={symbol-normal,symbol-down}]

% startattachment -> temp file

\newbox\scrn_attachment_box_collect
\newbox\scrn_attachment_box_link
\newbox\scrn_attachment_box_symbol

\installcommandhandler\??at{attachment}\??at

\let\setupattachments\setupattachment % convenience and compatibility

\setupattachment
  [\c!state=\v!start,
   \c!color=\interactionparameter\c!color,
  %\c!textlayer=,
  %\c!symbol=,
  %\c!title=,
  %\c!subtitle=,
  %\c!file=, % input filename
  %\c!name=, % new filename
  %\c!author=,
  %\c!method=, % \v!hidden = not in menu
  %\c!buffer=
   \c!symbol=,
   \c!distance=1em,
   \c!width=\v!fit,
   \c!height=\v!fit,
   \c!depth=\v!fit,
   \c!location=\v!high]

\unexpanded\def\registerattachment
  {\dodoubleempty\scrn_attachment_register}

\def\scrn_attachment_register[#tag][#settings]% we save (globally) at the lua end
  {\ifsecondargument
     \begingroup
     \def\currentattachment{_}%
     \setupattachment[_][#settings,\s!parent=\??at]%
     \ctxcommand{registerattachment{
        tag      = "#tag",
        title    = "\attachmentparameter\c!title",
        subtitle = "\attachmentparameter\c!subtitle",
        author   = "\attachmentparameter\c!author",
        file     = "\attachmentparameter\c!file",
        name     = "\attachmentparameter\c!name",
        buffer   = "\attachmentparameter\c!buffer",
     }}%
     \endgroup
   \fi}

\appendtoks
    \setuevalue         \currentattachment {\scrn_attachment_direct{\currentattachment}}%
    \setuevalue{\e!start\currentattachment}{\scrn_attachment_start {\currentattachment}}%
    \setuevalue{\e!stop \currentattachment}{\scrn_attachment_stop                     }%
\to \everydefineattachment

\unexpanded\def\scrn_attachment_direct#tag%
  {\edef\currentattachment{#tag}%
   \doifelselocation
     {\dodoubleempty\scrn_attachment_direct_status}
     {\dodoubleempty\scrn_attachment_direct_ignore}}

\def\scrn_attachment_direct_status
  {\doifelse{\attachmentparameter\c!state}\v!start
     \scrn_attachment_direct_indeed
     \scrn_attachment_direct_ignore}

\def\scrn_attachment_direct_indeed[#registered][#settings]%
  {\bgroup
   \doifelsenothing{#registered}
      {\scrn_attachment_inject[\v!auto][]}
      {\doifassignmentelse{#registered}
         {\scrn_attachment_inject[\v!auto][#registered]}
         {\scrn_attachment_inject[#registered][#settings]}}%
   \egroup}

\def\scrn_attachment_direct_ignore[#tag][#settings]%
  {}

\unexpanded\def\scrn_attachment_start#tag%
  {\edef\currentattachment{#tag}%
   \doifelselocation
     {\dodoubleempty\scrn_attachment_start_indeed}
     {\dodoubleempty\scrn_attachment_start_ignore}}

\unexpanded\def\scrn_attachment_stop
  {}

\def\scrn_attachment_start_indeed
  {\doif{\attachmentparameter\c!state}\v!start
     {\scrn_attachment_start_indeed}
     {\scrn_attachment_start_ignore}}

\def\scrn_attachment_start_indeed[#registered][#settings]%
  {\bgroup
   \doifelsenothing{#registered}
     {\def\scrn_attachment_stop{\scrn_attachment_inject[\v!auto][\c!buffer=\v!attachment]\egroup}}%
     {\doifassignmentelse{#registered}
        {\def\scrn_attachment_stop{\scrn_attachment_inject[\v!auto][\c!buffer=\v!attachment,#registered]\egroup}}%
        {\def\scrn_attachment_stop{\scrn_attachment_inject[#registered][\c!buffer=\v!attachment,#settings]\egroup}}}%
   \dostartbuffer[\v!attachment][\e!start\currentattachment][\e!stop\currentattachment]}

\def\scrn_attachment_start_ignore
  {\expandafter\gobbleuntil\csname\e!stop\currentattachment\endcsname}

\def\scrn_attachment_inject[#registered][#settings]%
  {\edef\currentattachmentregistered{#registered}%
   \setupattachment[\currentattachment][#settings]%
   \expandcheckedcsname{scrn_attachment_method_}{\attachmentparameter\c!method}\v!normal}

\setvalue{scrn_attachment_method_\v!normal}%
  {\edef\currentattachmentsymbol{\attachmentparameter\c!symbol}%
   \edef\currentattachmentwidth {\attachmentparameter\c!width }%
   \edef\currentattachmentheight{\attachmentparameter\c!height}%
   \edef\currentattachmentdepth {\attachmentparameter\c!depth }%
   \ifx\currentattachmentsymbol\empty
     \ifx\currentattachmentwidth \v!fit\edef\currentattachmentwidth {.5em}\fi
     \ifx\currentattachmentheight\v!fit\edef\currentattachmentheight{.5em}\fi
     \ifx\currentattachmentdepth \v!fit\let \currentattachmentdepth \zeropoint\fi
   \else
     \ctxcommand{presetsymbollist("\attachmentparameter\c!symbol")}%
     % we cannot yet ask for the wd/ht/dp of an xform else we could use those
     \setbox\scrn_attachment_box_symbol\hbox{\symbol[\lastpredefinedsymbol]}%
     \ifx\currentattachmentwidth \v!fit\edef\currentattachmentwidth {\wd\scrn_attachment_box_symbol}\fi
     \ifx\currentattachmentheight\v!fit\edef\currentattachmentheight{\ht\scrn_attachment_box_symbol}\fi
     \ifx\currentattachmentdepth \v!fit\edef\currentattachmentdepth {\dp\scrn_attachment_box_symbol}\fi
   \fi
   \ctxcommand{insertattachment{
     tag               = "\currentattachment",
     registered        = "\currentattachmentregistered",
     width             = \number\dimexpr\currentattachmentwidth \relax,
     height            = \number\dimexpr\currentattachmentheight\relax,
     depth             = \number\dimexpr\currentattachmentdepth \relax,
     color             = "\attachmentparameter\c!color",
     colormodel        = \number\currentcolormodel,
     colorvalue        = \thecolorattribute{\attachmentparameter\c!color},
     transparencyvalue = \thetransparencyattribute{\attachmentparameter\c!color},
     symbol            = "\currentattachmentsymbol",
     layer             = "\attachmentparameter\c!textlayer",
     % these will be overloaded by registered when available
     title             = "\attachmentparameter\c!title",
     subtitle          = "\attachmentparameter\c!subtitle",
     author            = "\attachmentparameter\c!author",
     file              = "\attachmentparameter\c!file",
     name              = "\attachmentparameter\c!name",
     buffer            = "\attachmentparameter\c!buffer",
   }}%
   \setbox\scrn_attachment_box_link\hbox{\scrn_attachment_place}%
   \wd\scrn_attachment_box_link\currentattachmentwidth
   \ht\scrn_attachment_box_link\currentattachmentheight
   \dp\scrn_attachment_box_link\currentattachmentdepth
   \box\scrn_attachment_box_link}

\setvalue{scrn_attachment_method_\v!hidden}%
  {\ctxcommand{insertattachment{
     tag        = "\currentattachment",
     registered = "\currentattachmentregistered",
     method     = "\v!hidden"
  }}}

\def\scrn_attachment_place
  {\executeifdefined
     {\??at:\c!location:\attachmentparameter\c!location}\hbox
     {\box\scrn_attachment_box_link}}

\setvalue{\??at:\c!location:\v!inmargin   }{\inmargin     }
\setvalue{\??at:\c!location:\v!leftedge   }{\inleftedge   }
\setvalue{\??at:\c!location:\v!rightedge  }{\inrightedge  }
\setvalue{\??at:\c!location:\v!leftmargin }{\inleftmargin }
\setvalue{\??at:\c!location:\v!rightmargin}{\inrightmargin}
\setvalue{\??at:\c!location:\v!high       }{\high}
\setvalue{\??at:\c!location:\v!none       }{\scrn_attachment_collect}

\def\scrn_attachment_collect#content%
  {\global\setbox\scrn_attachment_box_collect\hbox\bgroup
     \ifvoid\scrn_attachment_box_collect\else
       \box\scrn_attachment_box_collect
       \hskip\attachmentparameter\c!distance
     \fi
     #content%
   \egroup}

\unexpanded\def\placeattachments
  {\ifvoid\scrn_attachment_box_collect\else
     \box\scrn_attachment_box_collect
   \fi}

\defineattachment[attachment]

% \ifx\currentinterface\defaultinterface \else
%     \defineattachment[\v!attachment]
% \fi

% backward compatible:

\unexpanded\def\useattachment
  {\doquadrupleempty\scrn_attachment_use}

\def\scrn_attachment_use[#tag][#title][#name][#file]%
  {\iffourthargument
     \registerattachment[#tag][title=#title,name=#name,file=#file]%
   \else\ifthirdargument
     \registerattachment[#tag][title=#title,name=#title,file=#name]%
   \else\ifsecondargument
     \registerattachment[#tag][title=#title,name=#title,file=#title]%
   \else
     \registerattachment[#tag][title=#title,name=#tag,file=#tag]%
   \fi\fi\fi}

%D Comments:

% test
%
% \startcomment
%   hello beautiful\\world
% \stopcomment
%
% test
%
% \startcomment[hello]
%   hello << eerste >>
%   beautiful
%   world
% \stopcomment
%
% test
%
% \startcomment[hello][color=green,width=10cm,height=3cm]
%   hello
%   beautiful
%   world
% \stopcomment
%
% test
%
% \startcomment[hello][color=red,width=4cm,height=3cm]
%   hello
%
%   beautiful
%
%   world
% \stopcomment
%
% test
%
% \startcomment[symbol=Balloon]
%   Do we want this kind of rubish?
% \stopcomment
%
% test
%
% \definesymbol [comment-normal][{\externalfigure[cow.pdf]}]
% \definesymbol [comment-down]  [{\externalfigure[cow.pdf]}]
%
% \def\CowSymbol#1#2%
%  {\scale
%     [\c!height=#1]
%     {\startMPcode
%        loadfigure "koe.mp" number 1 ;
%        refill currentpicture withcolor #2 ;
%      \stopMPcode}}
%
% \definesymbol [comment-normal]
%   [\CowSymbol{4ex}{red}]
%
% \definesymbol [comment-down]
%   [\CowSymbol{4ex}{green}]
%
% \setupcomment
%   [\c!symbol={comment-normal,comment-down},
%    \c!option=\v!buffer]
%
% \startcomment[hello]
%     oeps
% \stopcomment
%
% test
%
% \setupcomment
%   [\c!symbol=normal,
%    \c!option=max,width=10cm]
%
% \startcomment[hello]
%     oeps
% \stopcomment
%
% test

\installcommandhandler\??cc{comment}\??cc

\newbox\scrn_comment_box_collect
\newbox\scrn_comment_box_rendering
\newbox\scrn_comment_box_link
\newbox\scrn_comment_box_symbol

\setupcomment
  [\c!state=\v!start,
   \c!distance=1em,
   \c!color=\interactionparameter\c!color,
   \c!space=\v!no,
   \c!symbol=,
  %\c!title=,
  %\c!option=,
  %\c!textlayer=,
   \c!width=\v!fit,
   \c!height=\v!fit,
   \c!depth=\v!fit,
   \c!nx=40,
   \c!ny=10,
   \c!location=\v!high]

\presetlocalframed[\??cc]

\appendtoks
    \setuevalue         \currentcomment {\scrn_comment_argument{\currentcomment}}%
    \setuevalue{\e!start\currentcomment}{\scrn_comment_start   {\currentcomment}}%
    \setuevalue{\e!stop \currentcomment}{\scrn_comment_stop                     }%
\to \everydefinecomment

\unexpanded\def\scrn_comment_argument#category%
  {\def\currentcomment{#category}%
   \doifelselocation
     {\dodoubleempty\scrn_comment_argument_status}
     {\dodoubleempty\scrn_comment_argument_ignore}}

\def\scrn_comment_argument_status
  {\doifelse{\commentparameter\c!state}\v!start
     \scrn_comment_argument_indeed
     \scrn_comment_argument_ignore}

\def\scrn_comment_argument_indeed[#title][#settings]#text%
  {\doifassignmentelse{#title}
     {\setupcomment[\currentcomment][#title]}
     {\setupcomment[\currentcomment][\c!title=#title,#settings]}%
   \ctxlua{buffers.assign("\v!comment",\!!bs#text\!!es)}% todo: expansion control, but expanded by default (xml)
   \scrn_comment_inject
   \ignorespaces}

\def\scrn_comment_argument_ignore[#title][#settings]#text%
  {\ignorespaces}

\unexpanded\def\scrn_comment_start#category%
  {\def\currentcomment{#category}%
   \doifelselocation
     {\dodoubleempty\scrn_comment_start_indeed}
     {\dodoubleempty\scrn_comment_start_ignore}}

\def\scrn_comment_start_indeed
  {\doifelse{\commentparameter\c!state}\v!start
     {\scrn_comment_start_indeed}
     {\scrn_comment_start_ignore}}

\def\scrn_comment_start_indeed[#title][#settings]%
  {\bgroup
   \doifassignmentelse{#title}
     {\setupcomment[\currentcomment][#title]}
     {\setupcomment[\currentcomment][\c!title=#title,#settings]}%
   \def\scrn_comment_stop{\scrn_comment_inject\egroup}%
   \dostartbuffer[\v!comment][\e!start\currentcomment][\e!stop\currentcomment]}

\def\scrn_comment_start_ignore
  {\expandafter\gobbleuntil\csname\e!stop\currentcomment\endcsname}

\unexpanded\def\scrn_comment_stop
  {}

\def\scrn_comment_inject
  {\expandcheckedcsname{scrn_comment_method_}{\commentparameter\c!method}\v!normal}

%D Beware: comments symbols don't scale in acrobat (cf. spec but somewhat
%D weird, esp because for instance attachment symbols do scale).

\setvalue{scrn_comment_method_\v!normal}%
  {\edef\currentcommentsymbol{\commentparameter\c!symbol}%
   \edef\currentcommentwidth {\commentparameter\c!width }%
   \edef\currentcommentheight{\commentparameter\c!height}%
   \edef\currentcommentdepth {\commentparameter\c!depth }%
   \ifx\currentcommentsymbol\empty
     \ifx\currentcommentwidth \v!fit\edef\currentcommentwidth {.5em}\fi
     \ifx\currentcommentheight\v!fit\edef\currentcommentheight{.5em}\fi
     \ifx\currentcommentdepth \v!fit\let \currentcommentdepth \zeropoint\fi
   \else
     \ctxcommand{presetsymbollist("\commentparameter\c!symbol")}%
     % we cannot yet ask for the wd/ht/dp of an xform else we could use those
     \setbox\scrn_comment_box_symbol\hbox{\symbol[\lastpredefinedsymbol]}%
     \ifx\currentcommentwidth \v!fit\edef\currentcommentwidth {\wd\scrn_comment_box_symbol}\fi
     \ifx\currentcommentheight\v!fit\edef\currentcommentheight{\ht\scrn_comment_box_symbol}\fi
     \ifx\currentcommentdepth \v!fit\edef\currentcommentdepth {\dp\scrn_comment_box_symbol}\fi
   \fi
   \ctxcommand{insertcomment{
        tag               = "\currentcomment",
        title             = "\commentparameter\c!title",
        subtitle          = "\commentparameter\c!subtitle",
        author            = "\commentparameter\c!author",
        width             = \number\dimexpr\currentcommentwidth,
        height            = \number\dimexpr\currentcommentheight,
        depth             = \number\dimexpr\currentcommentdepth,
        nx                = \commentparameter\c!nx,
        ny                = \commentparameter\c!ny,
        colormodel        = \number\currentcolormodel,
        colorvalue        = \thecolorattribute{\commentparameter\c!color},
        transparencyvalue = \thetransparencyattribute{\commentparameter\c!color},
        option            = "\commentparameter\c!option", % todo
        symbol            = "\commentparameter\c!symbol",
        buffer            = "\v!comment",
        layer             = "\commentparameter\c!textlayer"
   }}%
   \wd\scrn_comment_box_link\currentcommentwidth
   \ht\scrn_comment_box_link\currentcommentheight
   \dp\scrn_comment_box_link\currentcommentdepth
   \scrn_comment_place}

\setvalue{scrn_comment_method_\v!hidden}%
  {}

% todo: dedicated margin classes

\def\scrn_comment_place
  {\executeifdefined
     {\??cc:\c!location:\commentparameter\c!location}\hbox
     {\hbox{\box\scrn_comment_box_link}}}

\setvalue{\??cc:\c!location:\v!inmargin   }{\inmargin     }
\setvalue{\??cc:\c!location:\v!leftedge   }{\inleftedge   }
\setvalue{\??cc:\c!location:\v!rightedge  }{\inrightedge  }
\setvalue{\??cc:\c!location:\v!leftmargin }{\inleftmargin }
\setvalue{\??cc:\c!location:\v!rightmargin}{\inrightmargin}
\setvalue{\??cc:\c!location:\v!high       }{\high}
\setvalue{\??cc:\c!location:\v!none       }{\scrn_comment_collect}

\def\scrn_comment_collect#content%
  {\global\setbox\scrn_comment_box_collect\hbox\bgroup
     \ifvoid\scrn_comment_box_collect\else
       \box\scrn_comment_box_collect
       \hskip\commentparameter\c!distance
     \fi
     #content%
   \egroup}

\unexpanded\def\placecomments
  {\ifvoid\scrn_comment_box_collect\else
     \box\scrn_comment_box_collect
   \fi}

\definecomment[comment]

% \ifx\currentinterface\defaultinterface \else
%     \definecomment[\v!comment]
% \fi

%D Soundclips:
%D
%D Defining sound tracks:
%D
%D \starttyping
%D \useexternalsoundtrack[label][file]
%D \stoptyping
%D
%D associated actions: StartSound StopSound PauseSound ResumeSound
%D
%D Todo: like external figures, also search on path,
%D although, they need to be present ar viewing time, so ...

\unexpanded\def\useexternalsoundtrack
  {\dodoubleargument\scrn_soundtrack_indeed}

\def\scrn_soundtrack_indeed[#tag][#filename]%
  {\ctxcommand{registersoundclip{
     tag  = "#tag",
     file = "#filename"
   }}}

\def\checksoundtrack#tag% yet untested in mkiv (also move management to lua)
  {\iflocation
     \ctxcommand{insertsoundclip{
       tag    = "#tag",
       repeat = "\@@sdoption", % not entirely ok but works
      }}%
   \fi}

\unexpanded\def\setupexternalsoundtracks
  {\dodoubleargument\getparameters[\??sd]}

\setupexternalsoundtracks
  [\c!option=]

%D Renderings (not yet tested in mkvi):

% Todo: multiple instances and inheritance .. will be done when
% needed i.e. when I see usage.

\let\currentrendering\empty

\definereference[StartCurrentRendering] [\v!StartRendering {\currentrendering}]
\definereference[StopCurrentRendering]  [\v!StopRendering  {\currentrendering}]
\definereference[PauseCurrentRendering] [\v!PauseRendering {\currentrendering}]
\definereference[ResumeCurrentRendering][\v!ResumeRendering{\currentrendering}]

\def\useexternalrendering{\doquadrupleempty\scrn_rendering_use}
\def\setinternalrendering{\dodoubleempty   \scrn_rendering_set}

\def\scrn_rendering_use[#tag][#mime][#file][#option]%
  {\ctxlua{interactions.renderings.register {
      type     = "external",
      label    = "#tag",
      mime     = "#mime",
      filename = "#file",
      option   = "#option",
  }}}

\def\scrn_rendering_set[#tag][#option]% {content}
  {\bgroup
   \dowithnextbox
     {\ctxlua{interactions.renderings.register {
         type     = "internal",
         label    = "#tag",
         mime     = "IRO", % brrr
         filename = "#tag",
         option   = "#option",
      }}%
      \let\objectoffset\zeropoint
      \setobject{IRO}{#tag}\hbox{\box\nextbox}%
      \egroup}%
     \hbox}

\def\renderingtype  #tag{\ctxlua{interactions.renderings.var("#tag","type")}}
\def\renderingoption#tag{\ctxlua{interactions.renderings.var("#tag","option")}}

\def\renderingwidth    {8cm} % will become private
\def\renderingheight   {6cm} % will become private

\unexpanded\def\definerenderingwindow
  {\dodoubleempty\scrn_rendering_define_window}

\def\scrn_rendering_define_window[#tag][#settings]%
  {\presetlocalframed[\??rw#tag]%
   \getparameters
     [\??rw#tag]%
     [\c!openpageaction=,\c!closepageaction=,%
      \c!width=\renderingwidth,\c!height=\renderingheight,%
      #settings]}

\unexpanded\def\setuprenderingwindow
  {\dodoubleargument\scrn_rendering_setup_window}

\def\scrn_rendering_setup_window[#tag]%
  {\getparameters[\??rw#tag]}

\unexpanded\def\placerenderingwindow
  {\dodoubleempty\scrn_rendering_place_window}

\def\scrn_rendering_place_window[#window][#rendering]%
  {\bgroup
   \edef\currentrendering{\ifsecondargument#rendering\else#window\fi}%
   \doifelse{\renderingtype\currentrendering}{internal} % an object
     {\getobjectdimensions{IRO}\currentrendering
      \edef\renderingheight{\the\dimexpr\objectheight+\objectdepth\relax}%
      \edef\renderingwidth{\objectwidth}%
      \dogetobjectreferencepage{IRO}\currentrendering\renderingpage}%
     {\def\renderingheight{\vsize}%
      \def\renderingwidth{\hsize}%
      \def\renderingpage{\realpageno}}%
   % create fall back if needed
   \ifcsname\??rw#window\c!width\endcsname
     \def\currentrenderingwindow{#window}%
   \else
     \let\currentrenderingwindow\s!default
     \scrn_rendering_define_window[\currentrenderingwindow]%
   \fi
% todo
%    \handlereferenceactions{\getvalue{\??rw\currentrenderingwindow\c!openpageaction }}\dosetuprenderingopenpageaction
%    \handlereferenceactions{\getvalue{\??rw\currentrenderingwindow\c!closepageaction}}\dosetuprenderingclosepageaction
   \localframed
     [\??rw\currentrenderingwindow][\c!offset=\v!overlay]%
     {\vfill
      \ctxcommand{insertrenderingwindow {
        label  = "\currentrendering",
        width  = \number\dimexpr\renderingwidth\relax,
        height = \number\dimexpr\renderingheight\relax,
        option = "\renderingoption\currentrendering",
        page   = \number\renderingpage,
      }}\hfill}%
   \egroup}

%D Linkedlists (not tested in mkvi):

% %D The next mechanism, linked lists, is quite old and
% %D is \MKIV'd for completeness. I will finish the
% %D configuration part when I need it.
% %D
% %D \starttyping
% %D \setupinteraction[state=start]
% %D \definelinkedlist[demo]
% %D \dorecurse{10}{\linkedlistelement[demo]{link \recurselevel} \page}
% %D \stoptyping
%
% \installcommandhandler\??lk{linkedlist}\??lk
%
% \let\setupbutton\setuplinkedlists\setuplinkedlist
%
% \appendtoks
%     \ctxcommand{definelinkedlist("\currentlinkedlist")}%
% \to \everydefinelinkedlist
%
% \def\setlinkedlistproperties#1#2#3#4#5#6%
%   {\def\currentlink {#1}%
%    \def\noflinks    {#2}%
%    \def\firstlink   {#3}%
%    \def\previouslink{#4}%
%    \def\nextlink    {#5}%
%    \def\lastlink    {#6}}
%
% \def\linkedlistelement[#1]#2% currently no view support
%   {\dontleavehmode\hbox\bgroup
%    #2%
%    \iflocation
%      \edef\currentlinkedlist{#1}%
%      \ifcsname\??lk\currentlinkedlist\s!parent\endcsname
%        \hskip\linkedlistparameter\c!distance
%        \ctxcommand{addlinklistelement("\currentlinkedlist")}%
%        \expanded{\ctxlatelua{commands.enhancelinkedlist("\currentlinkedlist",\currentlink)}}% can also be done at the lua end
%        \dogotosomepage  {\??lk\currentlinkedlist}\gotobegincharacter \firstlink
%        \ifnum\noflinks>\plustwo
%          \dogotosomepage{\??lk\currentlinkedlist}\gobackwardcharacter\previouslink
%          \dogotosomepage{\??lk\currentlinkedlist}\goforwardcharacter \nextlink
%        \fi
%        \dogotosomepage  {\??lk\currentlinkedlist}\gotoendcharacter   \lastlink
%      \else
%        \writestatus\m!interactions{no such linked list: \currentlinkedlist}%
%      \fi
%    \fi
%    \egroup}
%
% \setuplinkedlists
%   [\c!distance=.25em,
%    \c!width=\v!fit,
%    \c!location=\v!low,
%    \c!color=\interactionparameter\c!color,
%    \c!frame=\v!off,
%    \c!background=,
%    \c!backgroundcolor=]

\protect \endinput