%D \module
%D   [       file=core-nav,
%D        version=1998.01.15,
%D          title=\CONTEXT\ Core Macros,
%D       subtitle=Navigation,
%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. Non||commercial use is
%C granted.

\writestatus{loading}{Context Core Macros / Navigation}

\unprotect

%D Support for interactive document is very present in
%D \CONTEXT\ and interwoven in many modules. This means that in
%D this module, where we deal with some common navigational 
%D features, there will be quite some forward references. 
%D 
%D When I started implementing hypertext support, the macros
%D were mostly dealing with things related to locations, that
%D is click in this location and goto that one. The
%D functionality of many macro depends on the output medium:
%D paper or screen. The next boolean holds the state: 

\newif\iflocation                

%D We also allocate a scratchbox:

\newbox\locationbox

%D There is no interaction at all unless enabled by saying:
%D 
%D \starttypen
%D \setupinteraction[state=start]
%D \stoptypen
%D 
%D The other settings are:
%D 
%D \showsetup{\y!stelinteractiein}
%D 
%D In the special driver modules we introduced a switch that
%D forces page destinations (instead of named ones). We set
%D this switch here. 

\def\stelinteractiein%
  {\dosingleargument\dostelinteractiein}

\def\dostelinteractiein[#1]%
  {\getparameters[\??ia][#1]%
   \dosetuppageview{\@@iascherm}%     
   \doifelse{\@@iastatus}{\v!start}
     {\iflocation\else
        \showmessage{\m!interactions}{2}{\ifusepagedestinations\space(PAGE)\fi}%
        \global\locationtrue
      \fi}
     {\iflocation
        \showmessage{\m!interactions}{3}{\ifusepagedestinations\space(PAGE)\fi}%
        \global\locationfalse
      \fi}%
   \doifelse{\@@iastrut}{\v!ja}
     {\locationstruttrue}
     {\locationstrutfalse}%
   \doifelse{\@@iapagina}{\v!ja}
     {\global\usepagedestinationstrue}
     {\global\usepagedestinationsfalse}}

%D We have to make sure of some settings:

\def\dolocationstartup%
  {\iflocation
     \dosetupinteraction
     \handlereferenceactions\@@iaopenactie\dosetupopenaction
     \handlereferenceactions\@@iasluitactie\dosetupcloseaction
     \setupinteractionscreens
     \global\let\dolocationstartup=\relax
   \fi}

\appendtoks \dolocationstartup \to \everyshipout

%D The next few macros are really horrible. For proper
%D navigation a in||line hypertext fragment must have
%D comfortable properties, so we must force some minimal
%D dimensions. On the other hand button, and here I mean those
%D pieces of text with fancy outlines and/or backgrounds, often
%D have fixed, preset dimensions. 
%D 
%D To make things even worse, if we choose to let the optimal
%D dimensions depend on the height and depth of a strut, a not
%D too uncommon practice in \TEX, we have to deal with the fact
%D that such a strut, set inside a box, is unknown too the
%D outside world. 
%D 
%D The solution lays in passing the strut characteristics in 
%D a proper way, in our case by applying \type{\presetgoto}: 
%D 
%D \starttypen 
%D {some piece of text \presetgoto}
%D \stoptypen
%D 
%D This macro stores the current strut values. 

\newif\iflocationstrut

\def\resetgoto%
  {\global\let\@@ia@@hoogte=\!!zeropoint
   \global\let\@@ia@@diepte=\!!zeropoint}
 
\resetgoto

\def\presetgoto% 
  {\iflocationstrut
     \setstrut
     \xdef\@@ia@@hoogte{\the\ht\strutbox}%
     \xdef\@@ia@@diepte{\the\dp\strutbox}%
   \else
     \global\let\@@ia@@hoogte=\@@iahoogte
     \global\let\@@ia@@diepte=\@@iadiepte
   \fi}

%D In the macros that deal with making areas into hyperlinks, 
%D we use:

\def\dostartgoto\data#1\start#2\stop#3\dostopgoto% 
  {\ifsecondaryreference
     \bgroup\setbox0=\hbox{#2#3}\egroup
   \else
     \hbox
       {\setbox0=\hbox{#1}%
        \ifdim\wd0<\@@iabreedte\relax
          \buttonwidth=\@@iabreedte\relax
        \else
          \buttonwidth=\wd0\relax
        \fi
        \ifdim\ht0<\@@ia@@hoogte\relax
          \buttonheight=\@@ia@@hoogte\relax
        \else
          \buttonheight=\ht0
        \fi
        \ifdim\dp0<\@@ia@@diepte\relax
          \dimen0=\@@ia@@diepte\relax
        \else
          \dimen0=\dp0\relax
        \fi
        \advance\buttonheight by \dimen0
        \setbox2=\hbox
          {\lower\dimen0\hbox
             {\mindermeldingen
              \dimen0=.5\wd0 % direct skipping is faster of course
              \advance\dimen0 by -.5\buttonwidth % buts this is nicer 
              \hskip\dimen0#2#3}}% when visualizing things
        \ifreversegoto
          \dimen0=\wd0\box0\kern-\dimen0\smashbox2\box2\kern\dimen0
        \else 
          \smashbox2\box2\box0
        \fi
        \resetgoto}%
   \fi}

%D The secondary references are processed but not typeset. The 
%D special driver must collect the data needed. 

%D The width of the active area depends on the dimensions
%D preset, the actual dimens and/or the height and depth of the
%D strut. 
%D 
%D Normally the hyper active area is laid on top of the text.
%D This enables stacking hyperlinks on top of each other. When,
%D for some reason the opposite is prefered, one can use the
%D next boolean to signal this wish. 

\newif\ifreversegoto \reversegotofalse

%D As long as there a natural feeling of what can be considered
%D hyper active or not, we have to tell users where they can
%D possibly click. We've already seen a few macros that deal
%D with this visualization, something we definitely do not let
%D up to the viewer. One way of telling is using a distinctive
%D typeface, another way is using color. 
%D 
%D There are two colors involved: one for normal hyperlinks,
%D and one for those that point to the currentpage, the
%D contrast color. 

\definecolor [interactioncolor]         [r=0,  g=.6, b=0]
\definecolor [interactioncontrastcolor] [r=.8, g=0,  b=0]

\definecolor [interactiekleur]          [interactioncolor]
\definecolor [interactiecontrastkleur]  [interactioncontrastcolor]

%D The next few macros are responsible for highlighting hyper
%D links. The first one, \type{\showlocation}, is used in those
%D situations where the typeface is handled by the calling
%D macro. 

\def\interactioncolor%
  {\iflocation
     \ifrealreferencepage
       \@@iacontrastkleur
     \else
       \@@iakleur
     \fi
   \fi}

%D CHECK WHERE USED / CONSISTENCY

\def\showlocation#1%
  {\iflocation\color[\@@iakleur]{#1\presetgoto}\else#1\fi}

%D When local color settings are to be used, we can use the 
%D next macro, where \type{#1} is a tag like \type{\??tg} and
%D \type{#2} some text.

\def\showcoloredlocation#1#2%
  {\iflocation
     \color[\getvalue{#1\c!kleur}]{#2\presetgoto}%
   \else
     #2%
   \fi}

%D When we're dealing with pure page references, contrast 
%D colors are used when we are already at the page mentioned. 

\def\showcontrastlocation#1#2#3% the \@EA is needed
  {\iflocation
     \ifnum#2=\realpageno\relax
       \doifelsevaluenothing{#1\c!kleur}
         {#3\presetgoto}
         {\color[\getvalue{#1\c!contrastkleur}]{#3\presetgoto}}%
     \else
       \color[\getvalue{#1\c!kleur}]{#3\presetgoto}%
     \fi
   \else
     #3%
   \fi}

%D The next simple macro can be used in color specifications,
%D like \type{\color[\locationcolor{green}]}. 

\def\locationcolor#1%
  {\iflocation#1\fi}

%D More tokens are spend when we want both typeface and color 
%D highlighting. 

\def\dolocationattributes#1#2#3#4% 
  {\bgroup
   \doifdefinedelse{#1#2}
     {\def\fontattribute{\getvalue{#1#2}}}
     {\let\fontattribute\empty}%
   \iflocation
     \doifdefinedelse{#1#3}
       {\def\colorattribute{\getvalue{#1#3}}}
       {\let\colorattribute\empty}%
   \else
     \let\colorattribute\empty
   \fi
   \startcolor[\colorattribute]%
   \@EA\doconvertfont\@EA{\fontattribute}{#4}% no \edef, but \@EA here
   \stopcolor
   \egroup}

%D Although not decently supported in current viewers, a 
%D provisory hiding mechanims is implemented. Areas marked as
%D such, are visible on screen, but invisible on paper. Don't
%D trust this mechanism yet!

\def\dostartinteractie%
  {\bgroup
   \let\stopinteractie=\egroup
   \dowithnextbox{\dostarthide\box\nextbox\dostophide\egroup}\hbox}

\let\startinteractie = \relax
\let\stopinteractie  = \relax

% in the future: 
%
% eerst boolean invoeren bij menu, achtergrond, balk, button
% enz; verder startinteractie een argument meegeven {#1} ->
% \getvalue{#1\c!print}=={\v!ja} enz. Consequent menubutton
% gebruiken!

\def\@@iatimestamp%
  {\the\normalyear
   \ifnum\normalmonth<10 0\fi\the\normalmonth
   \ifnum\normalday  <10 0\fi\the\normalday}

% happens in core-fld 
%
% \definereference [AtOpenInitializeForm] [\v!geen] 

\stelinteractiein % start fit page and reset form 
  [\c!status=\v!stop,
   \c!pagina=\v!nee,
  %\c!openactie={\v!eerstepagina,AtOpenInitializeForm},
   \c!openactie={\v!eerstepagina,\v!ResetForm},
   \c!sluitactie=,
   \c!scherm=\v!passend,
   \c!menu=\v!uit,
   \c!letter=\v!vet,
   \c!strut=\v!ja,
   \c!kleur=interactioncolor,
   \c!contrastkleur=interactioncontrastcolor,  
   \c!symboolset=,
   \c!breedte=1em,
   \c!hoogte=\!!zeropoint,
   \c!diepte=\!!zeropoint,
   \c!titel=,
   \c!subtitel=,
   \c!auteur=,
   \c!datum=\@@iatimestamp]

\protect 

\endinput 
