path: root/Master/texmf-dist/tex/context/base/strc-ref.mkiv

%D \module
%D   [       file=strc-ref,
%D        version=2008.10.20,
%D          title=\CONTEXT\ Structure Macros,
%D       subtitle=Cross Referencing,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright=PRAGMA-ADE / Hans Hagen]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

% todo: (1) configure references, (2) rendering => with presets
%
% \definestructureconversionset[default][Character,number,Romannumerals,Character][number]
% \definestructureseparatorset [default][.,.,--][.]
% \setupstructurehead[subsection][sectionstopper=),sectionsegments=4:4]
% \setupreferencestructureprefix[default][prefixsegments=2:4]
% \setupreferencestructureprefix[figure][default][prefixsegments=3:4]
% \chapter {One}
% \section {One}
% \subsection[sec:test]{Two}
% See \in[sec:test] and \in[fig:xx] and \in[fig:yy]
% \placefigure[here][fig:xx]{}{}
% \placefigure[here][fig:yy]{}{}

\writestatus{loading}{ConTeXt Structure Macros / Cross Referencing}

\registerctxluafile{strc-ref}{1.001}
\registerctxluafile{node-ref}{1.001}

\unprotect

%D This module is a (partial) rewrite of core-ref.tex for \MKIV. As
%D such it will be a moving target for a while.

%D Later we will do a further cleanup and move much of the code to
%D \LUA\ (i.e.\ better backend integration).

\let\mainreference\gobblefivearguments

% this will go when we got rid of the tuo file

\let\currentfolioreference \!!zerocount % only used in xml-fo
\let\resetreferences       \relax
\let\setreferences         \relax
\let\showcurrentreference  \relax
\let\setexecutecommandcheck\gobbletwoarguments

\def\s!full{full}
\def\s!user{user}
\def\s!text{text}
\def\s!page{page}

% todo : unknown/illegal reference no arg
% todo : +n pages check on 'samepage' (contrastcolor)
% todo : multiple text in reference

% Makes more sense to build action data first, especially now
% openaction etc are supported.
%
% \definespecial\doexecuteactionchain w h
% \definespecial\dosetgotolocation
% \definespecial\dosetexecuteJScode
% ...

%D This module deals with referencing. In \CONTEXT\ referencing
%D is one of the core features, although at a first glance
%D probably nobody will notice. This is good, because
%D referencing should be as hidden as possible.
%D
%D In paper documents, referencing comes down to cross
%D referencing, but in their interactive counterparts, is also
%D involves navigation. Many features implemented here are
%D therefore closely related to navigation.
%D
%D Many \CONTEXT\ commands can optionally be fed with a
%D reference. Such a reference, when called upon, returns the
%D number of a figure, table, chapter etc, a piece of text, or
%D a pagenumber.
%D
%D There are three ways of defining a reference:
%D
%D \starttyping
%D \pagereference[here]
%D \textreference[here]{some text}
%D \stoptyping
%D
%D the third alternative combines them in:
%D
%D \starttyping
%D \reference[here]{some text}
%D \stoptyping

\unexpanded\def\textreference {\dosingleargument\dotextreference}
\unexpanded\def\pagereference {\dosingleargument\dopagereference}
\unexpanded\def\reference     {\dosingleargument\doreference    }
\unexpanded\def\setreference  {\dodoubleargument\dosetreference }

%D These are implemented in a low level form as:

\def\dotextreference   [#1]{\dodosetreference\s!text{#1}{}}
\def\dopagereference   [#1]{\dodosetreference\s!page{#1}{}{}}
\def\doreference       [#1]{\dodosetreference\s!full{#1}{}}
\def\dosetreference[#1][#2]{\dodosetreference\s!user{#1}{#2}{}}

%D Actually there is not much difference between a text and a
%D full reference, but it's the concept that counts. The low
%D level implementation is:

\newcount\lastreferenceattribute
\newcount\lastdestinationattribute

\def\dofinishfullreference#1#2{\normalexpanded{\ctxlatelua{structures.references.enhance("#1","#2")}}}
\def\dofinishtextreference#1#2{\normalexpanded{\ctxlatelua{structures.references.enhance("#1","#2",{})}}}

\let\dofinishpagereference\dofinishfullreference
\let\dofinishuserreference\dofinishfullreference

\def\dofinishsomereference#1{\executeifdefined{dofinish#1reference}\gobbletwoarguments}

\def\dodosetreference
  {\ifreferencing
      \expandafter\dododosetreference
   \else
      \expandafter\gobblefourarguments
   \fi}

\def\dododosetreference#1#2#3#4% kind labels userdata text -> todo: userdata
  {\ifreferencing
     % we could have a more efficient one for page references but for the moment
     % we don't care too much
     \edef\currentreferencekind{#1}%
     \edef\currentreferencelabels{#2}%
     \edef\currentreferenceuserdata{#3}%
     \edef\currentreferenceexpansion{\@@rfexpansion}% {\referenceparameter\c!expansion}
     \ifx\currentreferencelabels\empty \else
       \ifx\currentreferenceexpansion\s!xml
         \xmlstartraw
           \xdef\currentreferencedata{#4}% data, no text else conflict
         \xmlstopraw
         \globallet\currentreferencecoding\s!xml
       \else
         \ifx\currentreferenceexpansion\v!yes
           \xdef\currentreferencedata{#4}%
         \else
           \xdef\currentreferencedata{\detokenize{#4}}%
         \fi
         \globallet\currentreferencecoding\s!tex
       \fi
       % beware, the structures.references.set writes a
       % \setnextinternalreference
       \ctxlua{structures.references.setandgetattribute("\currentreferencekind", "\referenceprefix","\currentreferencelabels",
            {
                references = {
                %   internal = \nextinternalreference, % no need for an internal as we have an explicit
                    block    = "\currentstructureblock",
                    section  = structures.sections.currentid(),
                },
                metadata = { % we could assume page to have no metadata
                    kind = "#1",
                    \ifx\currentreferencekind\s!page\else
                        catcodes = \the\catcodetable,
                        xmlroot  = \ifx\currentreferencecoding\s!xml "\xmldocument" \else nil \fi, % only useful when text
                    \fi
                },
                \ifx\currentreferencedata\empty\else
                    entries = {
                        text = \!!bs\currentreferencedata\!!es
                    },
                \fi
                \ifx\currentreferenceuserdata\empty\else
                    userdata = structures.helpers.touserdata(\!!bs\detokenize{#3}\!!es)
                \fi
            },"\interactionparameter\c!focus")
       }%
       % todo: optional
       \xdef\currentdestinationattribute{\number\lastdestinationattribute}%
       \begingroup\attribute\destinationattribute\currentdestinationattribute\emptyhbox\endgroup % todo
     \fi
   \fi}

\def\defaultreferencepage#1{[[[#1]]]}
\def\defaultreferencetext#1{[[[#1]]]}

%D For internal usage:

\def\dosetsimplepagereference#1% label
  {\iflocation
     \ctxlua{structures.references.setandgetattribute("\s!page", "\referenceprefix","#1",
        {
            references = {
            %   block    = "\currentstructureblock",
            %   section  = structures.sections.currentid(),
            },
            metadata = { % we could assume page to have no metadata
                kind = "\s!page",
            },
        },"\interactionparameter\c!focus")
     }%
     \xdef\currentdestinationattribute{\number\lastdestinationattribute}%
   \else
     \xdef\currentdestinationattribute{\number\attributeunsetvalue}%
   \fi}

\def\dogetsimplepagereference#1%
  {\iflocation
     \ctxlua{structures.references.inject("\referenceprefix","#1",\number\ht\strutbox,\number\dp\strutbox,\extrareferencearguments)}%
     \xdef\currentreferenceattribute{\number\lastreferenceattribute}%
   \else
     \xdef\currentreferenceattribute{\number\attributeunsetvalue}%
   \fi}

%D These macros depend on three other ones,
%D \type {\makesectionformat}, that generated \type
%D {\sectionformat}, \type {\pagenumber}. The not yet used
%D argument \type{#1} is a tag that specifies the type of
%D reference.

%D \macros
%D   {everyreference}
%D
%D For rather tricky purposes, one can assign sanitizing
%D macros to \type{\everyreference} (no longer that relevant).

\newevery \everyreference \relax

%D This is really needed, since for instance Polish has a
%D different alphabet and needs accented entries in registers.

\appendtoks
  \cleanupfeatures
\to \everyreference

%D We did not yet discuss prefixing. Especially in interactive
%D documents, it's not always easy to keep track of duplicate
%D references. The prefix mechanism, which we will describe
%D later on, solves this problem. By (automatically) adding a
%D prefix one keeps references local, but the global ones in
%D view. To enable this feature, we explictly split the prefix
%D from the reference.

\let\referenceprefix\empty

%D For a long time the only way to access an external file was
%D to use the file prefix (\type {somefile::}. However, when
%D you split up a document, redefining the references may be
%D such a pain, that another approach is feasible. By setting
%D the \type {autofile} variable to \type {yes} or \type
%D {page}, you can access the reference directly.
%D
%D \starttabulate[||||]
%D \NC filename::tag \NC page(filename::pnum) \NC tag     \NC\NR
%D \NC   $\star$     \NC                      \NC         \NC\NR
%D \NC   $\star$     \NC $\star$              \NC $\star$ \NC\NR
%D \NC               \NC $\star$              \NC         \NC\NR
%D \stoptabulate

\def\usereferences[#1]% not yet
  {\writestatus\m!system{references from other files are handled automatically}}

%D As mentioned we will also use the cross reference mechanism
%D for navigational purposes. The main reason for this is that
%D we want to treat both categories alike:
%D
%D \starttyping
%D \goto{go back}[PreviousJump]
%D \goto{colofon}[colofon page]
%D \stoptyping
%D
%D Here \type{PreviousJump} is handled by the viewer, while the
%D \type{colofon page} reference is, apart from hyperlinking, a
%D rather normal reference.
%D
%D We already saw that cross refences are written to and read
%D from a file. The pure navigational ones don't need to be
%D written to file, but both for fast processing and
%D transparant integration, they are saved internally as a sort
%D of reference. We can easily distinguish such system
%D references from real cross reference ones by their tag.
%D
%D We also use the odd/even characteristic to determine the
%D page state.

\let\currentrealreference      \empty
\let\currentpagereference      \empty
\let\currenttextreference      \empty
\let\currentreferenceorder     \empty
\let\currentsubtextreference   \empty
\let\currentsubsubtextreference\empty

\newcount\referencepagestate   % set in backend
\newcount\referencehastexstate % set in backend

% referencepagestate:
%
% 0 = no page ref, 1=same page, 2=before, 3=after

%D Text references can contain more than one entry and
%D therefore we check for
%D
%D \starttyping
%D {entry}
%D \stoptyping
%D
%D or
%D
%D \starttyping
%D {{entry}{entry}{entry}}
%D \stoptyping
%D
%D and split accordingly.

%D Cross references appear as numbers (figure~1.1, chapter~2)
%D or pagenumbers (page~2, page 3--2), and are called with
%D \type{\in} and \type{\at}. In interactive documents we also
%D have \type{\goto}, \type{\button} and alike. These are more
%D versatile and look like:
%D
%D \starttyping
%D \goto[reference]
%D \goto[outer reference::]
%D \goto[outer reference::inner reference]
%D \goto[operation(argument)]
%D \goto[operation(action{argument,argument})]
%D \goto[action]
%D \goto[action{argument}]
%D \stoptyping
%D
%D The first one is a normal reference, the second and third
%D are references to a file or \URL. The brace delimited
%D references for instance refer to a \JAVASCRIPT. The last
%D example shows that we can pass arguments to the actions.
%D
%D When we split off the components of such a reference, the
%D results are available in:
%D
%D \starttyping
%D \currentreferencespecial
%D \currentreferenceoperation
%D \currentreferencearguments
%D \currentinnerreference
%D \currentouterreference
%D \currentfullreference
%D \stoptyping

\newif\ifreferencefound

% \let\currentfullreference     \empty
% \let\currentreferencespecial  \empty
% \let\currentreferenceoperation\empty
% \let\currentreferencearguments\empty
% \let\currentouterreference    \empty
% \let\currentinnerreference    \empty

%D Now we've come to the testing step. As we can see below,
%D this macro does bit more than testing: it also resolves
%D the reference. This means that whenever we test for the
%D existance of a reference at an outer level, we have all the
%D relevant properties of that reference avaliable inside the
%D true branche~(\type{#2}).
%D
%D The prefix has to do with localizing references. When a
%D prefix is set, looking for a reference comes to looking for
%D the prefixed one, and when not found, looking for the non
%D prefixed one. Consider for instance the prefix set to
%D \type{sidetrack}.
%D
%D \starttyping
%D \pagereference[important]
%D \pagereference[unimportant]
%D \setupreferencing[prefix=sidetrack]
%D \pagereference[important]
%D \stoptyping
%D
%D results in saving (writing) the references
%D
%D \starttyping
%D ...{}{important}
%D ...{}{unimportant}
%D ...{sidetrack}{important}...
%D \stoptyping
%D
%D Now when we call for \type{unimportant}, we will indeed get
%D the pagenumber associated to this reference. But when we
%D call for \type{important}, while the prefix is still set, we
%D will get the pagenumber bound to the prefixed one.
%D
%D {\em Some day, when processing time and memory are no longer
%D performance factors, we will introduce multi||level
%D prefixes.}
%D
%D Before we start analyzing, I introduce a general
%D definition macro. Consider:
%D
%D \starttyping
%D \goto{do}[JS(My_Script{"test",123}),titlepage]
%D \stoptyping
%D
%D This can also be achieved by:
%D
%D \starttyping
%D \definereference[startup][JS(My_Script{"test",123}),titlepage]
%D \goto{do}[startup]
%D \stoptyping
%D
%D Now is this is a handy feature or not?
%D
%D \showsetup{definereference}
%D
%D We can trace references by setting the next switch to
%D true.

\unexpanded\def\definereference
  {\dodoubleempty\dodefinereference}

\def\dodefinereference[#1][#2]%
  {\ctxlua{structures.references.define("\referenceprefix","#1",\!!bs\detokenize{#2}\!!es)}}

\def\resetreference[#1]%
  {\ctxlua{structures.references.reset("\referenceprefix","#1")}}

\def\setpagereference#1#2% name, specification
  {\ctxlua{structures.references.define("","#1",\!!bs\v!page(\luaescapestring{#2})\!!es)}}

%D Chained references are defined as:
%D
%D \starttyping
%D \goto{somewhere}[JS(somescript),nextpage,JS(anotherscript)]
%D \stoptyping
%D
%D Actually supporting chains is up to the special driver. Here
%D we only provide the hooks.

%D \macros
%D   {highlighthyperlinks}
%D
%D The next switch can be used to make user hyperlinks are
%D not highlighted when clicked on.

\newconditional\highlighthyperlinks \settrue\highlighthyperlinks

%D \macros
%D   {gotonewwindow}
%D
%D To make the {\em goto previous jump} feature more
%D convenient when using more than one file, it makes sense
%D to force the viewer to open a new window for each file
%D opened.

\newconditional\gotonewwindow \setfalse\gotonewwindow

\def\expandtexincurrentreference % will happen in lua some time
  {\ifcase\referencehastexstate\else\ctxlua{structures.references.expandcurrent()}\fi}

\def\expandreferenceoperation#1#2{\ctxcommand{setreferenceoperation(#1,\!!bs#2\!!es)}}
\def\expandreferencearguments#1#2{\ctxcommand{setreferencearguments(#1,\!!bs#2\!!es)}}

\def\doifreferencefoundelse#1#2#3%
  {\ctxlua{structures.references.doifelse("\referenceprefix","#1",\luaconditional\highlighthyperlinks,\luaconditional\gotonewwindow)}%
     {\expandtexincurrentreference#2}%
     {#3}}

%D The tester only splits the reference in components but does
%D not look into them. The following macro does a preroll and
%D determines for instance the current real reference pagenumber.
%D The \type {\currentrealreference} macro does the same so unless
%D one wants to use the pagestate the next macro seldom needs to
%D be called.

\def\analyzecurrentreference
  {\ctxlua{structures.references.analyze()}}

%D The inner case is simple. Only two cases have to be taken
%D care of:
%D
%D \starttyping
%D \goto{some text}[reference]
%D \goto{some text}[prefix:reference]
%D \stoptyping
%D
%D References to other files however are treated strict or
%D tolerant, depending on their loading and availability:
%D
%D \starttyping
%D \useexternaldocument[somefile][filename][a nice description]
%D
%D \goto{checked   reference}[somefile::reference]
%D \goto{unchecked reference}[somefile::]
%D \goto{unchecked reference}[anotherfile::reference]
%D \stoptyping
%D
%D An unknown reference is reported on the screen, in the log
%D file and, when enabled, in the left margin of the text.

% \def\unknownreference#1%
%   {\iftrialtypesetting \else
%      \ifinpagebody \else
%        \doifconcepttracing{\doifsomething{#1}{\inleft{\infofont\doboundtext{#1}{\dimexpr\leftmarginwidth-2em\relax}{..}->}}}%
%      \fi
%    \fi}

\let\unknownreference\gobbleoneargument

%D When a reference is not found, we typeset a placeholder
%D (two glyphs are often enough to represent the reference
%D text).

\def\dummyreference{{\tttf ??}}

%D To prevent repetitive messages concerning a reference
%D being defined, we set such an unknown reference to an empty
%D one after the first encounter.

%D Apart from cross references supplied by the user, \CONTEXT\
%D generates cross references itself. Most of them are not
%D saved as a reference, but stored with their source, for
%D instance a list or an index entry. Such automatically
%D generated, for the user invisible, references are called
%D {\em internal references}. The user supplied ones are
%D labeled as {\em external references}.
%D
%D A second important characteristic is that when we want to
%D support different backends (viewers), we need to support
%D named destinations as well as page numbers. I invite readers
%D to take a glance at the special driver modules to understand
%D the fine points of this. As a result we will deal with {\em
%D locations} as well as {\em real page numbers}. We explictly
%D call this pagenumber a real one, because it is independant
%D of the page numbering scheme used in the document.
%D
%D One of the reasons for \CONTEXT\ being the first \TEX\ base
%D macropackage to support sophisticated interactive \PDF\
%D files, lays in the mere fact that real page numbers are
%D available in most two pass data, like references, list data
%D and index entries.
%D
%D We will speak of \type{thisis...} when we are marking a
%D location, and \type{goto...} when we point to such a
%D location. The latter one can be seen as a hyperlink to the
%D former one. In the next macros one we use constructs like:
%D
%D \starttyping
%D \dostart...
%D \dostop...
%D \stoptyping
%D
%D Such macros are used to invoke the relevant specials from
%D the special driver modules (see \type{spec-ini}). The flag
%D \type{\iflocation} signals if we're in interactive mode.

\ifx\buttonheight\undefined \newdimen\buttonheight \fi
\ifx\buttonwidth \undefined \newdimen\buttonwidth  \fi

%D Internal references can best be set using the next few
%D macros. Setting such references to unique values is
%D completely up to the macros that call them.
%D
%D \starttyping
%D \thisissomeinternal{tag}{identifier}
%D \gotosomeinternal  {tag}{identifier}{pagenumber}{text}
%D \stoptyping

%D We could do this in lua ...

\newif   \iflocation
\newcount\locationcount
\newcount\locationorder
\newbox  \locationbox

\def\nextinternalreference     {\the\locationcount}
\def\nextinternalorderreference{\the\locationorder}

\def\setnextinternalreference
  {\global\advance\locationcount\plusone}

\def\setnextinternalreferences#1#2% plural
  {\ctxlua{structures.references.setnextinternal("#1","#2")}}

\def\getinternalorderreference#1#2%
  {\ctxlua{structures.references.currentorder("#1","#2")}}

\def\thisissomeinternal#1#2%  tag reference (only for old time sake)
  {\begingroup
   \ctxlua{structures.references.setinternalreference("","#1:#2")}%
   \hbox attr \destinationattribute\lastdestinationattribute{}%
   \endgroup}

\newconditional\preferpagereferences

\def\gotosomeinternal#1#2#3#4%
  {\ifconditional\preferpagereferences
     \directgoto{#4}[page(#3)]%
   \else
     \directgoto{#4}[#1:#2]%
   \fi}

\def\gotonextinternal#1#2%
  {\directgoto{#1}[internal(#2)]}

%D In this module we define three system references: one for
%D handling navigational, viewer specific, commands, another
%D for jumping to special pages, like the first or last one,
%D and a third reference for linking tree like lists, like
%D tables of contents. The latter two adapt themselves to the
%D current state.
%D
%D An example of an action is:
%D
%D \starttyping
%D \goto{some action}[PreviousJump]
%D \stoptyping
%D
%D as well as:
%D
%D \starttyping
%D \goto{some text}[\v!action(PreviousJump]
%D \stoptyping

% compatibility hack

\def\setglobalsystemreference#1#2#3{\definereference[#2][\v!action(#3)]}

\newif\ifreferencing \referencingtrue

%D One can also activate an automatic prefix mechanism. By
%D setting the \type{\prefix} variable to \type{+}, the prefix
%D is incremented, when set to \type{-} or empty, the prefix is
%D reset. Other values become the prefix.

\newcount\prefixcounter

%D These settings are accomplished by:
%D
%D \showsetup{setupreferencing}
%D
%D In interactive documents verbose references don't always
%D make sense (what is a page number in an unnumbered
%D document). By setting the \type{interaction} variable, one
%D can influences the way interactive references are set.

\newconstant\autocrossfilereferences  % not yet supported in mkiv
\newconstant\referencefilecaseswap    % not yet supported in mkiv

\newtoks \everysetupreferencing

\unexpanded\def\setupreferencing
  {\dosingleargument\dosetupreferencing}

\def\dosetupreferencing[#1]%
  {\getparameters[\??rf][\c!prefix=\s!unknown,#1]%
   \the\everysetupreferencing}

\appendtoks
   \processaction
     [\@@rfstate]
     [  \v!stop=>\referencingfalse,
       \v!start=>\referencingtrue]%
\to \everysetupreferencing

% \newconstant \referencecontentmode
%
% \appendtoks
%     \processaction
%       [\@@rfinteraction]
%       [   \v!all=>\referencecontentmode\zerocount,
%         \v!label=>\referencecontentmode\plusone,
%          \v!text=>\referencecontentmode\plustwo,
%        \v!symbol=>\referencecontentmode\plusthree]%
% \to \everysetupreferencing

\appendtoks
   \autocrossfilereferences\zerocount
   \processaction
     [\@@rfautofile] % not yet in mkiv
     [  \v!yes=>\autocrossfilereferences\plusone,
       \v!page=>\autocrossfilereferences\plustwo]%
\to \everysetupreferencing

\appendtoks
    \referencefilecaseswap\zerocount
    \processaction[\@@rfconvertfile] % not yet in mkiv
      [  \v!yes=>\referencefilecaseswap\plusone,
         \v!big=>\referencefilecaseswap\plusone,
       \v!small=>\referencefilecaseswap\plustwo]%
\to \everysetupreferencing

\appendtoks
   \setupreferenceprefix[\@@rfprefix]%
   \doifelse\@@rfglobal\v!yes
     {\settrue \autoglobalfilereferences}%
     {\setfalse\autoglobalfilereferences}%
\to \everysetupreferencing

% \appendtoks\ctxlua{structures.references.export("whatever")}\to\everystoptext
% \starttext
%     \chapter[test]{test}
%     test \in{IN}[more]           and \in{IN}[test]           or \at{AT}[more]           and \at{AT}[test]\par
%     test \in{IN}[whatever::more] and \in{IN}[whatever::test] or \at{AT}[whatever::more] and \at{AT}[whatever::test] \page
%     reference\reference[more]{oeps}
% \stoptext

\def\exportreferences
  {\doif\@@rfexport\v!yes{\ctxlua{structures.references.export()}}}

\appendtoks
  \exportreferences
\to \everygoodbye

\def\incrementreferenceprefix{+}
\def\decrementreferenceprefix{-}

\unexpanded\def\setupreferenceprefix[#1]%
  {\edef\@@rfprefix{#1}%
   \ifx\@@rfprefix\empty
     \let\referenceprefix\empty
   \else\ifx\@@rfprefix\incrementreferenceprefix
     \advance\prefixcounter \plusone % should be global
     \edef\referenceprefix{\the\prefixcounter:}%
     \let\@@rfprefix\s!unknown
   \else\ifx\@@rfprefix\decrementreferenceprefix
     \let\referenceprefix\empty
     \let\@@rfprefix\s!unknown
   \else\ifx\@@rfprefix\s!unknown
     % forget about it
   \else
     \edef\referenceprefix{\@@rfprefix:}%
   \fi\fi\fi\fi}

%D The most straightforward way of retrieving references is
%D using \type{\ref}. Consider the reference:
%D
%D \startbuffer
%D \reference[my ref]{{Look}{Here}{I am}}
%D \stopbuffer
%D
%D \typebuffer
%D
%D \getbuffer
%D
%D We can ask for upto five reference components:
%D
%D \startbuffer
%D user page reference:  \ref[p][my ref]
%D text reference:       \ref[t][my ref]
%D real page reference:  \ref[r][my ref]
%D sub text reference:   \ref[s][my ref]
%D extra text reference: \ref[e][my ref]
%D \stopbuffer
%D
%D \typebuffer
%D
%D And get back:
%D
%D \startlines
%D \getbuffer
%D \stoplines
%D
%D This is a cheap compatibility hack. Don't use this command
%D as there will be more advanced access to user data.

\def\ref{\dodoubleargument\doref}

\def\reftypep{\currentreferencepage}
\def\reftypet{\currentreferencetext}
\def\reftyper{\currentreferencepage}
\def\reftypes{\currentreferencetext}
\def\reftypee{\currentreferencetext}

\def\doref[#1][#2]%
  {\ifsecondargument
     \doifreferencefoundelse{#2}
       {\executeifdefined{reftype#1}\reftypep}
       {\dummyreference}%
   \else
     \dummyreference
   \fi}

%D We can typeset a reference using \type{\in}, \type{\at} and
%D \type{\about} and goto specific locations using
%D \type{\goto}. The last one does not make that much sense in
%D a paper document. To complicate things, \PLAIN\ \TEX\ also
%D implements an \type {\in} but fortunately that one only
%D makes sense in math mode.
%D
%D Typesetting the reference is a bit more complicated than one
%D would at first sight expect. This is due to the fact that we
%D distinguish three (five) alternative calls:
%D
%D \placefigure
%D   [here][three calls]
%D   {Three alternatives reference calls.}
%D   {\startcombination[1*3]
%D      {\framed{\type{ \in }}} {a}
%D      {\framed{\type{ \at }}} {b}
%D      {\framed{\type{\goto}}} {c}
%D    \stopcombination}
%D
%D \startbuffer
%D \in figure[fig:three calls]
%D \in{figure}[fig:three calls]
%D \in figure a[fig:three calls]
%D \in{figure}{a}[fig:three calls]
%D figure~\in[fig:three calls]
%D \stopbuffer
%D
%D \typebuffer
%D
%D This turns up as:
%D
%D \startlines
%D \getbuffer
%D \stoplines
%D
%D The dual \type{{}} results in a split reference. In a
%D document meant for paper, one is tempted to use the last
%D (most straightforward) alternative. When a document is also
%D meant voor electronic distribution, the former alternatives
%D have preference, because everything between the \type{\in}
%D and~\type{[} becomes active (and when asked for, typeset
%D in a different color and typeface).

% \unexpanded\def\in   {\mathortext\donormalmathin   \dospecialin}
% \unexpanded\def\at   {\mathortext\donormalmathat   \dospecialat}
% \unexpanded\def\about{\mathortext\donormalmathabout\dospecialabout}
% \unexpanded\def\from {\mathortext\donormalmathfrom \dospecialfrom}
% \unexpanded\def\over {\mathortext\donormalmathover \dospecialabout}

% \definecommand in    {\dospecialin}
% \definecommand at    {\dospecialat}
% \definecommand about {\dospecialabout}
% \definecommand from  {\dospecialfrom}
% \definecommand over  {\dospecialabout} % needed here, else math problems

\def\currentreferencenumber  {\ctxlua{structures.references.filter("number")}}
\def\currentreferencepage    {\ctxlua{structures.references.filter("page")}}
\def\currentreferencetitle   {\ctxlua{structures.references.filter("title")}}
\def\currentreferencetext    {\ctxlua{structures.references.filter("text")}}
\def\currentreferencedefault {\ctxlua{structures.references.filter("default")}}
\def\currentreferencerealpage{\ctxlua{structures.references.realpage()}}

\def\getreferenceentry#1{\ctxlua{structures.references.filter("#1")}} % user entry

\unexpanded\def\dospecialabout[#1]%
  {\dontleavehmode
   \begingroup
   \let\crlf\space
   \let\\\space
   \postponenotes
   \@@rfleft
   \doifreferencefoundelse{#1}
     {\goto{\limitatetext\currentreferencetitle\@@rfwidth\unknown}[#1]}% not so efficient (dup lookup)
     {}% todo
   \@@rfright
   \endgroup}

%D The previously discussed setup macro lets us specify the
%D representation of references. A symbol reference does not
%D show the specific data, like the number of a figure, but
%D shows one of: \hbox {$^\goforwardcharacter$
%D $^\gobackwardcharacter$ $^\gonowherecharacter$}, depending
%D on the direction to go.

% 1 = whatever
% 2 = forward, following page
% 3 = backward, preceding page
% 4 = forward, same page
% 5 = backward, same page

% Yet untested:

\unexpanded\def\somewhere#1#2#3[#4]% #3 gobbles space around #2 % todo
  {\doifreferencefoundelse{#4}% kind of inefficient as \goto also analyzes
     {\goto{\analyzecurrentreference\ifcase\referencepagestate\relax#1/#2\or#2\or#1\or#2\fi}[#4]}
     {[#1/#2]}}

\unexpanded\def\atpage[#1]% todo
  {\doifreferencefoundelse{#1}% kind of inefficient as \goto also analyzes
     {\goto{\analyzecurrentreference\ifcase\referencepagestate
        \labeltexts\v!page\dummyreference
      \or
        \labeltexts\v!atpage\currentreferencepage
      \or
        \labeltexts\v!atpage\currentreferencepage
      \or
        \labeltexts\v!atpage\currentreferencepage
      \or
        \labeltext\v!hereafter
      \or
        \labeltext\v!hencefore
      \fi}[#1]}
     {[?]}}

\unexpanded\def\referencesymbol
  {\hbox{\strut\high
     {\setupsymbolset[\interactionparameter\c!symbolset]%
      \symbol
        [\ifcase\referencepagestate
           \v!somewhere
         \or % same
           \v!nowhere
         \or % before
           \v!previous
         \or % after
           \v!next%
         \fi]}}}

%D The other alternatives just conform their names: only the
%D label, only the text, or the label and the text.

% \dounknownreference -> \dummyreference

\def\symbolreference[#1]% for old times sake
  {\goto{\referencesymbol}[#1]}

% \referencecontentmode 0=all 1=label 2=text 3=symbol

\newtoks\leftreferencetoks
\newtoks\rightreferencetoks
\newtoks\defaultleftreferencetoks
\newtoks\defaultrightreferencetoks

\def\leftofreferencecontent {\nobreakspace} % we cannot do \definereferenceformat[at] .. so we need this
\let\rightofreferencecontent \empty
\let\leftofreference         \empty
\let\rightofreference        \empty

\setvalue{\??rf\c!interaction\v!all}%
  {\leftofreference
   \the\leftreferencetoks
   \doifsometokselse\leftreferencetoks \leftofreferencecontent \donothing
   \currentreferencecontent
   \doifsometokselse\rightreferencetoks\rightofreferencecontent\donothing
   \the\rightreferencetoks
   \rightofreference}

\setvalue{\??rf\c!interaction\v!label}%
  {\leftofreference
   \the\leftreferencetoks
   \the\rightreferencetoks
   \rightofreference}

\setvalue{\??rf\c!interaction\v!text}%
  {\leftofreference
   \currentreferencecontent
   \rightofreference}

\setvalue{\??rf\c!interaction\v!symbol}%
  {\referencesymbol}

\def\referencesequence
  {\csname \??rf\c!interaction
     \ifcsname\??rf\c!interaction\@@rfinteraction\endcsname
       \@@rfinteraction
     \else
       \v!all
     \fi
   \endcsname}

\newtoks\everyresetinatreference

\appendtoks
    \glet\leftofreference \relax
    \glet\rightofreference\relax
\to \everyresetinatreference

\def\dostartgotoreference
  {\dontleavehmode
   \begingroup}

\def\dostopgotoreference
  {\the\everyresetinatreference
   \endgroup}

\def\dopickupgotoreference
  {\dodoublegroupempty\dodopickupgotoreference}

\def\dodopickupgotoreference#1#2#3[#4]% #3 gobbles spaces (really needed)
  {\leftreferencetoks
     \iffirstargument
       {#1}%
     \else
       \defaultleftreferencetoks
       \let\leftofreferencecontent\empty
     \fi
   \rightreferencetoks
     \ifsecondargument
       {#2}%
     \else
       \defaultrightreferencetoks
       \let\rightofreferencecontent\empty
     \fi
   \doifreferencefoundelse{#4} % we need to resolve the text
     {\goto{\referencesequence}[#4]}
     {\let\currentreferencecontent\dummyreference
      \goto{\referencesequence}[#4]}%
   \dostopgotoreference}

\unexpanded\def\dospecialin{\dostartgotoreference\let\currentreferencecontent\currentreferencedefault\dopickupgotoreference}
\unexpanded\def\dospecialat{\dostartgotoreference\let\currentreferencecontent\currentreferencepage   \dopickupgotoreference}

%D \macros
%D   {definereferenceformat}
%D
%D The next few macros were made for for David Arnold and Taco
%D Hoekwater. They can be used for predefining reference
%D texts, and thereby stimulate efficiency.
%D
%D \starttyping
%D \definereferenceformat[informula]  [left=(,right=),text=formula]
%D \definereferenceformat[informulas] [left=(,right=),text=formulas]
%D \definereferenceformat[andformula] [left=(,right=),text=and]
%D \definereferenceformat[andformulas][left=(,right=),text=and]
%D
%D \informula [b] and \informula [for:c]
%D the \informula {formulas}[b] \informula {and} [for:c]
%D the \informulas {formulas}[b] \informula {and} [for:c]
%D the \informulas [b] \informula {en} [for:c]
%D the \informulas [b] \andformula [for:c]
%D \stoptyping
%D
%D Instead of a text, one can specify a label, which should
%D be defined with \type {\setuplabeltext}.
%D
%D
%D Watch out: the second argument is somewhat special and mostly
%D meant for a suffix to a number:
%D
%D \startbuffer
%D \definereferenceformat [intesta] [left=(,right=),text=Whatever~]
%D \definereferenceformat [intestb] [left=(,right=),label=figure]
%D
%D \placeformula[x]\startformula a \stopformula
%D
%D \starttabulate[|||||]
%D \NC \in     [x] \NC \in     {left}[x] \NC \in     {}{right}[x] \NC \in     {left}{right}[x] \NC \NR
%D \NC \intesta[x] \NC \intesta{left}[x] \NC \intesta{}{right}[x] \NC \intesta{left}{right}[x] \NC \NR
%D \NC \intestb[x] \NC \intestb{left}[x] \NC \intestb{}{right}[x] \NC \intestb{left}{right}[x] \NC \NR
%D \stoptabulate
%D \stopbuffer
%D
%D \typebuffer \getbuffer

% todo: inherit

\let\currentreferenceformat\empty

\def\referenceformatparameter#1% some day we will add inheritance
  {\ifcsname\??rf\currentreferenceformat#1\endcsname\csname\??rf\currentreferenceformat#1\expandafter\endcsname\fi}

\unexpanded\def\definereferenceformat
  {\dodoubleargument\dodefinereferenceformat}

% left right text label

\def\dodefinereferenceformat[#1][#2]%
  {\iffirstargument
     \getparameters[\??rf#1][\c!left=,\c!right=,\c!text=,\c!label=,\c!autocase=v!no,#2]%
     \setuvalue{#1}{\doexecutereferenceformat{#1}}%
   \fi}

\def\doexecutereferenceformat#1% quite slow due to all assignments but we will speed it up
  {\dostartgotoreference       % once it's stable
   \edef\currentreferenceformat{#1}%
   \gdef\leftofreference {\referenceformatparameter\c!left }%
   \gdef\rightofreference{\referenceformatparameter\c!right}%
   % we can make a helper for this .. we will use the new parameter handler anyway
   % but at least aditya can play with it now
   \doifsomething{\referenceformatparameter\c!style}
     {\dosetfontattribute{\??rf\currentreferenceformat}\c!style
      \resetinteractionparameter\c!style}%
   \doifsomething{\referenceformatparameter\c!color}
     {\dosetcolorattribute{\??rf\currentreferenceformat}\c!color
      \resetinteractionparameter\c!contrastcolor
      \resetinteractionparameter\c!color}%
   %
   \edef\currentreferenceformatlabel{\referenceformatparameter\c!label}%
   \ifx\currentreferenceformatlabel\autoreferencelabeltextflag
      \edef\currentreferenceformatlabel{\autoreferencelabeltext}%
   \fi
   \doif{\referenceformatparameter\c!autocase}\v!yes
     {\setcharactercleaning[1]}%
   \ifx\currentreferenceformatlabel\empty
     \defaultleftreferencetoks {\referenceformatparameter\c!text}%
     \defaultrightreferencetoks\emptytoks
   \else
     \defaultleftreferencetoks {\leftlabeltext \currentreferenceformatlabel}%
     \defaultrightreferencetoks{\rightlabeltext\currentreferenceformatlabel}%
   \fi
   \doifelse{\referenceformatparameter\c!type}\v!page
     {\let\currentreferencecontent\currentreferencepage}
     {\let\currentreferencecontent\currentreferencedefault}%
   \let\leftofreferencecontent \empty
   \let\rightofreferencecontent\empty
   \dopickupgotoreference}

\def\autoreferencelabeltextflag{*} % a proper key like 'auto' or 'name' can clash with a label key

\unexpanded\def\autoreferencelabeltext
  {\ctxlua{structures.references.getcurrentmetadata("name")}}

% \starttext
%     \definereferenceformat[inxx]  [left=(,right=),text=txt]
%     \setupinteraction[state=start]
%     \chapter[one]{xx}
%     [\goto{state}[file(mk-last-state)]]
%     [\goto{state} [file(mk-last-state)]]
%     [\at{page} [one]]
%     [\at{page}[one]]
%     [\at{page}{okay}[one]]
%     [\inxx{a}{b}[one]]
% \stoptext

%D In interactive documents going to a specific location is not
%D bound to cross references. The \type{\goto} commands can be
%D used to let users access another part of the document. In
%D this respect, interactive tables of contents and registers
%D can be considered goto's. Because in fact a \type{\goto} is
%D just a reference without reference specific data, the
%D previous macros are implemented using the goto
%D functionality.
%D
%D \showsetup{goto}
%D
%D One important characteristic is that the first argument of
%D \type{\goto} (and therefore \type{\at} and \type{\in} is
%D split at spaces. This means that, although hyphenation is
%D prevented, long references can cross line endings.

% \starttext
%     \setupinteraction[state=start]
%     [\goto{state}[file(mk-last-state)]]
%     [\goto{state} [file(mk-last-state)]]
% \stoptext

\newconditional\uselocationstrut \settrue\uselocationstrut

\def\extrareferencearguments{\luaconditional\highlighthyperlinks,\luaconditional\gotonewwindow,"\currentviewerlayer"}

\unexpanded\def\directgoto{\ifconditional\uselocationstrut\expandafter\dodirectgoto\else\expandafter\directgotohtdp\fi}
\unexpanded\def\goto      {\ifconditional\uselocationstrut\expandafter\dogoto      \else\expandafter\gotohtdp      \fi}

% The unbox trick is needed in order to permit \par inside a reference. Otherwise
% the reference attribute migrates to the outer boxes.

\newcount\lastsavedreferenceattribute

\newbox\referencebox

\def\revivesavedreferenceattribute % sometimes handy as no test etc needed
  {\attribute\referenceattribute\lastsavedreferenceattribute}

\def\dodirectgoto#1[#2]% no test for valid references
  {\dontleavehmode
   \begingroup
   \attribute\referenceattribute\attributeunsetvalue
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.inject("\referenceprefix","#2",\number\ht\strutbox,\number\dp\strutbox,\extrareferencearguments)}%
     \setlocationattributes\??ia
     \setstrut % can be option
     \global\lastsavedreferenceattribute\lastreferenceattribute
     \attribute\referenceattribute\lastreferenceattribute
     \dostarttagged\t!link\empty % not here
     #1%
     \dostoptagged
   \else
     #1%
   \fi
   \endgroup}

\def\dodirectgotohtdp#1[#2]% no test for valid references
  {\dontleavehmode
   \begingroup
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.inject("\referenceprefix","#2",\number\dimexpr\interactionparameter\c!height\relax,\number\dimexpr\interactionparameter\c!depth\relax,\extrareferencearguments)}%
     \setlocationattributes\??ia
     \attribute\referenceattribute\lastreferenceattribute
     \global\lastsavedreferenceattribute\lastreferenceattribute
     \dostarttagged\t!link\empty
     #1%
     \dostoptagged
   \else
     #1%
   \fi
   \endgroup}

\def\dogoto#1#2[#3]% #2 gobbles spaces after #1 so that \goto{xx} [yy] works ok
  {\dontleavehmode
   \begingroup
  %\setbox\referencebox\hbox\bgroup % experiment, might change again to non \par support
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.doifelse("\referenceprefix","#3",\extrareferencearguments)}%
       {\expandtexincurrentreference
        \ctxlua{structures.references.injectcurrentset(\number\ht\strutbox,\number\dp\strutbox)}%
        \setlocationattributes\??ia
        \setstrut % can be option
        \global\lastsavedreferenceattribute\lastreferenceattribute
        \attribute\referenceattribute\lastreferenceattribute
        \dostarttagged\t!link\empty
        #1%
        \dostoptagged}%
       {#1}%
   \else
     #1%
   \fi
  %\egroup\unhbox\referencebox}
   \endgroup}

\def\dogotohtdp#1#2[#3]% #2 gobbles spaces after #1 so that \goto{xx} [yy] works ok
  {\dontleavehmode
   \begingroup
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.doifelse("\referenceprefix","#3",\extrareferencearguments)}%
       {\expandtexincurrentreference
        \ctxlua{structures.references.injectcurrentset(\number\dimexpr\interactionparameter\c!height\relax,\number\dimexpr\interactionparameter\c!depth\relax)}%
        \setlocationattributes\??ia
        \global\lastsavedreferenceattribute\lastreferenceattribute
        \attribute\referenceattribute\lastreferenceattribute
        \dostarttagged\t!link\empty
        #1%
        \dostoptagged}%
       {#1}%
   \else
     #1%
   \fi
   \endgroup}

\unexpanded\def\directgotobox#1[#2]% no test for valid references
  {\dontleavehmode
   \begingroup
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.inject("\referenceprefix","#2",nil,nil,\extrareferencearguments)}%
     \setlocationattributes\??ia
     \global\lastsavedreferenceattribute\lastreferenceattribute
     \dostarttagged\t!link\empty
     \hbox attr \referenceattribute \lastreferenceattribute {#1}%
     \dostoptagged
   \else
     #1%
   \fi
   \endgroup}

\unexpanded\def\directgotospecbox#1#2[#3]% no test for valid references
  {\dontleavehmode
   \begingroup
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.inject("\referenceprefix","#3",nil,nil,\extrareferencearguments)}%
     \setlocationcolorspec{#1}% no consequence for strut
     \global\lastsavedreferenceattribute\lastreferenceattribute
     \dostarttagged\t!link\empty
     \hbox attr \referenceattribute \lastreferenceattribute {#2}%
     \dostoptagged
   \else
     #2%
   \fi
   \endgroup}

\unexpanded\def\directgotodumbbox#1[#2]% no test for valid references
  {\dontleavehmode
   \begingroup
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.inject("\referenceprefix","#2",nil,nil,\extrareferencearguments)}%
     \global\lastsavedreferenceattribute\lastreferenceattribute
     \dostarttagged\t!link\empty
     \hbox attr \referenceattribute \lastreferenceattribute {#1}%
     \dostoptagged
   \else
     #1%
   \fi
   \endgroup}

\unexpanded\def\gotobox#1[#2]% no test for valid references
  {\dontleavehmode
   \begingroup
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \iflocation
     \ctxlua{structures.references.doifelse("\referenceprefix","#2",\extrareferencearguments)}%
       {\expandtexincurrentreference
        \ctxlua{structures.references.injectcurrentset(nil,nil)}%
        \setlocationattributes\??ia
        \global\lastsavedreferenceattribute\lastreferenceattribute
        \dostarttagged\t!link\empty
        \hbox attr \referenceattribute \lastreferenceattribute {#1}%
        \dostoptagged}%
       {#1}%
   \else
     #1%
   \fi
   \endgroup}

\unexpanded\def\gotowdhtbox#1#2[#3]% fast variant for overlays
  {\dontleavehmode
   \begingroup
   \setbox\scratchbox\emptyhbox\wd\scratchbox#1\ht\scratchbox#2%
   \global\lastsavedreferenceattribute\attributeunsetvalue
   \attribute\referenceattribute\attributeunsetvalue
   \ctxlua{structures.references.doifelse("\referenceprefix","#3",\extrareferencearguments)}%
     {\ctxlua{structures.references.injectcurrentset(nil,nil)}%
      \global\lastsavedreferenceattribute\lastreferenceattribute
      \hbox attr \referenceattribute \lastreferenceattribute {\box\scratchbox}}
     {\box\scratchbox}%
   \endgroup}

%D An reference to another document can be specified as a file
%D or as an \URL. Both are handled by the same mechanism and
%D can be issued by saying something like:
%D
%D \starttyping
%D \goto[dictionary::the letter a]
%D \stoptyping
%D
%D One can imagine that many references to such a dictionary
%D are made, so in most cases such a document reference in an
%D indirect one.
%D
%D \showsetup{useexternaldocument}
%D
%D For example:
%D
%D \starttyping
%D \useexternaldocument
%D   [dictionary][engldict]
%D   [The Famous English Dictionary]
%D \stoptyping
%D
%D The next macro implements these relations, and also take
%D care of loading the document specific references.
%D
%D The \URL\ alternative takes four arguments:
%D
%D \showsetup{useURL}
%D
%D like:
%D
%D \starttyping
%D \useURL
%D   [dictionary][http://www.publisher.com/public][engldict]
%D   [The Famous English Dictionary]
%D \stoptyping
%D
%D Several specifications are possible:
%D
%D \starttyping
%D \useURL [id] [url] [file] [description]
%D \useURL [id] [url] [file]
%D \useURL [id] [url]
%D \stoptyping
%D
%D This time we don't load the references when no file is
%D specified. This is logical when one keeps in mind that a
%D valid \URL\ can also be a mail address.

\unexpanded\def\usefile{\dotripleargument\dousefile}  % so that they can be used in expanded arguments
\unexpanded\def\useurl {\doquadrupleempty\douseurl }  % so that they can be used in expanded arguments

\let\useURL             \useurl
\let\useexternaldocument\usefile

\def\douseurl[#1][#2][#3][#4]%
  {\ctxlua{structures.references.urls.define("#1",\!!bs\detokenize{#2}\!!es,\!!bs\detokenize{#3}\!!es,\!!bs\detokenize{#4}\!!es)}}

\def\dousefile[#1][#2][#3]%
  {\ctxlua{structures.references.files.define("#1",\!!bs\detokenize{#2}\!!es,\!!bs\detokenize{#3}\!!es)}}

\def\doifurldefinedelse #1{\ctxcommand{doifurldefinedelse ("#1")}}
\def\doiffiledefinedelse#1{\ctxcommand{doiffiledefinedelse("#1")}}

%D \macros
%D   {url,setupurl}
%D
%D We also have: \type{\url} for directly calling the
%D description. So we can say:
%D
%D \starttyping
%D \useURL [one] [http://www.test.nl]
%D \useURL [two] [http://www.test.nl] [] [Some Site]
%D
%D \url[one] or \from[two] or \goto{Whatever Site}[URL(two)]
%D \stoptyping
%D
%D An \URL\ can be set up with
%D
%D \showsetup{setupurl}

\unexpanded\def\setupurl
  {\dodoubleargument\getparameters[\??ur]}

\unexpanded\def\url[#1]%
  {\dontleavehmode
   \begingroup
   \dosetfontattribute\??ur\c!style
   \dosetcolorattribute\??ur\c!color
   \hyphenatedurl{\ctxlua{structures.references.urls.get("#1","\@@uralternative","\@@urspace")}}%
   \endgroup}

% # fails

%D This macro is hooked into a support macro, and thereby
%D \URL's break ok, according to the setting of a switch,
%D
%D \startbuffer
%D \useURL
%D   [test]
%D   [sentence_sentence~sentence//sentence:sentence.sentence]
%D \stopbuffer
%D
%D \typebuffer
%D
%D Such an \URL\ is, depending on the settings, hyphenated as:
%D
%D \getbuffer
%D
%D \startlinecorrection
%D \hbox to \hsize
%D   {\hss\en
%D    \setupreferencing[urlalternative=both]%
%D    \vbox{\hsize.25cm\hbox{\bf both}\prewordbreak\url[test]}%
%D    \hss
%D    \setupreferencing[urlalternative=before]%
%D    \vbox{\hsize.25cm\hbox{\bf before}\prewordbreak\url[test]}%
%D    \hss
%D    \setupreferencing[urlalternative=after]%
%D    \vbox{\hsize.25cm\hbox{\bf after}\prewordbreak\url[test]}%
%D    \hss}
%D \stoplinecorrection
%D
%D By setting \type{urlspace=yes} one can get slightly better
%D spacing when using very long \URL's.
%D
%D When defining the external source of information, one can
%D also specify a suitable name (the last argument). This name
%D can be called upon with:
%D
%D \showsetup{from}

%D We keep this for compatibility reasons, hence the hackery.

\unexpanded\def\dospecialfrom
  {\dosingleempty\dodospecialfrom}

\def\dodospecialfrom[#1]%
  {\dontleavehmode
   \goto{\ctxlua{structures.references.from("#1")}}[fileorurl(#1)]}

\def\dofromurldescription#1%
  {#1}

\def\dofromurlliteral#1%
  {\dosetfontattribute \??ur\c!style
   \dosetcolorattribute\??ur\c!color
   \hyphenatedurl{#1}}

\let\dofromfiledescription\dofromurldescription
\let\dofromfileliteral    \dofromurlliteral     % maybe some day setupfile that inherits from url

%D We also support:
%D
%D \starttyping
%D \goto{some text}[file(identifier{location}]
%D \stoptyping
%D
%D which is completely equivalent with
%D
%D \starttyping
%D \goto{some text}[identifier::location]
%D \stoptyping

%D A special case of references are those to programs. These,
%D very system dependant references are implemented by abusing
%D some of the previous macros.
%D
%D \showsetup{setupprograms}
%D \showsetup{defineprogram}
%D \showsetup{program} % changed functionality !
%D
%D The latter gives access to the description of the program,
%D being the last argument to the definition command.

% also lua, like urls and files

\unexpanded\def\setupprograms
  {\dodoubleargument\getparameters[\??pr]}

\unexpanded\def\defineprogram
  {\dotripleargument\dodefineprogram}

\def\dodefineprogram[#1][#2][#3]%
  {\ctxlua{structures.references.programs.define("#1","#2","#3")}}

\def\program[#1]% incompatible, more consistent, hardy used anyway
  {\dontleavehmode
   \begingroup
   \dosetfontattribute\??pr\c!style
   \dosetcolorattribute\??pr\c!color
   \ctxlua{structures.references.programs.get("#1","\@@pralternative","\@@prspace")}%
   \endgroup}

%D As we can see, we directly use the special reference
%D mechanism, which means that
%D
%D \starttyping
%D \goto{some text}[program(name{args})]
%D \stoptyping
%D
%D is valid.

%D The next macro provides access to the actual pagenumbers.
%D When documenting and sanitizing the original reference
%D macros, I decided to keep the present meaning as well as to
%D make this meaning available as a special reference method.
%D So now one can use:
%D
%D \starttyping
%D \gotopage{some text}[location]
%D \gotopage{some text}[number]
%D \gotopage{some text}[file::number]
%D \stoptyping
%D
%D as well as:
%D
%D \starttyping
%D \goto{some text}[page(location)]
%D \goto{some text}[page(number)]
%D \goto{some text}[file::page(number)]
%D \stoptyping
%D
%D Here location is a keyword like \type{nextpage}.
%D
%D \showsetup{gotopage}

\unexpanded\def\definepage
  {\dodoubleargument\dodefinepage}

\def\dodefinepage[#1][#2]%
  {\definereference[#1][page(#1)]}

\def\gotopage#1[#2]%
  {\goto{#1}[\v!page(#2)]}

%D The previous definitions are somewhat obsolete so we don't
%D use it here.

%D A still very rudimentary|/|experimental forward|/|backward
%D reference mechanism is provided by the macro \type{\atpage}:
%D
%D \starttyping
%D ... \somewhere{backward text}{forward text}[someref] ...
%D ... \atpage[someref] ...
%D \stoptyping
%D
%D In future versions there will be more sophisticated

% 0 = no page reference
% 1 = same page
% 2 = preceding page
% 3 = following page
% 4 = backward, same page (todo)
% 5 = forward, same page  (todo)

%D We can cross link documents by using:
%D
%D \showsetup{coupledocument}
%D
%D like:
%D
%D \starttyping
%D \coupledocument[print][somefile][chapter,section]
%D \stoptyping
%D
%D After which when applicable, we have available the
%D references:
%D
%D \starttyping
%D \goto{print version}[print::chapter]
%D \stoptyping
%D
%D and alike. The title placement definition macros have a
%D key \type{file}, which is interpreted as the file to jump
%D to, that is, when one clicks on the title.

\def\coupledocument
  {\doquadrupleempty\docoupledocument}

\def\docoupledocument[#1][#2][#3][#4]% [name] [file] [sections] [description]
  {\ifthirdargument
     % this will be done differently (when it's needed)
   \fi}

%D \macros
%D   {dotextprefix}
%D
%D In previous macros we used \type {\dotextprefix} to
%D generate a space between a label and a number.
%D
%D \starttyping
%D \dotextprefix{text}
%D \stoptyping
%D
%D Only when \type {text} is not empty, a space is inserted.

\def\dotextprefix#1%
  {\begingroup
   \setbox\scratchbox\hbox{#1}% to be solved some day
   \ifdim\wd\scratchbox>\zeropoint
     \unhbox\scratchbox
     \doifsomething\@@rfseparator{\removeunwantedspaces\@@rfseparator}% remove is new
   \else
     \unhbox\scratchbox
   \fi
   \endgroup}

%D In the next settings we see some variables that were not
%D used here and that concern the way the pagenumbers refered
%D to are typeset.

\setupreferencing
  [\c!state=\v!start,
   \c!autofile=\v!no,
   \v!part\c!number=\v!yes,
   \v!chapter\c!number=\v!no,
   \c!interaction=\v!all,
   \c!convertfile=\v!no,
  %\c!strut=\v!no, % some day an option
   \c!prefix=,
   \c!width=.75\makeupwidth,
   \c!left=\quotation\bgroup,
   \c!right=\egroup,
   \c!global=\v!no,
   \c!expansion=\v!no,
   \c!separator=\nonbreakablespace,
   \c!export=\v!no]

\setupurl
  [\c!alternative=\v!both,
   \c!space=\v!no,
   \c!style=\v!type,
   \c!color=]

\setupprograms
  [\c!directory=,
   \c!alternative=\v!both,
   \c!space=\v!no,
   \c!style=\v!type,
   \c!color=]

\definereference [\v!CloseDocument    ] [action(close)]
\definereference [\v!ExitViewer       ] [action(exit)]
\definereference [\v!FirstPage        ] [action(first)]
\definereference [\v!LastPage         ] [action(last)]
\definereference [\v!NextJump         ] [action(forward)]
\definereference [\v!NextPage         ] [action(next)]
\definereference [\v!PauseMovie       ] [action(pausemovie)]
\definereference [\v!PauseSound       ] [action(pausesound)]
\definereference [\v!PauseRendering   ] [action(pauserendering)]
\definereference [\v!PreviousJump     ] [action(backward)]
\definereference [\v!PreviousPage     ] [action(previous)]
\definereference [\v!PrintDocument    ] [action(print)]
\definereference [\v!SaveForm         ] [action(exportform)]
\definereference [\v!LoadForm         ] [action(importform)]
\definereference [\v!ResetForm        ] [action(resetform)]
\definereference [\v!ResumeMovie      ] [action(resumemovie)]
\definereference [\v!ResumeSound      ] [action(resumesound)]
\definereference [\v!ResumeRendering  ] [action(resumerendering)]
\definereference [\v!SaveDocument     ] [action(save)]
\definereference [\v!SaveNamedDocument] [action(savenamed)]
\definereference [\v!OpenNamedDocument] [action(opennamed)]
\definereference [\v!SearchDocument   ] [action(search)]
\definereference [\v!SearchAgain      ] [action(searchagain)]
\definereference [\v!StartMovie       ] [action(startmovie)]
\definereference [\v!StartSound       ] [action(startsound)]
\definereference [\v!StartRendering   ] [action(startrendering)]
\definereference [\v!StopMovie        ] [action(stopmovie)]
\definereference [\v!StopSound        ] [action(stopsound)]
\definereference [\v!StopRendering    ] [action(stoprendering)]
\definereference [\v!SubmitForm       ] [action(submitform)]
\definereference [\v!ToggleViewer     ] [action(toggle)]
\definereference [\v!ViewerHelp       ] [action(help)]
\definereference [\v!HideField        ] [action(hide)]
\definereference [\v!ShowField        ] [action(show)]
\definereference [\v!GotoPage         ] [action(gotopage)]
\definereference [\v!Query            ] [action(query)]
\definereference [\v!QueryAgain       ] [action(queryagain)]
\definereference [\v!FitWidth         ] [action(fitwidth)]
\definereference [\v!FitHeight        ] [action(fitheight)]
\definereference [\v!ShowThumbs       ] [action(thumbnails)]
\definereference [\v!ShowBookmarks    ] [action(bookmarks)]

\definereference [\v!HideLayer        ] [action(hidelayer)]
\definereference [\v!VideLayer        ] [action(videlayer)]
\definereference [\v!ToggleLayer      ] [action(togglelayer)]

\definereference [\v!firstpage]       [page(firstpage)]
\definereference [\v!previouspage]    [page(previouspage)]
\definereference [\v!nextpage]        [page(nextpage)]
\definereference [\v!lastpage]        [page(lastpage)]
\definereference [\v!forward]         [page(forward)]
\definereference [\v!backward]        [page(backward)]
\definereference [\v!firstsubpage]    [page(firstsubpage)]
\definereference [\v!previoussubpage] [page(previoussubpage)]
\definereference [\v!nextsubpage]     [page(nextsubpage)]
\definereference [\v!lastsubpage]     [page(lastsubpage)]

% we can do this but only when later in resolve (else problems with \chapter[first]{...}
%
% \definereference [\v!first]           [page(firstpage)]
% \definereference [\v!previous]        [page(prevpage)]
% \definereference [\v!next]            [page(nextpage)]
% \definereference [\v!last]            [page(lastpage)]
% \definereference [\v!first\v!sub]     [page(firstsubpage)]
% \definereference [\v!previous\v!sub]  [page(prevsubpage)]
% \definereference [\v!next\v!sub]      [page(nextsubpage)]
% \definereference [\v!last\v!sub]      [page(lastsubpage)]

%D We cannot set up buttons (not yet, this one calls a menu macro):

%D New (and experimental):

% \starttext
%     \chapter{test}
%     \placefigure[here][xx:1]{}{\framed{one}} \placefigure[here][xx:2]{}{\framed{three}}
%     \placetable [here][xx:3]{}{\framed{two}} \placetable [here][xx:4]{}{\framed{four}}
%     \start
%         \in{fig}[xx:1] and \in{fig}[xx:2] \in{tab}[xx:3] and \in{tab}[xx:4]
%     \stop \blank \start
%         \setupreferencestructureprefix[default][prefix=no]
%         \in{fig}[xx:1] and \in{fig}[xx:2] \in{tab}[xx:3] and \in{tab}[xx:4]
%     \stop \blank \start
%         \setupreferencestructureprefix[float][default][prefix=no]
%         \in{fig}[xx:1] and \in{fig}[xx:2] \in{tab}[xx:3] and \in{tab}[xx:4]
%     \stop \blank \start
%         \setupreferencestructureprefix[figure][default][prefix=no]
%         \in{fig}[xx:1] and \in{fig}[xx:2] \in{tab}[xx:3] and \in{tab}[xx:4]
%     \stop \blank
% \stoptext

\unexpanded\def\setupreferencestructureprefix
  {\dotripleargument\dosetupreferencestructureprefix}

\def\getreferencestructureprefix#1#2#3%
  {{
        prefix        = "\referencestructureprefixparameter{#1}{#2}{#3}\c!prefix",
        separatorset  = "\referencestructureprefixparameter{#1}{#2}{#3}\c!prefixseparatorset",
        conversion    = "\referencestructureprefixparameter{#1}{#2}{#3}\c!prefixconversion",
        conversionset = "\referencestructureprefixparameter{#1}{#2}{#3}\c!prefixconversionset",
        set           = "\referencestructureprefixparameter{#1}{#2}{#3}\c!prefixset",
        segments      = "\referencestructureprefixparameter{#1}{#2}{#3}\c!prefixsegments",
        connector     = \!!bs\referencestructureprefixparameter{#1}{#2}{#3}\c!prefixconnector\!!es,
  }}

\unexpanded\def\setupreferencestructureprefix
  {\dotripleempty\dosetupreferencestructureprefix}

\def\dosetupreferencestructureprefix[#1][#2][#3]%
  {\ifthirdargument
     \getparameters[\??rf:\c!prefix:#1:#2][#3]%
   \else\ifsecondargument
     \getparameters[\??rf:\c!prefix::#1][#2]%
   \fi\fi}

\def\referencestructureprefixparameter#1#2#3#4% kind name category parameter
  {\ifcsname\??rf:\c!prefix:#2:#3#4\endcsname
     \csname\??rf:\c!prefix:#2:#3#4\endcsname
   \else\ifcsname\??rf:\c!prefix:#1:#3#4\endcsname
     \csname\??rf:\c!prefix:#1:#3#4\endcsname
   \else\ifcsname\??rf:\c!prefix::#3#4\endcsname
     \csname\??rf:\c!prefix::#3#4\endcsname
   \fi\fi\fi}

% \def\getreferencestructureprefixspec#1% we can save one call by moving this to the lua end
%   {\getreferencestructureprefix
%      {\ctxlua{structures.references.getcurrentmetadata("kind")}}
%      {\ctxlua{structures.references.getcurrentmetadata("name")}}
%      {#1}}
% \def\currentreferencedefault
%   {\ctxlua{structures.references.filter("default",\getreferencestructureprefixspec\v!default)}}
%
% this is shortcut for:

\def\currentreferencedefault
  {\ctxlua{structures.references.filter("default",\ctxlua{structures.references.getcurrentprefixspec("\v!default")})}}

\protect \endinput

% tricky:
%
% \enabletrackers[nodes.references]
% \setupinteraction[state=start]
% \def\KnuthTest{\input knuth }
% \def\KnuthTest{\input tufte }
% \def\TufteTest{\input tufte }
% \defineoverlay[xxx][\overlaybutton{page(3)}]
% \setupbackgrounds[text][background=xxx]
% \starttext
% test {\red \KnuthTest} test \par
% \button{test}[page(1)] \par
% \goto{page 2 \TeX}[page(2)] \goto{page 2 \TeX}[page(2)] \goto{\TufteTest}[page(2)] test \page
% test \goto{page 3}[page(3)] \goto{\TufteTest\space\par\TufteTest}[page(4)] test \page
% \goto{page 1}[page(1)] \goto{\TufteTest\space test}[page(1)] \page
% \goto{page 1}[page(1)] \goto{\KnuthTest\space test}[page(1)] \page
% test \goto{page 1}[page(1)] {\goto{\KnuthTest\space test}[page(1)]} test
% \goto{page 1}[page(1)] \goto{\TufteTest}[page(1)] test \page
% \stoptext