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+%D \module
+%D   [       file=pack-obj,
+%D        version=1998.01.15,
+%D          title=\CONTEXT\ Packaging Macros,
+%D       subtitle=Objects,
+%D         author=Hans Hagen,
+%D           date=\currentdate,
+%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
+%C
+%C This module is part of the \CONTEXT\ macro||package and is
+%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
+%C details.
+
+% todo, move more to mkiv, get rid of blabelgroup
+
+\writestatus{loading}{ConTeXt Packaging Macros / Objects}
+
+\unprotect
+
+%D \macros
+%D   {setobject,getobject,ifinobject}
+%D
+%D Boxes can be considered reuable objects. Unfortunaltely once
+%D passed to the \DVI\ file, such objects cannot be reused. In
+%D \PDF\ however, reusing is possible and sometimes even a
+%D necessity. Therefore, \CONTEXT\ supports reusable objects.
+%D
+%D During the \TEX\ processing run, boxes can serve the purpose
+%D of objects, and the \DVI\ driver module implements objects
+%D using packed boxes.
+%D
+%D The \PDF\ and \PDFTEX\ driver modules implement objects
+%D using \PDF\ forms. There is no (real) restriction on the
+%D number of objects there.
+%D
+%D The first application of objects in \CONTEXT\ concerned
+%D \METAPOST\ graphics and fill||in form fields. The first
+%D application can save lots of bytes, while the latter use is
+%D more a necessity than byte saving.
+%D
+%D \starttyping
+%D \setobject{class}{name}\somebox{}
+%D \getobject{class}{name}
+%D \stoptyping
+%D
+%D Here \type{\somebox} can be whatever box specification suits
+%D \TEX. We save the dimensions of an object, although some
+%D drivers will do so themselves. This means that when for
+%D instance using \PDFTEX\ we could save a hash entry plus some
+%D 20+ memory locations per object by delegating this
+%D housekeeping to the driver. The current approach permits
+%D us to keep the box characteristic too.
+
+\newif\ifinobject
+
+\def\checkobjectreferences
+  {\startnointerference
+   \protectlabels
+   \ifx\usedoutputdriver\currentoutput
+     \doutilities{objectreferences}\jobname\empty\relax\relax
+   \else
+     % different format (will fails on \purenumber)
+   \fi
+   \global\let\checkobjectreferences\relax
+   \stopnointerference}
+
+\def\objectplaceholder{NOT YET FLUSHED}%
+
+\def\presetobject#1#2% \global added
+  {\blabelgroup
+   \ifcsname\r!object#1::#2\endcsname\else
+     \global\@EA\let\csname\r!object#1::#2\endcsname\objectplaceholder
+   \fi
+   \elabelgroup}
+
+\def\dosetobject#1#2#3% \initializepaper this will move to \everyshipout
+  {\initializepaper
+   \blabelgroup
+   \ifcsname\r!object#2::#3\endcsname
+     \elabelgroup \expandafter\gobblefivearguments
+   \else % tzt, overload internal referenced objects to save entries
+     \elabelgroup \expandafter\dodosetobject
+   \fi
+   {#1}{#2}{#3}}
+
+\def\resetobject#1#2%
+  {\checkobjectreferences
+   \letbeundefined{\r!object#1::#2}}
+
+%D \macros
+%D   {finalizeobjectbox}
+%D
+%D This one provides a hook for last minute object box processing
+%D we need this in \MKIV.
+
+\ifx\finalizeobjectbox\undefined
+    \let\finalizeobjectbox\gobbleoneargument
+\fi
+
+%D Somehow there is a rounding error problem in either \PDFTEX\
+%D or in viewers, or maybe it is conforming the specs. The next
+%D variable compensate for it by removing the rather tight
+%D clip.
+
+\def\objectoffset{1cm}
+
+% \def\dodosetobject#1#2#3%
+%   {\bgroup
+%    \inobjecttrue
+%    \dowithnextbox{\dododosetobject{#1}{#2}{#3}\egroup}}
+
+\def\dodosetobject#1#2#3%
+  {\bgroup
+   \globalpushmacro\crossreferenceobject \objectreferenced
+   \inobjecttrue
+   \dowithnextbox
+     {\globalpopmacro\crossreferenceobject
+      \dododosetobject{#1}{#2}{#3}\egroup}}
+
+\def\dododosetobject#1#2#3%
+  {\blabelgroup
+   \dontshowcomposition % rather fuzzy in \setxvalue ... \hbox
+   \scratchdimen\objectoffset
+   \@EA\xdef\csname\r!object#2::#3\endcsname
+     {\noexpand\dohandleobject{#2}{#3}%
+        {\ifhbox\nextbox\hbox\else\vbox\fi}%
+       %{\the\nextboxwd}{\the\nextboxht}{\the\nextboxdp}}%
+        {\number\nextboxwd}{\number\nextboxht}{\number\nextboxdp}%
+        {\number\scratchdimen}}%
+   \expanded % freeze the dimensions since \dostartobject may use \nextbox
+     {\dostartobject
+        {#2}{#3}{\the\nextboxwd}{\the\nextboxht}{\the\nextboxdp}}%
+   \ifcase#1\relax\else \ifdim\objectoffset>\zeropoint
+     \setbox\nextbox\vbox spread 2\scratchdimen
+       {\forgetall \offinterlineskip
+        \vss\hbox spread 2\scratchdimen{\hss\flushnextbox\hss}\vss}%
+   \fi \fi
+   \flushnextbox
+   \dostopobject
+   \elabelgroup}
+
+\def\getobject#1#2%
+  {\blabelgroup
+   \let\dohandleobject\dogetobject
+   \csname\r!object#1::#2\endcsname}
+
+% \def\dogetobject#1#2#3#4#5#6%
+%   {\initializepaper
+%    \forgetall
+%    \dontshowcomposition
+%    \setbox\scratchbox\vbox
+%      {\doinsertobject{#1}{#2}}%
+%    \setbox\scratchbox#3%
+%      {\vbox to #5\scaledpoint
+%         {\ifdim\ht\scratchbox>#5\scaledpoint
+%     % or \ifdim\wd\scratchbox>#4\scaledpoint
+%            \vss\hbox to #4\scaledpoint{\hss\box\scratchbox\hss}\vss
+%          \else
+%            \vss\box\scratchbox
+%          \fi}}%
+%    \wd\scratchbox#4\scaledpoint
+%    \ht\scratchbox#5\scaledpoint
+%    \dp\scratchbox#6\scaledpoint
+%    \box\scratchbox
+%    \elabelgroup}
+
+% \def\dogetobject#1#2#3#4#5#6#7%
+%   {\initializepaper
+%    \forgetall
+%    \dontshowcomposition
+%    \setbox\scratchbox\vbox
+%      {\doinsertobject{#1}{#2}}%
+%    \setbox\scratchbox#3%
+%      {\vbox to #5\scaledpoint
+%         {\ifdim\ht\scratchbox>#5\scaledpoint
+%     % or \ifdim\wd\scratchbox>#4\scaledpoint
+%            \vss\hbox to #4\scaledpoint{\hss\box\scratchbox\hss}\vss
+%          \else
+%            \vss\box\scratchbox
+%          \fi}}%
+%    \scratchdimen#7\scaledpoint
+%    \setbox\nextbox\hbox
+%      {\hskip-\scratchdimen\lower\scratchdimen\flushnextbox}%
+%    \wd\scratchbox#4\scaledpoint
+%    \ht\scratchbox#5\scaledpoint
+%    \dp\scratchbox#6\scaledpoint
+%    \box\scratchbox
+%    \elabelgroup}
+
+\def\dogetobject#1#2#3#4#5#6#7% don't change this, should work for dvi & pdf
+  {\initializepaper
+   \forgetall
+   \dontshowcomposition
+   \setbox\scratchbox\vbox
+     {\doinsertobject{#1}{#2}}%
+   \setbox\scratchbox#3%
+     {\vbox to #5\scaledpoint
+        {\ifdim\ht\scratchbox>#5\scaledpoint
+           \vss\hbox to #4\scaledpoint{\hss\box\scratchbox\hss}\vss
+         \else\ifdim\wd\scratchbox>#4\scaledpoint
+           \vss\hbox to #4\scaledpoint{\hss\box\scratchbox\hss}\vss
+         \else
+          %\vss\box\scratchbox
+           \vss\hbox to #4\scaledpoint{\box\scratchbox\hss}% fix Chof
+         \fi\fi}}%
+   \box\scratchbox
+   \elabelgroup}
+
+%D If needed one can ask for the dimensions of an object with:
+%D
+%D \starttyping
+%D \getobjectdimensions{class}{name}
+%D \stoptyping
+%D
+%D The results are reported in \type {\objectwidth}, \type
+%D {\objectheight} and \type {\objectdepth}.
+
+% \def\dogetobjectdimensions#1#2#3#4#5#6%
+%   {\def\objectwidth {#4\s!sp}%
+%    \def\objectheight{#5\s!sp}%
+%    \def\objectdepth {#6\s!sp}}
+
+\def\dogetobjectdimensions#1#2#3#4#5#6#7%
+  {\def\objectwidth {#4\s!sp}%
+   \def\objectheight{#5\s!sp}%
+   \def\objectdepth {#6\s!sp}%
+   \def\objectmargin{#7\s!sp}}
+
+\def\getobjectdimensions#1#2%
+  {\let\dohandleobject\dogetobjectdimensions
+   \let\objectwidth \!!zeropoint
+   \let\objectheight\!!zeropoint
+   \let\objectdepth \!!zeropoint
+   \labelcsname\r!object#1::#2\endcsname}
+
+%D Apart from this kind of objects, that have typeset content,
+%D we can have low level driver specific objects. Both types
+%D can have references to internal representations, hidden for
+%D the user. We keep track of such references by means of a
+%D dedicated cross reference mechanism. Normally, objects are
+%D defined before they are used, but forward referencing
+%D sometimes occurs.
+%D
+%D \starttyping
+%D \dosetobjectreference {class} {identifier} {reference value} {page}
+%D \dogetobjectreference {class} {identifier} \csname
+%D \stoptyping
+%D
+%D These commands are to be called by the \type{\startobject},
+%D \type{\stopobject} and \type{\insertobject} specials.
+
+\def\objectreferenced{\global\chardef\crossreferenceobject\plusone}
+\def\driverreferenced{\global\chardef\crossreferenceobject\zerocount}
+
+\objectreferenced
+
+% no undefined test ! ! ! ! (pdftex fails on undefined objects)
+
+\def\setobjectreferences
+  {\def\objectreference##1##2##3##4%
+     {\ifundefined{\r!driver##1::##2}%
+        \setxvalue{\r!driver##1::##2}{{##3}{##4}}%
+      \else
+        \showmessage\m!references{31}{[##1 ##2=>##3/##4]}%
+      \fi}}
+
+\def\resetobjectreferences
+  {\let\objectreference\gobblefourarguments}
+
+\resetobjectreferences
+
+\def\doregisterobjectreference#1#2#3%
+  {\checkobjectreferences
+   \blabelgroup
+   \expanded{\writeutilitycommand{\noexpand\objectreference{#1}{#2}{#3}{\noexpand\realfolio}}}%
+   \setxvalue{\r!driver#1::#2}{{#3}{\noexpand\realfolio}}%
+   \elabelgroup}
+
+\def\dooverloadobjectreference#1#2#3%
+  {\checkobjectreferences
+   \blabelgroup
+   \setxvalue{\r!driver#1::#2}{{#3}{\noexpand\realfolio}}%
+   \elabelgroup}
+
+\def\dosetobjectreference
+  {\ifcase\crossreferenceobject
+     \objectreferenced
+     \expandafter\dooverloadobjectreference
+   \else
+     \expandafter\doregisterobjectreference
+   \fi}
+
+\def\dosetdriverreference
+  {\driverreferenced\dosetobjectreference}
+
+\def\defaultobjectreference#1#2{0} % driver dependent
+\def\defaultobjectpage     #1#2{\realfolio}
+
+\def\dogetobjectreference    {\dodogetobjectreference\firstoftwoarguments\defaultobjectreference}
+\def\dogetobjectreferencepage{\dodogetobjectreference\secondoftwoarguments\defaultobjectpage}
+
+\def\dodogetobjectreference#1#2#3#4#5%
+  {\checkobjectreferences
+   \blabelgroup
+   \ifundefined{\r!driver#3::#4}%
+     \showmessage\m!references{30}{[#3 #4=>#3/#4]}%
+     \xdef#5{#2{#3}{#4}}%
+   \else
+     \xdef#5{\@EAEAEA#1\csname\r!driver#3::#4\endcsname}%
+   \fi
+   \elabelgroup}
+
+\def\setobject     {\driverreferenced\dosetobject1}
+\def\settightobject{\driverreferenced\dosetobject0}
+
+%D \macros
+%D   {doifobjectfoundelse,doifobjectreferencefoundelse}
+%D
+%D To prevent redundant definition of objects, one can use
+%D the next tests:
+%D
+%D \starttyping
+%D \doifobjectfoundelse{class}{object}{do then}{do else}
+%D \doifobjectreferencefoundelse{class}{object}{do then}{do else}
+%D \stoptyping
+
+\def\doifobjectfoundelse#1#2%
+  {\blabelgroup \ifcsname\r!object#1::#2\endcsname
+     \elabelgroup \expandafter\firstoftwoarguments
+   \else
+     \elabelgroup \expandafter\secondoftwoarguments
+   \fi}
+
+\def\doifobjectreferencefoundelse#1#2%
+  {\checkobjectreferences
+   \blabelgroup \ifcsname\r!driver#1::#2\endcsname
+     \elabelgroup \expandafter\firstoftwoarguments
+   \else
+     \elabelgroup \expandafter\secondoftwoarguments
+   \fi}
+
+%D \macros
+%D   {doifobjectssupportedelse}
+%D
+%D Starting with reuse of graphics, we will implement object
+%D reuse when possible. To enable mechanisms to determine
+%D what method to use, we provide:
+%D
+%D \starttyping
+%D \doifobjectssupportedelse{true action}{false action}
+%D \stoptyping
+%D
+%D As we can see, currently objects depend on the special
+%D driver.
+
+\newif\ifobjectssupported \objectssupportedtrue
+
+\def\doifobjectssupportedelse
+  {\ifobjectssupported
+     \@EA\doifspecialavailableelse\@EA\doinsertobject
+   \else
+     \@EA\secondoftwoarguments
+   \fi}
+
+%D There is a conceptual problem here. Objects are not possible
+%D in \DVI, unless faked like in \type {spec-dvi}. This means
+%D that we must be careful in loading special drivers that do
+%D support objects while we still want to be able to use the
+%D \DVI\ output.
+
+\protect \endinput