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%D \module
%D [ file=core-obj,
%D version=1998.01.15,
%D title=\CONTEXT\ Core Macros,
%D subtitle=Object Handling,
%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 Core Macros / Object Handling}
\unprotect
\startmessages dutch library: references
30: onbekend object --
31: dubbel object --
\stopmessages
\startmessages english library: references
30: unknown object --
31: duplicate object --
\stopmessages
\startmessages german library: references
30: unbekanntes Object --
31: doppeltes Object --
\stopmessages
\startmessages czech library: references
30: neznamy objekt --
31: duplicitni object --
\stopmessages
%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 \starttypen
%D \setobject{class}{name}\somebox{}
%D \getobject{class}{name}
%D \stoptypen
%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\presetobject#1#2%
{\doifundefined{\r!object#1::#2}
{\setxvalue{\r!object#1::#2}{NOT YET FLUSHED}}}
\def\setobject#1#2% evt \initializepaper naar \everyshipout
{\initializepaper
\ifundefined{\r!object#1::#2}%
\expandafter\dosetobject
\else
\expandafter\gobblefourarguments
\fi
{#1}{#2}}
\def\dosetobject#1#2%
{\bgroup
\inobjecttrue
\dowithnextbox
{\bgroup
\dontshowcomposition % rather fuzzy in \setxvalue ... \hbox
\setxvalue{\r!object#1::#2}%
{\noexpand\dohandleobject{#1}{#2}
{\ifhbox\nextbox\hbox\else\vbox\fi}
%{\the\wd\nextbox}{\the\ht\nextbox}{\the\dp\nextbox}}%
{\number\wd\nextbox}{\number\ht\nextbox}{\number\dp\nextbox}}%
\dostartobject
{#1}{#2}
{\number\wd\nextbox}{\number\ht\nextbox}{\number\dp\nextbox}%
\box\nextbox
\dostopobject
\egroup
\egroup}}
\def\dogetobject#1#2#3#4#5#6%
{\initializepaper
\bgroup
\dontshowcomposition
% \setbox0=\vbox to #5{\vfill\doinsertobject{#1}{#2}}%
\setbox0=\vbox to #5sp{\vfill\doinsertobject{#1}{#2}}%
\setbox0=#3{\box0}%
% \wd0=#4\ht0=#5\dp0=#6\relax
\wd0=#4sp\ht0=#5sp\dp0=#6sp%
\box0
\egroup}
\def\getobject#1#2%
{\let\dohandleobject\dogetobject
\getvalue{\r!object#1::#2}}
%D If needed one can ask for the dimensions of an object with:
%D
%D \starttypen
%D \getobjectdimensions{class}{name}
%D \stoptypen
%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}%
% \def\objectheight{#5}%
% \def\objectdepth {#6}}
{\def\objectwidth {#4sp}%
\def\objectheight{#5sp}%
\def\objectdepth {#6sp}}
\def\getobjectdimensions#1#2%
{\let\dohandleobject\dogetobjectdimensions
\let\objectwidth \!!zeropoint
\let\objectheight\!!zeropoint
\let\objectdepth \!!zeropoint
\getvalue{\r!object#1::#2}}
%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 \starttypen
%D \dosetobjectreference {class} {identifier} {reference value}
%D \dogetobjectreference {class} {identifier} \csname
%D \stoptypen
%D
%D These commands are to be called by the \type{\startobject},
%D \type{\stopobject} and \type{\insertobject} specials.
\newif\ifobjectreferencing \objectreferencingtrue
\def\checkobjectreferences%
{\bgroup
\setbox0=\hbox
{\doutilities{objectreferences}{\jobname}{}{}{}}%
\global\let\checkobjectreferences=\relax
\egroup}
\def\setobjectreferences%
{\def\objectreference##1##2##3%
{\doifundefinedelse{\r!driver##1::##2}
{\setxvalue{\r!driver##1::##2}{##3}}
{\showmessage{\m!references}{31}{[##1 ##2=>##3]}}}}
\def\resetobjectreferences%
{\let\objectreference=\gobblethreearguments}
\resetobjectreferences
\def\dosetobjectreference#1#2#3%
{\checkobjectreferences
\ifobjectreferencing
\bgroup
\edef\dowritereference%
{\writeutilitycommand{\objectreference{#1}{#2}{#3}}}%
\dowritereference
\egroup
\else
\global\objectreferencingtrue
\fi
\setxvalue{\r!driver#1::#2}{#3}}
\def\defaultobjectreference#1#2{0}
\def\dogetobjectreference#1#2#3%
{\checkobjectreferences
\doifdefinedelse{\r!driver#1::#2}
{\@EA\xdef\@EA#3\@EA{\csname\r!driver#1::#2\endcsname}}
{\showmessage{\m!references}{30}{[#1 #2=>\defaultobjectreference{#1}{#2}]}%
\xdef#3{\defaultobjectreference{#1}{#2}}}}
\let\normalsetobject=\setobject
\def\setobject%
{\global\objectreferencingfalse\normalsetobject}
\def\setreferenceobject%
{\global\objectreferencingtrue\normalsetobject}
%D \macros
%D {doifobjectfoundelse,doifobjectreferencefoundelse}
%D
%D To prevent redundant definition of objects, one can use
%D the next tests:
%D
%D \starttypen
%D \doifobjectfoundelse{class}{object}{do then}{do else}
%D \doifobjectreferencefoundelse{class}{object}{do then}{do else}
%D \stoptypen
\def\doifobjectfoundelse#1#2#3#4%
{\doifundefinedelse{\r!object#1::#2}{#4}{#3}}
\def\doifobjectreferencefoundelse#1#2#3#4%
{\checkobjectreferences
\doifundefinedelse{\r!driver#1::#2}{#4}{#3}}
%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 \starttypen
%D \doifobjectssupportedelse{true action}{false action}
%D \stoptypen
%D
%D As we can see, currently objects depend on the special
%D driver.
\newif\ifobjectssupported \objectssupportedtrue
\def\doifobjectssupportedelse#1#2%
{\ifobjectssupported
\doifspecialavailableelse\doinsertobject{#1}{#2}%
\else
#2%
\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
|
