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+%D \module
+%D [ file=mult-ini,
+%D version=2008.10.22, % 1996.06.01,
+%D title=\CONTEXT\ Multilingual Macros,
+%D subtitle=Initialization,
+%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.
+
+%D This module is a stripped down version of \type {mult-ini.tex},
+%D which we keep around as \type {mult-kep.tex} for sentimental
+%D reasons. There you will find some more historic information.
+
+\writestatus{loading}{ConTeXt Multilingual Macros / Initialization}
+
+\unprotect
+
+\registerctxluafile{mult-ini}{1.001}
+
+%D \macros
+%D [constanten,variabelen,commands]
+%D {v!,c!,k!,s!,e!,m!,l!,r!,f!,p!,x!,y!}
+%D
+%D In the system modules we introduced some prefixed constants,
+%D variables (both macros) and registers. Apart from a
+%D tremendous saving in terms of memory and a gain in speed we
+%D use from now on prefixes when possible for just another
+%D reason: consistency and multi||linguality. Systematically
+%D using prefixed macros enables us to implement a
+%D multi||lingual user interface. Redefining these next set of
+%D prefixes therefore can have desastrous results.
+%D
+%D \startlinecorrection
+%D \starttable[|c|c|c|]
+%D \HL
+%D \NC \bf prefix \NC \bf meaning \NC \bf application \NC\SR
+%D \HL
+%D \NC \type{\c!prefix!} \NC c! \NC constant (direct) \NC\FR
+%D \NC \type{\k!prefix!} \NC k! \NC constant (indirect) \NC\FR
+%D \NC \type{\e!prefix!} \NC e! \NC element \NC\MR
+%D \NC \type{\f!prefix!} \NC f! \NC file \NC\MR
+%D \NC \type{\m!prefix!} \NC m! \NC age \NC\MR
+%D \NC \type{\s!prefix!} \NC s! \NC system \NC\MR
+%D \NC \type{\v!prefix!} \NC v! \NC variable \NC\MR
+%D \HL
+%D \stoptable
+%D \stoplinecorrection
+%D
+%D In the single||lingual version we used \type{!}, \type{!!},
+%D \type{!!!} and \type{!!!!}. In the meantime some of these
+%D are obsolete (we had some 12 originally).
+
+\def\c!prefix!{c!}
+\def\k!prefix!{k!}
+\def\e!prefix!{e!}
+\def\f!prefix!{f!} % for the moment we keep this one
+\def\m!prefix!{m!}
+\def\s!prefix!{s!}
+\def\v!prefix!{v!}
+
+%D \macros
+%D [constants,variables,commands]
+%D {@@,??}
+%D
+%D Variables generated by the system can be recognized on their
+%D prefix \type{@@}. They are composed of a command (class)
+%D specific tag, which can be recognized on \type{??}, and a
+%D system constant, which has the prefix \type{c!}. We'll se
+%D some more of this.
+
+\def\??prefix {??}
+\def\@@prefix {@@}
+
+%D Just to be complete we repeat some of the already defined
+%D system constants here. Maybe their prefix \type{\s!} now
+%D falls into place.
+
+\def\s!next {next} \def\s!default {default}
+\def\s!dummy {dummy} \def\s!unknown {unknown}
+
+\def\s!do {do} \def\s!dodo {dodo}
+
+\def\s!complex {complex} \def\s!start {start}
+\def\s!simple {simple} \def\s!stop {stop}
+
+\def\s!true {true}
+\def\s!false {false}
+
+%D The word \type{height} takes 6~token memory cells. The
+%D control sequence \type{\height} on the other hand uses only
+%D one. Knowing this, we can improve the performance of \TEX,
+%D both is terms of speed and memory usage, by using control
+%D sequences instead of the words written in full.
+%D
+%D Where in the \ASCII\ file the second lines takes nine extra
+%D characters, \TEX\ saves us 13~tokens.
+%D
+%D \starttyping
+%D \hrule width 10pt height 2pt depth 1pt
+%D \hrule \s!width 10pt \s!height 2pt \s!depth 1pt
+%D \stoptyping
+%D
+%D One condition is that we have defined \type {\s!height},
+%D \type {\s!width} and \type {\s!depth} as respectively
+%D \type {height}, \type {width} and \type {depth}. Using this
+%D scheme therefore only makes sense when a token sequence is
+%D used more than once. Savings like this should of course be
+%D implemented in english, just because \TEX\ is english.
+
+\def\s!width {width} \let\!!width \s!width % obsolete
+\def\s!height{height} \let\!!height\s!height % obsolete
+\def\s!depth {depth} \let\!!depth \s!depth % obsolete
+\def\s!spread{spread} \let\!!spread\s!spread % obsolete
+\def\s!plus {plus} \let\!!plus \s!plus % obsolete
+\def\s!minus {minus} \let\!!minus \s!minus % obsolete
+\def\s!fil {fil}
+\def\s!fill {fill} \let\!!fill \s!fill % obsolete
+\def\s!filll {filll}
+\def\s!to {to} \let\!!to \s!to % obsolete
+\def\s!attr {attr}
+
+\def\s!bottom{bottom}
+\def\s!top {top}
+\def\s!both {both}
+
+%D Kind of special:
+
+\edef\!!TLT{\detokenize{TLT}}
+\edef\!!TRT{\detokenize{TRT}}
+
+%D \macros
+%D {defineinterfaceconstant,
+%D defineinterfacevariable,
+%D defineinterfaceelement,
+%D definesystemvariable,
+%D definesystemconstant,
+%D definemessageconstant,
+%D definefileconstant}
+%D
+%D The first part of this module is dedicated to dealing with
+%D multi||lingual constants and variables. When \CONTEXT\ grew
+%D bigger and bigger in terms of bytes and used string space,
+%D we switched to predefined constants. At the cost of more
+%D hash table entries, the macros not only becase more compact,
+%D they became much faster too. Maybe an even bigger advantage
+%D was that mispelling could no longer lead to problems. Even a
+%D multi||lingual interface became possible.
+%D
+%D Constants --- we'll introduce the concept of variables later
+%D on --- are preceded by a type specific prefix, followed by a
+%D \type{!}. To force consistency, we provide a few commands
+%D for defining such constants.
+%D
+%D \starttyping
+%D \defineinterfaceconstant {name} {meaning}
+%D \defineinterfacevariable {name} {meaning}
+%D \defineinterfaceelement {name} {meaning}
+%D \stoptyping
+%D
+%D Which is the same as:
+%D
+%D \starttyping
+%D \def\c!name{meaning}
+%D \def\v!name{meaning}
+%D \def\e!name{meaning}
+%D \stoptyping
+
+\unexpanded\def\defineinterfaceconstant #1#2{\expandafter\def\csname\c!prefix!#1\endcsname{#2}}
+\unexpanded\def\defineinterfacevariable #1#2{\expandafter\def\csname\v!prefix!#1\endcsname{#2}}
+\unexpanded\def\defineinterfaceelement #1#2{\expandafter\def\csname\e!prefix!#1\endcsname{#2}}
+
+%D Next come some interface independant constants:
+%D
+%D \starttyping
+%D \definefileconstant {name} {meaning}
+%D \stoptyping
+
+\unexpanded\def\definefileconstant #1#2{\expandafter\def\csname\f!prefix!#1\endcsname{#2}}
+
+%D And finaly we have the one argument, space saving constants
+%D
+%D \starttyping
+%D \definesystemconstant {name}
+%D \definemessageconstant {name}
+%D \stoptyping
+
+\unexpanded\def\definesystemconstant #1{\expandafter\def\csname\s!prefix!#1\endcsname{#1}}
+\unexpanded\def\definemessageconstant #1{\expandafter\def\csname\m!prefix!#1\endcsname{#1}}
+
+%D In a parameter driven system, some parameters are shared
+%D by more system components. In \CONTEXT\ we can distinguish
+%D parameters by a unique prefix. Such a prefix is defined
+%D with:
+%D
+%D \starttyping
+%D \definesystemvariable {name}
+%D \stoptyping
+
+\unexpanded\def\definesystemvariable#1{\expandafter\edef\csname\??prefix#1\endcsname{\@@prefix#1}}
+
+\definesystemvariable{ms}
+
+%D \macros
+%D {selectinterface,
+%D defaultinterface, currentinterface, currentresponses}
+%D
+%D With \type{\selectinterface} we specify the language we are
+%D going to use. The system asks for the language wanted, and
+%D defaults to \type{\currentinterface} when we just give
+%D \type{enter}. By default the message system uses the
+%D current interface language, but \type{\currentresponses}
+%D can specify another language too.
+%D
+%D Because we want to generate formats directly too, we do
+%D not ask for interface specifications when these are already
+%D defined (like in cont-nl.tex and alike).
+
+\ifdefined\defaultinterface
+
+ \def\selectinterface
+ {\writestatus{interface}{defining \currentinterface\space interface}%
+ \writeline
+ \writestatus{interface}{using \currentresponses\space messages}%
+ \writeline
+ \let\selectinterface\relax}
+
+\else
+
+ \def\defaultinterface{english}
+
+ \def\selectinterface
+ {\def\selectinterface##1##2%
+ {\bgroup
+ \endlinechar\minusone
+ \global\read16 to ##1
+ \egroup
+ \doifnothing\currentinterface{\let##1=##2}%
+ \doifundefined{\s!prefix!##1}{\let##1=##2}}%
+ \selectinterface\currentinterface\defaultinterface
+ \writestatus{interface}{defining \currentinterface\space interface}%
+ \writeline
+ \selectinterface\currentresponses\currentinterface
+ \writestatus{interface}{using \currentresponses\space messages}%
+ \writeline
+ \let\selectinterface\relax}
+
+\fi
+
+\ifdefined\currentinterface \else \let\currentinterface\defaultinterface \fi
+\ifdefined\currentresponses \else \let\currentresponses\defaultinterface \fi
+
+%D \macros
+%D {startinterface}
+%D
+%D Sometimes we want to define things only for specific
+%D interface languages. This can be done by means of the
+%D selector:
+%D
+%D \starttyping
+%D \startinterface language
+%D
+%D language specific definitions & commands
+%D
+%D \stopinterface
+%D \stoptyping
+
+\unexpanded\def\startinterface #1
+ {\doifnot{#1}{all}{\doifnotinset\currentinterface{#1}{\gobbleuntil\stopinterface}}}
+
+\let\stopinterface\relax
+
+%D \macros
+%D {startmessages,
+%D getmessage,
+%D showmessage,
+%D makemessage}
+%D
+%D A package as large as \CONTEXT\ can hardly function without
+%D a decent message mechanism. Due to its multi||lingual
+%D interface, the message subsystem has to be multi||lingual
+%D too. A major drawback of this feature is that we have to
+%D code messages. As a result, the source becomes less self
+%D documented. On the other hand, consistency will improve.
+%D
+%D Because the overhead in terms of entries in the (already
+%D exhausted) hash table has to be minimal, messages are packed
+%D in libraries. We can extract a message from such a library
+%D in three ways:
+%D
+%D \starttyping
+%D \getmessage {library} {tag}
+%D \showmessage {library} {tag} {data}
+%D \makemessage {library} {tag} {data}
+%D \stoptyping
+%D
+%D The first command gets the message \type{tag} from the
+%D \type{library} specified. The other commands take an extra
+%D argument: a list of items to be inserted in the message
+%D text. While \type{\showmessage} shows the message at the
+%D terminal, the other commands generate the message as text.
+%D Before we explain the \type{data} argument, we give an
+%D example of a library.
+%D
+%D \starttyping
+%D \startmessages english library: alfa
+%D title: something
+%D 1: first message
+%D 2: second (--) message --
+%D \stopmessages
+%D \stoptyping
+%D
+%D The first message is a simple one and can be shown with:
+%D
+%D \starttyping
+%D \showmessage {alfa} {1} {}
+%D \stoptyping
+%D
+%D The second message on the other hand needs some extra data:
+%D
+%D \starttyping
+%D \showmessage {alfa} {2} {and last,to you}
+%D \stoptyping
+%D
+%D This message is shown as:
+%D
+%D \starttyping
+%D something : second (and last) message to you
+%D \stoptyping
+%D
+%D As we can see, the title entry is shown with the message.
+%D The data fields are comma separated and are specified in the
+%D message text by \type{--}.
+%D
+%D It is not required to define all messages in a library at
+%D once. We can add messages to a library in the following way:
+%D
+%D \starttyping
+%D \startmessages english library: alfa
+%D 10: tenth message
+%D \stopmessages
+%D \stoptyping
+%D
+%D Because such definitions can take place in different
+%D modules, the system gives a warning when a tag occurs more
+%D than once. The first occurrence takes preference over later
+%D ones, so we had better use a save offset, as shown in the
+%D example. As we can see, the title field is specified only
+%D the first time!
+%D
+%D Because we want to check for duplicate tags, the macros
+%D are a bit more complicated than neccessary. The \NEWLINE\
+%D token is used as message separator.
+%D
+%D For internal purposes one can use \type {\setmessagetext},
+%D which puts the message text asked for in \type
+%D {\currentmessagetext}.
+
+%D These will become obsolete:
+
+\unexpanded\def\startmessages #1 library: #2 %
+ {\bgroup
+ \ifcsname\m!prefix!#2\endcsname\else\setgvalue{\m!prefix!#2}{#2}\fi
+ \catcode\endoflineasciicode\activecatcode
+ \doifelseinset{#1}{\currentresponses,all}\mult_messages_start_yes\mult_messages_start_nop{#2}}
+
+\def\mult_messages_start_yes#1#2\stopmessages
+ {\clf_setinterfacemessages{#1}{#2}%
+ \egroup}
+
+\def\mult_messages_start_nop#1#2\stopmessages
+ {\egroup}
+
+\let\stopmessages\relax
+
+\unexpanded\def\setinterfacemessage#1#2#3%
+ {\ifcsname\m!prefix!#1\endcsname\else\setgvalue{\m!prefix!#1}{#1}\fi
+ \clf_setinterfacemessage{#1}{#2}{#3}}
+
+\unexpanded\def\setmessagetext #1#2{\edef\currentmessagetext{\clf_getmessage{#1}{#2}}}
+\unexpanded\def\getmessage #1#2{\clf_getmessage{#1}{#2}}
+\unexpanded\def\doifelsemessage #1#2{\clf_doifelsemessage{#1}{#2}}
+\unexpanded\def\showmessage #1#2#3{\clf_showmessage{#1}{#2}{#3}}
+\unexpanded\def\writestatus #1#2{\clf_writestatus{#1}{#2}}
+\unexpanded\def\message {\clf_message}
+
+\let\doifmessageelse\doifelsemessage
+
+%D \macros
+%D {ifshowwarnings, ifshowmessages}
+%D
+%D Sometimes displaying message can slow down processing
+%D considerably. We therefore introduce warnings. Users can
+%D turn of warnings and messages by saying:
+%D
+%D \starttyping
+%D \showwarningstrue
+%D \showmessagestrue
+%D \stoptyping
+%D
+%D Turning off messages also turns off warnings, which is
+%D quote logical because they are less important.
+
+% not yet mkiv
+
+\newif\ifshowwarnings \showwarningstrue
+\newif\ifshowmessages \showmessagestrue
+
+\let\normalshowmessage\showmessage
+
+\unexpanded\def\showwarning
+ {\ifshowwarnings
+ \expandafter\showmessage
+ \else
+ \expandafter\gobblethreearguments
+ \fi}
+
+\unexpanded\def\showmessage
+ {\ifshowmessages
+ \expandafter\normalshowmessage
+ \else
+ \expandafter\gobblethreearguments
+ \fi}
+
+%D \macros
+%D {dosetvalue,dosetevalue,dosetgvalue,dosetxvalue,docopyvalue,doresetvalue} % dogetvalue
+%D
+%D We already defined these auxiliary macros in the system
+%D modules. Starting with this module however, we have to take
+%D multi||linguality a bit more serious.
+
+%D In due time, when we exclusively use the parameter handler code, we can drop
+%D the backmapping (\type{\c!k...}) and make \type {\c!c...} similar to
+%D \type {\v!...}. In that case we can simply the following setters.
+
+\unexpanded\def\doletvalue #1#2{\expandafter\let \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
+\unexpanded\def\dosetvalue #1#2{\expandafter\def \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
+\unexpanded\def\dosetevalue #1#2{\expandafter\edef\csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
+\unexpanded\def\dosetgvalue #1#2{\expandafter\gdef\csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
+\unexpanded\def\dosetxvalue #1#2{\expandafter\xdef\csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
+\unexpanded\def\doresetvalue #1#2{\expandafter\let \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname\empty}
+\unexpanded\def\doignorevalue#1#2#3{\expandafter\let \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname\empty}
+
+\unexpanded\def\docopyvalue#1#2#3%
+ {\ifcsname\k!prefix!#3\endcsname
+ \expandafter\def\csname#1\csname\k!prefix!#3\endcsname\expandafter\endcsname\expandafter
+ {\csname#2\csname\k!prefix!#3\endcsname\endcsname}%
+ \else
+ \expandafter\def\csname#1#3\expandafter\endcsname\expandafter
+ {\csname#2#3\endcsname}%
+ \fi}
+
+\startinterface english
+
+ \unexpanded\def\doletvalue #1#2{\expandafter \let\csname#1#2\endcsname}
+ \unexpanded\def\dosetvalue #1#2{\expandafter \def\csname#1#2\endcsname}
+ \unexpanded\def\dosetevalue #1#2{\expandafter\edef\csname#1#2\endcsname}
+ \unexpanded\def\dosetgvalue #1#2{\expandafter\gdef\csname#1#2\endcsname}
+ \unexpanded\def\dosetxvalue #1#2{\expandafter\xdef\csname#1#2\endcsname}
+ \unexpanded\def\doresetvalue #1#2{\expandafter \let\csname#1#2\endcsname\empty}
+ \unexpanded\def\doignorevalue#1#2#3{\expandafter \let\csname#1#2\endcsname\empty}
+
+ \unexpanded\def\docopyvalue#1#2#3%
+ {\expandafter\def\csname#1#3\expandafter\endcsname\expandafter
+ {\csname#2#3\endcsname}}
+
+\stopinterface
+
+%D We can now redefine some messages that will be
+%D introduced in the multi||lingual system module.
+
+\unexpanded\def\showassignerror #1#2{\showmessage\m!check1{#1,#2}\waitonfatalerror}
+\unexpanded\def\showargumenterror#1#2{\showmessage\m!check2{#1,#2}\waitonfatalerror}
+\unexpanded\def\showdefinederror #1#2{\showmessage\m!check3{#1,#2}\waitonfatalerror}
+
+%D \CONTEXT\ is a parameter driven package. This means that
+%D users instruct the system by means of variables, values and
+%D keywords. These instructions take the form:
+%D
+%D \starttyping
+%D \setupsomething[some variable=some value, another one=a keyword]
+%D \stoptyping
+%D
+%D or by keyword only:
+%D
+%D \starttyping
+%D \dosomething[this way,that way,no way]
+%D \stoptyping
+%D
+%D Because the same variables can occur in more than one setup
+%D command, we have to be able to distinguish them. This is
+%D achieved by assigning them a unique prefix.
+%D
+%D Imagine a setup command for boxed text, that enables us to
+%D specify the height and width of the box. Behide the scenes
+%D the command
+%D
+%D \starttyping
+%D \setupbox [width=12cm, height=3cm]
+%D \stoptyping
+%D
+%D results in something like
+%D
+%D \starttyping
+%D \<box><width> {12cm}
+%D \<box><height> {3cm}
+%D \stoptyping
+%D
+%D while a similar command for specifying the page dimensions
+%D of an \cap{A4} page results in:
+%D
+%D \starttyping
+%D \<page><width> {21.0cm}
+%D \<page><height> {27.9cm}
+%D \stoptyping
+%D
+%D The prefixes \type{<box>} and \type{<page>} are hidden from
+%D users and can therefore be language independant. Variables
+%D on the other hand, differ for each language:
+%D
+%D \starttyping
+%D \<box><color> {<blue>}
+%D \<box><kleur> {<blauw>}
+%D \<box><couleur> {<blue>}
+%D \stoptyping
+%D
+%D In this example we can see that the assigned values or
+%D keywords are language dependant too. This will be a
+%D complication when defining multi||lingual setup files.
+%D
+%D A third phenomena is that variables and values can have a
+%D similar meaning.
+%D
+%D \starttyping
+%D \<pagenumber><location> {<left>}
+%D \<skip><left> {12cm}
+%D \stoptyping
+%D
+%D A (minor) complication is that where in english we use
+%D \type{<left>}, in dutch we find both \type{<links>} and
+%D \type{<linker>}. This means that when we use some sort of
+%D translation table, we have to distinguish between the
+%D variables at the left side and the fixed values at the
+%D right.
+%D
+%D The same goes for commands that are composed of different
+%D user supplied and/or language specific elements. In english
+%D we can use:
+%D
+%D \starttyping
+%D \<empty><figure>
+%D \<empty><intermezzo>
+%D \stoptyping
+%D
+%D But in dutch we have the following:
+%D
+%D \starttyping
+%D \<lege><figuur>
+%D \<leeg><intermezzo>
+%D \stoptyping
+%D
+%D These subtle differences automatically lead to a solution
+%D where variables, values, elements and other components have
+%D a similar logical name (used in macro's) but a different
+%D meaning (supplied by the user).
+%D
+%D Our solution is one in which the whole system is programmed
+%D in terms of identifiers with language specific meanings. In
+%D such an implementation, each fixed variable is available as:
+%D
+%D \starttyping
+%D \<prefix><variable>
+%D \stoptyping
+%D
+%D This means that for instance:
+%D
+%D \starttyping
+%D \setupbox[width=12cm]
+%D \stoptyping
+%D
+%D expands to something like:
+%D
+%D \starttyping
+%D \def\boxwidth{12cm}
+%D \stoptyping
+%D
+%D because we don't want to recode the source, a setup command
+%D in another language has to expand to this variable, so:
+%D
+%D \starttyping
+%D \setupblock[width=12cm]
+%D \stoptyping
+%D
+%D has to result in the definition of \type{\boxwidth} too.
+%D This method enables us to build compact, fast and readable
+%D code.
+%D
+%D An alternative method, which we considered using, uses a
+%D more indirect way. In this case, both calls generate a
+%D different variable:
+%D
+%D \starttyping
+%D \def\boxwidth {12cm}
+%D \def\boxbreedte {12cm}
+%D \stoptyping
+%D
+%D And because we don't want to recode those megabytes of
+%D already developed code, this variable has to be called with
+%D something like:
+%D
+%D \starttyping
+%D \valueof\box\width
+%D \stoptyping
+%D
+%D where \type{\valueof} takes care of the translation of
+%D \type{width} or \type{breedte} to \type{width} and
+%D combining this with \type{box} to \type{\boxwidth}.
+%D
+%D One advantage of this other scheme is that, within certain
+%D limits, we can implement an interface that can be switched
+%D to another language at will, while the current approach
+%D fixes the interface at startup. There are, by the way,
+%D other reasons too for not choosing this scheme. Switching
+%D user generated commands is for instance impossible and a
+%D dual interface would therefore give a strange mix of
+%D languages.
+%D
+%D Now let's work out the first scheme. Although the left hand
+%D of the assignment is a variable from the users point of
+%D view, it is a constant in terms of the system. Both
+%D \type{width} and \type{breedte} expand to \type{width}
+%D because in the source we only encounter \type{width}. Such
+%D system constants are presented as
+%D
+%D \starttyping
+%D \c!width
+%D \stoptyping
+%D
+%D This constant is always equivalent to \type{width}. As we
+%D can see, we use \type{c!} to mark this one as constant. Its
+%D dutch counterpart is:
+%D
+%D \starttyping
+%D breedte
+%D \stoptyping
+%D
+%D When we interpret a setup command each variable is
+%D translated to it's \type{c!} counterpart. This means that
+%D \type{breedte} and \type{width} expand to \type{breedte}
+%D and \type{\c!width} which both expand to \type{width}. That
+%D way user variables become system constants.
+%D
+%D The interpretation is done by means of a general setup
+%D command \type{\getparameters} that we introduced in the
+%D system module. Let us define some simple setup command:
+%D
+%D \starttyping
+%D \unexpanded\def\setupbox[#1]%
+%D {\getparameters[\??bx][#1]}
+%D \stoptyping
+%D
+%D This command can be used as:
+%D
+%D \starttyping
+%D \setupbox [width=3cm, height=1cm]
+%D \stoptyping
+%D
+%D Afterwards we have two variables \type{\@@bxwidth} and
+%D \type{\@@bxheight} which have the values \type{3cm} and
+%D \type{1cm} assigned. These variables are a combinatiom of
+%D the setup prefix \type{\??bx}, which expands to \type{@@bx}
+%D and the translated user supplied variables \type{width} and
+%D \type{height} or \type{breedte} and \type{hoogte},
+%D depending on the actual language. In dutch we just say:
+%D
+%D \starttyping
+%D \stelblokin [breedte=3cm,hoogte=1cm]
+%D \stoptyping
+%D
+%D and get ourselves \type{\@@bxwidth} and \type{\@@bxheight}
+%D too. In the source of \CONTEXT, we can recognize constants
+%D and variables on their leading \type{c!}, \type{v!} etc.,
+%D prefixes on \type{??} and composed variables on \type{@@}.
+%D
+%D We already saw that user supplied keywords need some
+%D special treatment too. This time we don't translate the
+%D keyword, but instead use in the source a variable which
+%D meaning depends on the interface language.
+%D
+%D \starttyping
+%D \v!left
+%D \stoptyping
+%D
+%D Which can be used in macro's like:
+%D
+%D \starttyping
+%D \processaction
+%D [\@@bxlocation]
+%D [ \v!left=>\dosomethingontheleft,
+%D \v!middle=>\dosomthinginthemiddle,
+%D \v!right=>\dosomethingontheright]
+%D \stoptyping
+%D
+%D Because variables like \type{\@@bxlocation} can have a lot
+%D of meanings, including tricky expandable tokens, we cannot
+%D translate this meaning when we compare. This means that
+%D \type{\@@bxlocation} can be \type{left} of \type{links} of
+%D whatever meaning suits the language. But because
+%D \type{\v!left} also has a meaning that suits the language,
+%D we are able to compare.
+%D
+%D Although we know it sounds confusing we want to state two
+%D important characteristics of the interface as described:
+%D
+%D \startnarrower \em
+%D user variables become system constants
+%D \stopnarrower
+%D
+%D and
+%D
+%D \startnarrower \em
+%D user constants (keywords) become system variables
+%D \stopnarrower
+
+%D The \type {\c!internal} is a left over from the time that
+%D the user interface documents were not using a specification
+%D alongside a keyword specification but used a shared file in
+%D which case we need to go in both directions.
+
+% temporary mkiv hack (we can best just store the whole table in memory)
+
+\unexpanded\def\setinterfaceconstant#1#2%
+ {\clf_setinterfaceconstant{#1}{#2}%
+ \expandafter\def\csname\c!prefix!#1\endcsname{#1}}
+
+\unexpanded\def\setinterfacevariable#1#2%
+ {\clf_setinterfacevariable{#1}{#2}%
+ \expandafter\def\csname\v!prefix!#1\endcsname{#2}}
+
+%D \macros
+%D {defineinterfaceconstant}
+%D
+%D Next we redefine a previously defined macro to take care of
+%D interface translation too. It's a bit redundant, because
+%D in these situations we could use the c||version, but for
+%D documentation purposes the x||alternative comes in handy.
+
+\unexpanded\def\defineinterfaceconstant#1#2%
+ {\expandafter\def\csname\c!prefix!#1\endcsname{#2}}
+
+%D \macros
+%D {startelements}
+%D
+%D Due to the object oriented nature of \CONTEXT, we also need
+%D to define the elements that are used to build commands.
+%D
+%D Such elements sometimes are the same in diferent
+%D languages, but mostly they differ. Things can get even
+%D confusing when we look at for instance the setup commands.
+%D In english we say \type{\setup<something>}, but in dutch we
+%D have: \type{\stel<iets>in}. Such split elements are no
+%D problem, because we just define two elements. When no second
+%D part is needed, we use a \type{-}:
+
+\unexpanded\def\setinterfaceelement#1#2%
+ {\clf_setinterfaceelement{#1}{#2}%
+ \ifcsname\e!prefix!#1\endcsname
+ \doifnotvalue{\e!prefix!#1}{#2}{\setvalue{\e!prefix!#1}{#2}}%
+ \else
+ \setvalue{\e!prefix!#1}{#2}%
+ \fi}
+
+\unexpanded\def\setinterfacecommand#1#2%
+ {\doifnot{#1}{#2}% todo: let when already defined
+ {\expandafter\def\csname#2\expandafter\endcsname\expandafter{\csname#1\endcsname}}}
+
+%D We just ignore these:
+
+\unexpanded\def\startvariables{\gobbleuntil\stopvariables} \let\stopvariables\relax
+\unexpanded\def\startconstants{\gobbleuntil\stopconstants} \let\stopconstants\relax
+\unexpanded\def\startelements {\gobbleuntil\stopelements } \let\stopelements \relax
+\unexpanded\def\startcommands {\gobbleuntil\stopcommands } \let\stopcommands \relax
+
+%D For at the \LUA\ end (experiment):
+
+% \def\do@sicon#1#2{\expandafter\gdef\csname\c!prefix!#1\endcsname{#1}%
+% \expandafter\gdef\csname\k!prefix!#2\endcsname{#1}} % backmapping from non english
+% \def\do@sivar#1#2{\expandafter\gdef\csname\v!prefix!#1\endcsname{#2}}
+% \def\do@siele#1#2{\expandafter\gdef\csname\e!prefix!#1\endcsname{#2}}
+% \def\do@sicom#1#2{\expandafter\gdef\csname#2\expandafter\endcsname\expandafter{\csname#1\endcsname}}
+%
+% \startinterface english
+%
+% \def\do@sicon#1#2{\expandafter\gdef\csname\c!prefix!#1\endcsname{#1}}
+%
+% \stopinterface
+
+\def\ui_c#1#2{\expandafter\gdef\csname\c!prefix!#1\endcsname{#1}%
+ \expandafter\gdef\csname\k!prefix!#2\endcsname{#1}} % backmapping from non english
+\def\ui_s #1{\expandafter\gdef\csname\c!prefix!#1\endcsname{#1}%
+ \expandafter\gdef\csname\k!prefix!#1\endcsname{#1}} % backmapping from non english
+\def\ui_v#1#2{\expandafter\gdef\csname\v!prefix!#1\endcsname{#2}}
+\def\ui_e#1#2{\expandafter\gdef\csname\e!prefix!#1\endcsname{#2}}
+\def\ui_m#1#2{\expandafter\gdef\csname#2\expandafter\endcsname\expandafter{\csname#1\endcsname}}
+
+\startinterface english
+
+ \def\ui_c#1#2{\expandafter\gdef\csname\c!prefix!#1\endcsname{#1}}
+ \def\ui_s #1{\expandafter\gdef\csname\c!prefix!#1\endcsname{#1}}
+
+\stopinterface
+
+%D So much for the basic multi||lingual interface commands. The
+%D macro's can be enhanced with more testing facilities, but
+%D for the moment they suffice.
+
+\ifdefined\zwnj \else \edef\zwnj{\directlua{utf.char(\number"200C)}} \fi % needed for cont-pe % maybe to char-utf.mkiv
+\ifdefined\zwj \else \edef\zwj {\directlua{utf.char(\number"200D)}} \fi % needed for cont-pe % maybe to char-utf.mkiv
+
+%D Out of convenience we define the banners here. This might move
+%D to the \LUA\ end.
+
+\def\contextbanner
+ {ConTeXt \space
+ ver: \contextversion \space \contextmark \space \contextkind \space \space
+ fmt: \formatversion \space \space
+ int: \currentinterface/\currentresponses}
+
+\unexpanded\def\showcontextbanner
+ {\writeline\writebanner{\contextbanner}\writeline}
+
+\edef\formatversion
+ {\the\normalyear .\the\normalmonth.\the\normalday}
+
+\ifx\contextversion\undefined
+ \def\contextversion {unknown}
+ \def\contextversionnumber{0}
+\else
+ %\def\contextversionnumber#1.#2.#3 #4:#5\relax{#1\ifnum#2<10 0\fi#2\ifnum#3<10 0\fi#3 #4:#5}
+ \def\contextversionnumber#1.#2.#3 #4:#5\relax{#1\ifnum#2<10 0\fi\purenumber{#2}\ifnum#3<10 0\fi\purenumber{#3} #4:#5}
+ \edef\contextversionnumber{\expandafter\contextversionnumber\contextversion\relax\space\contextmark}
+\fi
+
+\ifx\undefined\everydump
+ \newtoks\everydump
+ \def\dump{\the\everydump\normaldump}
+\fi
+
+\appendtoks \showcontextbanner \to \everydump
+
+\protect \endinput
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