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|
% language=us
\usemodule[present-boring,abbreviations-logos]
\startdocument
[title={ECMASCRIPT},
banner={just because it can be done},
location={context\enspace {\bf 2020}\enspace meeting}]
\starttitle[title=Why oh why]
\startitemize
\startitem
We use a \type {mupdf} based \PDF\ viewer: \type {SumatraPDF}.
\stopitem
\startitem
And occasionally we use the tools that come with \type {mupdf}.
\stopitem
\startitem
So when checking if that viewer supports \JAVASCRIPT\ in widgets I noticed
the stand alone interpreter. \footnote {The official name is \ECMASCRIPT\
which is the standardized core language.}
\stopitem
\startitem
Which made me wonder how easy it would be to interface to it.
\stopitem
\blank
\startitem
It uses the lightweight library subsystem: like \FFI\ the library interface
is setup dynamically.
\stopitem
\startitem
Support is {\em not} integrated in \LUAMETATEX, so there is no overhead and
there are no dependencies.
\stopitem
\startitem
We assume that the library is on the system, and when not, then there is also
also no support.
\stopitem
\startitem
We stick to the absolute minimum of interfacing needed and delegate
everything else to \LUA.
\stopitem
\startitem
We assume a stable \API, and if not, well \unknown\ sorry.
\stopitem
\stopitemize
\stoptitle
\starttitle[title=The components]
\startitemize
\startitem
The optional, delayed loading, interface, adds only a few KB to \LUAMETATEX.
\stopitem
\startitem
The \LUA\ library interface that is part of the \CONTEXT\ distribution which means
that it's officially supported.
\stopitem
\startitem
There is a \TEX\ module that loads the lot and provides the user interface.
\stopitem
\startitem
And of course, somewhere on the system, there should be the \type {mujs}
library. \footnote {Taco compiled the library for his system during the talk
and confirmed that it also works out of the box on \OSX.}
\stopitem
\startitem
A module like this should conform to the \CONTEXT\ \LMTX\ standards (a
minimalistic not bloated \API, interfacing in \LUA\ and \TEX, etc.).
\stopitem
\stopitemize
\blank[2*line]
In \CONTEXT\ libraries go into the platform tree, like:
\starttyping
/tex/texmf-win64/bin/lib/luametatex/mujs/libmujs.dll
/tex/texmf-linux-64/bin/lib/luametatex/mujs/libmujs.so
/tex/texmf-osx-64/bin/lib/luametatex/mujs/libmujs.so
\stoptyping
\stoptitle
\starttitle[title=An example]
\startbuffer
\usemodule[ecmascript]
\ecmacode {
console("");
console("When you see this, the loading has succeeded!");
console("");
}
\ecmacode {texprint("Just a {\\bf short} sentence.")}
\startecmacode
texprint("And this is \\inframed{\\bs a bit longer} sentence.")
\stopecmacode
\stopbuffer
\typebuffer
\getbuffer
\stoptitle
\starttitle[title=Catcodes]
As with the \LUA\ interface, catcode regimes are supported:
\startbuffer
\ecmacode {texprint(catcodes.vrb,"Just a {\\bf short} sentence.")}
\stopbuffer
\typebuffer
\getbuffer
Possible values are:
\starttabulate
\NC \type {tex} \NC regular \TEX\ catcode regime \NC \NR
\NC \type {ctx} \NC standard \CONTEXT\ catcode regime \NC \NR
\NC \type {vrb} \NC verbatim catcode regime \NC \NR
\NC \type {prt} \NC protected \CONTEXT\ catcode regime \NC \NR
\stoptabulate
\stoptitle
\starttitle[title=Print whatever you want]
\startbuffer
\startecmacode
console("We're doing some MetaPost!");
texsprint(
"\\startMPcode "
+ 'fill fullsquare xyscaled (6cm,1cm) withcolor "darkgray";'
+ 'fill fullsquare xyscaled (4cm,1cm) withcolor "middlegray";'
+ 'fill fullsquare xyscaled (2cm,1cm) withcolor "lightgray";'
+ "\\stopMPcode "
);
\stopecmacode
\stopbuffer
\typebuffer
\startlinecorrection
\getbuffer
\stoplinecorrection
Of course the code doesn't look pretty but it can serve as a step|-|up to the real
deal: coding in \CONTEXT\ speak (or \LUA).
\stoptitle
\starttitle[title=Files]
Because the interpreter is pretty bare, interfacing to the file system has to be
provided but we can just use what we already have (controlled by \LUA).
\startbuffer
\startecmacode
var f = File("\jobname","r");
var l = f.read("*a");
f.close();
texprint(
"This file has "
+ l.length // or: l.length.toString()
+ " bytes!"
)
\stopecmacode
\stopbuffer
\typebuffer
\getbuffer
We support the usual arguments, like \type {*a}, \type {*l}, a number indicating
the bytes to read etc. There is no support for writing files (let's use the
security excuse).
\page
A file with some script:
\startluacode
io.savedata("context-2020-ecmascript.js",[[
function filesize(name) {
var f = File(name,"r");
if (f != undefined) {
var l = f.seek("end");
f.close();
return l;
} else {
return 0;
}
}
]])
\stopluacode
\typefile{context-2020-ecmascript.js}
Loading that file:
\startbuffer
\ecmafile{context-2020-ecmascript.js}
\stopbuffer
\typebuffer \getbuffer
Using that function:
\startbuffer
\ecmacode{texsprint("This file has " + filesize("\jobname.tex") + " bytes!")}
\stopbuffer
\typebuffer \getbuffer
\stoptitle
\starttitle[title=Ecmascript from \LUA]
\startbuffer
\startluacode
optional.loaded.mujs.execute [[
var MyMax = 10; // an example of persistence
]]
optional.loaded.mujs.execute [[
texsprint("\\startpacked");
for (var i = 1; i <= MyMax; i++) {
texprint(
"Here is some rather dumb math test: "
+ Math.sqrt(i/MyMax)
+ "!\\par"
);
}
texsprint("\\stoppacked");
]]
\stopluacode
\stopbuffer
\typebuffer \page The result: \getbuffer
\stoptitle
\starttitle[title=So what good is it]
\startitemize
\startitem Not that much value is added compared to what we already have. \stopitem
\startitem But at least we can say that we can do \ECMASCRIPT\ (aka \JAVASCRIPT). \stopitem
\startitem And it might convince (new) users to use the \LUA\ interfaces instead. \stopitem
\startitem So we pay a low price and have no overhead anyway. \stopitem
\stopitemize
\stoptitle
\stopdocument
|
