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diff --git a/doc/context/presentations/context/2021/context-2021-luametafun.tex b/doc/context/presentations/context/2021/context-2021-luametafun.tex new file mode 100644 index 000000000..333c68682 --- /dev/null +++ b/doc/context/presentations/context/2021/context-2021-luametafun.tex @@ -0,0 +1,362 @@ +% language=us + +\usemodule[present-boring,abbreviations-logos] + +\setuptolerance[verytolerant,stretch] + +\startdocument + [title={LUAMETAFUN}, + banner={the new interfaces}, + location={context\enspace {\bf 2021}\enspace meeting}] + +\starttitle[title=Three subsystems] + +\startitemize + +\startitem + The core of the engine in still \TEX. It all starts there. +\stopitem + +\startitem + The \TEX\ internals are opened up via \LUA. We can call out to \LUA\ from + \TEX\ and to some extend from \LUA\ to \TEX. Quite often we push back + something via the input channels. +\stopitem + +\startitem + The \METAPOST\ library is accessed from \LUA. So from within \TEX\ there is + always \LUA\ in between. Results go back via \LUA. The library can also call + out to \LUA\ and from there to \TEX. +\stopitem + +\startitem + This means that all three major components of \LUAMETATEX\ can talk to each + other and use each others capabilities. +\stopitem + +\startitem + With \LUA\ in the center, we also have access to other mechanism, for instance + fonts, graphics and libraries. +\stopitem + +\startitem + In \CONTEXT\ the \LUA\ language also permits using \XML, \JSON, \CSV, \SQL\ + databases and other input that can be dealt with programmatically. +\stopitem + +\startitem + All has been reasonably optimized for efficiency and performance. +\stopitem + +\stopitemize + +\stoptitle + +\starttitle[title=The (\LUATEX) library] + +\startitemize + +\startitem + Turning \METAPOST\ into a library has been a subproject of the \LUATEX\ project. The + semi|-|official team (Taco, Jacko, Hans, Luigi) got John Hobbies blessing. +\stopitem + +\startitem + This was a rather massive (and impressive) operation by Taco because multiple + number models were to be supported and the internals had to be made such that + different backends were possible. All with remaining perfect (DEK) compatibility. +\stopitem + +\startitem + The \METAPOST\ library serves both the stand alone program and \LUATEX. +\stopitem + +\startitem + That means the \POSTSCRIPT\ backend is built in plus some basic (\TYPEONE) + font handling. We support \PDF\ output via the \METAPOST\ \LUA\ backend (in + \MKII\ that is done by parsing the \POSTSCRIPT\ and specials). +\stopitem + +\startitem + In addition there is \PNG\ and \SVG\ output. It helps that \METAPOST\ output is + rather simple. +\stopitem + +\startitem + The \LUATEX\ engine uses the \LUA\ backend which represents the result in \LUA\ tables + resembling the \METAPOST\ internal representation. +\stopitem + +\startitem + The library supports scaled and double (internal) but also binary and decimal + number models that use (linked in) libraries. +\stopitem + +% this would force a page +% +% \startitem +% The library is quite stable and Taco transferred maintenance to Luigi. +% \stopitem + +\stopitemize + +\stoptitle + +\starttitle[title=The (\LUAMETATEX) library] + +\startitemize + +\startitem + We don't need the \POSTSCRIPT\ backend (which only does \TYPEONE\ anyway). +\stopitem + +\startitem + We also have no use for \SVG\ and \PNG\ output. +\stopitem + +\startitem + The binary number model has no advantages over the decimal one but brings + quite some dependency with it (library code). +\stopitem + +\startitem + The \TYPEONE\ font support is not used in \CONTEXT\ because we handle text + differently. +\stopitem + +\startitem + All this means that we can do with a smaller (simplified) \METAPOST\ library. +\stopitem + +\startitem + The codebase has been overhauled. We still have \type {.w} files (\CWEB) but + use a \LUA\ script to convert that to \CCODE\ which means that we have better + control over how it comes out. +\stopitem + +\startitem + As with \LUATEX\ the file \IO, message handling etc.\ now largely goes via \LUA; + it is more integrated. +\stopitem + +\startitem + The same is true for scanning interfaces and return values (injectors). That also + made for more symbolic coding. +\stopitem + +\startitem + Memory management (allocation) is under engine control (as with \TEX\ and \LUA); + we use a common high performance allocator library. +\stopitem + +\stopitemize + +\stoptitle + +\starttitle[title=The (\LUAMETATEX) library] + +\startitemize + +\startitem + Some already present mechanism have been extended, for instance clips have + pre- and postscripts. +\stopitem + +\startitem + A grouping wrapper has been added (handy for some graphic trickery supported in the + backend.) +\stopitem + +\startitem + The \type {runscript} primitive supports symbolic references to functions (of course to + be provided at the \LUA\ end). +\stopitem + +\startitem + The \type {runscript} return values can be more native, in addition to the already + present (default) \type {scantokens} support. +\stopitem + +\startitem + Internals are extended with booleans and strings. +\stopitem + +\startitem + Output (paths, clips etc) can be stacked in a different order. +\stopitem + +\startitem + There are additional statistics available. +\stopitem + +\startitem + In some places performance could be improved. +\stopitem + +\startitem + In the meantime it can be considered a major upgrade and (for various + reasons) backporting to \LUATEX\ makes no sense. And yes, all errors are + mine. +\stopitem + +\stopitemize + +\starttitle[title=The \LUA fication] + + {\em See Taco's presentation where he gives some examples.} + +\stoptitle + +\starttitle[title=Callbacks] + +We need to hook in some functions: \blank[2*big] + +\starttabulate[|T|T|T|p|] + \HL + \NC \NC find_file \NC (name,mode,kind) \NC locate a file (usually within the \TDS\ setup) \NC \NR + \NC f \NC open_file \NC (name,mode,kind) \NC open given file \NC \NR + \NC \NC close_file \NC (handle) \NC close opened file \NC \NR + \NC s \NC read_file \NC (handle,size) \NC read from file \NC \NR + \NC \NC write_file \NC (handle,str) \NC write to file \NC \NR + \HL + \NC s \NC run_script \NC (code,size,index) \NC run the given string as \LUA\ script \NC \NR + \NC s \NC make_text \NC (str,size,mode) \NC process btex/etex \NC \NR + \HL + \NC \NC run_internal \NC (action,index,kind,name) \NC act on internal definition \NC \NR + \HL + \NC n \NC run_overload \NC (property,name,mode) \NC process overload check \NC \NR + \HL + \NC \NC run_logger \NC (target,str,size) \NC process log message \NC \NR + \NC \NC run_error \NC (message,help,interaction) \NC handle error (message) \NC \NR + \NC \NC run_warning \NC (message) \NC handle warning \NC \NR + \HL +\stoptabulate + +% check_overload shipout_backend + +\stoptitle + +\starttitle[title=Two calling methods] + +The runner can be called as: + +\starttyping +runscript("mp.MyFunction()") +\stoptyping + +which implies at the \LUA\ end: + +\starttyping +function mp.MyFunction() + ... +end +\stoptyping + +Here the callback function is responsible for loading the string and executing it. + +Alternatively one can say: + +\starttyping +runscript <number> +\stoptyping + +The number can be intercepted at the \LUA\ end to do some associated action. + +\stoptitle + +\starttitle[title=Variables] + +We can do: + +\starttyping +lua.mp.MyFunction("foo",123,true) +\stoptyping + +which in the end is equivalent to: + +\starttyping +runscript("mp.MyFunction('foo',123,true)") +\stoptyping + +Alternatively one can pick up values by scanning: like \type {scannext}, \type +{scanexpression}, \type {scantoken}, \type {scansymbol}, \type {scannumeric}, +\type {scaninteger}, \type {scanboolean}, \type {scanstring}, \type {scanpair}, +\type {scancolor}, \type {scancmykcolor}, \type {scantransform}, \type +{scanpath}, \type {scanpen}, etc. + +\stoptitle + +\starttitle[title=Return values] + +The runner can return: + +\startitemize + +\startitem + a string that gets fed into the \type {scantokens} primitive +\stopitem + +\startitem + a numeric or boolean that gets injected as native \METAPOST\ object +\stopitem + +\startitem + a table that gets concatenated and fed into the \type {scantokens} primitive +\stopitem + +\startitem + \type {true} and a second argument that gets converted into a native \METAPOST\ object +\stopitem + +\startitem + in the last case the number of table elements determines the object +\stopitem + +\stopitemize + +Instead of returning a value one can inject: \type {injectnumeric}, \type +{injectinteger}, \type {injectboolean}, \type {injectstring}, \type {injectpair}, +\type {injectcolor}, \type {injectcmykcolor}, \type {injecttransform}, \type +{injectpath}, \type {injectwhatever}, etc.\ and these accept one or more values +and|/|or tables. + +These mechanisms might evolve a bit over time. Lots of examples can be found in +the \type {mlib-*.lmt} files. + +\stoptitle + +\starttitle[title=Parameters] + +\startitemize + \startitem + The new interfaces permit us to program quite robust parameter driven + interfaces that (sort of) match the way we do things at the \TEX\ end. + \stopitem + \startitem + The distribution has several examples of usage and more will be added. + \stopitem + \startitem + Macros that use the new mechanisms can be recognized by the \type {lmt_} + prefix. + \stopitem +\stopitemize + +\starttyping +lmt_mytrick [ + somestring = "test", + somenumeric = 123, + someboolean = true, + somecolor = (1, 0, 1), + somepath = fullsquare scaled 10cm, + somelist = { (0, 0), (1, 3), (8, 9) }, + sometable = [ + somenumeric = 321, + ], +] ; +\stoptyping + +{\em Show the pattern of defining these at the \LUA\ end and in \METAPOST\ files.} + +\stoptitle + +\stopdocument |