Re: Reading ConTeXt metadata values into Lua

[Wolfgang Schuster via ntg-context <ntg-context@ntg.nl>]

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Ramkumar KB via ntg-context schrieb am 16.10.2021 um 06:00:
> Hello All,
>
> I was trying to read the value of '\totalnumberofpages' into lua to do 
> something with it. As an example, see below.
>
> Now, as I understand it, my example would not work as TeX gets the 
> first go at this and therefore the variable 'pages' is the string 
> '\totalnumberofpages' and not the actual value itself. And Lua cannot 
> process this "calculation".
>
> I tried to go thru the manual - *cld-mkiv.pdf *- in the distro but 
> could not catch on how to read a metadata value (not print). I am sure 
> that I am missing a small trick somewhere (or is it something more 
> involved?).
>
> \startluacode
> function myFancyCalculations(pages)
>   -- some fancy stuff but as an example
> local myCal = tonumber(pages) + 1
> return myCal
> \stopluacode
> \starttext
>
> \blah
>
> \ctxlua{context(myFancyCalculations("\\totalnumberofpages"))}
>
> \stoptext

Everything gets easier when you use the Lua functions to access the 
counter values but be aware the values can be wrong when you're at a 
page break.

\startbuffer[pagenumber]
\startluacode
context.starttabulate()
     context.NC()
         context("Current page")
     context.EQ()
         context(structures.counters.get("realpage",1,"number"))
     context.NC()
     context.NR()
     context.NC()
         context("Last page")
     context.EQ()
         context(structures.counters.get("realpage",1,"last"))
     context.NC()
     context.NR()
context.stoptabulate()
\stopluacode
\stopbuffer

\starttext

\dorecurse
     {\randomnumber{5}{10}}
     {\getbuffer[pagenumber]
      \page}

\stoptext

Wolfgang


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