Re: [NTG-context] Setting and measuring boxes TeX/Lua

25 Nov 2020


      On 11/25/2020 7:31 PM, Jano Kula wrote:
...
Hello!
I would like to set framed boxes, measure their dimensions and proceed 
based on the measurement. It is a combination of TeX and Lua ends.
* Boxes are set on the TeX side. Stacking boxes (hbox, framed, vbox)
    in Lua looked too complex.
  * The content of the inner box is set on the Lua side (some computations).
On TeX side boxes and their dimensions are accessible, but not at Lua 
side, until luacode is finished (iterations over boxes happen here). I 
would say Hans already named the problem in the list: /that is always 
tricky as what happens is postponing till the group ends/.
Do you have an idea how to expand the box sooner or would you use a 
different approach?
Sorry for longer MWE (attached also).
Thank you,
Jano
\def\StartBox{\setbox0=\hbox\bgroup% open hbox
                 \framed[frame=on]\bgroup% open framed
                     \vbox\bgroup% open vbox (\par needed)
              }
\def\StopBox{\egroup\egroup\egroup% close vbox, framed, hbox
              \setvariable{Test}{Height}{\the\ht0}%
             }%
\startluacode
ctx = context
function TestBox()
     ctx("TeX Box: ")    ctx.copy(false,0)ctx.par()
     ctx("TeX Getvar: ") ctx.getvariable("Test", "Height")ctx.par()
     var = tokens.getters.macro(tokens.getters.macro("??variables") .. 
"Test:Height")
     ctx("Lua Type: ")   ctx(type(var))ctx.par()
     ctx("Lua Value: ")  ctx(var)ctx.par()
end
\stopluacode
\starttext
\startluacode
     ctx.bold("First luacode (more boxes)")ctx.par()
     ctx.StartBox()
     ctx("AAA")ctx.par()
     ctx("BBB")ctx.par()
     ctx.StopBox()
     TestBox()
     ctx.StartBox()
     ctx("CCC")ctx.par()
     ctx.StopBox()
     TestBox()
\stopluacode
\blank[4*big]
\startluacode
     ctx.bold("Second luacode (last content of box0)")ctx.par()
     TestBox()
\stopluacode
\stoptext
\startluacode
  context.stepwise (function()
     ctx.bold("First luacode (more boxes)")ctx.par()
     ctx.StartBox()
     ctx("AAA")ctx.par()
     ctx("BBB")ctx.par()
     ctx.StopBox()
     context.step()
     TestBox()
     context.step()
     ctx.StartBox()
     ctx("CCC")ctx.par()
     ctx.StopBox()
     context.step()
     TestBox()
     context.step()
end)
\stopluacode
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