[NTG-context] Testing the changing dimensions of boxes (in cycles) via Lua

14 Jun 2012

      Hello ConTeXist and Lua experts.

In a my Lua project I need to determine the changing dimensions of the 
TeX \vbox through Lua.
In ConTeXt cycle, it works fine, but in the Lua cycle does not change 
the dimensions of the box.
What am I doing wrong?

Thank you.

Jaroslav Hajtmar

Here is my minimal example:
--------------------------------------------------------------------
\newdimen\lsize

\def\contentofvbox{\input ward }

\def\setmybox{\setbox0=\vbox{\hsize=\lsize \contentofvbox}}

\starttext

Height of box via ConTeXt (works fine):

\setmybox

\lsize=5cm
\dorecurse{3}{%
     \lsize=\dimexpr(\lsize+7mm)
     \setmybox
     height of box: \the\ht0\par
     width of box: \the\wd0\par
\box0\par
}

\page

... and Height of box via Lua (do not working):

\setmybox

\ctxlua{
tex.dimen.lsize=5*72.27*65536/25.4

for i=1, 3 do
     tex.dimen.lsize=tex.dimen.lsize+7*72.27*65536/25.4
     context([[\setmybox]])
     local heightbox=tex.box[0].height
     local widthbox=tex.box[0].width
     heightbox=(heightbox*2.84527559067*25.4)/(72.27*65536)
     widthbox=(widthbox*2.84527559067*25.4)/(72.27*65536)
     context([[height of box:]]..heightbox.."pt\\par")
     context([[width of box:]]..widthbox.."pt\\par")
     context([[\box0\par]])
end
}

\stoptext