[NTG-context] Getting width of text to be typeset

[Hans Hagen]

On 5/22/2020 11:22 AM, context at vivaldi.net wrote:
> Hello,
> 
> is it possible to get somehow the width of the "material" (box?) of the 
> current line which is "ready" to be typeset?
> 
> See the case:
> 
> ----
> \starttext
> 
>    some text
> 
>    pqrs % Here I need to get width (or content) of the text from the 
> begin of the current line,
>         % i.e. width of the text "pqrs".
>         % (Depending of the width I will decide what to do later.)
> 
> \stoptext
> ----
> 
> I am too laical to know how to "inject" TeX workflow or whether to 
> access LuaTeX internals (nodes?) to get the desired information.
> 
> - Is it possible somehow?
Too easy ...

\startluacode
     function document.whatever()
         context(nodes.hpack(tex.getnest().head.next).width)
     end
\stopluacode

\unexpanded\def\widthuptohere{\dimexpr\ctxlua{document.whatever()}sp\relax}

\starttext

     \dorecurse {10} {
         snippet #1\scratchdimen\widthuptohere\ has \the\scratchdimen\ 
width\par
     }

\stoptext

but still you have to wikify it ... maybe i'll make it a low level 
helper (but than you also need to wikify that because i have no clue 
where to explain it)

Hans


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