On Tue, Mar 24, 2020 at 04:43:17PM +0100, Wolfgang Schuster wrote:
> > \setbox0=\vbox{... somehow flushed text ...} wount work, i.e \wd0 or \ht0
> > will both result in 0. With "unflushed" text this means will work perfectly.
> 
> I have no idea where you get 0 (0pt?).

Nor do I, in the meantime. Sorry for my noise, I don't know what sort of
mistakes I did to get "0.0pt".
Corona? :-)

This is my test, which is essentially the same what Aditya suggests:
-----------------------------------------
\starttext

\setbox0=\vbox{\hsize=300pt\input ward }
\copy0

wd0=\the\wd0, ht0=\the\ht0

\vskip12pt

\startalign[flushleft]
\setbox1=\vbox{\hsize=300pt\input ward }
\stopalign
\copy1

wd1=\the\wd1, ht1=\the\ht1

\stoptext
-----------------------------------------
The .pdf-file is appended


Now to your proposal, Wolfgang:
> 
> \starttexdefinition NextboxDimension
>   \starttabulate
>   \NC Width  \EQ \the\nextboxwd \NC\NR
>   \NC Height \NC \the\nextboxht \NC\NR
>   \stoptabulate
> \stoptexdefinition
> 
> \starttext
> 
> \dowithnextboxcs
>   \NextboxDimension
>   \vbox
>     {\samplefile{ward}}
> 
> \dowithnextboxcs
>   \NextboxDimension
>   \vbox
>     {\setupalign[flushright]
>      \samplefile{ward}}
> 
> \dowithnextboxcs
>   \NextboxDimension
>   \vbox
>     {\hsize=200pt
>      \samplefile{ward}}
> 
> \dowithnextboxcs
>   \NextboxDimension
>   \vbox
>     {\hsize=200pt
>      \setupalign[flushright]
>      \samplefile{ward}}
> 
> \stoptext

Up to now I cannot say anything about it, because there are some
commands which are new to me. I have to study them first.
Thank you for your effort!

Rudolf