Get Height/Width of Parent Box

Question

In cases when input text to be typeset is separate from the structured template, can the input determine the height and width of its containing box?

An example input. Question marks (?) to be substituted (Lua or TeX).

The width of the parent box is ?

The height of the parent box is ?

Several possible templates:

\ruledhbox to 10cm{\vbox to 4cm{ \input input }} % 10cm by 4cm

\ruledvbox to 4cm{\hsize=10cm \input input } % 10cm by 4cm

\framed
    [width=10cm,
     height=4cm,
     align={middle,lohi},
     offset=0.5cm]
    { \input input } % 9cm by 3cm

Dimensions are meaningless until the box has been stored, so that's probably the place to start.

---

My expansion of the \aftergroup+\lastbox answer:

\typeset{\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}}

{   \let\parht\askparent\let\parwd\askparent\let\pardp\askparent
    \setbox0=\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
    \hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
}

{   \let\parht\askparent\let\parwd\askparent\let\pardp\askparent
    \setbox0=\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
    \hbox to50pt{\vbox to40pt{\hbox to30pt{width: \askparent }}}
}

{   \let\parht\askparent\let\parwd\askparent\let\pardp\askparent
    \setbox0=\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
    \hbox to50pt{\vbox to40pt{\hbox to30pt{width: } \afterafter }}
}

{   \let\parht\askparent\let\parwd\askparent\let\pardp\askparent
    \setbox0=\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
    \hbox to50pt{\vbox to40pt{\hbox to30pt{width: }} \after }
}

{   \let\parht\askparent\let\parwd\askparent\let\pardp\askparent
    \setbox0=\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
    \hbox to50pt{
        \setbox\storelast=\vbox to40pt{\hbox to30pt{width: }}
        \xdef\parht{\the\ht\storelast}
        \xdef\parwd{\the\wd\storelast}
        \xdef\pardp{\the\dp\storelast}
        \ifvmode\nointerlineskip\fi\box\storelast}
}

{   \let\parht\askparent\let\parwd\askparent\let\pardp\askparent
    \setbox0=\hbox to50pt{\vbox to40pt{\hbox to30pt{width: \parwd }}}
    \hbox to50pt{
        \setbox\storelast=\vbox to40pt{\hbox to30pt{width: }}
        \xdef\parht{\the\ht\storelast}
        \xdef\parwd{\the\wd\storelast}
        \xdef\pardp{\the\dp\storelast}
        \vbox to40pt{\hbox to30pt{width: }}}
}

Answer 1

When you use \framed for your texts you can get the width of the content in the box with the \framedwidth and \framedheight commands. A restriction here is that you get only usable value when the width or height settings contains a length larger than 0pt.

\starttext

\startframed[width=200pt,height=80pt,offset=10pt,rulethickness=0.5pt]
     Width: \framedwidth \par
    Height: \framedheight
\stopframed

\stoptext

To get the values of the width and height keys you can use the \localwidth and \localheight commands. Here you should be ware of that ConTeXt delivers whathever value was set with the key, i.e. when you set width=fit the \localwidth commands gives you fit as argument.

\starttext

\startframed[width=200pt,height=80pt,offset=10pt,rulethickness=0.5pt]
     Width: \localwidth \par
    Height: \localheight
\stopframed

\stoptext

The last possible value can be used for the background of a frame but unlike the previous methods you get the correct width or height of the frame even with settings like width=fit.

\defineoverlay
  [boxdimensions]
  [\vbox\bgroup
     \hbox {Width: \overlaywidth}
     \hbox{Height: \overlayheight}
   \egroup]

\setupframed % don't make global framed settings in a document
  [background=boxdimensions]

\starttext

\startframed[width=200pt,height=80pt,offset=10pt,rulethickness=0.5pt]
    %
\stopframed

\stoptext

Answer 2

This "solution" is surely not universal and well thought through, but it works for me in simple cases, with plain TeX:

\newbox\storelast
\def\after{\setbox\storelast=\lastbox
  {\globaldefs=1
  \edef\parht{\the\ht\storelast}
  \edef\parwd{\the\wd\storelast}
  \edef\pardp{\the\dp\storelast}}
  \ifvmode\nointerlineskip\fi\box\storelast}
\def\afterafter{\aftergroup\after}
\def\askparent{\aftergroup\afterafter}

\def\typeset#1{\let\parht\askparent\let\parwd\askparent\let\pardp\askparent
  {\globaldefs=-1 \setbox0#1}#1}

Afterwards, you can typeset the template with \typeset{...}. In the input, you can use \parwd, \parht and \pardp to get the width, height and depth of the parent box, respectively. The argument of \typeset has to be a box (it has to start with \hbox, \vbox ...).

For example, I have a file called input.tex that contains

width \parwd\ height \parht.

Then, the following lines

\typeset{\hbox to50pt{\vbox to40pt{\hbox to30pt{\input input }}}}
\typeset{\vbox to50pt{\hbox to40pt{\vbox to30pt{\input input }}}}

print (apart from many over/underfull boxes)

width 30.0pt height 40.0pt
width 40.0pt height 30.0pt

correctly. However,

• I have no idea how well this behaves for more complex constructs;
• Edit: As pointed out by Henri Menke in the comments, typesetting the box twice (with \setbox0#1 followed by #1) might lead to unexpected side effects, for example if counters are increased in the box. I tried to reduce that problem by evaluating the \setbox0#1 in a group with \globaldefs=-1, but this might change the dimensions of the box if packages relying on global definitions are used, such as tikz, yielding incorrect results;
• it assumes that the commands \parht etc. are not used inside a group other than the ones created by the boxes;
• it will only work if the parent box is not on the main vertical list as it uses \lastbox to determine the box dimensions, which is empty in external vertical mode.

For the last point, consider the example above, but now we are interested in the dimensions of the outermost box:

\typeset{\hbox to50pt{\vbox to40pt{\hbox to30pt{\input input }}}}
\typeset{\vbox to50pt{\hbox to40pt{\vbox to30pt{\input input }}}}

would print

width 0.0pt height 0.0pt
width 0.0pt height 0.0pt

because the outermost box is set in external vertical mode. In this case, you would have to wrap your template with another box, like

\typeset{\hbox{\hbox to50pt{\vbox to40pt{\hbox to30pt{}\input input }}}}
\typeset{\hbox{\vbox to50pt{\hbox to40pt{\vbox to30pt{}\input input }}}}

printing

width 50.0pt height 40.0pt
width 40.0pt height 50.0pt

as expected.