Equivalent of pdfsavepos for a box?

Question

Suppose I typeset some text using an environment that places it in a box with a width that I specify. (I don't really care if this is a minipage, tabular, or something else.) I want to write the coordinates of the box to a file. (I will probably use xetex, because this involves Greek text, and that seems too painful in the other tex implementations I've tried.) In pdftex and its extensions such as xetex, I can use pdfsavepos at the beginning and end of the text, and use write18 to write the coordinates. But I think this won't really give me the coordinates of the upper-left and lower-right coordinates of the box. I imagine it will record the positions of a point on the baseline (?) just before the first character and just after the last character.
Is there a way to output the actual coordinates of the box, or do I have to somehow estimate this by doing arithmetic based on the width of the box, the ascender and descender height of the font, and possibly the box/environment's margins? If I have to do the arithmetic muself, is there some convenient, automated way to find out the relevant font dimensions for whatever font is being typeset?

David Carlisle · Accepted Answer

You can place content in a box register then access its width height and depth along with the position from pdfsavepos (which takes multiple runs of latex)

documentclass{article}

newsaveboxzzz

makeatletter
newcommandusewithpos[2]{%
  ifcsname zz#1endcsnameelse
  expandaftergdefcsname zz#1endcsname{{}{}{}{}{}}%
   fi
pdfsavepos
protected@write@auxout{}{%
  gdefexpandafterstringcsname zz#1endcsname{%
  {noexpandthepdflastxpos}{noexpandthepdflastypos}{thewd#2}{theht#2}{thedp#2}}}%
  usebox{#2}}
makeatother
newcommandboxdims[5]{%
 par
  position (#1sp,#2sp)par width #3, height #4, depth #5
}
begin{document}

saveboxzzz{parbox{3cm}{onetwooooothreeeeeeeee}}

A paragraph with no interest.

and here we use the box fbox{usewithpos{a}{zzz}}

saveboxzzz{makebox[2cm]{x}}

and a second box fbox{usewithpos{b}{zzz}}.

The first box is:

expandafterboxdimszza.

The second box is:

expandafterboxdimszzb.

end{document}

Equivalent of pdfsavepos for a box?

One Answer

Add your own answers!

Ask a Question