Message-Id: <9306151849.AA29715@sc.zib-berlin.dbp.de>
Reply-To: Mailing list for the LaTeX3 project <LATEX-L@vm.urz.Uni-Heidelberg.de>
Date:         Tue, 15 Jun 93 20:44:38 +0200
From: Frank Mittelbach <MITTELBACH@MZDMZA.ZDV.UNI-MAINZ.DE>
Sender: Mailing list for the LaTeX3 project <LATEX-L@vm.urz.Uni-Heidelberg.de>
To: Multiple Recipients of <LATEX-L@vm.urz.Uni-Heidelberg.de>
Subject:      getting information about the x/y values for a given point
Status: R


> I would find it incredibly useful if there were a special form of
> \label that would report to the aux file on the position, say in x and
> y coordinates, of the baseline under a given point on the page of output.

I would find this useful too. Unfortunately, short of using \special's
and letting some driver doing the work for you there is no way in TeX
to get at this information. You can get some approximation as far as
the y coordinate is concerned (but then you never know what happens to
your text in the output routine (it might even get thrown away) but x
in a paragraph is impossible unless you are prepared to pay the price
of getting bad line breaks nearby (some Heisenberg effect, the
experiment changes the outcome).

But perhaps the idea of using \specials for this purpose isn't so dumb
after all. One could have some extra dvidriver that would do nothing
except retrieving the information which would mean some extra step when
applications use the feature but at least it would be available. This
approach is used even more extensively in Type&Set (where the whole
page layout is done externally to TeX and the information is passed
via specials) and as far as I know Graham would be willing to give
away his special-analysing driver. Anyway, it wouldn't be much of an
effort to produce such a beast from a dvitype source.

Any thoughts on this?

cheers

Frank