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<h2>18. Interface to TeX
<a name="18. Interface to TeX"></a>
</h2>
<p style="margin-top: 1em"><font color="#000000">TeX mode
is enabled by the <b>−t</b> option. In TeX mode, pic
defines a vbox called <b>\graph</b> for each picture; the
name can be changed with the pseudo-variable <b>figname</b>
(which is actually a specially parsed command). You must
yourself print that vbox using, for example, the
command</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><tt>\centerline{\box\graph}</tt></font></p>
<p style="margin-top: 1em"><font color="#000000">Actually,
since the vbox has a height of zero (it is defined with
\vtop) this produces slightly more vertical space above the
picture than below it;</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><tt>\centerline{\raise
1em\box\graph}</tt></font></p>
<p style="margin-top: 1em"><font color="#000000">would
avoid this.</font></p>
<p style="margin-top: 1em"><font color="#000000">To make
the vbox having a positive height and a depth of zero (as
used e.g. by LaTeX’s <tt>graphics.sty</tt>), define
the following macro in your document:</font></p>
<pre style="margin-left:10%; margin-top: 1em">\def\gpicbox#1{%
\vbox{\unvbox\csname #1\endcsname\kern 0pt}}</pre>
<p style="margin-top: 1em"><font color="#000000">Now you
can simply say <b>\gpicbox{graph}</b> instead of
\box\graph.</font></p>
<p style="margin-top: 1em"><font color="#000000">You must
use a TeX driver that supports the <b>tpic</b> specials,
version 2.</font></p>
<p style="margin-top: 1em"><font color="#000000">Lines
beginning with <b>\</b> are passed through transparently; a
<b>%</b> is added to the end of the line to avoid unwanted
spaces. You can safely use this feature to change fonts or
to change the value of <b>\baselineskip</b>. Anything else
may well produce undesirable results; use at your own risk.
Lines beginning with a period are not given any special
treatment.</font></p>
<p style="margin-top: 1em"><font color="#000000">The TeX
mode of <i>pic</i>(1) does <i>not</i> translate <b>troff</b>
font and size changes included in text strings!</font></p>
<p style="margin-top: 1em"><font color="#000000">Here an
example how to use <b>figname</b>.</font></p>
<pre style="margin-left:10%; margin-top: 1em">.PS
figname = foo;
...
.PE
.PS
figname = bar;
...
.PE
\centerline{\box\foo \hss \box\bar}</pre>
<p style="margin-top: 1em"><font color="#000000">Use this
feature sparsingly and only if really needed: A different
name means a new box register in TeX, and the maximum number
of box registers is only 256. Also be careful not to use a
predefined TeX or LaTeX macro name as an argument to
<b>figname</b> since this inevitably causes an
error.</font></p>
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