[XeTeX] text depth and height

[Stephen Moye]

If I typeset this (v 0.94):

%&program=xetex

\font\title="Zapfino" at 24pt \title

\def\reverseit#1{\setbox0=\hbox{%
\special{color push}\special{color cmyk 0 0 0 0}\enskip#1\special{color pop}}%
\hbox to 0pt{\vrule width1.1\wd0 height\ht0 depth\dp0 \hss}\box0}

\noindent \reverseit{SDFH} \quad \reverseit{Big ypqjkl}

\bye

the depth (and the height for that matter) does not seem to change -- this appears to be the case both for AAT and OT fonts. Is there a way around this, or is this a limitation imposed by the fonts?

Thanks.

Stephen Moye