[metapost] Open/True Type Fonts

[Troy Henderson]

Has anyone been successful at using Open/True Type fonts in MetaPost
figures?  I have read that some have done it with ConTeXt, but since I
am a LaTeX user, it would be nice if MetaPost could call XeLaTeX
(similar to the way it can call TeX or LaTeX) to process the labels.
For example, instead of using something like

verbatimtex
%&latex
\documentclass{minimal}
\begin{document}
etex

perhaps something similar like

verbatimtex
%&xelatex
\documentclass{minimal}
\usepackage{fontspec}
\setmainfont{Adobe Garamond Pro} % For example
\begin{document}
etex

could be used.  This specific method does not work even with calling
MetaPost by `mpost -tex=xelatex`.  Any ideas on how to facilitate
this?

Thanks,

Troy Henderson