[XeTeX] Full height lines

[Jeff Marion]

Hi All,

I'm trying to replicate the behavior of a non-tex based renderer and 
have each line of text take up a "full" line in the current font. So all 
else being equal, "Foo" and "oo" would render with the same baseline 
position, rather than the usual tex behavior of the "oo" shifting up.

I'm able to achieve almost what I need by bottom aligning text within a 
minipage, descenders flow out (good) and my baseline is unaffected by 
height changes. Unfortunately it's necessary to have the text be top 
aligned.

Does anyone know of anyway to do this or something similar? I've gone 
through my copy of The TextBook twice now and scoured the web looking 
for any way to do this. I know the standard fontdimens don't expose 
enough data to do it but is there more metrics data available that I can 
pull possibly?

Any help is appreciated.

-Jeff

----- Example Script Follows -----

\documentclass{letter}
\usepackage[papersize={3.944in,4.847in},total={1.944in, 
2.847in},margin=1in,nohead,nofoot]{geometry}
\usepackage{fontspec}
\pagestyle{empty}
\setmainfont{Machia}
\renewcommand{\baselinestretch}{1.2}
\begin{document}
    \begin{minipage}[b][2.778in][t]{1.771in}
        \fontsize{48bp}{48bp}\selectfont
        \begin{flushleft}Foo\end{flushleft}
    \end{minipage}
\end{document}