\begin{itemize}
    \item `font' is a number: 0 is the built-in system font, 1 is the
    user-selected font.
  \end{itemize}

\begin{example}
    \config{ui viewport: 15,20,100,150,-}
\end{example}
This displays the menu starting at 15px from the left of the screen and 20px
from the top of the screen.  It is 100px wide and 150px high. The font is
defined in the theme \fname{.cfg} file or in the \setting{Theme Settings} menu.