[R] Mac OS X R.app has trouble rendering certain fonts.

[Carlo Tambuatco]

I noticed this running a few graphics demos the other day.

In particular the plotmath and the persp graphics demos, certain fonts
don't seem to render on the demos.

The plotmath demo displays certain math equations on a quartz window
that don't render properly, and the persp demo displays a 3D model of
a mountain with labels on the graph rendered in a certain font. (None
of the data labels render at all.)

This problem appeared recently, (like last week), and has not happened
before. I'm fairly new to using the R gui and R in general, so I don't
really know where to check if I have the proper true type fonts
available on my computer or if it is a problem within R itself. This
doesn't appear to be a problem with the functioning of R itself, just
an inability for it to render certain fonts on graphical displays. I
just want to fix it now before I use it in a major project that
requires the rendering of fonts onto the screen for presentations
etc...