Re: quick change of face-size?

["knubee" <knubee@gmail.com>]

>     How can I ensure that my emacs has the correct fonts (or font
>     definitions) so that your zoom utility will do the right thing?
>
> I dunno. Zooming in this way just changes the font _size_ parameter. If you
> try to set a font size that you don't have, you'll get an error.

Ok. I poked around a bit in the different files associated with
zoom-frame.el and I think I see what is happening. Your code relies on
frame-parameter to extract the frame font info. In my case, this is:

"-Misc-Fixed-Medium-R-SemiCondensed--13-120-75-75-C-60-ISO8859-1"

Then, your code simply changes the frame font with the size value
incremented by value of 1 (or some user-specified value).

I understand that this makes the code fairly straight-forward to write,
but it relies on the existence of fonts that correspond to those size
increments. It seems to me that a more general solution would:

a) get a listing of the existing fonts in different sizes for the
current frame's font-family
b) zoom in/out by "one unit", where this means the next available size
of the font-family

My question: do you or someone else know how to return such a listing
of the installed fonts within emacs? I tried a few things, but wasn't
able to do it.