RE: quick change of face-size?

["Drew Adams" <drew.adams@oracle.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.

Yes. But, as I said, you can control the increment size.

    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

Yes, probably.

    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.

Not I.  I know next to nothing about fonts in Emacs.  Someone else can
probably help you though.