How to determine what face is associated with a bit of text?

[Stephen J. Turnbull]

skip at pobox.com writes:
 > 
 >     jeff> Or you can use this:
 > 
 >     jeff>   (global-set-key [(control button3)] 'describe-face-at-mouse-point)
 > 
 >     ...
 > 
 > Ooh, cool.  Just what I needed.

I have a more general facility I call introspector, which pops up a
tooltip describing practically anything you could want to know about
buffer point, and is bound to a keystroke (by default C-h =).
Extension to a mouse binding like Jeff's is trivial, just bind
`introspect-cursor-position' instead of d-f-a-m-p in the above.
(Extensions like a hovering tooltip that follows mouse are conceivable
but not high priority unless somebody asks for them with a plausible
use case.)  It's packaged as an XEmacs package, just drop it in your
system site-packages or in ~/.xemacs/xemacs-packages or
~/.xemacs/site-packages, and add `(require 'introspector)' to your
init file.  (This last requirement will become unnecessary in the
future, but to create a default keybinding is invasive.)

http://turnbull.sk.tsukuba.ac.jp/Tools/XEmacs/introspector-0.80-pkg.tar.gz