How to detect if gnome is running

[Ben Campbell <ben campbell ntlworld com>]

Is there any good way to detect if the user is currently running a Gnome 
desktop?

I'm writing a routine to try and determine and launch the users preferred web 
browser. If I detect a Gnome desktop, I plan to use 
gnome-moz-remote (or gnome_url_show() if I can reliably use libgnome with 
dlopen()).
I don't want to rely on the gnome libraries being installed (just as I don't 
want to rely on the presence of any kde libs, for example).

I'm sure there are some rule-of-thumb solutions using the output from the 
'ps' command... not ideal, but better than nothing.

Any ideas welcome!

Thanks,
Ben.