Nikos Chantziaras posted on Sat, 31 Mar 2012 12:16:06 +0300 as excerpted:
In case you missed it, you should install the Gtk port of Oxygen:
x11-themes/oxygen-gtk (and x11-themes/oxygen-gtk3 in case you need Gtk 3
later.) This isn't a "fake" theme btw. It's a real Gtk engine and
pretty much the official Gtk port of KDE's Oxygen style.
Thanks! I had seen the package mentioned, but FWIW I wasn't clear on
what oxygen bits it ported, etc. Your clarification that it's oxygen
widgets helps quite a bit there. (I run oxygen widget-styles but not
window trim