Its called GtkGLExt - an OpenGL extension to GTK 2.0 or later.
But there are other things you can do such as embedding a sdl window in a gtk window
or you can also use opengl in sdl and then embed sdl in a gtk window.
using gtk plug & socket.
Or you could use irrlich and wxgtk
http://irrlicht.sourceforge.net/phpBB2/ ... ight=wxgtk
here is a free linux game programming pdf book
http://www.losersjuegos.com.ar/referenc ... s-time.pdf
There are a bunch of other ways also.
GTK_SDL is for gtk1 not gtk2