1 Just as GTK+ is built on top of GDK, GtkGLArea is built on top of
2 gdkgl which is basically a wrapper around GLX functions. The widget
3 itself is derived from GtkDrawinigArea widget and adds only few
4 extra functions. Lower level gdkgl functions make it easy to render
5 on any widget that has OpenGL capable visual, rendering to off-screen
6 pixmaps is also supported.