Just as GTK+ is build on top of GDK, GtkGLArea is built on top of gdkgl which is basically wrapper around GLX functions. The widget itself is derived from GtkDrawinigArea widget and adds only few extra functions. Lower level gdkgl functions make it easy to render on any widget that has OpenGL capable visual, rendering to off-screen pixmaps is also supported. Related project which may interest those who use GTK-- is GtkGLArea--. It is a C++ wrapper for gtkglarea written by Karl Nelson .