OpenGL rendering with GTK2.0

[ole <ole physik tu-berlin de>]

hello everyone, 
 i'm trying to get an opengl (gtkgl) area widget without flickering but : 
 the widget redraws the background (gray) everytime : the rendering is 
 overdrawed by gray (sometimes : draw event and not expose or something).
 so my QUESTION is : is there a way to tell a widget NOT to draw the
 background ? 
 THANKS IN ADVANCE 
  ole physik tu-berlin de (i am not subscribed)