[GtkGLExt] how do I caption mouse motion events?

[Peter <pgaston siscom leavethisout net>]

Howdy,

I'm trying to get a very simple OpenGL application going in gtkmm.  I have 
experience with glut, and at this point I'm just trying to figure out how to 
do very simple things in gtk.  In fact, I started with the gtkglextmm gears 
demo on the web site, and gradually made changes putting in my drawing 
instead.  The next thing I need for porting our app from glut is to capture 
mouse motion on the gl drawing area and react accordingly.  I've tried 
overriding the on_motion_notify_event method for both the drawing area and 
the GtkWindow, but I can't seem to get that event to come through.  I can get 
other events, such as on_expose_event to come through obviously because I'm 
getting my drawing up on the screen.  Am I going after the wrong event or do 
I need to do more than just override on_motion_notify_event?

TIA,
Peter