[GtkGLExt] rubber band effect

["mn" <nischan allmail net>]

Hello,

I am VERY new to OpenGL and GtkGlExt.  I want to display a 2D image and
implement a "rubber band" type selection tool for the user.  What is the
best way to go about this?  Searching on the net I found two different
solutions, using glLogicOp or overlay planes.  Is the ability to use
overlay planes built into openGL, or does it depend on the windowing
wrapper being used (e.g. gtkglext)?  Does gtkglext support overlay
planes?  I am a bit fuzzy about where the overlay plane capability comes
from....

thanks
Melissa