[GtkGLExt] transparent background for opengl canvas

["Karl Ostmo" <kostmo purdue edu>]

Hi All,
I posted this on sourceforge also, but I wasn't sure if this list sees
sourceforge activity:
https://sourceforge.net/tracker/?func=detail&atid=473436&aid=1896647&group_id=54333

Is there any possibility of using the alpha channel of the OpenGL
canvas to make it transparent (in the "transparent GIF" sense) or
translucent on top of GTK? I am aware that a Cairo canvas with
gtk.DrawingArea can do this, and it looks great.  A specific example
that would benefit tremendously from this is "button.c" in the
"examples/" directory.  Transparency would achieve a "seamless" look,
rather than having an unsightly white frame around the "donut".

Karl