OpenGL and overlapping widget

[Michael Goffioul <michael goffioul gmail com>]

Hi,

I'm trying to use OpenGL with regular GTK+ widgets within the same
window and I want to make the widgets (buttons, text fields...) to
overlap the OpenGL area and appears in front of it. I tried with GtkGLArea
and GtkGLExt, but all my tests were unsuccessful so far. In all cases,
the OpenGL area will always appear in front, overlapping any GTK+ widget.

My test case is the following: create a GtkFixed widget with 2 children
(added in that order):
- 1 OpenGL area filling the whole allocated space of the GtkFixed
  (GtkGLArea widget, or GtkGLExt-enabled GtkDrawingArea)
- 1 button placed somewhere in the GtkFixed

What I need is to make the button to appear in front of the OpenGL area.
I'm using Windows (but the target app must be cross-platform).

Any idea how can I achieve this?
Thanks.

Michael.