gdk_window_get_toplevels -> only 2 strange windows

[PedroAC <pac_projects netcabo pt>]

( note to the admistration: please ignore/purge my last mail - I sent it
with a not subscribed email ,pactmp netcabo pt, by mistake )

  When I use "gdk_window_get_toplevels" function or "
gdk_window_get_children(gdk_get_default_root_window ())" I only get 2
windows.
 When I execute the program from the following compiled code:
"
#include <gtk/gtk.h>

int main( guint argc, gchar **argv) {

  gtk_init (&argc, &argv);

  GdkRectangle rectangle = { 0, 0, 640, 480 };
  GdkWindow *window;

  GList *list = gdk_window_get_children(gdk_get_default_root_window ());
  
  window = GDK_WINDOW(list->data);

  gdk_window_show(window);

  gtk_main();

}
"
... a new window with black background is created ( or becomes visible
). When I try the second window ( from the list ), the new window has a
white background. I don't understand why ...

 I was trying to get all windows from the desktop ( or window manager ),
and turn them to GL Windows ( with GtkGLExt API ); this maybe impossible
( or not ), but I wanted to experiment that, and I can't without windows
pointers.

 Why I only get 2 windows ( I'm using Gnome Desktop ), and I can't I get
all windows from screen ?

 Regards.
   Pedro Amaral Couto