a question about GtkFixed

[Jiang XU <jiang xu echostar com>]

I use  a GtkFixed widget as the container.   The GtkFixed widget covered
whole area of the GtkWindow, which is the main window.

then,what I did is:

1.  set the background pixmap for the GtkFixed by using set
"style->bg_pixmap[..]" ,
2.   In the call back function of "configure_event" and "expose_event"
of the GtkWindow and GtkFixed, I draw something on the GtkFixed->window
3. call gtk_main()

What happened on the screen is:
Shows up GtkWindow, GtkFixed with the background pixmap, the thing I
draw on the GtkFixed->window.

BUT it just shows once, then it reflashs and only shows GtkWindow,
GtkFixed with the background pixmap.  It lost the thing I draw on the
GtkFixed->window.

I wonder why? and How to solve this problem?
IS there a way that I could set the GtkFixed transparent to the
GtkWindow?