The difference of mapping between toplevel window and popup window

[eric_zhang <eric_zhang newsoft com cn>]

Hello,

I'm new to GTK+ programming.I encountered a problem in my program.

There is a window which contain more widgets in my program, the widgets
were mapped with more pictures(via gtkrc file ).

The problem is: if the window is a toplevel window,you would saw flicker
phenomenon; if the window is a popup window,you wouldn't saw flicker
phenomenon,and mapped normally(no flikcer phenomenon).

The flicker phenomenon not serious,but you could saw it with eyes.and
popup window mapped normally( Why ?).

The version of gtk is gtk+ - 2.12.9 (the OS is ubuntu 8.04 ), and it
already set double buffer mechanism. 

How could I do to avoid flicker phenomenon ?

Thanks,

Eric