Problem with window attribute topmost and combobox

[Sylvain Thibault]

Toplevel window with g_wm_attributes(-topmost => 1)
When creating a combobox with different values on the window, it is unuseable 
as no value can be selected from the combobox...
Removing the -topmost attribute fixes the problem.
Note that a Spinbox works fine.

System Windows XP with ActivePerl 5.10

 $wl_window = $mw->new___toplevel();
 $wl_window->g_wm_withdraw();

 $wl_window->g_wm_iconbitmap($IconFile);
 $wl_window->g_wm_title('Watch List');

 $wl_window->g_wm_attributes(-topmost => 1);
 $wl_window->g_wm_protocol('WM_DELETE_WINDOW', 
sub{$wl_window->g_wm_withdraw()});
(...)

 $fu = $wl_window->new_ttk__frame();
 $fu->g_pack(-side => 'top', -fill => 'x', -padx => 10);

 $cb = $fu->new_ttk__combobox(-state => 'readonly',
                                                -width => 4,
                                                -values => [15,10,5]);

 $cb->g_pack(-side => 'left', -padx => '10');

(...)

Sylvain