How to achieve functionality of GTK_WINDOW_POPUP but with keyboard input

[Andrew Wood <a j w me com>]

How can I achieve the same 'screen invasion' effect (i.e covers 
everything including the Gnome Panels and prevents other windows being 
brought to the front with Alt-Tab) that GTK_WINDOW_POPUP has but also 
allow keyboard input to the widgets in the window.

Ive tried  GDK_WINDOW_TYPE_HINT_DOCK  which invades screen ok but has no 
keyboard input

GDK_WINDOW_TYPE_HINT_SPLASHSCREEN doesnt invade screen - other windows 
can be placed on top, alt-tab works, but keyboard input works

GDK_WINDOW_TYPE_HINT_DESKTOP no display

GDK_WINDOW_TYPE_HINT_UTILITY
    doesnt invade screen - other windows can be placed on top, alt-tab 
works
GDK_WINDOW_TYPE_HINT_TOOLBAR
    doesnt invade screen - other windows can be placed on top, alt-tab 
works
GDK_WINDOW_TYPE_HINT_MENU
    doesnt invade screen - other windows can be placed on top, alt-tab 
works

The reason is Im trying to write a program for a public kiosk hence I 
effectively want to lock the screen.