А WStype_NoBorder или WStype_NoBorderEx недостаточно?

commonproblems.html:
[QUOTE]
Using Qt on X11 without a window manager

When using Qt without a window manager on Unix/X11, you will very likely experience focus problems. Without a window manager, there is no focus handling on X11, and no concept of an active window either. If you want your application to work in such an environment, you have to explicitly mark a window as active after showing it:

yourWindow->show();
yourWindow->setActiveWindow();

Note that setActiveWindow() won't work if the widget does not become physically visible during this event cycle. However, without a window manager running, this is guaranteed to happen. For the curious reader: setActiveWindow() emulates a window manager by explicitly setting the X Input Focus to a widget's toplevel window.
[/QUOTE]

Как я понимаю, работа вобход ВМ аналогична работе без ВМ вообще.