X11: How to make the application to be on top

Situation I'm using matchbox keyboard which is X11 based application. When any application is in full screen mode matchbox keyboard cannot be visible as the full开发者_C百科 screened application is on TOP. So is there a way to launch X11 based application over full screened applictions ?

You can look at the source of those GTK functions and see how they are implemented for the X11 backend:

gtk_window_set_keep_above()
gtk_window_set_keep_below()
gtk_window_set_transient_for()

I think it is the best way to know how you can do that, surely the solution GTK adopted should be portable.