XDirectFB is a rootless X Server using DirectFB Windows for X11 toplevel windows. This way the opacity of every application can be adjusted with your mouse wheel. Window movements are initiated by the application or the window manager. The graphical movement is done by DirectFB using the available hardware acceleration. Overlapping toplevel windows does not cause expose events, i.e. redrawing of the window contents, as they are DirectFB windows and therefore have an own surface, or backing store.
