It is possible create Qt-application window with transparent part in which Android desktop is visible. But it is not possible now transmit user's activity to it. Qt application completely blocks taps and gestures for all underlaying Android activity. I suggest add an option to transmit user's actions if Android screen is visible through Qt window parts. For application programmer this can look just as working call

setAttribute( Qt::WA_TransparentForMouseEvents );

Now this call does not allow finger taps to underlaying Android activity. I suggest allow it. Specific code must be added to QtExtras. This will allow create for Android "windows" lower than full screen. This greately increates usability of applications especially on large screens.