Design a combobox

{Windows 7, Qt/QML 5.2, MinGW 32 bit}

I am writing a code for my own combobox in qml. The problem was with the drop-down - it needs to be on top of any other item. I've approached it in 2 different ways so far:

<1> Whenever the dropdown needs to be made visible, set the most-root-qml-item as its parent (just like we do in case of drags as dragged component needs to be visible on top of all other qml components). Additionally I'd put a MouseArea over the entire UI which would tell me if there was a click somewhere so that i can close the combobox. This has some disadvantage ofcourse - i can click on the main window title bar and the combobox won't close; i cannot make combobox dropdown go beyond the main qml window etc.

<2> Since Qt 5.2, i now have the facility of "onActiveChanged" signal for the Window component. So now my drop-down is a window which when shown has requestActivate() called and onActiveChanged monitored to close it in case the mouse is clicked elsewhere. This takes care of the short-comings of <1> and also feels more right that covering the entire UI with a MouseArea.

Now I'm having some problems. Initially i had set the flags: as Qt.Popup and things were working fine. However if I turn to fullscreen mode then the dropdown would never be shown - I suspected it was hidden behind the UI window. On experimenting I found that setting flags to Qt.SplashScreen does the job. Though it sounds strange it works pretty much as Qt.Popup additionally working even in fullscreen mode. So i left it there. The problem now is that there is flickering of entire UI on many machines in fullscreen mode everytime the dropdown is shown or hidden. This does not happen in the maximized or any other mode. Also the behaviour of Window with flags: set a Qt.Popup or Qt.SplashScreen does not work properly on MAC.

<Q> Is this a known issue?
<Q> Is what i'm doing right or is there any other way to show the dropdown (with the requirement that it will be over any other item and will close if the mouse is clicked anywhere)?