Run attached application against Qt 5.3.1 and see that Mainwindow minimize, maximize and close buttons doesn't work after closing QuicView dialog. Works fine when using Qt 5.2.1.

There's workaround and couple comments in application source. Point is that in Qt 5.3.1 close()/hide() doesn't work correctly (looks like focus doesn't go back to mainwindow) after eventloop.exec() but works in Qt 5.2.1.