Start the window drag from the QStyle
make again the root item accept mouse clicks, so the qwidget part won't take over. also ungrab the mouse of the QQuickItem as soon as the system move start, so won't eat the first click after the system move has been performed. Being a QQuickItem that accepts the mouse press, Input Handlers know how to steal the event from it even if they don't accept it
Edited by Marco Martin