closeWindow.qml

import QtQuick 2.3
import QtQuick.Controls 1.1
import QtQuick.Window 2.1

ApplicationWindow {
    visible: true
    width: 300
    height: 300
    title: qsTr("Hello World")

    Window {
        id: childWindow
        title: qsTr("Child Window")
        visible: true
        width: 200
        height: 200

        onClosing: {
            console.log("Child window is closing …")
            close.accepted = false
        }

        function close() {
            var closeEvent = { accepted: true };
            childWindow.closing(closeEvent)
            if (closeEvent.accepted)
            {
                visible = false
            }
            else
            {
                console.log("Closing denied")
            }
        }

        Column {
            anchors.centerIn: parent

            Button {
                text: qsTr("Run close()")
                onClicked: childWindow.close()
            }

            Button {
                text: qsTr("Set visible = false")
                onClicked: childWindow.visible = false
            }
        }
    }
}