/*** main.qml ***/
import QtQuick 1.0

Rectangle {

    property variant theme: defaulttheme


    DefaultTheme {
        id: defaulttheme
    }
    DefaultTheme {
        id: crazyTheme
        fontColor: "yellow"
        backgroundColor: "red"
    }


    width: 360
    height: 360
    color: theme.backgroundColor

    Text {
        anchors.centerIn: parent
        text: "Hello World"
        color: theme.fontColor
    }
    MouseArea {
        anchors.fill: parent
        onClicked: {
            theme = crazyTheme
        }
    }
}


/*** DefaultTheme.qml ***/
import QtQuick 1.0

QtObject {
    property string backgroundColor: "steelblue"
    property string fontColor: "white"
}