FactCheckBox.qml

import QtQuick 2.2
import QtQuick.Controls 1.2
import QtQuick.Controls.Styles 1.2

import QGroundControl.FactSystem 1.0
import QGroundControl.Palette 1.0
import QGroundControl.Controls 1.0

QGCCheckBox {
    property Fact fact: Fact { }
    property variant checkedValue: 1
    property variant uncheckedValue: 0

    partiallyCheckedEnabled: fact ? fact.value !== checkedValue && fact.value !== uncheckedValue : false
    checkedState: fact ? fact.value === checkedValue ? Qt.Checked : (fact.value === uncheckedValue ? Qt.Unchecked : Qt.PartiallyChecked) : false

    text: qsTr("Label")

    onClicked: {
        fact.value = checked ? checkedValue : uncheckedValue
    }
}