import QtQuick 2.12

ApplicationWindow {
    width: 1280
    height: 720

    Rectangle {
        id: rectangle
        width: parent.width * 0.2
        height: parent.height
        anchors.right: parent.right
        color: "red"
        state: "closed"
        states: [
            State {
                name: "closed"
                AnchorChanges { target: rectangle; anchors.right: undefined; anchors.left: parent.right }
            }
        ]
    }

    MouseArea {
        anchors.fill: parent
        onClicked: rectangle.state = (rectangle.state == "closed" ? "" : "closed")
    }
}