如何使GridLayout中的QML子对象具有自动宽高

import QtQuick 2.0
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

GridLayout {
    columns: 2
    spacing: 10

    Rectangle {
        width: 100
        height: 50
        color: "red"
        Layout.fillWidth: true
        Layout.fillHeight: true
    }

    Rectangle {
        width: 200
        height: 100
        color: "blue"
        Layout.fillWidth: true
        Layout.fillHeight: true
    }

    Rectangle {
        width: 150
        height: 75
        color: "green"
        Layout.fillWidth: true
        Layout.fillHeight: true
    }

    Rectangle {
        width: 120
        height: 60
        color: "yellow"
        Layout.fillWidth: true
        Layout.fillHeight: true
    }
}