Scene that can be dragged with middle mouse button

main.qml

import QtQuick
import QtQuick.Window

import Qt.labs.animation

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Test")

    // Useful to be able to give this margins and see if everything is rendered as we expect it.
    Item {
        id: viewport
        anchors.fill: parent
        anchors.margins: 100

        Rectangle {
            anchors.fill: parent
            color: "transparent"
            border.color: "darkorange"
            z: 1000
        }

        Item {
            id: scene
            width: 2000
            height: 400

            Rectangle {
                anchors.fill: parent
                color: "steelblue"
            }

            Rectangle {
                y: parent.height - height
                color: "brown"
                width: parent.width
                height: 128
            }

            DragHandler {
                acceptedButtons: Qt.MiddleButton
            }

            BoundaryRule on x {
                minimum: -scene.width + Math.min(scene.width, viewport.width)
                maximum: viewport.width - scene.width > 0 ? viewport.width - scene.width : 0
            }
            BoundaryRule on y {
                minimum: -scene.height + Math.min(scene.height, viewport.height)
                maximum: viewport.height - scene.height > 0 ? viewport.height - scene.height : 0
            }
        }
    }
}