import QtQuick 2.15
import QtQuick.Window 2.0
import QtQuick.Controls 2.15

Window {
    id: window
    width: 1000
    height: 1000
    visible: true

    Rectangle {
        id: area
        color: "lightgrey"
        anchors.centerIn: parent
        width: 900
        height: 900

        Rectangle {
            width: 50
            height: width
            color: dragHandler.active ? "red" : "lightblue"
        }

        Button { // no problem if this is a Rectangle
            width: 40
            height: 40
            anchors {left: parent.left; verticalCenter: parent.verticalCenter}

            Rectangle {
                id: icon
                color: "steelblue"
                width: parent.width / 2
                height: width
                Drag.active: dragHandler.active
                Drag.hotSpot.x: dragHandler.centroid.pressPosition.x
                Drag.hotSpot.y: dragHandler.centroid.pressPosition.y
                states: [
                    State {
                        when: !icon.Drag.active
                        AnchorChanges {
                            target: icon
                            anchors.horizontalCenter: parent.horizontalCenter
                            anchors.verticalCenter: parent.verticalCenter
                        }
                    }
                ]
            }
            DragHandler {
                id: dragHandler
                target: icon
            }
        }
    }

    DropArea {
        anchors.fill: area
    }
}