1 pixel residual border when drag rectangleitem in QML scene

//代码占位符
import QtQuick 2.4Rectangle {
    id: box
    width: 320; height: 480
    Rectangle {
        id: blueSquare
        width: 120; height: 120
        x: box.width - width - 10; y: 10    // making this item draggable, so don't use anchors
        color: "blue"
        radius: 8;
        smooth: true;
        clip: true;
        border {
            color: root.focus ? "#3498DB" : "#AED6F1";
            width: 1;            Behavior on color {
                PropertyAnimation {
                    duration: 150;
                }
            }
        }
        Text { text: "Drag"; font.pixelSize: 16; color: "white"; anchors.centerIn: parent }
        MouseArea {
            anchors.fill: parent
            //! [drag]
            drag.target: blueSquare
            drag.axis: Drag.XAndYAxis
            drag.minimumX: 0
            drag.maximumX: box.width - parent.width
            drag.minimumY: 0
            drag.maximumY: box.height - parent.width
            //! [drag]
        }
    }
}