Box2D鼠标旋转

Question

我想实现一个零重力世界，用鼠标可以拖拽世界各地的物体。

import QtQuick 2.2
import Box2D 1.1

Rectangle {
    width: 1000
    height: 500
    id: global
    property bool dragged: false
    property variant joint: null
    property variant body: null

    Component {
        id: jointComponent
        MouseJoint {
            world: world
            bodyA: anchor
            dampingRatio: 0.8
            target: Qt.point(350.0,200.0);
            maxForce: 100

        }
    }

    MouseArea {
        id: mouseArea
        onPressed: {
            global.createJoint(mouse.x,mouse.y);
        }
        onReleased: {
            global.destroyJoint();
        }

        onPositionChanged: {
            if(global.dragged == true)
            {
                global.joint.target = Qt.point(mouse.x,mouse.y);
            }
        }
        anchors.fill: parent


    }

    function createJoint(x,y) {
        if(global.joint != null) destroyJoint();
        var body = global.body;
        if(body == null) return;
        var mouseJoint = jointComponent.createObject(world);
        mouseJoint.target = Qt.point(x,y);
        mouseJoint.bodyB = body;
        mouseJoint.maxForce = body.getMass() * 30.0;
        global.dragged = true;
        global.joint = mouseJoint;
    }

    function destroyJoint() {
        if(global.dragged == false) return;
        if(global.joint != null) {
            global.dragged = false;
            global.joint.destroy();
            global.joint = null;
            global.body = null;
        }
    }

    World {
        id: world
        anchors.fill: parent
        gravity: Qt.point(0,0)

        Body {
            id: anchor
            x:300
            y: 300
            width: 10
            height: 10
        }
            Body {
                id: forrepeat
                x: (40 + Math.random() * 720)
                y: (40 + Math.random() * 520)
                width: 100
                height: 50
                bodyType: Body.Dynamic
                //rotation: Math.random() * 360
                fixtures: Polygon {
                    density: .5
                    friction: 0
                    restitution: 0.5
                    vertices: [
                        Qt.point(0, 0),
                        Qt.point(0, 50),
                        Qt.point(100, 50),
                        Qt.point(100, 0)
                    ]
                    categories: Polygon.Category10
                    collidesWith: Box.Category1 | Box.Category2 | Box.Category3 | Box.Category4

                }

                Rectangle {
                    anchors.fill: parent
                    color: Qt.rgba(Math.random(),Math.random(),Math.random(),Math.random())
                    border.color:Qt.rgba(Math.random(),Math.random(),Math.random(),Math.random())
                    smooth: true

                }
                MouseArea {
                    anchors.fill: parent
                    propagateComposedEvents: true
                    onPressed: {
                        global.body = parent
                        mouse.accepted = false
                    }
                }
            }




    }
}

世界在X和Y中它的重力设置为0。然而，当我拿起任何一个物体时，它们在鼠标点击上很好，但是一旦我移动，物体就会旋转，只要我点击鼠标在对象内。如果我放开鼠标，它们就会开始失控。

理想情况下，我想用鼠标移动我的物体上只有一点点动作。如果它是一个矩形，比如说，然后定向对象，使矩形的右侧边缘朝向鼠标移动的方向。