问避免鼠标移动的QGraphicsItem形状的碰撞

EN

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *
import pymunk

class Circle(QGraphicsEllipseItem):

    def __init__(self, r, **kwargs):
        super().__init__(-r, -r, r * 2, r * 2, **kwargs)
        self.setFlag(QGraphicsItem.ItemIsSelectable)
        self.static = pymunk.Body(body_type=pymunk.Body.STATIC)
        self.circle = pymunk.Circle(self.static, r)
        self.circle.friction = 0
        mass = 10
        self.dynamic = pymunk.Body(mass, pymunk.moment_for_circle(mass, 0, r))
        self.updatePos = lambda: self.setPos(*self.dynamic.position, dset=False)

    def setPos(self, *pos, dset=True):
        super().setPos(*pos)
        if len(pos) == 1:
            pos = pos[0].x(), pos[0].y()
        self.static.position = pos
        if dset:
            self.dynamic.position = pos

    def itemChange(self, change, value):
        if change == QGraphicsItem.ItemSelectedChange:
            space = self.circle.space
            space.remove(self.circle.body, self.circle)
            self.circle.body = self.dynamic if value else self.static
            space.add(self.circle.body, self.circle)
        return super().itemChange(change, value)

    def paint(self, painter, option, widget):
        option.state &= ~QStyle.State_Selected
        super().paint(painter, option, widget)


class Scene(QGraphicsScene):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.space = pymunk.Space()
        self.space.damping = 0.02
        self.body = pymunk.Body(body_type=pymunk.Body.KINEMATIC)
        self.space.add(self.body)
        self.timer = QTimer(self, timerType=Qt.PreciseTimer, timeout=self.step)
        self.selectionChanged.connect(self.setConstraint)

    def setConstraint(self):
        selected = self.selectedItems()
        if selected:
            shape = selected[0].circle
            if not shape.body.constraints:
                self.space.remove(*self.space.constraints)
                spring = pymunk.DampedSpring(
                    self.body, shape.body, (0, 0), (0, 0),
                    rest_length=0, stiffness=100, damping=10)
                spring.collide_bodies = False
                self.space.add(spring)

    def step(self):
        for i in range(10):
            self.space.step(1 / 30)
        self.selectedItems()[0].updatePos()

    def mousePressEvent(self, event):
        super().mousePressEvent(event)
        if self.selectedItems():
            self.body.position = event.scenePos().x(), event.scenePos().y()
            self.timer.start(1000 / 30)
            
    def mouseMoveEvent(self, event):            
        super().mouseMoveEvent(event)
        if self.selectedItems():
            self.body.position = event.scenePos().x(), event.scenePos().y()
        
    def mouseReleaseEvent(self, event):
        super().mouseReleaseEvent(event)
        self.timer.stop()

    def addCircle(self, x, y, radius):
        item = Circle(radius)
        item.setPos(x, y)
        self.addItem(item)
        self.space.add(item.circle.body, item.circle)
        return item


if __name__ == '__main__':
    app = QApplication(sys.argv)
    scene = Scene(0, 0, 1000, 800)
    for i in range(7, 13):
        item = scene.addCircle(150 * (i - 6), 400, i * 5)
        item.setBrush(Qt.GlobalColor(i))    
    view = QGraphicsView(scene, renderHints=QPainter.Antialiasing)
    view.show()
    sys.exit(app.exec_())