def wheelEvent(self, wheel_event):
if wheel_event.modifiers() == Qt.NoModifier:
delta = wheel_event.delta()
delta = max(min(delta, 480), -480)
mouse_before_scale_in_scene = self.mapToScene(wheel_event.pos())
scale_factor = 1 + (0.2 * (delta / 120.0))
scaling = QTransform(scale_factor, 0, 0, scale_factor, 0, 0)
self.setTransform(self.transform() * scaling)
mouse_after_scale_in_scene = self.mapToScene(wheel_event.pos())
center_in_scene = self.mapToScene(self.frameRect().center())
self.centerOn(center_in_scene + mouse_before_scale_in_scene - mouse_after_scale_in_scene)
wheel_event.accept()
else:
QGraphicsView.wheelEvent(self, wheel_event)
