# Source code for pymunk.body

    __docformat__ = "reStructuredText"

    import logging
    from typing import TYPE_CHECKING, Any, Callable, Optional, Set, Tuple, Union
    from weakref import WeakSet

    if TYPE_CHECKING:
        from .space import Space
        from .constraints import Constraint
        from .shapes import Shape

    from ._chipmunk_cffi import ffi, lib
    from ._pickle import PickleMixin, _State
    from ._typing_attr import TypingAttrMixing
    from .arbiter import Arbiter
    from .vec2d import Vec2d

    _BodyType = int  # Literal['lib.CP_BODY_TYPE_DYNAMIC', 'lib.CP_BODY_TYPE_KINEMATIC', 'lib.CP_BODY_TYPE_STATIC']
    _PositionFunc = Callable[["Body", float], None]
    _VelocityFunc = Callable[["Body", Vec2d, float, float], None]

    class Body(PickleMixin, TypingAttrMixing, object):
        """A rigid body

        * Use forces to modify the rigid bodies if possible. This is likely to be
          the most stable.
        * Modifying a body's velocity shouldn't necessarily be avoided, but
          applying large changes can cause strange results in the simulation.
          Experiment freely, but be warned.
        * Don't modify a body's position every step unless you really know what
          you are doing. Otherwise you're likely to get the position/velocity badly
          out of sync.

        A Body can be copied and pickled. Sleeping bodies that are copied will be
        awake in the fresh copy. When a Body is copied any spaces, shapes or
        constraints attached to the body will not be copied.
        """

        DYNAMIC = lib.CP_BODY_TYPE_DYNAMIC
        """Dynamic bodies are the default body type.

        They react to collisions,
        are affected by forces and gravity, and have a finite amount of mass.
        These are the type of bodies that you want the physics engine to
        simulate for you. Dynamic bodies interact with all types of bodies
        and can generate collision callbacks.
        """

        KINEMATIC = lib.CP_BODY_TYPE_KINEMATIC
        """Kinematic bodies are bodies that are controlled from your code
        instead of inside the physics engine.

        They arent affected by gravity and they have an infinite amount of mass
        so they don't react to collisions or forces with other bodies. Kinematic
        bodies are controlled by setting their velocity, which will cause them
        to move. Good examples of kinematic bodies might include things like
        moving platforms. Objects that are touching or jointed to a kinematic
        body are never allowed to fall asleep.
        """

        STATIC = lib.CP_BODY_TYPE_STATIC
        """Static bodies are bodies that never (or rarely) move.

        Using static bodies for things like terrain offers a big performance
        boost over other body types- because Chipmunk doesn't need to check for
        collisions between static objects and it never needs to update their
        collision information. Additionally, because static bodies don't
        move, Chipmunk knows it's safe to let objects that are touching or
        jointed to them fall asleep. Generally all of your level geometry
        will be attached to a static body except for things like moving
        platforms or doors. Every space provide a built-in static body for
        your convenience. Static bodies can be moved, but there is a
        performance penalty as the collision information is recalculated.
        There is no penalty for having multiple static bodies, and it can be
        useful for simplifying your code by allowing different parts of your
        static geometry to be initialized or moved separately.
        """

        _pickle_attrs_init = PickleMixin._pickle_attrs_init + [
            "mass",
            "moment",
            "body_type",
        ]
        _pickle_attrs_general = PickleMixin._pickle_attrs_general + [
            "force",
            "angle",
            "position",
            "center_of_gravity",
            "velocity",
            "angular_velocity",
            "torque",
        ]
        _pickle_attrs_skip = PickleMixin._pickle_attrs_skip + [
            "is_sleeping",
            "_velocity_func",
            "_position_func",
        ]

        _position_func_base: Optional[_PositionFunc] = None  # For pickle
        _velocity_func_base: Optional[_VelocityFunc] = None  # For pickle

        _id_counter = 1

        def __init__(
            self, mass: float = 0, moment: float = 0, body_type: _BodyType = DYNAMIC
        ) -> None:
            """Create a new Body

            Mass and moment are ignored when body_type is KINEMATIC or STATIC.

            Guessing the mass for a body is usually fine, but guessing a moment
            of inertia can lead to a very poor simulation so it's recommended to
            use Chipmunk's moment calculations to estimate the moment for you.

            There are two ways to set up a dynamic body. The easiest option is to
            create a body with a mass and moment of 0, and set the mass or
            density of each collision shape added to the body. Chipmunk will
            automatically calculate the mass, moment of inertia, and center of
            gravity for you. This is probably preferred in most cases. Note that
            these will only be correctly calculated after the body and shape are
            added to a space.

            The other option is to set the mass of the body when it's created,
            and leave the mass of the shapes added to it as 0.0. This approach is
            more flexible, but is not as easy to use. Don't set the mass of both
            the body and the shapes. If you do so, it will recalculate and
            overwrite your custom mass value when the shapes are added to the body.

            Examples of the different ways to set up the mass and moment:

            >>> import pymunk
            >>> radius = 2
            >>> mass = 3
            >>> density = 3
            >>> def print_mass_moment(b):
            ...    print("mass={:.0f} moment={:.0f}".format(b.mass, b.moment))

            >>> # Using Shape.density
            >>> s = pymunk.Space()
            >>> b = pymunk.Body()
            >>> c = pymunk.Circle(b, radius)
            >>> c.density = density
            >>> print_mass_moment(b)
            mass=0 moment=0
            >>> s.add(b, c)
            >>> print_mass_moment(b)
            mass=38 moment=75

            >>> # Using Shape.mass
            >>> b = pymunk.Body()
            >>> c = pymunk.Circle(b, radius)
            >>> c.mass = mass
            >>> print_mass_moment(b)
            mass=0 moment=0
            >>> s.add(b, c)
            >>> print_mass_moment(b)
            mass=3 moment=6

            >>> # Using Body constructor
            >>> moment = pymunk.moment_for_circle(mass, 0, radius)
            >>> b = pymunk.Body()
            >>> c = pymunk.Circle(b, radius)
            >>> c.mass = mass
            >>> print_mass_moment(b)
            mass=0 moment=0
            >>> s.add(b, c)
            >>> print_mass_moment(b)
            mass=3 moment=6

            It becomes even more useful to use the mass or density properties of
            the shape when you attach multiple shapes to one body, like in this
            example with density:

            >>> # Using multiple Shape.density
            >>> b = pymunk.Body()
            >>> c1 = pymunk.Circle(b, radius, offset=(10,0))
            >>> c1.density = density
            >>> c2 = pymunk.Circle(b, radius, offset=(0,10))
            >>> c2.density = density
            >>> s.add(b, c1, c2)
            >>> print_mass_moment(b)
            mass=75 moment=3921

            """

            def freebody(cp_body):  # type: ignore
                logging.debug("bodyfree start %s", cp_body)
                cp_shapes = []

                @ffi.callback("cpBodyShapeIteratorFunc")
                def cf1(cp_body, cp_shape, _):  # type: ignore
                    cp_shapes.append(cp_shape)

                lib.cpBodyEachShape(cp_body, cf1, ffi.NULL)

                for cp_shape in cp_shapes:
                    logging.debug("bodyfree remove shape %s %s", cp_body, cp_shape)
                    cp_space = lib.cpShapeGetSpace(cp_shape)
                    if cp_space != ffi.NULL:
                        lib.cpSpaceRemoveShape(cp_space, cp_shape)

                cp_constraints = []

                @ffi.callback("cpBodyConstraintIteratorFunc")
                def cf2(cp_body, cp_constraint, _):  # type: ignore
                    cp_constraints.append(cp_constraint)

                lib.cpBodyEachConstraint(cp_body, cf2, ffi.NULL)
                for cp_constraint in cp_constraints:
                    logging.debug(
                        "bodyfree remove constraint %s %s", cp_body, cp_constraint
                    )
                    cp_space = lib.cpConstraintGetSpace(cp_constraint)
                    if cp_space != ffi.NULL:
                        lib.cpSpaceRemoveConstraint(cp_space, cp_constraint)

                cp_space = lib.cpBodyGetSpace(cp_body)
                # print(cp_space, cp_space == ffi.NULL)
                if cp_space != ffi.NULL:
                    lib.cpSpaceRemoveBody(cp_space, cp_body)

                logging.debug("bodyfree free %s", cp_body)
                lib.cpBodyFree(cp_body)

            if body_type == Body.DYNAMIC:
                self._body = ffi.gc(lib.cpBodyNew(mass, moment), freebody)
            elif body_type == Body.KINEMATIC:
                self._body = ffi.gc(lib.cpBodyNewKinematic(), freebody)
            elif body_type == Body.STATIC:
                self._body = ffi.gc(lib.cpBodyNewStatic(), freebody)

            self._position_func = None  # To prevent the gc to collect the callbacks.
            self._velocity_func = None  # To prevent the gc to collect the callbacks.
            self._position_func_base = None  # For pickle
            self._velocity_func_base = None  # For pickle

            self._space: Optional[
                "Space"
            ] = None  # Weak ref to the space holding this body (if any)

            self._constraints: WeakSet[
                "Constraint"
            ] = WeakSet()  # weak refs to any constraints attached
            self._shapes: WeakSet["Shape"] = WeakSet()  # weak refs to any shapes attached

            self._set_id()

        @property
        def _id(self) -> int:
            """Unique id of the Body

            .. note::
                Experimental API. Likely to change in future major, minor orpoint
                releases.
            """
            return int(ffi.cast("int", lib.cpBodyGetUserData(self._body)))

        def _set_id(self) -> None:
            lib.cpBodySetUserData(self._body, ffi.cast("cpDataPointer", Body._id_counter))
            Body._id_counter += 1

        def __repr__(self) -> str:
            if self.body_type == Body.DYNAMIC:
                return "Body(%r, %r, Body.DYNAMIC)" % (self.mass, self.moment)
            elif self.body_type == Body.KINEMATIC:
                return "Body(Body.KINEMATIC)"
            else:
                return "Body(Body.STATIC)"

        def _set_mass(self, mass: float) -> None:
            lib.cpBodySetMass(self._body, mass)

        def _get_mass(self) -> float:
            return lib.cpBodyGetMass(self._body)

        mass = property(_get_mass, _set_mass, doc="""Mass of the body.""")

        def _set_moment(self, moment: float) -> None:
            lib.cpBodySetMoment(self._body, moment)

        def _get_moment(self) -> float:
            return lib.cpBodyGetMoment(self._body)

        moment = property(
            _get_moment,
            _set_moment,
            doc="""Moment of inertia (MoI or sometimes just moment) of the body.

            The moment is like the rotational mass of a body.
            """,
        )

        def _set_position(self, pos: Union[Vec2d, Tuple[float, float]]) -> None:
            assert len(pos) == 2
            lib.cpBodySetPosition(self._body, pos)

        def _get_position(self) -> Vec2d:
            v = lib.cpBodyGetPosition(self._body)
            return Vec2d(v.x, v.y)

        position = property(
            _get_position,
            _set_position,
            doc="""Position of the body.

            When changing the position you may also want to call
            :py:func:`Space.reindex_shapes_for_body` to update the collision
            detection information for the attached shapes if plan to make any
            queries against the space.""",
        )

        def _set_center_of_gravity(self, cog: Tuple[float, float]) -> None:
            assert len(cog) == 2
            lib.cpBodySetCenterOfGravity(self._body, cog)

        def _get_center_of_gravity(self) -> Vec2d:
            v = lib.cpBodyGetCenterOfGravity(self._body)
            return Vec2d(v.x, v.y)

        center_of_gravity = property(
            _get_center_of_gravity,
            _set_center_of_gravity,
            doc="""Location of the center of gravity in body local coordinates.

            The default value is (0, 0), meaning the center of gravity is the
            same as the position of the body.
            """,
        )

        def _set_velocity(self, vel: Tuple[float, float]) -> None:
            assert len(vel) == 2
            lib.cpBodySetVelocity(self._body, vel)

        def _get_velocity(self) -> Vec2d:
            v = lib.cpBodyGetVelocity(self._body)
            return Vec2d(v.x, v.y)

        velocity = property(
            _get_velocity,
            _set_velocity,
            doc="""Linear velocity of the center of gravity of the body.""",
        )

        def _set_force(self, f: Tuple[float, float]) -> None:
            assert len(f) == 2
            lib.cpBodySetForce(self._body, f)

        def _get_force(self) -> Vec2d:
            v = lib.cpBodyGetForce(self._body)
            return Vec2d(v.x, v.y)

        force = property(
            _get_force,
            _set_force,
            doc="""Force applied to the center of gravity of the body.

            This value is reset for every time step. Note that this is not the
            total of forces acting on the body (such as from collisions), but the
            force applied manually from the apply force functions.""",
        )

        def _set_angle(self, angle: float) -> None:
            lib.cpBodySetAngle(self._body, angle)

        def _get_angle(self) -> float:
            return lib.cpBodyGetAngle(self._body)

        angle = property(
            _get_angle,
            _set_angle,
            doc="""Rotation of the body in radians.

            When changing the rotation you may also want to call
            :py:func:`Space.reindex_shapes_for_body` to update the collision
            detection information for the attached shapes if plan to make any
            queries against the space. A body rotates around its center of gravity,
            not its position.

            .. Note::
                If you get small/no changes to the angle when for example a
                ball is "rolling" down a slope it might be because the Circle shape
                attached to the body or the slope shape does not have any friction
                set.""",
        )

        def _set_angular_velocity(self, w: float) -> None:
            lib.cpBodySetAngularVelocity(self._body, w)

        def _get_angular_velocity(self) -> float:
            return lib.cpBodyGetAngularVelocity(self._body)

        angular_velocity = property(
            _get_angular_velocity,
            _set_angular_velocity,
            doc="""The angular velocity of the body in radians per second.""",
        )

        def _set_torque(self, t: float) -> None:
            lib.cpBodySetTorque(self._body, t)

        def _get_torque(self) -> float:
            return lib.cpBodyGetTorque(self._body)

        torque = property(
            _get_torque,
            _set_torque,
            doc="""The torque applied to the body.

            This value is reset for every time step.""",
        )

        def _get_rotation_vector(self) -> Vec2d:
            v = lib.cpBodyGetRotation(self._body)
            return Vec2d(v.x, v.y)

        rotation_vector = property(
            _get_rotation_vector, doc="""The rotation vector for the body."""
        )

        @property
        def space(self) -> Optional["Space"]:
            """Get the :py:class:`Space` that the body has been added to (or
            None)."""
            if self._space is not None:
                return self._space._get_self()  # ugly hack because of weakref
            else:
                return None

        def _set_velocity_func(self, func: _VelocityFunc) -> None:
            @ffi.callback("cpBodyVelocityFunc")
            def _impl(_: ffi.CData, gravity: ffi.CData, damping: float, dt: float) -> None:
                func(self, Vec2d(gravity.x, gravity.y), damping, dt)

            self._velocity_func_base = func
            self._velocity_func = _impl
            lib.cpBodySetVelocityUpdateFunc(self._body, _impl)

        velocity_func = property(
            fset=_set_velocity_func,
            doc="""The velocity callback function.

            The velocity callback function is called each time step, and can be
            used to set a body's velocity.

                ``func(body : Body, gravity, damping, dt)``

            There are many cases when this can be useful. One example is individual
            gravity for some bodies, and another is to limit the velocity which is
            useful to prevent tunneling.

            Example of a callback that sets gravity to zero for a object.

            >>> import pymunk
            >>> space = pymunk.Space()
            >>> space.gravity = 0, 10
            >>> body = pymunk.Body(1,2)
            >>> space.add(body)
            >>> def zero_gravity(body, gravity, damping, dt):
            ...     pymunk.Body.update_velocity(body, (0,0), damping, dt)
            ...
            >>> body.velocity_func = zero_gravity
            >>> space.step(1)
            >>> space.step(1)
            >>> print(body.position, body.velocity)
            Vec2d(0.0, 0.0) Vec2d(0.0, 0.0)

            Example of a callback that limits the velocity:

            >>> import pymunk
            >>> body = pymunk.Body(1,2)
            >>> def limit_velocity(body, gravity, damping, dt):
            ...     max_velocity = 1000
            ...     pymunk.Body.update_velocity(body, gravity, damping, dt)
            ...     l = body.velocity.length
            ...     if l > max_velocity:
            ...         scale = max_velocity / l
            ...         body.velocity = body.velocity * scale
            ...
            >>> body.velocity_func = limit_velocity

            """,
        )

        def _set_position_func(self, func: Callable[["Body", float], None]) -> None:
            @ffi.callback("cpBodyPositionFunc")
            def _impl(_: ffi.CData, dt: float) -> None:
                return func(self, dt)

            self._position_func_base = func
            self._position_func = _impl
            lib.cpBodySetPositionUpdateFunc(self._body, _impl)

        position_func = property(
            fset=_set_position_func,
            doc="""The position callback function.

            The position callback function is called each time step and can be
            used to update the body's position.

                ``func(body, dt) -> None``
            """,
        )

        @property
        def kinetic_energy(self) -> float:
            """Get the kinetic energy of a body."""
            # todo: use ffi method
            # return lib._cpBodyKineticEnergy(self._body)

            vsq: float = self.velocity.dot(self.velocity)
            wsq: float = self.angular_velocity * self.angular_velocity
            return (vsq * self.mass if vsq else 0.0) + (wsq * self.moment if wsq else 0.0)

        @staticmethod
        def update_velocity(
            body: "Body", gravity: Tuple[float, float], damping: float, dt: float
        ) -> None:
            """Default rigid body velocity integration function.

            Updates the velocity of the body using Euler integration.
            """
            assert len(gravity) == 2
            lib.cpBodyUpdateVelocity(body._body, gravity, damping, dt)

        @staticmethod
        def update_position(body: "Body", dt: float) -> None:
            """Default rigid body position integration function.

            Updates the position of the body using Euler integration. Unlike the
            velocity function, it's unlikely you'll want to override this
            function. If you do, make sure you understand it's source code
            (in Chipmunk) as it's an important part of the collision/joint
            correction process.
            """
            lib.cpBodyUpdatePosition(body._body, dt)

        def apply_force_at_world_point(
            self, force: Tuple[float, float], point: Tuple[float, float]
        ) -> None:
            """Add the force force to body as if applied from the world point.

            People are sometimes confused by the difference between a force and
            an impulse. An impulse is a very large force applied over a very
            short period of time. Some examples are a ball hitting a wall or
            cannon firing. Chipmunk treats impulses as if they occur
            instantaneously by adding directly to the velocity of an object.
            Both impulses and forces are affected the mass of an object. Doubling
            the mass of the object will halve the effect.
            """
            assert len(force) == 2
            assert len(point) == 2
            lib.cpBodyApplyForceAtWorldPoint(self._body, force, point)

        def apply_force_at_local_point(
            self, force: Tuple[float, float], point: Tuple[float, float] = (0, 0)
        ) -> None:
            """Add the local force force to body as if applied from the body
            local point.
            """
            assert len(force) == 2
            assert len(point) == 2
            lib.cpBodyApplyForceAtLocalPoint(self._body, force, point)

        def apply_impulse_at_world_point(
            self, impulse: Tuple[float, float], point: Tuple[float, float]
        ) -> None:
            """Add the impulse impulse to body as if applied from the world point."""
            assert len(impulse) == 2
            assert len(point) == 2
            lib.cpBodyApplyImpulseAtWorldPoint(self._body, impulse, point)

        def apply_impulse_at_local_point(
            self, impulse: Tuple[float, float], point: Tuple[float, float] = (0, 0)
        ) -> None:
            """Add the local impulse impulse to body as if applied from the body
            local point.
            """
            assert len(impulse) == 2
            assert len(point) == 2
            lib.cpBodyApplyImpulseAtLocalPoint(self._body, impulse, point)

        def activate(self) -> None:
            """Reset the idle timer on a body.

            If it was sleeping, wake it and any other bodies it was touching.
            """
            lib.cpBodyActivate(self._body)

        def sleep(self) -> None:
            """Forces a body to fall asleep immediately even if it's in midair.

            Cannot be called from a callback.
            """
            if self._space == None:
                raise Exception("Body not added to space")
            lib.cpBodySleep(self._body)

        def sleep_with_group(self, body: "Body") -> None:
            """Force a body to fall asleep immediately along with other bodies
            in a group.

            When objects in Pymunk sleep, they sleep as a group of all objects
            that are touching or jointed together. When an object is woken up,
            all of the objects in its group are woken up.
            :py:func:`Body.sleep_with_group` allows you group sleeping objects
            together. It acts identically to :py:func:`Body.sleep` if you pass
            None as group by starting a new group. If you pass a sleeping body
            for group, body will be awoken when group is awoken. You can use this
            to initialize levels and start stacks of objects in a pre-sleeping
            state.
            """
            if self._space == None:
                raise Exception("Body not added to space")
            lib.cpBodySleepWithGroup(self._body, body._body)

        @property
        def is_sleeping(self) -> bool:
            """Returns true if the body is sleeping."""
            return bool(lib.cpBodyIsSleeping(self._body))

        def _set_type(self, body_type: _BodyType) -> None:
            lib.cpBodySetType(self._body, body_type)

        def _get_type(self) -> _BodyType:
            return lib.cpBodyGetType(self._body)

        body_type = property(
            _get_type,
            _set_type,
            doc="""The type of a body (:py:const:`Body.DYNAMIC`,
            :py:const:`Body.KINEMATIC` or :py:const:`Body.STATIC`).

            When changing an body to a dynamic body, the mass and moment of
            inertia are recalculated from the shapes added to the body. Custom
            calculated moments of inertia are not preserved when changing types.
            This function cannot be called directly in a collision callback.
            """,
        )

        def each_arbiter(
            self,
            func: Callable[..., None],  # TODO: Fix me once PEP 612 is ready
            *args: Any,
            **kwargs: Any
        ) -> None:
            """Run func on each of the arbiters on this body.

                ``func(arbiter, *args, **kwargs) -> None``

                Callback Parameters
                    arbiter : :py:class:`Arbiter`
                        The Arbiter
                    args
                        Optional parameters passed to the callback function.
                    kwargs
                        Optional keyword parameters passed on to the callback function.

            .. warning::

                Do not hold on to the Arbiter after the callback!
            """

            @ffi.callback("cpBodyArbiterIteratorFunc")
            def cf(_body: ffi.CData, _arbiter: ffi.CData, _data: ffi.CData) -> None:
                assert self._space is not None
                arbiter = Arbiter(_arbiter, self._space)
                func(arbiter, *args, **kwargs)

            data = ffi.new_handle(self)
            lib.cpBodyEachArbiter(self._body, cf, data)

        @property
        def constraints(self) -> Set["Constraint"]:
            """Get the constraints this body is attached to.

            The body only keeps a weak reference to the constraints and a
            live body wont prevent GC of the attached constraints"""
            return set(self._constraints)

        @property
        def shapes(self) -> Set["Shape"]:
            """Get the shapes attached to this body.

            The body only keeps a weak reference to the shapes and a live
            body wont prevent GC of the attached shapes"""
            return set(self._shapes)

        def local_to_world(self, v: Tuple[float, float]) -> Vec2d:
            """Convert body local coordinates to world space coordinates

            Many things are defined in coordinates local to a body meaning that
            the (0,0) is at the center of gravity of the body and the axis rotate
            along with the body.

            :param v: Vector in body local coordinates
            """
            assert len(v) == 2
            v2 = lib.cpBodyLocalToWorld(self._body, v)
            return Vec2d(v2.x, v2.y)

        def world_to_local(self, v: Tuple[float, float]) -> Vec2d:
            """Convert world space coordinates to body local coordinates

            :param v: Vector in world space coordinates
            """
            assert len(v) == 2
            v2 = lib.cpBodyWorldToLocal(self._body, v)
            return Vec2d(v2.x, v2.y)

        def velocity_at_world_point(self, point: Tuple[float, float]) -> Vec2d:
            """Get the absolute velocity of the rigid body at the given world
            point

            It's often useful to know the absolute velocity of a point on the
            surface of a body since the angular velocity affects everything
            except the center of gravity.
            """
            assert len(point) == 2
            v = lib.cpBodyGetVelocityAtWorldPoint(self._body, point)
            return Vec2d(v.x, v.y)

        def velocity_at_local_point(self, point: Tuple[float, float]) -> Vec2d:
            """Get the absolute velocity of the rigid body at the given body
            local point
            """
            assert len(point) == 2
            v = lib.cpBodyGetVelocityAtLocalPoint(self._body, point)
            return Vec2d(v.x, v.y)

        def __getstate__(self) -> _State:
            """Return the state of this object

            This method allows the usage of the :mod:`copy` and :mod:`pickle`
            modules with this class.
            """
            d = super(Body, self).__getstate__()

            d["special"].append(("is_sleeping", self.is_sleeping))
            d["special"].append(("_velocity_func", self._velocity_func_base))
            d["special"].append(("_position_func", self._position_func_base))

            return d

        def __setstate__(self, state: _State) -> None:
            """Unpack this object from a saved state.

            This method allows the usage of the :mod:`copy` and :mod:`pickle`
            modules with this class.
            """
            super(Body, self).__setstate__(state)

            for k, v in state["special"]:
                if k == "is_sleeping" and v:
                    pass
                elif k == "_velocity_func" and v != None:
                    self.velocity_func = v
                elif k == "_position_func" and v != None:
                    self.position_func = v