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// MIT License
// Copyright (c) 2019 Erin Catto
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
#ifndef B2_WORLD_CALLBACKS_H
#define B2_WORLD_CALLBACKS_H
#include "b2_api.h"
#include "b2_settings.h"
struct b2Vec2;
struct b2Transform;
class b2Fixture;
class b2Body;
class b2Joint;
class b2Contact;
struct b2ContactResult;
struct b2Manifold;
/// Joints and fixtures are destroyed when their associated
/// body is destroyed. Implement this listener so that you
/// may nullify references to these joints and shapes.
class B2_API b2DestructionListener
{
public:
virtual ~b2DestructionListener() {}
/// Called when any joint is about to be destroyed due
/// to the destruction of one of its attached bodies.
virtual void SayGoodbye(b2Joint* joint) = 0;
/// Called when any fixture is about to be destroyed due
/// to the destruction of its parent body.
virtual void SayGoodbye(b2Fixture* fixture) = 0;
};
/// Implement this class to provide collision filtering. In other words, you can implement
/// this class if you want finer control over contact creation.
class B2_API b2ContactFilter
{
public:
virtual ~b2ContactFilter() {}
/// Return true if contact calculations should be performed between these two shapes.
/// @warning for performance reasons this is only called when the AABBs begin to overlap.
virtual bool ShouldCollide(b2Fixture* fixtureA, b2Fixture* fixtureB);
};
/// Contact impulses for reporting. Impulses are used instead of forces because
/// sub-step forces may approach infinity for rigid body collisions. These
/// match up one-to-one with the contact points in b2Manifold.
struct B2_API b2ContactImpulse
{
float normalImpulses[b2_maxManifoldPoints];
float tangentImpulses[b2_maxManifoldPoints];
int32 count;
};
/// Implement this class to get contact information. You can use these results for
/// things like sounds and game logic. You can also get contact results by
/// traversing the contact lists after the time step. However, you might miss
/// some contacts because continuous physics leads to sub-stepping.
/// Additionally you may receive multiple callbacks for the same contact in a
/// single time step.
/// You should strive to make your callbacks efficient because there may be
/// many callbacks per time step.
/// @warning You cannot create/destroy Box2D entities inside these callbacks.
class B2_API b2ContactListener
{
public:
virtual ~b2ContactListener() {}
/// Called when two fixtures begin to touch.
virtual void BeginContact(b2Contact* contact) { B2_NOT_USED(contact); }
/// Called when two fixtures cease to touch.
virtual void EndContact(b2Contact* contact) { B2_NOT_USED(contact); }
/// This is called after a contact is updated. This allows you to inspect a
/// contact before it goes to the solver. If you are careful, you can modify the
/// contact manifold (e.g. disable contact).
/// A copy of the old manifold is provided so that you can detect changes.
/// Note: this is called only for awake bodies.
/// Note: this is called even when the number of contact points is zero.
/// Note: this is not called for sensors.
/// Note: if you set the number of contact points to zero, you will not
/// get an EndContact callback. However, you may get a BeginContact callback
/// the next step.
virtual void PreSolve(b2Contact* contact, const b2Manifold* oldManifold)
{
B2_NOT_USED(contact);
B2_NOT_USED(oldManifold);
}
/// This lets you inspect a contact after the solver is finished. This is useful
/// for inspecting impulses.
/// Note: the contact manifold does not include time of impact impulses, which can be
/// arbitrarily large if the sub-step is small. Hence the impulse is provided explicitly
/// in a separate data structure.
/// Note: this is only called for contacts that are touching, solid, and awake.
virtual void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse)
{
B2_NOT_USED(contact);
B2_NOT_USED(impulse);
}
};
/// Callback class for AABB queries.
/// See b2World::Query
class B2_API b2QueryCallback
{
public:
virtual ~b2QueryCallback() {}
/// Called for each fixture found in the query AABB.
/// @return false to terminate the query.
virtual bool ReportFixture(b2Fixture* fixture) = 0;
};
/// Callback class for ray casts.
/// See b2World::RayCast
class B2_API b2RayCastCallback
{
public:
virtual ~b2RayCastCallback() {}
/// Called for each fixture found in the query. You control how the ray cast
/// proceeds by returning a float:
/// return -1: ignore this fixture and continue
/// return 0: terminate the ray cast
/// return fraction: clip the ray to this point
/// return 1: don't clip the ray and continue
/// @param fixture the fixture hit by the ray
/// @param point the point of initial intersection
/// @param normal the normal vector at the point of intersection
/// @param fraction the fraction along the ray at the point of intersection
/// @return -1 to filter, 0 to terminate, fraction to clip the ray for
/// closest hit, 1 to continue
virtual float ReportFixture( b2Fixture* fixture, const b2Vec2& point,
const b2Vec2& normal, float fraction) = 0;
};
#endif
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