text: /*
  * Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
  *
  * This software is provided 'as-is', without any express or implied
  * warranty.  In no event will the authors be held liable for any damages
  * arising from the use of this software.
  * Permission is granted to anyone to use this software for any purpose,
  * including commercial applications, and to alter it and redistribute it
  * freely, subject to the following restrictions:
  * 1. The origin of this software must not be misrepresented; you must not
  * claim that you wrote the original software. If you use this software
  * in a product, an acknowledgment in the product documentation would be
  * appreciated but is not required.
  * 2. Altered source versions must be plainly marked as such, and must not be
  * misrepresented as being the original software.
  * 3. This notice may not be removed or altered from any source distribution.
  */
  
  #ifndef B2_WORLD_CALLBACKS_H
  #define B2_WORLD_CALLBACKS_H
  
  #include <Common/b2Settings.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 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 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 b2ContactImpulse
  {
  	b2_float32 normalImpulses[b2_maxManifoldPoints];
  	b2_float32 tangentImpulses[b2_maxManifoldPoints];
  	b2_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 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 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 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
  	/// @return -1 to filter, 0 to terminate, fraction to clip the ray for
  	/// closest hit, 1 to continue
  	virtual b2_float32 ReportFixture(	b2Fixture* fixture, const b2Vec2& point,
  									const b2Vec2& normal, b2_float32 fraction) = 0;
  };
  
  #endif
  