text: /* Copyright (c) 2013 Scott Lembcke and Howling Moon Software
   * 
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
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   * 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
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   * SOFTWARE.
   */
  
  /// @defgroup cpArbiter cpArbiter
  /// The cpArbiter struct tracks pairs of colliding shapes.
  /// They are also used in conjuction with collision handler callbacks
  /// allowing you to retrieve information on the collision or change it.
  /// A unique arbiter value is used for each pair of colliding objects. It persists until the shapes separate.
  /// @{
  
  #define CP_MAX_CONTACTS_PER_ARBITER 2
  
  /// Get the restitution (elasticity) that will be applied to the pair of colliding objects.
  CP_EXPORT cpFloat cpArbiterGetRestitution(const cpArbiter *arb);
  /// Override the restitution (elasticity) that will be applied to the pair of colliding objects.
  CP_EXPORT void cpArbiterSetRestitution(cpArbiter *arb, cpFloat restitution);
  /// Get the friction coefficient that will be applied to the pair of colliding objects.
  CP_EXPORT cpFloat cpArbiterGetFriction(const cpArbiter *arb);
  /// Override the friction coefficient that will be applied to the pair of colliding objects.
  CP_EXPORT void cpArbiterSetFriction(cpArbiter *arb, cpFloat friction);
  
  // Get the relative surface velocity of the two shapes in contact.
  CP_EXPORT cpVect cpArbiterGetSurfaceVelocity(cpArbiter *arb);
  
  // Override the relative surface velocity of the two shapes in contact.
  // By default this is calculated to be the difference of the two surface velocities clamped to the tangent plane.
  CP_EXPORT void cpArbiterSetSurfaceVelocity(cpArbiter *arb, cpVect vr);
  
  /// Get the user data pointer associated with this pair of colliding objects.
  CP_EXPORT cpDataPointer cpArbiterGetUserData(const cpArbiter *arb);
  /// Set a user data point associated with this pair of colliding objects.
  /// If you need to perform any cleanup for this pointer, you must do it yourself, in the separate callback for instance.
  CP_EXPORT void cpArbiterSetUserData(cpArbiter *arb, cpDataPointer userData);
  
  /// Calculate the total impulse including the friction that was applied by this arbiter.
  /// This function should only be called from a post-solve, post-step or cpBodyEachArbiter callback.
  CP_EXPORT cpVect cpArbiterTotalImpulse(const cpArbiter *arb);
  /// Calculate the amount of energy lost in a collision including static, but not dynamic friction.
  /// This function should only be called from a post-solve, post-step or cpBodyEachArbiter callback.
  CP_EXPORT cpFloat cpArbiterTotalKE(const cpArbiter *arb);
  
  /// Mark a collision pair to be ignored until the two objects separate.
  /// Pre-solve and post-solve callbacks will not be called, but the separate callback will be called.
  CP_EXPORT cpBool cpArbiterIgnore(cpArbiter *arb);
  
  /// Return the colliding shapes involved for this arbiter.
  /// The order of their cpSpace.collision_type values will match
  /// the order set when the collision handler was registered.
  CP_EXPORT void cpArbiterGetShapes(const cpArbiter *arb, cpShape **a, cpShape **b);
  
  /// A macro shortcut for defining and retrieving the shapes from an arbiter.
  #define CP_ARBITER_GET_SHAPES(__arb__, __a__, __b__) cpShape *__a__, *__b__; cpArbiterGetShapes(__arb__, &__a__, &__b__);
  
  /// Return the colliding bodies involved for this arbiter.
  /// The order of the cpSpace.collision_type the bodies are associated with values will match
  /// the order set when the collision handler was registered.
  CP_EXPORT void cpArbiterGetBodies(const cpArbiter *arb, cpBody **a, cpBody **b);
  
  /// A macro shortcut for defining and retrieving the bodies from an arbiter.
  #define CP_ARBITER_GET_BODIES(__arb__, __a__, __b__) cpBody *__a__, *__b__; cpArbiterGetBodies(__arb__, &__a__, &__b__);
  
  /// A struct that wraps up the important collision data for an arbiter.
  struct cpContactPointSet {
  	/// The number of contact points in the set.
  	int count;
  	
  	/// The normal of the collision.
  	cpVect normal;
  	
  	/// The array of contact points.
  	struct {
  		/// The position of the contact on the surface of each shape.
  		cpVect pointA, pointB;
  		/// Penetration distance of the two shapes. Overlapping means it will be negative.
  		/// This value is calculated as cpvdot(cpvsub(point2, point1), normal) and is ignored by cpArbiterSetContactPointSet().
  		cpFloat distance;
  	} points[CP_MAX_CONTACTS_PER_ARBITER];
  };
  
  /// Return a contact set from an arbiter.
  CP_EXPORT cpContactPointSet cpArbiterGetContactPointSet(const cpArbiter *arb);
  
  /// Replace the contact point set for an arbiter.
  /// This can be a very powerful feature, but use it with caution!
  CP_EXPORT void cpArbiterSetContactPointSet(cpArbiter *arb, cpContactPointSet *set);
  
  /// Returns true if this is the first step a pair of objects started colliding.
  CP_EXPORT cpBool cpArbiterIsFirstContact(const cpArbiter *arb);
  /// Returns true if the separate callback is due to a shape being removed from the space.
  CP_EXPORT cpBool cpArbiterIsRemoval(const cpArbiter *arb);
  
  /// Get the number of contact points for this arbiter.
  CP_EXPORT int cpArbiterGetCount(const cpArbiter *arb);
  /// Get the normal of the collision.
  CP_EXPORT cpVect cpArbiterGetNormal(const cpArbiter *arb);
  /// Get the position of the @c ith contact point on the surface of the first shape.
  CP_EXPORT cpVect cpArbiterGetPointA(const cpArbiter *arb, int i);
  /// Get the position of the @c ith contact point on the surface of the second shape.
  CP_EXPORT cpVect cpArbiterGetPointB(const cpArbiter *arb, int i);
  /// Get the depth of the @c ith contact point.
  CP_EXPORT cpFloat cpArbiterGetDepth(const cpArbiter *arb, int i);
  
  /// If you want a custom callback to invoke the wildcard callback for the first collision type, you must call this function explicitly.
  /// You must decide how to handle the wildcard's return value since it may disagree with the other wildcard handler's return value or your own.
  CP_EXPORT cpBool cpArbiterCallWildcardBeginA(cpArbiter *arb, cpSpace *space);
  /// If you want a custom callback to invoke the wildcard callback for the second collision type, you must call this function explicitly.
  /// You must decide how to handle the wildcard's return value since it may disagree with the other wildcard handler's return value or your own.
  CP_EXPORT cpBool cpArbiterCallWildcardBeginB(cpArbiter *arb, cpSpace *space);
  
  /// If you want a custom callback to invoke the wildcard callback for the first collision type, you must call this function explicitly.
  /// You must decide how to handle the wildcard's return value since it may disagree with the other wildcard handler's return value or your own.
  CP_EXPORT cpBool cpArbiterCallWildcardPreSolveA(cpArbiter *arb, cpSpace *space);
  /// If you want a custom callback to invoke the wildcard callback for the second collision type, you must call this function explicitly.
  /// You must decide how to handle the wildcard's return value since it may disagree with the other wildcard handler's return value or your own.
  CP_EXPORT cpBool cpArbiterCallWildcardPreSolveB(cpArbiter *arb, cpSpace *space);
  
  /// If you want a custom callback to invoke the wildcard callback for the first collision type, you must call this function explicitly.
  CP_EXPORT void cpArbiterCallWildcardPostSolveA(cpArbiter *arb, cpSpace *space);
  /// If you want a custom callback to invoke the wildcard callback for the second collision type, you must call this function explicitly.
  CP_EXPORT void cpArbiterCallWildcardPostSolveB(cpArbiter *arb, cpSpace *space);
  
  /// If you want a custom callback to invoke the wildcard callback for the first collision type, you must call this function explicitly.
  CP_EXPORT void cpArbiterCallWildcardSeparateA(cpArbiter *arb, cpSpace *space);
  /// If you want a custom callback to invoke the wildcard callback for the second collision type, you must call this function explicitly.
  CP_EXPORT void cpArbiterCallWildcardSeparateB(cpArbiter *arb, cpSpace *space);
  
  /// @}
  