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 /*
 * Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
 *
 * 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_MOUSE_JOINT_H
 #define B2_MOUSE_JOINT_H
 
 #include <Box2D/Dynamics/Joints/b2Joint.h>
 
 /// Mouse joint definition. This requires a world target point,
 /// tuning parameters, and the time step.
 struct b2MouseJointDef : public b2JointDef
 {
     b2MouseJointDef()
     {
         type = e_mouseJoint;
         target.Set(0.0f, 0.0f);
         maxForce = 0.0f;
         frequencyHz = 5.0f;
         dampingRatio = 0.7f;
     }
 
     /// The initial world target point. This is assumed
     /// to coincide with the body anchor initially.
     b2Vec2 target;
 
     /// The maximum constraint force that can be exerted
     /// to move the candidate body. Usually you will express
     /// as some multiple of the weight (multiplier * mass * gravity).
     qreal maxForce;
 
     /// The response speed.
     qreal frequencyHz;
 
     /// The damping ratio. 0 = no damping, 1 = critical damping.
     qreal dampingRatio;
 };
 
 /// A mouse joint is used to make a point on a body track a
 /// specified world point. This a soft constraint with a maximum
 /// force. This allows the constraint to stretch and without
 /// applying huge forces.
 /// NOTE: this joint is not documented in the manual because it was
 /// developed to be used in the testbed. If you want to learn how to
 /// use the mouse joint, look at the testbed.
 class b2MouseJoint : public b2Joint
 {
 public:
 
     /// Implements b2Joint.
     b2Vec2 GetAnchorA() const override;
 
     /// Implements b2Joint.
     b2Vec2 GetAnchorB() const override;
 
     /// Implements b2Joint.
     b2Vec2 GetReactionForce(qreal inv_dt) const override;
 
     /// Implements b2Joint.
     qreal GetReactionTorque(qreal inv_dt) const override;
 
     /// Use this to update the target point.
     void SetTarget(const b2Vec2& target);
     const b2Vec2& GetTarget() const;
 
     /// Set/get the maximum force in Newtons.
     void SetMaxForce(qreal force);
     qreal GetMaxForce() const;
 
     /// Set/get the frequency in Hertz.
     void SetFrequency(qreal hz);
     qreal GetFrequency() const;
 
     /// Set/get the damping ratio (dimensionless).
     void SetDampingRatio(qreal ratio);
     qreal GetDampingRatio() const;
 
 protected:
     friend class b2Joint;
 
     b2MouseJoint(const b2MouseJointDef* def);
 
     void InitVelocityConstraints(const b2TimeStep& step) override;
     void SolveVelocityConstraints(const b2TimeStep& step) override;
     bool SolvePositionConstraints(qreal baumgarte) override { B2_NOT_USED(baumgarte); return true; }
 
     b2Vec2 m_localAnchor;
     b2Vec2 m_target;
     b2Vec2 m_impulse;
 
     b2Mat22 m_mass;     // effective mass for point-to-point constraint.
     b2Vec2 m_C;             // position error
     qreal m_maxForce;
     qreal m_frequencyHz;
     qreal m_dampingRatio;
     qreal m_beta;
     qreal m_gamma;
 };
 
 #endif