text: /*
  * Copyright (c) 2008-2009 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 SENSOR_TEST_H
  #define SENSOR_TEST_H
  
  // This is used to test sensor shapes.
  class SensorTest : public Test
  {
  public:
  
      enum
      {
          e_count = 7
      };
  
      SensorTest()
      {
          {
              b2BodyDef bd;
              b2Body* ground = m_world->CreateBody(&bd);
  
              {
                  b2EdgeShape shape;
                  shape.Set(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
                  ground->CreateFixture(&shape, 0.0f);
              }
  
  #if 0
              {
                  b2FixtureDef sd;
                  sd.SetAsBox(10.0f, 2.0f, b2Vec2(0.0f, 20.0f), 0.0f);
                  sd.isSensor = true;
                  m_sensor = ground->CreateFixture(&sd);
              }
  #else
              {
                  b2CircleShape shape;
                  shape.m_radius = 5.0f;
                  shape.m_p.Set(0.0f, 10.0f);
  
                  b2FixtureDef fd;
                  fd.shape = &shape;
                  fd.isSensor = true;
                  m_sensor = ground->CreateFixture(&fd);
              }
  #endif
          }
  
          {
              b2CircleShape shape;
              shape.m_radius = 1.0f;
  
              for (int32 i = 0; i < e_count; ++i)
              {
                  b2BodyDef bd;
                  bd.type = b2_dynamicBody;
                  bd.position.Set(-10.0f + 3.0f * i, 20.0f);
                  bd.userData = m_touching + i;
  
                  m_touching[i] = false;
                  m_bodies[i] = m_world->CreateBody(&bd);
  
                  m_bodies[i]->CreateFixture(&shape, 1.0f);
              }
          }
      }
  
      // Implement contact listener.
      void BeginContact(b2Contact* contact)
      {
          b2Fixture* fixtureA = contact->GetFixtureA();
          b2Fixture* fixtureB = contact->GetFixtureB();
  
          if (fixtureA == m_sensor)
          {
              void* userData = fixtureB->GetBody()->GetUserData();
              if (userData)
              {
                  bool* touching = (bool*)userData;
                  *touching = true;
              }
          }
  
          if (fixtureB == m_sensor)
          {
              void* userData = fixtureA->GetBody()->GetUserData();
              if (userData)
              {
                  bool* touching = (bool*)userData;
                  *touching = true;
              }
          }
      }
  
      // Implement contact listener.
      void EndContact(b2Contact* contact)
      {
          b2Fixture* fixtureA = contact->GetFixtureA();
          b2Fixture* fixtureB = contact->GetFixtureB();
  
          if (fixtureA == m_sensor)
          {
              void* userData = fixtureB->GetBody()->GetUserData();
              if (userData)
              {
                  bool* touching = (bool*)userData;
                  *touching = false;
              }
          }
  
          if (fixtureB == m_sensor)
          {
              void* userData = fixtureA->GetBody()->GetUserData();
              if (userData)
              {
                  bool* touching = (bool*)userData;
                  *touching = false;
              }
          }
      }
  
      void Step(Settings* settings)
      {
          Test::Step(settings);
  
          // Traverse the contact results. Apply a force on shapes
          // that overlap the sensor.
          for (int32 i = 0; i < e_count; ++i)
          {
              if (m_touching[i] == false)
              {
                  continue;
              }
  
              b2Body* body = m_bodies[i];
              b2Body* ground = m_sensor->GetBody();
  
              b2CircleShape* circle = (b2CircleShape*)m_sensor->GetShape();
              b2Vec2 center = ground->GetWorldPoint(circle->m_p);
  
              b2Vec2 position = body->GetPosition();
  
              b2Vec2 d = center - position;
              if (d.LengthSquared() < FLT_EPSILON * FLT_EPSILON)
              {
                  continue;
              }
  
              d.Normalize();
              b2Vec2 F = 100.0f * d;
              body->ApplyForce(F, position);
          }
      }
  
      static Test* Create()
      {
          return new SensorTest;
      }
  
      b2Fixture* m_sensor;
      b2Body* m_bodies[e_count];
      bool m_touching[e_count];
  };
  
  #endif
  