#ifndef _SKELETON_APPLICATION_H
#define _SKELETON_APPLICATION_H
 
#include "Ogre.h"
 
namespace Skeleton {
    class Application : public Ogre::FrameListener {
    private:
        Ogre::Root *_root;
        Ogre::RenderWindow *_window;
 
        Ogre::SceneManager *_sceneManager;
        Ogre::Camera *_cam;
        Ogre::Viewport *_viewport;
 
    public:
        Application() {
            // Load resources and config (borrowed from the tutorial framework)
            this->_root = new Ogre::Root("plugins_d.cfg", "resources_d.cfg");
            this->_root->addFrameListener(this);
        }
 
        ~Application() {
	        delete this->_root;
        }
 
        bool init() {
            // Get the settings from the config dialog
            if (!this->_root->showConfigDialog()) return false;
 
            // Auto create the window and store the pointer
            this->_window = this->_root->initialise(true, "Ogre Skeleton");
 
            // Create the scene manager and camera
            this->_sceneManager = this->_root->createSceneManager(Ogre::ST_GENERIC);
            this->_cam = this->_sceneManager->createCamera("MainCamera");
 
	        // Set up the defaults for the camera
            this->_cam->setPosition(Ogre::Vector3(0, 0, 80));
            this->_cam->lookAt(Ogre::Vector3(0, 0, -300));
            this->_cam->setNearClipDistance(5);
 
	        // Add the viewport to the window
            this->_viewport = this->_window->addViewport(this->_cam);
            this->_viewport->setBackgroundColour(Ogre::ColourValue(0, 0, 0)); // Black
 
            return true;
        }
 
        void run() {
            if (this->init()) {
                // Let Ogre handle the render loop
    	        this->_root->startRendering();
            }
        }
 
        virtual bool frameRenderingQueued(const Ogre::FrameEvent& evt) {
            if (this->_window->isClosed()) {
                // Returning false in the frame listener callback triggers shutdown
    	        return false;
            }
 
            return true;
        }
    };
}
 
#endif // _SKELETON_APPLICATION_H

// car.h
 
#include "engine.h"
 
class Car {
private:
    Engine *_engine;
public:
   // ...
};
 
//engine.h
 
#include "car.h"
 
class Engine {
private:
    Car *_car;
public:
    // ...
}

//engine.h
 
#include "car.h"
 
class Car; // <- Forward declaration
class Engine {
    // ...
}