#include <GL/glut.h>
#include <GL/gl.h>
#include <math.h>

class SceneManager
{
protected:
    unsigned int _Example;
	int _Width, _Height;

public:
    SceneManager(void) : _Example(1)
    {
    }

    void init(void)
    {
    }

    void reshape(int w, int h)
    {
		_Width = w;
		_Height = h;
        glutPostRedisplay();
    }

    void drawTwoViewports(void) const
    {
        glViewport(0,0,_Width/2.0,_Height);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-_Width/4.0,_Width/4.0,-_Height/2.0,_Height/2.0,-10.0,10.0);

        glMatrixMode(GL_MODELVIEW);

        //Clear the Draw Buffer
        glClear(GL_COLOR_BUFFER_BIT);

		
		//Draw big plane in distance
		drawPlane(1.0,1.0,1.0);
		
		//Red box
		drawBox(1.0,0.0,0.0);
		
        glViewport(_Width/2.0,0,_Width/2.0,_Height);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-_Width/4.0,_Width/4.0,-_Height/2.0,_Height/2.0,-10.0,10.0);

        glMatrixMode(GL_MODELVIEW);

		//Green box
		drawBox(0.0,1.0,0.0);

        glFlush();  /* Single buffered, so needs a flush. */
    }

	void drawBox(GLfloat red, GLfloat green, GLfloat blue) const
	{
        //Draw  a single quad
        glBegin(GL_QUADS);
            glColor3f(red,green,blue);
            glVertex2i(-75, -75);
            glVertex2i(75, -75);
            glVertex2i(75, 75);
            glVertex2i(-75, 75);
        glEnd();
	}
	
	void drawPlane(GLfloat red, GLfloat green, GLfloat blue) const
	{
        //Draw  a single quad
        glBegin(GL_QUADS);
		    glColor3f(red,green,blue);
		    glVertex3i(-500, -500, 5);
		    glVertex3i(500, -500, 5);
		    glVertex3i(500, 500, 5);
		    glVertex3i(-500, 500, 5);
        glEnd();
	}

    void display(void) const
    {
        switch(_Example)
        {
        case 1:
        default:
            drawTwoViewports();
            break;
        }
    }
    
    void keyboard(unsigned char key, int x, int y)
    {
        switch(key)
        {
        case 'q':
            //exit(0);
            break;
        case '1':
            _Example = 1;
            break;
        }
        glutPostRedisplay();
    }
};

SceneManager mgr;

void reshape(int w, int h)
{
    mgr.reshape(w,h);
}

void display(void)
{
    mgr.display();
}
void keyboard(unsigned char key, int x, int y)
{
    mgr.keyboard(key,x,y);
}

int
main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGBA | GLUT_SINGLE);
  glutCreateWindow("Viewport Examples");
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutReshapeWindow(800,640);
  glutPositionWindow(50,50);
  glutKeyboardFunc(keyboard);
  mgr.init();
  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}