#include <iostream>
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <GL/glext.h>

#include <iomanip>

using namespace std;

GLfloat Left, Right, Top, Bottom, Near, Far;


void DisplayString(void * font, string s) {
    int i;

    for(i=0; i < s.size(); i++) {
        glutStrokeCharacter(font, s[i]);
    }

    return;
}

void display() {
   glClear(GL_COLOR_BUFFER_BIT);
   glLoadIdentity();
   glColor3f(0,.87, .68);
   glutWireTeapot(0.25);

   glFlush();
   return;
}

void reset() {
   Left = -1;
   Right = 1;
   Bottom = -1;
   Top = 1;
   Near = -1;
   Far = 1;

   return;
}

void setup() {
   reset();
   glClearColor(1,1,1,1);

   return;
}

void ReportFromGL(){
   GLfloat matrix[16];
   int i,j;

   glGetFloatv(GL_PROJECTION_MATRIX, matrix);

   cout << "The matrix from OpenGL is " << endl;
   for(i=0;i<4;i++) {
      for (j=0;j<4;j++) {
          cout << setw(10)  << matrix[i+j*4];
      }
      cout << endl;
   }

   return;
}

void ReportFromMatrix(){
    GLfloat sx, sy, sz;
    GLfloat tx, ty, tz;

    sx = 2.0/(Right-Left);
    sy = 2.0/(Top - Bottom);
    sz = 2.0/(Near - Far);

    tx = -(Right+Left)/(Right-Left);
    ty = -(Top+Bottom)/(Top-Bottom);
    tz = -(Far+Near)/(Far-Near);

    cout << endl ;
    cout << "The derived matrix is " << endl;
    cout << setw(10) << sx << setw(10) << 0 << setw(10) << 0 << setw(10) << tx << endl;
    cout << setw(10) << 0 << setw(10) << sy << setw(10) << 0 << setw(10) << ty << endl;
    cout << setw(10) << 0 << setw(10) << 0 << setw(10) << sz << setw(10) << tz << endl;
    cout << setw(10) << 0 << setw(10) << 0 << setw(10) << 0 << setw(10) << 1 << endl;
}

void Ortho() {
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(Left, Right, Bottom, Top, Near, Far);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   cout << endl ;
   cout << "The box is now " << endl;
   cout << "\tLeft = " << Left << endl;
   cout << "\tRight = " << Right << endl;
   cout << "\tBottom = " << Bottom << endl;
   cout << "\tTop = " << Top << endl;
   cout << "\tNear = " << Near << endl;
   cout << "\tFar = " << Far << endl;

   cout << endl;
   ReportFromGL();
   ReportFromMatrix();
   return;
}

void resize(int w, int h) {
   glViewport(0, 0, w, h);
   Ortho();

   return;
}

void  keypress (unsigned char key, int x, int y) {

   const GLfloat INCREMENT = 0.5;
   switch(key) {
     case 'l':
         Left -=INCREMENT;
	 Ortho();
	 break;
     case 'L':
         Left +=INCREMENT;
	 Ortho();
	 break;
     case 'r':
         Right -=INCREMENT;
	 Ortho();
	 break;
     case 'R':
         Right +=INCREMENT;
	 Ortho();
	 break;
     case 't':
         Top -=INCREMENT;
	 Ortho();
	 break;
     case 'T':
         Top +=INCREMENT;
	 Ortho();
	 break;
     case 'b':
         Bottom -=INCREMENT;
	 Ortho();
	 break;
     case 'B':
         Bottom +=INCREMENT;
	 Ortho();
	 break;
     case 'n':
         Near -=INCREMENT;
	 Ortho();
	 break;
     case 'N':
         Near +=INCREMENT;
	 Ortho();
	 break;
     case 'f':
         Far -=INCREMENT;
	 Ortho();
	 break;
     case 'F':
         Far +=INCREMENT;
	 Ortho();
	 break;
     case 'q':
          exit(0);
   }
   glutPostRedisplay();
   return;
}

int main(int argc, char * argv[]) {
   
   reset();
   glutInit(&argc, argv);

   glutInitContextVersion(3, 0);
   glutInitContextProfile(GLUT_COMPATIBILITY_PROFILE);

   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
   glutInitWindowSize(500, 500);
   glutCreateWindow("A Demo");
   glutDisplayFunc(display);
   glutReshapeFunc(resize);
   glutKeyboardFunc(keypress);

   glewExperimental = GL_TRUE;
   glewInit();

   setup();

   glutMainLoop();
}