/***********************************************************************
 * hello.cpp  (C) Elie De Brauwer, elie@de-brauwer.be                  *
 *            this file originated from http://mindfuck.de-brauwer.be  *
 *                                                                     *
 * Compile with: g++ -Wall -lglut hello.cpp                            *
 ***********************************************************************/

#include <iostream>
#include <cstdlib>                // for exit()
#include <GL/glut.h>              // also includes GL/gl.h and GL/glu.h
using namespace std;

typedef unsigned char uchar;

// callback prototypes
void disp(void);
void reshape(int x, int y);
void reshape1(int x, int y);
void reshape2(int x, int y);
void keyb(uchar key, int x, int y);


////////////////////////////////
// main
int main(int argc, char **argv){

  glutInit(&argc, argv);
  // no double buffering since we don't need no animations
  glutInitDisplayMode(GLUT_RGBA | GLUT_SINGLE);
  glutInitWindowSize(400,400);
  glutCreateWindow("hello world");

  // clear to black
  glClearColor(0.0,0.0,0.0,0.0);

  glutDisplayFunc(disp);
  glutKeyboardFunc(keyb);
  glutReshapeFunc(reshape);

  glutMainLoop();
  return 0;
}


////////////////
// disp
void disp(void){
  glClear(GL_COLOR_BUFFER_BIT);
  // draw a white rectangle (only 3 parameters, no alpha)
  glColor3d(1.0,1.0,1.0);
  glRectf(25,25,75,75);
  // update the screen, not needed when using double
  // buffering and glutSwapBuffers()
  glFlush();
}

//////////////////////////
// reshape
void reshape(int x,int y){
  glViewport(0,0,x,y);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0,100,0,100);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  /* this reshape maps the coordinates of the screen to [0,100] and [0,100] this can
     take everything out of proportion when resized
  */
}

///////////////////////////
// reshape1
void reshape1(int x,int y){
  glViewport(0,0,x,y);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0,x,0,y);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  /* this won't take anything out of proportion but it won't scale the image either
     the height and width of the window in pixels determine the size of the square
   */
}

//////////////////////////
// reshape2
void reshape2(int x,int y){
  if(x<y)
    glViewport(0,(y-x)/2,x,x);
  else
    glViewport((x-y)/2,0,y,y);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0,100,0,100);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  /* this will scale the image but keep the area available to OpenGL for drawing a square
     so nothing will be taken out of proportion, not the entire window is accesible.
  */

}

///////////////////////////////////
// keyb
void keyb(uchar key, int x, int y){
  switch(key){
  case '1':
    glutReshapeFunc(reshape);
    cout << "Selected reshape " << endl;
    glutPostRedisplay();
    break;
  case '2':
    glutReshapeFunc(reshape1);
    cout << "Selected reshape1" << endl;
    glutPostRedisplay();
    break;
  case '3':
    glutReshapeFunc(reshape2);
    cout << "Selected reshape2" << endl;
    glutPostRedisplay();
    break;
  case 'g':
    glClearColor(0.0,1.0,0.0,0.0);
    cout << "Will now clear to green" << endl;
    glutPostRedisplay();
    break;
  case 'b':
    glClearColor(0.0,0.0,0.0,0.0);
    cout << "Will now clear to black" << endl;
    glutPostRedisplay();
    break;
  case 'q':
    exit(0);
    break;
  }
}