/* Auteur: Nicolas JANEY           */
/* nicolas.janey@univ-fcomte.fr    */
/* Septembre 2004                  */
/* Un programme OpenGL fonctionnel */

#include <stdlib.h>
#include <stdio.h>

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

static int l = 1;

void key(unsigned char key,int x,int y) {
  switch ( key ) {
    case 0x0D : l = !l ;
                glutPostRedisplay();
                break;
    case 0x1B : exit(0); }
}

void reshape(int tx,int ty) {
  glViewport(0,0,tx,ty);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho((double) -tx/ty,(double) tx/ty,-1.0,1.0,-1.0,1.0) ;
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

void scene(void) {
  glPushMatrix();
  glutSolidSphere(0.8,36,36);
  glPopMatrix();
}

void display(void) {
  glClearColor(0.8F,0.8F,0.8F,1.0F) ;
  glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT) ;
  glEnable(0);
  if ( l )
    glEnable(GL_LIGHTING);
    else
    glDisable(GL_LIGHTING);
  glPushMatrix();
  scene();
  glPopMatrix();
  glFlush();
  glutSwapBuffers();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("Attention, erreur OpenGL %d\n",error);
}

void init(void) {
  GLfloat l_pos[] = { 0.0F,0.0F,1.0F,0.0F };
  GLfloat c[4] = { 0.5F,0.2F,0.6F,1.0F };
  glMaterialfv(GL_FRONT,GL_DIFFUSE,c);
  glLightfv(GL_LIGHT0,GL_POSITION,l_pos);
  glEnable(GL_LIGHT0);
  glColor4fv(c) ;
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
}

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE);
  glutInitWindowSize(200,200); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("OpenGL");
  init(); 
  glutReshapeFunc(reshape);
  glutKeyboardFunc(key);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}