/* Gestion de camera et animation automatique   */
/* d'une sphere par rebond sur les bords        */
/* de la fenetre d'affichage                    */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Mars 2015                                    */

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

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

/* Variables et constantes globales             */
/* pour les angles et les couleurs utilises     */

static int aff = 1;
static int lum = 1;
static int posx = 250;
static int posy = 150;
static int dx = 1;
static int dy = 1;
static int n = 100;
static int tx = 500;
static int ty = 300;
        
static const float blanc[] = { 1.0F,1.0F,1.0F,1.0F };
static const float jaune[] = { 1.0F,1.0F,0.0F,1.0F };
static const float rouge[] = { 1.0F,0.0F,0.0F,1.0F };
static const float vert[] = { 0.0F,1.0F,0.0F,1.0F };
static const float bleu[] = { 0.0F,0.0F,1.0F,1.0F };

/* Fonction d'initialisation des parametres     */
/* OpenGL ne changeant pas au cours de la vie   */
/* du programme                                 */

void init(void) {
  const GLfloat shininess[] = { 50.0 };
  glMaterialfv(GL_FRONT,GL_SPECULAR,blanc);
  glMaterialfv(GL_FRONT,GL_SHININESS,shininess);
  glLightfv(GL_LIGHT0,GL_DIFFUSE,rouge);
  glLightfv(GL_LIGHT1,GL_DIFFUSE,jaune);
  glLightfv(GL_LIGHT2,GL_DIFFUSE,bleu);
  glEnable(GL_LIGHT0);
  glEnable(GL_LIGHT1);
  glEnable(GL_LIGHT2);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
  glEnable(GL_AUTO_NORMAL);
}

/* Scene dessinee                               */

void scene(void) {
  glPushMatrix();
  glTranslatef(posx,posy,0.0F);
  glutSolidSphere(20.0,n,n);
  glPopMatrix();
}

/* Fonction executee lors d'un changement       */
/* de la taille de la fenetre OpenGL            */

void reshape(int x,int y) {
  tx = x;
  ty = y;
  glViewport(0,0,x,y); 
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0.0,x,0.0,y,-30.0,30.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

/* Fonction executee lors d'un rafraichissement */
/* de la fenetre de dessin                      */

void display(void) {
  glClearColor(0.5F,0.5F,0.5F,0.5F);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  const GLfloat light0_position[] = { 0.0,0.0,0.0,1.0 };
  const GLfloat light1_position[] = { -1.0,1.0,1.0,0.0 };
  const GLfloat light2_position[] = { 1.0,-1.0,1.0,0.0 };
  glLightfv(GL_LIGHT0,GL_POSITION,light0_position);
  glLightfv(GL_LIGHT1,GL_POSITION,light1_position);
  glLightfv(GL_LIGHT2,GL_POSITION,light2_position);
  if ( lum )
    glEnable(GL_LIGHTING);
    else
    glDisable(GL_LIGHTING);
  glPolygonMode(GL_FRONT_AND_BACK,(aff) ? GL_FILL : GL_LINE);
  glPushMatrix();
  scene();
  glPopMatrix();
  glFlush();
  glutSwapBuffers();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("Erreur : %d\n",error);
}

/* Fonction executee quand aucun evenement      */
/* n'est en file d'attente                      */

void idle(void) {
  /* Deplacement                                */
  posx += dx;
  posy += dy;
  /* Gestion du fenetrage                       */
  if ( posx+20 > tx )
    posx = tx-20;
  if ( posy+20 > ty )
    posy = ty-20;
  /* Gestion des rebonds                        */
  if ( ( posx-20 == 0 ) || ( posx+20 == tx ) )
    dx = -dx;
  if ( ( posy+20 == ty ) || ( posy-20 == 0 ) )
    dy = -dy;
  /* Rafraichissement                           */
  glutPostRedisplay();
}

/* Fonction executee lors de l'appui            */
/* d'une touche alphanumerique du clavier:      */
/* - lettres minuscules et majuscules           */
/* - chiffres                                   */
/* - /+-*,.;:                                   */
/* - autres touches a code ASCII:               */
/*   - espace                                   */
/*   - enter                                    */
/*   - escape                                   */

void keyboard(unsigned char key,int x,int y) {
  switch (key) {
    case 0x0D :
      { static int anim = 1;
        anim = !anim;
        glutIdleFunc(( anim ) ? idle : NULL); }
      break;
    case 'm' :
      aff = !aff;
      glutPostRedisplay();
      break;
    case 'l' :
      lum = !lum;
      glutPostRedisplay();
      break;
    case 43 :
      n++;
      glutPostRedisplay();
      break;
    case 45 :
      n--;
      if ( n == 2 )
        n = 3;
      glutPostRedisplay();
      break;
    case 0x1B :
      exit(0);
      break; }
}

/* Fonction principale                          */

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
  glutInitWindowSize(tx,ty); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("Boule rebondissante"); 
  init();
  glutKeyboardFunc(keyboard);
  glutReshapeFunc(reshape);
  glutDisplayFunc(display);
  glutIdleFunc(idle);
  glutMainLoop();
  return(0);
}