/* Auteur: Nicolas JANEY                     */
/* nicolas.janey@univ-fcomte.fr              */
/* Janvier 2004                              */
/* Un programme de deplacement d'une sphere  */
/* par drag and drop et clic de souris       */

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

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

static int lumiere = 0;
static float px = 100.0F;
static float py = 100.0F;
static float destx = 100.0F;
static float desty = 100.0F;
static float r = 10.0F;
static GLfloat couleurBlanc[] = { 1.0F,1.0F,1.0F,1.0F };
static GLfloat couleurRouge[] = { 1.0F,0.0F,0.0F,1.0F };
static GLfloat couleurVert[] = { 0.0F,1.0F,0.0F,1.0F };
static GLfloat couleurBleu[] = { 0.0F,0.0F,1.0F,1.0F };
static GLfloat couleurNoir[] = { 0.0F,0.0F,0.0F,1.0F };
static int dragdrop = 0;

void init(void) {
  GLfloat mat_shininess[] = { 50.0F };
  GLfloat light0_position[] = { 1.0F,1.0F,1.0F,0.0F };
  GLfloat light1_position[] = { -1.0F,1.0F,1.0F,0.0F };
  GLfloat light2_position[] = { 1.0F,-1.0F,1.0F,0.0F };
  glMaterialfv(GL_FRONT,GL_SPECULAR,couleurBlanc);
  glMaterialfv(GL_FRONT,GL_SHININESS,mat_shininess);
  glLightfv(GL_LIGHT0,GL_DIFFUSE,couleurRouge);
  glLightfv(GL_LIGHT1,GL_DIFFUSE,couleurVert);
  glLightfv(GL_LIGHT2,GL_DIFFUSE,couleurBleu);
  glLightfv(GL_LIGHT0,GL_POSITION,light0_position);
  glLightfv(GL_LIGHT1,GL_POSITION,light1_position);
  glLightfv(GL_LIGHT2,GL_POSITION,light2_position);
  glEnable(GL_LIGHT0);
  glEnable(GL_LIGHT1);
  glEnable(GL_LIGHT2);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
  glEnable(GL_AUTO_NORMAL);
  glClearColor(0.0F,0.0F,0.0F,1.0F);
}

void scene(void) {
  glPushMatrix();
  glTranslatef(px,py,0.0F);
  glutSolidSphere(r,60,60);
  glPopMatrix();
}

void display(void) {
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  if ( lumiere )
    glEnable(GL_LIGHTING);
    else
    glDisable(GL_LIGHTING);
  glPushMatrix();
  scene();
  glPopMatrix();
  glFlush();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("\nAttention erreur %d\n",error);
  glutSwapBuffers();
}

void idle(void) {
  float d = pow((double) ((px-destx)*(px-destx)+(py-desty)*(py-desty)),0.5);
  if ( d < 2.0 ) {
    px = destx;
    py = desty;
    glutIdleFunc(NULL); }
    else {
    px -= 2*(px-destx)/d;
    py -= 2*(py-desty)/d; }
  glutPostRedisplay() ;
}

void souris(int bouton,int etat,int x,int y) {
  if ( etat == GLUT_DOWN ) {
    if ( (px-x)*(px-x)+(py-y)*(py-y) < r*r ) {
      dragdrop = 1;
      glutIdleFunc(NULL); }
      else {
      destx = x;
      desty = y;
      glutIdleFunc(idle); } }
  if ( etat == GLUT_UP )
    dragdrop = 0;
}

void motion(int x,int y) {
  if ( dragdrop ) {
    px = x;
    py = y;
    glutPostRedisplay(); }
}

void key(unsigned char key,int x,int y) {
  switch ( key ) {
    case 32     : lumiere = !lumiere;
                  glutPostRedisplay();
                  break; }
}

void reshape(int w,int l) {
  glViewport(0,0,w,l);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0,w,l,0,-100.0F,100.0F);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
  glutInitWindowSize(300,300); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("Interface utilisateur en GLUt"); 
  init();
  glutReshapeFunc(reshape);
  glutKeyboardFunc(key);
  glutMouseFunc(souris);
  glutMotionFunc(motion);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}