/* Fonctions de dessin OpenGL                   */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Novembre 2010                                */

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

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

void traceSegment(int xi,int yi,int xf,int yf) {
  glBegin(GL_POINTS);
  int i,cumul;
  int x = xi;
  int y = yi;
  int dx = xf - xi;
  int dy = yf - yi;
  int xinc = ( dx > 0 ) ? 1 : -1;
  int yinc = ( dy > 0 ) ? 1 : -1;
  dx = abs(dx);
  dy = abs(dy);
  glVertex2i(x,y);
  if ( dx > dy ) {
    cumul = dx / 2;
    for ( i = 1 ; i <= dx ; i++ ) {
      x += xinc;
      cumul += dy;
      if (cumul >= dx) {
        cumul -= dx;
        y += yinc; }
      glVertex2i(x,y); } }
    else {
    cumul = dy / 2;
    for ( i = 1 ; i <= dy ; i++ ) {
      y += yinc;
      cumul += dx;
      if ( cumul >= dy ) {
        cumul -= dy;
        x += xinc; }
      glVertex2i(x,y); } }
  glEnd();
}