/* Auteur: Nicolas JANEY            */
/* nicolas.janey@univ-fcomte.fr     */
/* Avril 2003                       */
/* Clipping de Cohen-Sutherland     */

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

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

#include "ModuleCouleurs.h"
#include "ModuleMenus.h"
#include "ModuleReshape.h"

struct point {
  int x ;
  int y ; } ;

struct segment {
  point pi ;
  point pf ; } ;

struct rectangle {
  point ig ;
  point sd ; } ;

struct code {
  int c1 ;
  int c2 ;
  int c3 ;
  int c4 ; } ;

static int aff = 0 ;
static segment s1 = { { 2,10 },
                      { 27,19 } } ;
static segment s2 = { { 5,9 }, 
                      { 28,4 } } ;

void pixel(int x,int y,float *c) {
  glColor4fv(c) ;
  glBegin(GL_QUADS) ;
  glVertex2f(x-1.0F,y-1.0F) ;
  glVertex2f(x-1.0F,y) ;
  glVertex2f(x,y) ;
  glVertex2f(x,y-1.0F) ;
  glEnd() ;
}

void line(point *pi,point *pf,float *c) {
  int dx,dy,i,xinc,yinc,cumul,x,y ;
  x = pi->x ;
  y = pi->y ;
  dx = pf->x - pi->x ;
  dy = pf->y - pi->y ;
  xinc = ( dx > 0 ) ? 1 : -1 ;
  yinc = ( dy > 0 ) ? 1 : -1 ;
  dx = abs(dx) ;
  dy = abs(dy) ;
  pixel(x,y,c) ;
  if ( dx > dy ) {
    cumul = dx / 2 ;
    for ( i = 1 ; i <= dx ; i++ ) {
      x += xinc ;
      cumul += dy ;
      if (cumul >= dx) {
        cumul -= dx ;
        y += yinc ; }
      pixel(x,y,c) ; } }
    else {
    cumul = dy / 2 ;
    for ( i = 1 ; i <= dy ; i++ ) {
      y += yinc ;
      cumul += dx ;
      if ( cumul >= dy ) {
        cumul -= dy ;
        x += xinc ; }
      pixel(x,y,c) ; } }
}

void traceRectangle(rectangle *r,float *c) {
  point id = { r->sd.x,r->ig.y };
  point sg = { r->ig.x,r->sd.y };
  line(&id,&r->ig,c) ;
  line(&id,&r->sd,c) ;
  line(&sg,&r->ig,c) ;
  line(&sg,&r->sd,c) ;
}

void getCode(point *p,rectangle *r,code *c) { 
  c->c1 = p->x < r->ig.x;
  c->c2 = p->x > r->sd.x;
  c->c3 = p->y < r->ig.y;
  c->c4 = p->y > r->sd.y;
}

void affichageCode(code *c) { 
  printf("%d%d%d%d\n",c->c1,c->c2,c->c3,c->c4);
}

int codeNul(code *c) { 
  return(!(c->c1 || c->c2 || c->c3 || c->c4)) ;
}

int pas1commun(code *c1,code *c2) {
  if ( c1->c1 && c2->c1 )
    return(0); 
  if ( c1->c2 && c2->c2 )
    return(0); 
  if ( c1->c3 && c2->c3 )
    return(0); 
  if ( c1->c4 && c2->c4 )
    return(0); 
  return(1) ;
}

int code0(code *c) { 
  return(c->c1) ;
}

int code1(code *c) { 
  return(c->c2) ;
}

int code2(code *c) { 
  return(c->c3) ;
}

int code3(code *c) { 
  return(c->c4) ;
}

int intersection(int ai,int bi,int af,int bf,int val) {
  int res = 0 ;
  if ( af-ai != 0 )
    res =(int) (0.499 + bi +(double) (val-ai) / (af-ai) * (bf-bi)) ;
    else
    res = 32767 ;
  return(res) ;
}

void clipperSegment(rectangle *r,segment *s,float *c) {
  segment se = *s ;
  code c1,c2 ;
  point p ;
  getCode(&s->pi,r,&c1) ;
  getCode(&s->pf,r,&c2) ;
  while ( ( !codeNul(&c1) || !codeNul(&c2) ) && ( pas1commun(&c1,&c2)  ) ) {
    if ( codeNul(&c1) ) {
      p = s->pi ;
      s->pi = s->pf ;
      s->pf = p ;
      c1 = c2 ; }
    if ( code0(&c1) ) {
      s->pi.y = intersection(s->pi.x,s->pi.y,s->pf.x,s->pf.y,r->ig.x) ;
      s->pi.x = r->ig.x ; }
      else
      if ( code1(&c1) ) {
        s->pi.y = intersection(s->pi.x,s->pi.y,s->pf.x,s->pf.y,r->sd.x) ;
        s->pi.x = r->sd.x ; }
        else
        if ( code2(&c1) ) {
          s->pi.x = intersection(s->pi.y,s->pi.x,s->pf.y,s->pf.x,r->ig.y) ;
          s->pi.y = r->ig.y ; }
          else
          if ( code3(&c1) ) {
            s->pi.x = intersection(s->pi.y,s->pi.x,s->pf.y,s->pf.x,r->sd.y) ;
            s->pi.y = r->sd.y ; }
    getCode(&s->pi,r,&c1) ;
    getCode(&s->pf,r,&c2) ; }
  if ( codeNul(&c1) && codeNul(&c2) )
    line(&s->pi,&s->pf,c) ;
  *s = se ;
}

void dessineQuadrillage(void) {
  float i;
  glColor4fv(couleurGrisMoyen()) ;
  glBegin(GL_LINES);
  for ( i = 0 ; i <= 30 ; i++ ) {
    glVertex3d(i,0,-10.0);
    glVertex3d(i,20,-10.0); }
  for ( i = 0 ; i <= 20 ; i++ ) {
    glVertex3d(0,i,-10.0);
    glVertex3d(30,i,-10.0); }
  glEnd() ;
}

void display() {
  rectangle r = { 6,5,26,15 } ;
  glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
  glPushMatrix();
  dessineQuadrillage();
  traceRectangle(&r,couleurRouge(0.6F));
  switch ( aff) {
    case 1 : line(&s1.pi,
                  &s1.pf,
                  couleurBleu(0.5));
             line(&s2.pi,
                  &s2.pf,
                  couleurVertFonce(0.5));
             break ;
    case 2 : line(&s1.pi,
                  &s1.pf,
                  couleurBleu(0.3));
             line(&s2.pi,
                  &s2.pf,
                  couleurVertFonce(0.3));
             clipperSegment(&r,
                            &s1,
                            couleurBleu(0.8));
             clipperSegment(&r,
                            &s2,
                            couleurVertFonce(0.8));
             break ;
    case 3 : clipperSegment(&r,
                            &s1,
                            couleurBleu(0.8));
             clipperSegment(&r,
                            &s2,
                            couleurVertFonce(0.8));
             break ; }
  glPopMatrix();
  glFlush();
  glutSwapBuffers() ;
}

void special(int key,int x,int y) {
}

void key(unsigned char key,int x,int y) {
  switch ( key ) {
    case 0x0D : aff = (aff+1)%4 ;
                glutPostRedisplay();
                break;
    case 0x1B : exit(0);
                break; }
}

void myinit() {
  glEnable(GL_ALPHA_TEST);
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
  glClearColor(0.8F,0.8F,0.8F,1.0F);
}

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
  glutInitWindowSize(375,252); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("Clipping Cohen-Sutherland"); 
  myinit(); 
  creationMenuBasique();
  setParametresOrthoBasique(-0.5,20.5,-0.5,20.5,-50.0,50.0);
  glutReshapeFunc(reshapeOrthoBasique);
  glutSpecialFunc(special);
  glutKeyboardFunc(key);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}