/* Auteur: Nicolas JANEY         */
/* nicolas.janey@univ-fcomte.fr  */
/* Avril 2002                    */
/* Clipping 2D                   */

#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 sg ;
  point id ; } ;

static int aff = 0 ;
static segment s1 = { 2,10,27,19 } ;
static segment s2 = { 5,9,28,4 } ;
static int disc = 1 ;

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 pixelClip(rectangle *r,int x,int y,float *c) {
  if ( ( x >= r->sg.x ) && ( y >= r->sg.y ) && ( x <= r->id.x ) && ( y <= r->id.y ) )
    pixel(x,y,c) ;
}

void line(int xi,int yi,int xf,int yf,float *c) {
  int dx,dy,i,xinc,yinc,cumul,x,y ;
  x = xi ;
  y = yi ;
  dx = xf - xi ;
  dy = yf - yi ;
  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) {
  line(r->id.x,r->id.y-1,r->id.x,r->sg.y+1,c) ;
  line(r->id.x,r->sg.y,r->sg.x,r->sg.y,c) ;
  line(r->id.x,r->id.y,r->sg.x,r->id.y,c) ;
  line(r->sg.x,r->id.y-1,r->sg.x,r->sg.y+1,c) ;
}

void clipperSegment(rectangle *r,int xi,int yi,int xf,int yf,float *c) {
  int dx,dy,i,xinc,yinc,cumul,x,y ;
  x = xi ;
  y = yi ;
  dx = xf - xi ;
  dy = yf - yi ;
  xinc = ( dx > 0 ) ? 1 : -1 ;
  yinc = ( dy > 0 ) ? 1 : -1 ;
  dx = abs(dx) ;
  dy = abs(dy) ;
  pixelClip(r,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 ; }
      pixelClip(r,x,y,c) ; } }
    else {
    cumul = dy / 2 ;
    for ( i = 1 ; i <= dy ; i++ ) {
      y += yinc ;
      cumul += dx ;
      if ( cumul >= dy ) {
        cumul -= dy ;
        x += xinc ; }
      pixelClip(r,x,y,c) ; } }
}

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.x,s1.pi.y,s1.pf.x,s1.pf.y,couleurBleu(0.5));
             line(s2.pi.x,s2.pi.y,s2.pf.x,s2.pf.y,couleurVertFonce(0.5));
             break ;
    case 2 : line(s1.pi.x,s1.pi.y,s1.pf.x,s1.pf.y,couleurBleu(0.3));
             line(s2.pi.x,s2.pi.y,s2.pf.x,s2.pf.y,couleurVertFonce(0.3));
             clipperSegment(&r,s1.pi.x,s1.pi.y,s1.pf.x,s1.pf.y,couleurBleu(0.8));
             clipperSegment(&r,s2.pi.x,s2.pi.y,s2.pf.x,s2.pf.y,couleurVertFonce(0.8));
             break ; }
  glPopMatrix();
  glFlush();
  glutSwapBuffers() ;
}

void key(unsigned char key,int x,int y) {
  switch ( key ) {
    case 0x0D : aff = (aff+1)%3 ;
                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 2D"); 
  myinit(); 
  creationMenuBasique();
  setParametresOrthoBasique(-0.5,20.5,-0.5,20.5,-50.0,50.0);
  glutReshapeFunc(reshapeOrthoBasique);
  glutKeyboardFunc(key);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}