#include <cstdlib>
#include <GL/glut.h>
using namespace std;

typedef unsigned char uchar;

// callbacks 
void disp(void);
void drawScene(void);
void keyb(uchar key, int x, int y);
void reshape(int x, int y);

static int width =0 , height=0;


////////////////////////////////
// main
int main(int argc, char **argv){

  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGBA | GLUT_SINGLE);
  glutInitWindowSize(600,600);
  glutInitWindowPosition(100,100);
  glutCreateWindow("scissor test");

  glClearColor(0.0,0.0,0.0,0.0);
  glutDisplayFunc(disp);
  glutKeyboardFunc(keyb);
  glutReshapeFunc(reshape);
  glutMainLoop();
  return 0;
}


////////////////
// disp
void disp(void){

  glEnable(GL_SCISSOR_TEST);
  glMatrixMode(GL_MODELVIEW);

  // lower left
  glViewport(0,0,width/2,height/2);
  glScissor(0,0,width/2,height/2);
  glLoadIdentity();
  glClear(GL_COLOR_BUFFER_BIT);
  drawScene();

  // lower right
  glViewport(width/2,0,width/2,height/2);
  glScissor(width/2,0,width/2,height/2);
  glLoadIdentity();
  glRotatef(90,0.0,1.0,0.0);
  glClear(GL_COLOR_BUFFER_BIT);
  drawScene();

  // upper left
  glViewport(0,height/2,width/2,height/2);
  glScissor(0,height/2,width/2,height/2);
  glLoadIdentity();
  glRotatef(90,1.0,0.0,0.0);
  glClear(GL_COLOR_BUFFER_BIT);
  drawScene();

  // upper right
  glViewport(width/2,height/2,width/2,height/2);
  glScissor(width/2,height/2,width/2,height/2);
  glLoadIdentity();
  glRotatef(90,0.0,0.0,1.0);
  glClear(GL_COLOR_BUFFER_BIT);
  drawScene();

  glFlush();
}

/////////////////////
// drawScene
void drawScene(void){
  glutWireTeapot(0.5);
}

////////////////////////////////////
// keyb
void keyb(uchar key, int x, int y ){
  if(key == 'q'){
    exit(0);
  }
}

//////////////////////////
// reshape
void reshape(int x,int y){
   width = x;
   height=y;
}