#include <stdlib.h>
#include <GL/glut.h>

/* Minimum stack space */
static USED const char *stack = "$STACK:65535"; 

void myinit(void)
{
    glDepthFunc(GL_LESS);
    glEnable(GL_DEPTH_TEST);
    glShadeModel(GL_FLAT);
}

void drawPlane(void)
{
    glBegin (GL_QUADS);
    glNormal3f (0.0, 0.0, 1.0);
    glVertex3f (-1.0, -1.0, 0.0);
    glVertex3f (0.0, -1.0, 0.0);
    glVertex3f (0.0, 0.0, 0.0);
    glVertex3f (-1.0, 0.0, 0.0);

    glNormal3f (0.0, 0.0, 1.0);
    glVertex3f (0.0, -1.0, 0.0);
    glVertex3f (1.0, -1.0, 0.0);
    glVertex3f (1.0, 0.0, 0.0);
    glVertex3f (0.0, 0.0, 0.0);

    glNormal3f (0.0, 0.0, 1.0);
    glVertex3f (0.0, 0.0, 0.0);
    glVertex3f (1.0, 0.0, 0.0);
    glVertex3f (1.0, 1.0, 0.0);
    glVertex3f (0.0, 1.0, 0.0);

    glNormal3f (0.0, 0.0, 1.0);
    glVertex3f (0.0, 0.0, 0.0);
    glVertex3f (0.0, 1.0, 0.0);
    glVertex3f (-1.0, 1.0, 0.0);
    glVertex3f (-1.0, 0.0, 0.0);
    glEnd();
}

void display (void)
{
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glPushMatrix ();
    glTranslatef (-2.1, 0.0, 0.0);
    glColor3f(1.0, 0.0, 0.0);
    drawPlane ();
    glPopMatrix ();

	glPushAttrib(GL_CURRENT_BIT);
	
    glPushMatrix ();
    glColor3f(0.0, 1.0, 0.0);
    glTranslatef (0.0, 0.0, 0.0);
    drawPlane ();
    glPopMatrix ();

	glPopAttrib();
	
    glPushMatrix ();
    glTranslatef (2.1, 0.0, 0.0);
    drawPlane ();
    glPopMatrix ();

    glFlush ();
}

void myReshape(int w, int h)
{
    glViewport (0, 0, w, h);
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    if (w <= h)
	glOrtho (-1.5, 1.5, -1.5*(GLdouble)h/(GLdouble)w,
	    1.5*(GLdouble)h/(GLdouble)w, -10.0, 10.0);
    else
	glOrtho (-1.5*(GLdouble)w/(GLdouble)h,
	    1.5*(GLdouble)w/(GLdouble)h, -1.5, 1.5, -10.0, 10.0);
    glMatrixMode (GL_MODELVIEW);
}

static void
key(unsigned char k, int x, int y)
{
  switch (k) {
  case 27:  /* Escape */
    exit(0);
    break;
  default:
    return;
  }
  glutPostRedisplay();
}

/*  Main Loop
 *  Open window with initial window size, title bar,
 *  RGBA display mode, and handle input events.
 */
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize (500, 200);
    glutCreateWindow (argv[0]);
    myinit();
    glutReshapeFunc (myReshape);
    glutDisplayFunc(display);
    glutKeyboardFunc(key);
    glutMainLoop();
    return 0;             /* ANSI C requires main to return int. */
}