#include "glut.h"

void display (void) {

/* clear all pixels */
        glClear (GL_COLOR_BUFFER_BIT);

/* draw white polygon (rectangle) with corners at
 * (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0) */

        glColor3f (1.0, 1.0, 1.0);
        glBegin (GL_POLYGON);
                glVertex3f (0.25, 0.25, 0.0);
                glVertex3f (0.75, 0.25, 0.0);
                glVertex3f (0.75, 0.75, 0.0);
                glVertex3f (0.25, 0.75, 0.0);
        glEnd ();

/* don't wait, start processing buffered OpenGL routines */
        glFlush ();
        }

void init (void) {

/* select clearing (background) color  */
        glClearColor (0.0, 0.0, 0.0, 1.0);

/* initialize viewing values */
        glMatrixMode (GL_PROJECTION);
        glLoadIdentity ();
        glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
        }

/* Declare initial window size, position, and display mode
 * (single buffer and RGBA). Open window with "hello"
 * in its title bar. Call initialization routines.
 * Register callback function to display graphics.
 * Enter main loop and process events. */

int main(int argc, char** argv) {
        glutInit (&argc, argv);
        glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
        glutInitWindowSize (250, 250);
        glutInitWindowPosition (100, 100);
        glutCreateWindow ("hello");
        init ();
        glutDisplayFunc (display);
        glutMainLoop ();
        return 0;        /* ISO C requires main to return int. */
        }