/**************************************************************
 *  srawsquare.c
 *  This program demonstrates the drawing of a square
 *  using OpenGL
 *
 **************************************************************/
#include << X11/Xlib.h>
#include << GLUT/glut.h>
#include << OpenGL/gl.h>
#include << stdlib.h>
#include << stdio.h>

void myInit(void) 
{
   // set black background (clearing) color
   glClearColor (1.0, 1.0, 1.0, 0.0);

   // initialize viewing values
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();                    // clear the matrix
           // viewing transformation 
   glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

void myDisplay(void)
{
  glClear(GL_COLOR_BUFFER_BIT);        // clear the screen

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

  glColor3f (0.0, 0.0, 0.0);           // set the drawing color
  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 rountines
  glFlush ();
}

void myMouse(int button, int state, int x, int y)
{
  switch (button) {
     case GLUT_RIGHT_BUTTON:
        if (state == GLUT_DOWN)
           exit (-1);
        break;
     default:
        break;
  }
} 
     
/*
 * Request double buffer display mode.
 * Register mouse input callback functions
 */
int main(int argc, char** argv)
{

   glutInit(&argc, argv);                            // initialize the toolkit
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);     // set display mode
   glutInitWindowSize (250, 250);                    // set screen window size
   glutInitWindowPosition (100, 100);       // set window position on screen
   glutCreateWindow (argv[0]);              // open the screen window
   myInit ();
   glutDisplayFunc(myDisplay);              // register redraw function
   glutMouseFunc(myMouse);                  // register myMouse function
   glutMainLoop();                          // go into a perpetual loop
   return 0;
}