Rectangle.c

/*
Created by: Abdallah Okasha
FCI-CU
*/

#include <GL/glut.h>

const int   A = 500;  /* length of a side of the monitor window */
const float B = 500;  /* length of a side of the clipping rectangle */
const float C = 200;  /* length of a side of the square the program draws */

void myinit(void)
{
  glClearColor(0.7, 0.7, 0.7, 0.0); /* gray background */
 
  glMatrixMode(GL_PROJECTION);      /* In World coordinates: */
  glLoadIdentity();                 /* position the "clipping rectangle" */
  gluOrtho2D( -B/2, B/2, -B/2, B/2);/* at -B/2, its right edge at +B/2, its bottom */
  glMatrixMode(GL_MODELVIEW);       /* edge at -B/2 and its top edge at +B/2 */
}

void display( void )
{
                                    
  glClear(GL_COLOR_BUFFER_BIT);     /* clear the window */
 
  glMatrixMode(GL_MODELVIEW);       /* The following coordinates are expressed */
  glLoadIdentity();                 /* in terms of World coordinates */

  glBegin(GL_POLYGON) ;             /* draw a filled polygon */
      glColor3f ( 1.0, 0.3, 0.2);       /* draw in light red */
      glVertex2f( -C/2, -C/2 );         /* (x,y) */
      glVertex2f(  C/2, -C/2 );         /* (x,y) */
      glVertex2f(  C/2,  C/2 );         /* (x,y) */
      glVertex2f( -C/2,  C/2 );         /* (x,y) */
  glEnd();

  glFlush();                        /* send all commands */
}

void main(int argc, char** argv)
{
  glutInit(&argc,argv);
  glutInitWindowSize( A, A );       /* A x A pixel screen window  */

  glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE);
  glutCreateWindow("My Rectangle"); /* window title                   */
  glutDisplayFunc(display);         /* tell OpenGL main loop what     */
  myinit();                         /* set attributes                 */

  glutMainLoop();                   /* pass control to the main loop  */
}