Program OpenGLDemo;

uses
  SysUtils,
  ctypes,
  gl,
  Glut;

procedure paint; cdecl;
begin
  glClearColor(0.3,0.3,0.3,0.0);
  glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);

  glShadeModel(GL_SMOOTH);

  glLoadIdentity();
  glTranslatef(-15.0, -15.0, 0.0);

  glBegin(GL_TRIANGLES);
  glColor3f(1.0, 0.0, 0.0);
  glVertex2f(0.0, 0.0);
  glColor3f(0.0, 1.0, 0.0);
  glVertex2f(30.0, 0.0);
  glColor3f(0.0, 0.0, 1.0);
  glVertex2f(0.0, 30.0);
  glEnd();

  glFlush();
end;

procedure reshape(width, height: cint); cdecl;
begin
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-30.0, 30.0, -30.0, 30.0, -30.0, 30.0);
  glMatrixMode(GL_MODELVIEW);
end;

begin
  glutInit(@argc, @argv);
  glutInitWindowSize(640, 480);
  glutCreateWindow('Triangle');

  glutDisplayFunc(@paint);
  glutReshapeFunc(@reshape);

  glutMainLoop();
end.