require 'opengl'
require 'glut'
require 'mathn'
require 'bizzielibrary'

$rotAngle = 0.0;

def init
   GL.Enable(GL::LINE_SMOOTH);
   GL.Enable(GL::BLEND);
   GL.BlendFunc(GL::SRC_ALPHA, GL::ONE_MINUS_SRC_ALPHA);
   GL.Hint(GL::LINE_SMOOTH_HINT, GL::DONT_CARE);
   GL.LineWidth(1.5);

   GL.ClearColor(0.0, 0.0, 0.0, 0.0);
end



def drawLine(x1, y1, x2, y2)
   
   
   GL.Begin(GL::LINES)
    GL.Vertex(x1, y1)
    GL.Vertex(x2, y2)
   GL.End
end

display = Proc.new {
   GL.Clear(GL::COLOR_BUFFER_BIT);



   GL.Rotate(-$rotAngle, 0.0, 0.0, 0.1);
   GL.Color(0.0, 1.0, 0.0);
   
   drawLine(0.1, 0.2, -0.5, -0.9)
   
   GL.Color(0.0, 0.0, 1.0);
   
   drawLine(0.5, 0.5, -0.5, -0.5)

   GL.Flush();
}


reshape = Proc.new {|w, h|
   GL.Viewport(0, 0, w, h);
   GL.MatrixMode(GL::PROJECTION);
   GL.LoadIdentity();
   if (w <= h) 
      GLU.Ortho2D(-1.0, 1.0, -1.0*h/w, 1.0*h/w);
   else 
      GLU.Ortho2D(-1.0*w/h, 1.0*w/h, -1.0, 1.0);
   end
   GL.MatrixMode(GL::MODELVIEW);
   GL.LoadIdentity();
}

# /* ARGSUSED1 */
keyboard = Proc.new {|key, x, y|
   case (key)
      when 'r'[0],'R'[0]
         $rotAngle = $rotAngle + 20.0;
         $rotAngle = 0.0 if ($rotAngle >= 360.0) 
         GLUT.PostRedisplay();
      when 27  #/*  Escape Key  */
         exit(0);
    end
}

GLUT.Init
GLUT.InitDisplayMode(GLUT::SINGLE | GLUT::RGB);
GLUT.InitWindowSize(300, 300);
GLUT.CreateWindow($0);
init();

GLUT.ReshapeFunc(reshape);
GLUT.KeyboardFunc(keyboard);
GLUT.DisplayFunc(display);
GLUT.MainLoop();