private void draw_letter (int [] [] letter) {
   gl.begin (GL.LINE_STRIP);

   for (int i=0; i<letter.length; i++) {
     int [] instruction = letter [i];
     int x = instruction [0];
     int y = instruction [1];
     int type = instruction [2];
     gl.vertex2f (x, y);

     switch (type) {
     case POINT:
       break;

     case STROKE: {
       gl.end ();
       gl.begin (GL.LINE_STRIP);
       break;

     } case END: {
       gl.end ();
       gl.translatef (8.0f, 0.0f, 0.0f);
       return;
     }
     }
   }
  }