code: protected void appendDirtySprite (DirtyItemList list, Sprite sprite)
      {
          MisoUtil.screenToTile(_metrics, sprite.getX(), sprite.getY(), _tcoords);
          list.appendDirtySprite(sprite, _tcoords.x, _tcoords.y);
      }
docs: Computes the tile coordinates of the supplied sprite and appends it to the supplied dirty
  item list.