code: function(el) {
        var intersect = false;
        if (el.getBoundingClientRect) {
          var elRect = el.getBoundingClientRect();
          intersect = {'top': Math.max(elRect.top, 0),
                           'left': Math.max(elRect.left, 0),
                           'bottom': Math.min(elRect.bottom, (win.innerHeight || doc.documentElement.clientHeight)),
                           'right': Math.min(elRect.right, (win.innerWidth || doc.documentElement.clientWidth))};
          if (intersect.bottom <= intersect.top ||
              intersect.right <= intersect.left) {
            intersect = false;
          } else {
            intersect.area = (intersect.bottom - intersect.top) * (intersect.right - intersect.left);
          }
        }
        return intersect;
      }
docs: **************************************************************************
  Support Routines
  ************************************************************************** Get the rect for the visible portion of the provided DOM element