code: function refreshPosition(item) {
        // Find the top of an item by adding to the offsetHeight until we reach the 
        // content element.
        var current = item.element[0];
        item.top = 0;
        item.left = 0;
        item.right = 0;
        while (current && current !== contentEl[0]) {
          item.top += current.offsetTop;
          item.left += current.offsetLeft;
          if ( current.offsetParent ){
            item.right += current.offsetParent.offsetWidth - current.offsetWidth - current.offsetLeft; //Compute offsetRight
          }
          current = current.offsetParent;
        }
        item.height = item.element.prop('offsetHeight');
  
        var defaultVal = $mdUtil.floatingScrollbars() ? '0' : undefined;
        $mdUtil.bidi(item.clone, 'margin-left', item.left, defaultVal);
        $mdUtil.bidi(item.clone, 'margin-right', defaultVal, item.right);
      }
docs: Find the `top` of an item relative to the content element, and also the height.