code: function isBlockStartPoint(node, offset) {
  	return (!node.parentNode && offset == 0)
  		|| (0 <= offset - 1
  		&& offset - 1 < node.childNodes.length
  		&& isVisible(node.childNodes[offset - 1])
  		&& (isBlockNode(node.childNodes[offset - 1])
  		|| isHtmlElement(node.childNodes[offset - 1], "br")));
  }
docs: "A boundary point (node, offset) is a block start point if either node's parent is null and offset is zero; or node has a child with index offset âˆ’ 1, and that child is either a visible block node or a visible br."