This callback can be used to do canonicalization in more complex case when constructing the nodeset can be very expensive. For example, you can take a look at how it is used inside xmlsec library: http://www.aleksey.com/xmlsec Aleksey pmd wrote:
Thank you for the quick response.I'm trying to understand the c14n code, so I'd be great if somebody can tell me what the is_visible_callback is for.