[Zope3-Users] How to make a new namespace for pagetemplates?

[FB]

Hi,

my employer want to have all external links marked with a small icon telling
anonymous users from the internet that everything behind given links is
beyond our responsibility.

Currenty I have to do something like that:

   <a tal:define="linkwriter nocall:context/@@linkwriter"
      tal:replace="structure linkwriter.link(context.url,text=context.urldescription)" />

... which doesn't really looks like a nice method to produce i.e. this:

   <a class="external" title="You're leaving out institute's domain. We're not responsible!"
      href="http://example.com">This is an example company</a>

The 'linkwriter' chooses the a-tag's class and title according to the domain of the href.
I would like to make writing those pagetemplates a bit easier - maybe like that:

   <a tal:attributes="href context/url" tal:content="context/urldescription"
      linkwriter:marklink="" />

How complicated is it to write an additional pagetemplate namespace which is able to
"postprocess" a tag, after 'tal', 'i18n' and 'metal' did their work?

Thank you,

Frank