This is an API that lets you write your own, customized export filters from scratch using a base class acting as a utility framework. Basically, you provide callback implementations similar to a SAX event handler. In these handlers, however, you get full access to each element's absolute style property vector.
Since the API still gets extended and is therefore a somewhat moving target, we felt it is better to not document it in its not-so-stable-as-we-would-like state at this time in this place to avoid you having to pull your hair while trying to implement a custom export filter based on a probably outdated specification.
If you are going about implementing a custom export filter, please contact us in advance at <support@infinity-loop.de> and we will send or point you to up-to-date API documentation and help you regarding your implementation questions and needs as much as we can.
We're sorry for the inconvenience!