[cairo] PDF layers (OCG)?

[Ian Britten]

Hi all,
Is there currently any support for creating PDFs that contain layers,
presumably via Optional Content Groups (OGC)?
 
http://www.planetpdf.com/developer/article.asp?ContentID=focus_on_pdf_layers_ocg_
If yes, is anyone aware of any apps that currently expose this?

If not, is there any support planned, or being worked on, in an
upcoming version of Cairo?
[ BTW - Is there any on-line documentation of the newer 1.9/1.10/trunk
versions of Cairo, to allow people to peruse the upcoming versions? ]

If there is nothing definitive planned, what are the thoughts of the
Cairo/PDF maintainers?  Is this something that could/should be
available to Cairo users?  Or is it not the realm of Cairo, and
should be handled by some other means?  (Suggestions?)

Many thanks for any info!
Ian