A few days ago I merged the first part of the CoreText backend into Pango’s master branch, after bitrotting on my disk for a full year (apologies for that). The upside is that it also got a year of testing on my machine :) The CoreText backend is enabled by default on machines running Mac OS X 10.5 or higher and used instead of the older ATSUI backend. Because the older ATSUI API has been deprecated since Mac OS X 10.5, and more importantly because the ATSUI API is not fully available in 64-bit mode on Mac OS X 10.6, we were in need of this CoreText backend. When using GTK+ on Mac OS X 10.4, nothing changes, since CoreText is not (publicly) available on these systems.
So far, the CoreText backend was mostly based on the existing ATSUI code, so it should be working nicely for most people. If not, you are welcome to file bugs in the new coretext component in the Pango module in GNOME bugzilla.
There is one missing piece and that is also where the CoreText backend’s structure is going to deviate from the ATSUI backend. The ATSUI backend has never been really good at handling font fallbacks and fonts for non-Latin languages (see 608929). This is one of the things I want to get right in the CoreText backend and will be the second part of this project. I do have some things in place in a local branch on my disk, but it is not working yet as it should. Hopefully, I can find some spare time in the coming months to finish this. Progress can be tracked in bug 647969.
Though up first is a context switch back to GTK+ to review and fix a couple of things around GtkTreeModelFilter, GtkTreeModel’s row-deleted signal and to further extend the unit tests in this area.