In the GTK+ 3.0 branch, GDK saw quite some changes recently. Firstly, a last part of Benjamin Otte’s rendering-cleanup was merged, which removes GdkDrawable. Now that GdkPixmap and GdkImage were already removed before (in favor of using their Cairo counterparts), there’s no need to abstract these away behind a GdkDrawable. Only GdkWindow is left to deal with basically.
The other large refactoring is the “GDK backend” branch that was recently merged. Before, you could only select a single backend at compile time, resulting in a libgdk-<platform> and libgtk-<platform>. GDK has now been refactored to properly separate the backends from the generic “core” GDK code. It is now possible to compile multiple backends into the GDK library. Perhaps in the future loadable backends will be possible as well. This work is in particular interesting for linking in both the X11 and Quartz backends on Mac OS X (for testing, comparing and debugging), and X11 and the upcoming Wayland backend on Linux. I am pretty eager to try a both X11 and Quartz enabled GDK on Mac OS X, but still some work is left to do sorting out the platform-specific code in libgtk. But once that is done, it should be possible, the GDK part is already done.
All in all, I am pretty excited about all the attention GDK has received in the last months after being neglected for a long time. In GTK+ 3.0, GDK is much easier to port to other platforms than it was before. I hope a trend has been set and GDK will be further simplified in the future.
I have tried my best to keep the OS X backend up to date over all these changes and refactorings. It seems to be working fine, so it is in shape for GTK+ 3.0. Let’s say it is at least as good as the last GTK+ 2.x releases, maybe even better.
I really hope we are done with refactoring for a while now, so I can focus again on reviewing and implementing missing features in the backend :).