Your starting point for online documentation about GNOME development should always be http://developer.gnome.org. This site contains the complete up-to-date API documentation for both GTK+ and GNOME, as well as an assortment of articles and white papers. Much of this information is distrib- uted with GNOME itself, so you don't necessarily have to go online for access to the developer documents.
The main GNOME Web site, at http://www.gnome.org, is oriented more toward the GNOME community and includes a software map (so you don't end up re-creating a GNOME application that already exists), instructions on how to subscribe to the dozens of GNOME-related mailing lists, interviews, the lat- est version of the GNOME FAQ, and lots of other goodies. For your conve- nience, the GNOME FAQ is also included in the Appendix of this book.
Also worthy of mention is the GNOME Documentation Project (GDP), located at http://www.gnome.org/gdp, a virtual treasure trove of user-level documentation and writing guides. After you've mastered Chapter 12, "Docu- mentation," you can further expand your writing prowess at the GDP site. Finally, the official GTK+ Web site is at http://www.gtk.org.
The documentation on the Web sites is excellent, but don't underestimate the collection of documents that already reside on your system, accessible through the man and info tools. With these, you can browse the X11 docu- ments (e.g., man XCreatePixmap), the build system documents (e.g., info automake), and much more.
The open-source paradigm also makes available another incredible resource unavailable in the closed-source world: thousands of lines of applica- tion source code. Don't be afraid to tap this resource. You can often save hours of work by cracking open an application that already implements the feature you're working on, to see how the original developers handled it. In fact, with the proper attributions you can often yank an entire chunk of code from an existing application and distribute it with your own application. Most GNOME applications are released under the GPL or LGPL licenses (described in Chap- ter 1), so take care to abide by the rules stated in those licenses, or whatever other license you're borrowing under.
The official Web site for Writing GNOME Applications is http://www. aw.com/cseng/titles/0-201-65791-0/. You can check there for errata and updates, and to download the source code from the book.