As we mentioned, GNOME is a window manager, but it’s also an entire framework within which you can build your own GUI applications. GNOME uses an object model based on CORBA (Common Object Request Broker Architecture) that allows distributed objects to communicate with one another. This capability allows GNOME to integrate its applications with the desktop and synchronize their activities in some very sophisticated ways.

GNOME’s capabilities include the following:

The main web site for GNOME is:

Figure 9-1. Displaying the GNOME Control Center

GTK+ is the main widget library for GNOME, and it’s the heart of the GNOME application development framework. GTK stands for the GIMP (GNU Image Manipulation Program) Toolkit. The original toolkit, GTK, got its name because it was developed as a widget toolkit for the GIMP project (described in the next section). Peter Mattis and Spencer Kimball, who also developed GIMP, developed the original version of GTK. Josh McDonald developed a newer version, which was dubbed GTK+ to distinguish it from the earlier version. Although developed originally for use with GIMP, GTK+ is now used by many different types of applications, including the Oracle applications described in Chapter 10.

For information on GTK+, see the following sites:

The GIMP is a GTK+-based application that was developed by Peter Mattis and Spencer Kimball (the original authors of GTK+). The GIMP is mainly an image manipulation program, although its many plug-ins allow it to perform a wide variety of functions, such as photo retouching, image composition, and image authoring. The goal of the GIMP project is to develop an open source alternative to Adobe’s commercial Photoshop product. Figure 9-2 shows the GIMP’s welcome screen.

Figure 9-2. The GIMP’s welcome screen

For more information on the GIMP, see the following sites:

If you’re running on a system without GNOME already installed, you’ll need to get a copy. The recommended, and by far the simplest and quickest, way to get up and running is to install from binaries. If you’re running any of the systems listed here, you can find precompiled binaries at this site:

Follow the specific directions for your platform:

The more ambitious can certainly choose to install from source; the GNOME web site has a page designed just for you. Find out all about installing from source at:

You can use the extensive set of widgets available in the GTK+ library when you build GNOME GUI applications. If you write a program using GTK+, it will have the consistent look and feel of all GNOME applications; for example, your buttons, scroll bars, and pop-up menus will have a consistent, standard look. The GNOME Desktop itself was built using the GTK+ library, and through the GNOME Control Center shown earlier in Figure 9-1, you can set such properties as screensaver, background image, themes, desktop sound events, and URL handlers.

You don’t even have to be limited by GNOME’s standard look and feel. Take a look at the XMMS application in Figure 9-3. XMMS is an audio player that lets its users play CDs and MP3 files. As you can see, its Preferences dialog looks like fairly standard GTK+ widgets, but its main window is reminiscent of a Macintosh application.

GNOME and GTK+ also provide your applications with capabilities that extend beyond widgets. If you’re using GNOME as your desktop environment, you’ll be able to control all of your GNOME applications in quite remarkable ways. You’ll be able to change the “theme” of your desktop and have all GNOME applications listen to those commands and respond accordingly. Figure 9-1 shows the “Theme Selector” option currently selected; that demonstrates a scrolling listbox, radio buttons, checkboxes, and so on.

GNOME does a fine job of synchronizing application activities and integrating them with desktop operations. For example, when you use GNOME as your window manager, your desktop applications will be able to respond to GNOME when you attempt to shut down your machine, log out, or restart your PC. Each application, in turn, will be sent a message to quit and take appropriate action. In some cases, your application will die gracefully; in other cases, the application will ask the user if it should save changes to a document. The point is that the window manager has knowledge of all your applications and can coordinate their activities.

Figure 9-3. XMMS, showing a nonstandard GTK+ user interface

Figure 9-4 shows a snapshot of a Linux desktop running some of the great GTK+-based applications that are currently available. From the upper left corner, running roughly clockwise, you’ll find these applications:

Figure 9-4. The world of GTK+ applications

What more could you want? The free world of GNOME is evolving so rapidly that you’ll soon have no excuses left for sticking with your Win32 PC. For now, you’re limited to Linux, but in a very short time, you’ll be in a far wider world, as we’ll describe in the next few sections. And, as more applications are ported, and more commercial vendors start using GNOME and GTK+, support for these products will surely grow until GNOME/GTK+ is viewed as being a complete, stable, and high-performing desktop solution.

And, of course, if you’re thinking of developing your own Oracle GTK+ applications, you have a chance to do so before the rest of the market catches on. You too could become part of this exponential growth. See Section 9.3 later in this chapter, and see Chapter 10 for examples of the first generation of GTK+ applications for Oracle.

Despite its Linux roots, GTK+ is currently being ported to the Win32 platform. The project is spearheaded by Tor Lillqvist. Tor had trouble getting a Minolta Slide Scanner to work under Linux, so he decided that the solution was to port the GIMP to Windows. Before getting the GIMP to work, however, he had to move the foundation—the GTK+ library—to Windows. Work on the port is proceeding well. To keep up with progress on the Windows port, check out this site:

As if a Windows port of GTK+ isn’t exciting enough, the GTK+ folks are also tackling a port to the BeOS operating system.

BeOS is a very interesting operating system, especially appropriate for those doing broadband digital media work. If you are interested in storing audio and video files directly in an Oracle database and then pumping them out to the Internet, BeOS provides an excellent operating environment. Once the GTK+ port is ready for general release, you’ll be able to take advantage of the various open source applications built on GTK+. We describe a number of these, including the excellent Orasoft suite of applications, in Chapter 10.

The BeOS project is apparently much further along than the Windows project, and the GTK+ port was in alpha release as we went to press. To find out more about the status of the GTK+ port for BeOS, check out this site:

For complete information about BeOS and to obtain a free download, go to the Be web site: