X resources and Classes

To promote a uniform look to the GUI, X allows you to set default preferences for options such as color and border thickness. These preferences are held in your X resources. The X server loads your resources and displays windows according to your settings.

It is important to understand how X structures resources because the relationship between applications and classes is crucial to setting your X resources.
The X Windows System places X applications into specific classes. When you specify class resources, X modifies the preferences for all applications in that class. For example, you can set the background color for the term class and all applications in the term class will use that preference.
An application's class is usually the base application's name with the first letter capitalized. For example, the xterm program, a member of the Xterm class, is the base application for all X Windows terminals. Xterm derivatives include kterm, nxterm, and rxterm; these programs all perform a similar function as xterm, but in different ways. Therefore, the class of all X terminals is Xterm, as illustrated in the graphic below

You can increase your productivity and your GUI's uniformity by keeping this scheme in mind when you create a set of resources. For example, you will save yourself a lot of time if you set your preferences for an entire class of applications, rather than setting them one by one.

The basic desktop is provided by the X.Org X server. The X server provides the framework on which GNOME, KDE, and other desktop applications and window managers rely. If you have used the XFree86 X server in other Linux distributions, special features of the X.org server described later in this module might interest you. This module takes you on a tour of your desktop, going through the process of logging in, trying out some features, and customizing how your desktop looks and behaves. Sections on KDE, GNOME, and Xfce desktops contain reference information on how to set preferences, run applications, configure panels, and work with the file managers. The last section describes how to use the Display Settings window to configure your video card and monitor, if they were not properly detected. Given the right video card and monitor, you can enable AIGLX desktop effects. With AIGLX, you can get interesting desktop effects, such as windows that wobble when you move them or changing workspaces on a revolving cube.
The next lesson shows you how to use the .Xdefault file to customize the look and feel of X applications.