Note: This section describes the general mechanism used to configure X programs. It doesn't relate specifically to window managers, and more recent trends mean that programs usually provide their own means of configuration, often using a GUI. Therefore knowing the details of X resource setting is less useful now than it used to be.
X programs can be customized by using resources. These resources can be specified in many different places. In order of increasing priority these include:
- Fallback resources programming into the application.
- Library resource files controlled with XFILESEARCHPATH variable.
- User resource files controlled with XUSERFILESEARCHPATH, and XAPPLRESDIR variables.
- X resource database, loaded with xrdb.
- X resource default files, $HOME/.Xdefaults or $HOME/.Xresources.
- Standard command line options.
- Hardcoded resources, set within the program.
Options nearer the end of the list override ones further up the list. For personal customization of X programs, the best method to use is a single $HOME/.Xresources file ($HOME/.Xdefaults will probably also work, but is now obsolete). This file gets read when you start X. If you have a lot of resources to set for a particular program, or you have your own version of an X program with a resource file, it would be best to create a directory for these files. This directory would be searched when an X program is started. These two methods are discussed in more detail below.
The .Xresources file
The simpliest and best way to customize X programs is to create a file called .Xresources in the top level of your home directory.
Any line beginning with a ! is ignored, so can be used for comments. Each resource specification appears on a separate line and is often of the form Client*resource: value. The client name is specified by the program, but unless stated otherwise, this is usually the name of the program with the first letter capitalized, e.g. netscape becomes Netscape, unless the first letter is an X, in which case the first two letters are capitalized, e.g. xterm becones XTerm. The resource name is usually a single string, such as scrollBar. After the colon, and any whitespace, comes the value you wish to set the resource to. This is always a string, which gets converted into the correct type. So an example of a complete specification is XTerm*scrollBar: True. This would cause all xterms to have a scrollbar.
The resource field of the specification can actually be preceded by a path through the widget hierarchy. In the specification XTerm.vt100.geometry: 80x25, the geometry resource is only specified for the vt100 widget of the xterm, which is the main text area. If XTerm*geometry: 80x25 was used instead, all widgets, such as the menus which popup with Control-Mouse button combinations, would be given the same geometry as the main text area. Notice that in the first case, the fields were separated by ".", and not "*". This causes the widget you are setting the resource of to be specified exactly, whereas the "*" means "any route through the widget hierarchy." Any combination for "." and "*" can be used in a resource specification.
The order of resource specifications in a file does not matter, as long as they do not conflict. If they do, a warning is usually given, and the one that appears last in the file is used. However the same resource can be specified twice if the generality of the specifications is different. For example Maker*background: gray70 would change the background colour of all widgets (unless overridden later) to be gray70. However, Maker*vertSB.background: gray65 could be used to change the background colour of all vertical scrollbars. Thus, the more specific resource is overriding the more general one.
Another way of specifying widgets is to name a particular class. For example, Editres*Command.background: yellow would set all widgets of class commandWidgetClass, that is normal buttons, to have a yellow background.
Examine this example .Xresources file. It demonstates valid resource specifications in more detail, and may contain some useful options for various programs.
Your .Xresources file may be processed when your start your X session. If not, add xrdb -merge ~/.Xresources to an X login script such as ~/.xinitrc. If you edit the resource file and you want the changes to take effect during the current X session, you can parse it by executing: xrdb -merge ~/.Xdefaults.
User resource files
You can also have a directory of resource files, with one file per program. To do this, create the directory, say $HOME/appres, and then set the environment variable XAPPLRESDIR to point to it. So you would have something like setenv XAPPLRESDIR $HOME/appres/ in your .cshrc file,if your shell is csh or tcsh.
Now, when you start an X program, this directory will be searched for a file with the same name as the resource name of the program. This is the client name used in .Xdefaults files. This file can contain identical specifications, but the client name is optional. For example, a file called XTerm could contain the line *background: deepskyblue.
Applications should document any specific resources that can be used with the program, but there are many standard options which can be used with virtually all X programs. These include:
- display - the X server to use
- geometry - the size and location
- background, or bg - background colour
- bordercolor, or bd - colour to use for borders
- foreground, or fg - foreground colour
- font, or fn - the font to use for displaying text
- iconic - the program should be initially iconified
- name - the name under which resources should be found
- title - the title for the program window
- xrm - specifies a resource name and value
For more details, see the man page for X.