14.1 Common Item Keywords

All kinds of customization declarations (for variables and groups, and for faces) accept keyword arguments for specifying various information. This section describes some keywords that apply to all kinds.

All of these keywords, except :tag, can be used more than once in a given item. Each use of the keyword has an independent effect. The keyword :tag is an exception because any given item can only display one name.

:tag label

Use label, a string, instead of the item's name, to label the item in customization menus and buffers. Don't use a tag which is substantially different from the item's real name; that would cause confusion. One legitimate case for use of :tag is to specify a dash where normally a hyphen would be converted to a space:

          (defcustom cursor-in-non-selected-windows ...
            :tag "Cursor In Non-selected Windows"
     

:group group

Put this customization item in group group. When you use :group in a defgroup, it makes the new group a subgroup of group.

If you use this keyword more than once, you can put a single item into more than one group. Displaying any of those groups will show this item. Please don't overdo this, since the result would be annoying.

:link link-data

Include an external link after the documentation string for this item. This is a sentence containing an active field which references some other documentation.

There are several alternatives you can use for link-data:

(custom-manual info-node)

Link to an Info node; info-node is a string which specifies the node name, as in "(emacs)Top". The link appears as `[Manual]' in the customization buffer and enters the built-in Info reader on info-node.

(info-link info-node)

Like custom-manual except that the link appears in the customization buffer with the Info node name.

(url-link url)

Link to a web page; url is a string which specifies the URL. The link appears in the customization buffer as url and invokes the WWW browser specified by browse-url-browser-function.

(emacs-commentary-link library)

Link to the commentary section of a library; library is a string which specifies the library name.

(emacs-library-link library)

Link to an Emacs Lisp library file; library is a string which specifies the library name.

(file-link file)

Link to a file; file is a string which specifies the name of the file to visit with find-file when the user invokes this link.

(function-link function)

Link to the documentation of a function; function is a string which specifies the name of the function to describe with describe-function when the user invokes this link.

(variable-link variable)

Link to the documentation of a variable; variable is a string which specifies the name of the variable to describe with describe-variable when the user invokes this link.

(custom-group-link group)

Link to another customization group. Invoking it creates a new customization buffer for group.

You can specify the text to use in the customization buffer by adding :tag name after the first element of the link-data; for example, (info-link :tag "foo" "(emacs)Top") makes a link to the Emacs manual which appears in the buffer as `foo'.

An item can have more than one external link; however, most items have none at all.

:load file

Load file file (a string) before displaying this customization item. Loading is done with load-library, and only if the file is not already loaded.

:require feature

Execute (require 'feature) when your saved customizations set the value of this item. feature should be a symbol.

The most common reason to use :require is when a variable enables a feature such as a minor mode, and just setting the variable won't have any effect unless the code which implements the mode is loaded.

:version version

This option specifies that the item was first introduced in Emacs version version, or that its default value was changed in that version. The value version must be a string.

:package-version '(package . version)

This option specifies that the item was first introduced in package version version, or that its meaning or default value was changed in that version. The value of package is a symbol and version is a string.

This keyword takes priority over :version.

package should be the official name of the package, such as MH-E or Gnus. If the package package is released as part of Emacs, package and version should appear in the value of customize-package-emacs-version-alist.

Packages distributed as part of Emacs that use the :package-version keyword must also update the customize-package-emacs-version-alist variable.