defgroup to declare new customization groups.
Declare symbol as a customization group containing members. symbol does not need to be quoted.
doc is the group documentation.
members should be an alist of the form ((name
widget)...) where name is a symbol and widget is a
widget for editing that symbol. Useful widgets are
custom-variable for editing variables,
editing faces, and
custom-group for editing groups.
Internally, custom uses the symbol property
custom-group to keep
track of the group members, and
group-documentation for the
The following additional keyword’s are defined:
value should be a string. If the string is a prefix for the name of a member of the group, that prefix will be ignored when creating a tag for that member.