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[xemacs-hg @ 2003-12-19 14:28:45 by youngs] 2003-12-15 Steve Youngs <sryoungs@bigpond.net.au> * wid-edit.el (lazy): New. (widget-child-value-get): New. (widget-child-value-inline): New. (widget-child-validate): New. (widget-type-value-create): New. (widget-type-default-get): New. (widget-type-match): New. This adds a "lazy" widget to allow the definition of recursive datatypes for customize. The composite widgets expand their subtypes immediately, which cause obvious problems for recursive datatypes. The "lazy" will only expand them when needed, hense the name. From Per Abrahamsen <abraham@dina.kvl.dk> 2003-12-15 Steve Youngs <sryoungs@bigpond.net.au> * lispref/customize.texi (Defining New Types): New node. From Per Abrahamsen <abraham@dina.kvl.dk>
author youngs
date Fri, 19 Dec 2003 14:29:07 +0000
parents 47c30044fc4e
children 4f0a1f4cc111
comparison
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1832:5d8dcaecc32b 1833:eed841acc858
323 @menu 323 @menu
324 * Simple Types:: 324 * Simple Types::
325 * Composite Types:: 325 * Composite Types::
326 * Splicing into Lists:: 326 * Splicing into Lists::
327 * Type Keywords:: 327 * Type Keywords::
328 * Defining New Types::
328 @end menu 329 @end menu
329 330
330 @node Simple Types 331 @node Simple Types
331 @subsection Simple Types 332 @subsection Simple Types
332 333
850 851
851 Called interactively, prompt the user for @var{behavior}, and take 852 Called interactively, prompt the user for @var{behavior}, and take
852 @var{force} from the prefix argument. 853 @var{force} from the prefix argument.
853 @end defun 854 @end defun
854 855
856 @node Defining New Types
857 @subsection Defining New Types
858
859 In the previous sections we have described how to construct elaborate
860 type specifications for @code{defcustom}. In some cases you may want to
861 give such a type specification a name. The obvious case is when you are
862 using the same type for many user options, rather than repeat the
863 specification for each option, you can give the type specification a
864 name once, and use that name each @code{defcustom}. The other case is
865 when a user option accept a recursive datastructure. To make it
866 possible for a datatype to refer to itself, it needs to have a name.
867
868 Since custom types are implemented as widgets, the way to define a new
869 customize type is to define a new widget. We are not going to describe
870 the widget interface here in details, see @ref{Top, , Introduction,
871 widget, The Emacs Widget Library}, for that. Instead we are going to
872 demonstrate the minimal functionality needed for defining new customize
873 types by a simple example.
874
875 @example
876 (define-widget 'binary-tree-of-string 'lazy
877 "A binary tree made of cons-cells and strings."
878 :offset 4
879 :tag "Node"
880 :type '(choice (string :tag "Leaf" :value "")
881 (cons :tag "Interior"
882 :value ("" . "")
883 binary-tree-of-string
884 binary-tree-of-string)))
885
886 (defcustom foo-bar ""
887 "Sample variable holding a binary tree of strings."
888 :type 'binary-tree-of-string)
889 @end example
890
891 The function to define a new widget is name @code{define-widget}. The
892 first argument is the symbol we want to make a new widget type. The
893 second argument is a symbol representing an existing widget, the new
894 widget is going to be defined in terms of difference from the existing
895 widget. For the purpose of defining new customization types, the
896 @code{lazy} widget is perfect, because it accept a @code{:type} keyword
897 argument with the same syntax as the keyword argument to
898 @code{defcustom} with the same name. The third argument is a
899 documentation string for the new widget. You will be able to see that
900 string with the @kbd{M-x widget-browse @key{ret} binary-tree-of-string
901 @key{ret}} command.
902
903 After these mandatory arguments follows the keyword arguments. The most
904 important is @code{:type}, which describes the datatype we want to match
905 with this widget. Here a @code{binary-tree-of-string} is described as
906 being either a string, or a cons-cell whose car and cdr are themselves
907 both @code{binary-tree-of-string}. Note the reference to the widget
908 type we are currently in the process of defining. The @code{:tag}
909 attribute is a string to name the widget in the user interface, and the
910 @code{:offset} argument are there to ensure that child nodes are
911 indented four spaces relatively to the parent node, making the tree
912 structure apparent in the customization buffer.
913
914 The @code{defcustom} shows how the new widget can be used as an ordinary
915 customization type.