usual(n)                           [incr Tk]                          usual(n)



NAME
       usual - access default option-handling commands
            for a mega-widget component

SYNOPSIS
       usual ??tag? ?commands?


DESCRIPTION
       The  usual command is used outside of an [incr Tcl] class definition to
       define the usual set of option-handling commands for a  component  wid-
       get.   Option-handling commands are used when a component is registered
       with the Archetype base class via the "itkcomponent add" method.  They
       specify  how the component's configuration options should be integrated
       into the composite option list for the  mega-widget.   Options  can  be
       kept, renamed, or ignored, as described in the Archetype man page.

       It is tedious to include the same declarations again and again whenever
       components are added.  The usual command allows a standard  code  frag-
       ment  to  be registered for each widget class, which is used by default
       to handle the options.  All of the standard Tk widgets have usual  dec-
       larations defined in the [incr Tk] library.  Similar usual declarations
       should be created whenever a new mega-widget class is conceived.   Only
       the most-generic options should be included in the usual declaration.

       The tag name is usually the name of a widget class, which starts with a
       capital letter; however, any string registered here can be  used  later
       with the usual command described on the Archetype man page.

       If  the  commands  argument is specified, it is associated with the tag
       string, and can be accessed later via itkcomponent add.

       If only the tag argument is specified, this command looks for an exist-
       ing tag name and returns the commands associated with it.  If there are
       no commands associated with tag, this command returns the null  string.

       If  no  arguments are specified, this command returns a list of all tag
       names previously registered.


EXAMPLE
       Following is the usual declaration for the standard Tk  button  widget:
       usual Button {
           keep -background -cursor -foreground -font
           keep -activebackground -activeforeground -disabledforeground
           keep -highlightcolor -highlightthickness
           rename  -highlightbackground  -background  background  Background }
       Only the options that would be common to all buttons in a single  mega-
       widget  are kept or renamed.  Options like "-text" that would be unique
       to a particular button are ignored.


KEYWORDS
       itk, Archetype, component, mega-widget



itk                                   3.0                             usual(n)