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  widget.   Option-handling  commands  are  used  when  a  component  is
       registered  with  the  Archetype  base  class  via  the "itk_component 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 fragment to be registered for each widget class, which is used by  default
       to  handle  the options.  All of the standard Tk widgets have usual declarations 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 itk_component add.

       If  only  the  tag  argument  is  specified,  this command looks for an existing 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: itk::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