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

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

       usual ?tag? ?commands?

       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 "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	 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 itk_component 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.

       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.

       itk, Archetype, component, mega-widget

itk				      3.0			      usual(n)


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