NAME

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


SYNOPSIS

       usual ?tag? ?commands?
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DESCRIPTION

       The  usual  command is used outside of an [incr Tcl] class
       definition to define the usual set of option-handling com­
       mands  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 spec­
       ify 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 decla­
       rations 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  regis­
       tered  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 associ­
       ated 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 -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


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