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

See the file man.macros.


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

itk                                   3.0                             usual(n)

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