Provided by: itk3-doc_3.3-4ubuntu1_all bug


       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 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


       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