DOKK / manpages / debian 11 / itk3-doc / usual.3itk.en
usual(3itk) [incr Tk] usual(3itk) 







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 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







  

    3.0
    itk