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 components 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
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
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.