itk User Commands - usual
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 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 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 Arche-
type 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 declara-
tions 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:
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