usual(n) [incr Tk] usual(n)______________________________________________________________________________NAMEusual - access default option-handling commands
for a mega-widget component
SYNOPSISusual ?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 wid‐
get. 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 frag‐
ment to be registered for each widget class, which is used by default
to handle the options. All of the standard Tk widgets have usual dec‐
larations 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 exist‐
ing 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)
