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 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.
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