NAME
usual - access default option-handling commands
for a mega-widget component
SYNOPSIS
usual ?tag? ?commands?
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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 spec
ify 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 decla
rations 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 regis
tered 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 associ
ated 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 -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
Man(1) output converted with
man2html