Provided by: itk3-doc_3.4.2-3.1build1_all 
NAME
Archetype - base class for all [incr Tk] mega-widgets
INHERITANCE
none
WIDGET-SPECIFIC OPTIONS
Name: clientData
Class: ClientData
Command-Line Switch: -clientdata
This does not affect the widget operation in any way. It is simply a hook that clients can use to
store a bit of data with each widget. This can come in handy when using widgets to build
applications.
_________________________________________________________________
DESCRIPTION
The Archetype class is the basis for all [incr Tk] mega-widgets. It keeps track of component widgets and
provides methods like "configure" and "cget" that are used to access the composite configuration options.
Each component widget must be registered with the Archetype base class using the "itk_component add"
method. When the component is registered, its configuration options are integrated into the composite
option list. Configuring a composite option like "-background" causes all of the internal components to
change their background color.
It is not used as a widget by itself, but is used as a base class for more specialized widgets. The
Widget base class inherits from Archetype, and adds a Tk frame which acts as the "hull" for the mega-
widget. The Toplevel base class inherits from Archetype, but adds a Tk toplevel which acts as the
"hull".
Each derived class must invoke the itk_initialize method within its constructor, so that all options are
properly integrated and initialized in the composite list.
PUBLIC METHODS
The following methods are provided to support the public interface of the mega-widget.
pathName cget option
Returns the current value of the configuration option given by option.
In this case, option refers to a composite configuration option for the mega-widget. Individual
components integrate their own configuration options onto the composite list when they are
registered by the "itk_component add" method.
pathName component ?name? ?command arg arg ...?
Used to query or access component widgets within a mega-widget. With no arguments, this returns a
list of symbolic names for component widgets that are accessible in the current scope. The
symbolic name for a component is established when it is registered by the "itk_component add"
method. Note that component widgets obey any public/protected/private access restriction that is
in force when the component is created.
If a symbolic name is specified, this method returns the window path name for that component.
Otherwise, the command and any remaining arg arguments are invoked as a method on the component
with the symbolic name name. This provides a well-defined way of accessing internal components
without relying on specific window path names, which are really details of the implementation.
pathName configure ?option? ?value option value ...?
Query or modify the configuration options of the widget. If no option is specified, returns a
list describing all of the available options for pathName (see Tk_ConfigureInfo for information on
the format of this list). If option is specified with no value, then the command returns a list
describing the one named option (this list will be identical to the corresponding sublist of the
value returned if no option is specified). If one or more option-value pairs are specified, then
the command modifies the given widget option(s) to have the given value(s); in this case the
command returns an empty string.
In this case, the options refer to composite configuration options for the mega-widget.
Individual components integrate their own configuration options onto the composite list when they
are registered by the "itk_component add" method.
PROTECTED METHODS
The following methods are used in derived classes as part of the implementation for a mega-widget.
itk_component add ?-protected? ?-private? ?--? name createCmds ?optionCmds?
Creates a component widget by executing the createCmds argument and registers the new component
with the symbolic name name. The -protected and -private options can be used to keep the
component hidden from the outside world. These options have a similar effect on component
visibility as they have on class members.
The createCmds code can contain any number of commands, but it must return the window path name
for the new component widget.
The optionCmds script contains commands that describe how the configuration options for the new
component should be integrated into the composite list for the mega-widget. It can contain any of
the following commands:
ignore option ?option option ...?
Removes one or more configuration options from the composite list. All options are ignored
by default, so the ignore command is only used to negate the effect of a previous keep or
rename command. This is useful, for example, when the some of the options added by the
usual command should not apply to a particular component, and need to be ignored.
keep option ?option option ...?
Integrates one or more configuration options into the composite list, keeping the name the
same. Whenever the mega-widget option is configured, the new value is also applied to the
current component. Options like "-background" and "-cursor" are commonly found on the keep
list.
rename option switchName resourceName resourceClass
Integrates the configuration option into the composite list with a different name. The
option will be called switchName on the composite list. It will also be modified by
setting values for resourceName and resourceClass in the X11 resource database. The
"-highlightbackground" option is commonly renamed to "-background", so that when the mega-
widget background changes, the background of the focus ring will change as well.
usual ?tag?
Finds the usual option-handling commands for the specified tag name and executes them. If
the tag is not specified, then the widget class name is used as the tag name. The "usual"
option-handling commands are registered via the usual command.
If the optionCmds script is not specified, the usual option-handling commands associated with the class
of the component widget are used by default.
itk_component delete name ?name name ...?
Removes the component widget with the symbolic name name from the mega-widget. The component
widget will still exist, but it will no longer be accessible as a component of the mega-widget.
Also, any options associated with the component are removed from the composite option list.
Note that you can destroy a component using the destroy command, just as you would destroy any Tk
widget. Components automatically detach themselves from their mega-widget parent when destroyed,
so "itk_component delete" is rarely used.
itk_initialize ?option value option value...?
This method must be invoked within the constructor for each class in a mega-widget hierarchy. It
makes sure that all options are properly integrated into the composite option list, and
synchronizes all components to the initial option values. It is usually invoked near the bottom
of the constructor, after all component widgets have been added.
If any option/value pairs are specified, they override settings determined from the X11 resource
database. The arguments to the constructor are usually passed along to this method as follows:
itcl::class MyWidget {
inherit Widget
constructor {args} {
.
.
.
eval itk_initialize $args
}
}
itk_option add optName ?optName optName ...?
Adds one or more options to the composite option list for a mega-widget. Here, optName can have
one of the following forms:
component.option
Accesses an option belonging to a component with the symbolic name component. The option
name is specified without a leading "-" sign.
className::option
Accesses an option defined by the "itk_option define" command in class className. The
option name is specified without a leading "-" sign.
Options are normally integrated into the composite option list when a component widget is first created.
This method can be used to add options at a later time. For example, the Widget and Toplevel base
classes keep only the bare minimum options for their "hull" component: -background and -cursor. A
derived class can override this decision, and add options that control the border of the "hull" component
as well:
itcl::class MyWidget {
inherit Widget
constructor {args} {
itk_option add hull.borderwidth hull.relief
itk_component add label {
label $itk_interior.l1 -text "Hello World!"
}
pack $itk_component(label)
eval itk_initialize $args
}
}
itk_option define switchName resourceName resourceClass init ?config?
This command is used at the level of the class definition to define a synthetic mega-widget
option. Within the configure and cget methods, this option is referenced by switchName, which
must start with a "-" sign. It can also be modified by setting values for resourceName and
resourceClass in the X11 resource database. The init value string is used as a last resort to
initialize the option if no other value can be used from an existing option, or queried from the
X11 resource database. If any config code is specified, it is executed whenever the option is
modified via the configure method. The config code can also be specified outside of the class
definition via the configbody command.
In the following example, a synthetic "-background" option is added to the class, so that whenever
the background changes, the new value is reported to standard output. Note that this synthetic
option is integrated with the rest of the "-background" options that have been kept from component
widgets:
itcl::class MyWidget {
inherit Widget
constructor {args} {
itk_component add label {
label $itk_interior.l1 -text "Hello World!"
}
pack $itk_component(label)
eval itk_initialize $args
}
itk_option define -background background Background #d9d9d9 {
puts "new background: $itk_option(-background)"
}
}
itk_option remove optName ?optName optName ...?
Removes one or more options from the composite option list for a mega-widget. Here, optName can
have one of the forms described above for the "itk_option add" command.
Options are normally integrated into the composite option list when a component widget is first
created. This method can be used to remove options at a later time. For example, a derived class
can override an option defined in a base class by removing and redefining the option:
itcl::class Base {
inherit itk::Widget
constructor {args} {
eval itk_initialize $args
}
itk_option define -foo foo Foo "" {
puts "Base: $itk_option(-foo)"
}
}
itcl::class Derived {
inherit Base
constructor {args} {
itk_option remove Base::foo
eval itk_initialize $args
}
itk_option define -foo foo Foo "" {
puts "Derived: $itk_option(-foo)"
}
}
Without the "itk_option remove" command, the code fragments for both of the "-foo" options would be
executed each time the composite "-foo" option is configured. In the example above, the Base::foo option
is suppressed in all Derived class widgets, so only the Derived::foo option remains.
PROTECTED VARIABLES
Derived classes can find useful information in the following protected variables.
itk_component(name)
The "itk_component" array returns the real window path name for a component widget with the
symbolic name name. The same information can be queried using the component method, but accessing
this array is faster and more convenient.
itk_interior
This variable contains the name of the window that acts as a parent for internal components. It
is initialized to the name of the "hull" component provided by the Widget and Toplevel classes.
Derived classes can override the initial setting to point to another interior window to be used
for further-derived classes.
itk_option(option)
The "itk_option" array returns the current option value for the composite widget option named
option. Here, the option name should include a leading "-" sign. The same information can be
queried using the cget method, but accessing this array is faster and more convenient.
KEYWORDS
itk, Widget, Toplevel, mega-widget