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widget, it must call the B<Construct> method from class B<Widget>.  That
method accepts the name of the new class to create, i.e. the package name
of your composite widget:

    Construct Tk::Widget 'MyNewWidget';

Here, B<MyNewWidget> is the package name (aka the widget's B<class>).  This
will define a constructor method for B<MyNewWidget>, normally named after the
widget's class.  Instanciating that composite in client code would
the look like:

    $mw = MainWindow->new;       # creates a top-level MainWindow

    $self = $mw->MyNewWidget();  # creates an instance of the
                                 # composite widget MyNewWidget

Whenever a composite is instanciated in client code,
C<Tk::Widget::new()> will be invoked via the widget's class
constructor.  That B<new> method will call

    $self->Populate(\%args);

where I<%args> is the arguments passed to the widget's constructor.  Note
that B<Populate> receives a B<reference> to the hash array
containing all arguments.

B<Populate> is typically defined in the composite class (package),
which creates the characteristic subwidgets of the class.

=head2 Creating Subwidgets

Subwidget creation happens usually in B<Populate()>.
The composite usually calls the
subwidget's constructor method either directly, for "private" subwidgets,
or indirectly through the B<Component> method for subwidgets that should
be advertised to clients.

B<Populate> may call B<Delegates> to direct calls to methods
of chosen subwidgets. For simple composites, typically most if not all
methods are directed
to a single subwidget - e.g. B<ScrListbox> directs all methods to the core
B<Listbox> so that I<$composite>-E<gt>B<get>(...) calls
I<$listbox>-E<gt>B<get>(...).

=head2 Defining mega-widget options

B<Populate> should also call B<ConfigSpecs()> to specify the
way that configure-like options should be handled in the composite.
Once B<Populate> returns, method B<Tk::Frame::ConfigDefault>
walks through the B<ConfigSpecs> entries and populates
%$args hash with defaults for options from X resources (F<.Xdefaults>, etc).

When  B<Populate> returns to B<Tk::Widget::new()>,
a call to B<$self>-E<gt>I<configure>(%$args) is made which sets *all*
the options.

=head1 SEE ALSO

L<Tk::ConfigSpecs|Tk::ConfigSpecs>
L<Tk::mega|Tk::mega>
L<Tk::Derived|Tk::Derived>

=cut