Derived(3pm)

NAME
Tk::Derived - Base class for widgets derived from others

SYNOPSIS
    package Tk::MyNewWidget;

    use Tk::widgets qw/ BaseWidget, list of Tk widgets /;
    use base qw/ Tk::Derived Tk::BaseWidget /;

    Construct Tk::Widget 'MyNewWidget';

    sub ClassInit {
        my( $class, $mw ) = @_;
        #... e.g., class bindings here ...
        $class->SUPER::ClassInit( $mw );
    }

    sub Populate {
        my( $self, $args ) = @_;

        my $flag = delete $args->{-flag};
        if( defined $flag ) {
            # handle -flag => xxx which can only be done at create
            # time the delete above ensures that new() does not try
            # and do  $self->configure( -flag => xxx );
        }

        $self->SUPER::Populate( $args );

        $self = $self->Component( ... );

        $self->Delegates( ... );

        $self->ConfigSpecs(
            '-cursor'    => [ SELF, 'cursor', 'Cursor',   undef ],
            '-something' => [ METHOD, dbName,  dbClass, default ],
            '-text'      => [ $label, dbName,  dbClass, default ],
            '-heading'   => [ {-text => $head},
                                heading, Heading,  'My Heading' ],
       );
   }

   sub something {
       my( $self, $value) = @_;
       if ( @_ > 1 ) {
          # set it
       }
       return # current value
   }

DESCRIPTION
Tk::Derived is used with Perl's multiple inheritance to override some methods normally inherited from Tk::Widget.

Tk::Derived should precede any Tk widgets in the class's base class definition.

Tk::Derived's main purpose is to apply wrappers to "configure" and "cget" methods of widgets to allow the derived widget to add to or modify behaviour of the configure options supported by the base widget.

The derived class should normally override the "Populate" method provided by Tk::Derived and call "ConfigSpecs" to declare configure options.

The public methods provided by Tk::Derived are as follows:

->ConfigSpecs(-key => [kind, name, Class, default], ...)

SEE ALSO
Tk::ConfigSpecs Tk::mega Tk::composite