Derived(3)						User Contributed Perl Documentation						Derived(3)

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

perl v5.12.1							    2007-05-05								Derived(3)