Derived - Online Linux Manual Page

Section : 3pm
Updated : 2020-11-09
Source : perl v5.32.0
Note : User Contributed Perl Documentation

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

], ...)