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=head1 NAME
Tk::Menu::Item - Base class for Menu items
=for pm Tk/Menu/Item.pm
=for category Implementation
=head1 SYNOPSIS
require Tk::Menu::Item;
my $but = $menu->Button(...);
$but->configure(...);
my $what = $but->cget();
package Whatever;
require Tk::Menu::Item;
@ISA = qw(Tk::Menu::Item);
sub PreInit
{
my ($class,$menu,$info) = @_;
$info->{'-xxxxx'} = ...
my $y = delete $info->{'-yyyy'};
}
=head1 DESCRIPTION
Tk::Menu::Item is the base class from which Tk::Menu::Button,
Tk::Menu::Cascade, Tk::Menu::Radiobutton and Tk::Menu::Checkbutton are derived.
There is also a Tk::Menu::Separator.
Constructors are declared so that $menu-E<gt>Button(...) etc. do what you would
expect.
The C<-label> option is pre-processed allowing ~ to be prefixed to the character
to derive a C<-underline> value. Thus
$menu->Button(-label => 'Goto ~Home',...)
is equivalent to
$menu->Button(-label => 'Goto Home', -underline => 6, ...)
The C<Cascade> menu item creates a sub-menu and accepts
these options:
=over 4
=item B<-menuitems>
A list of items for the sub-menu.
Within this list (which is also accepted by Menu and Menubutton) the first
two elements of each item should be the "constructor" name and the label:
-menuitems => [
[Button => '~Quit', -command => [destroy => $mw]],
[Checkbutton => '~Oil', -variable => \$oil],
]
=item B<-postcommand>
A callback to be invoked before posting the menu.
=item B<-tearoff>
Specifies whether sub-menu can be torn-off or not.
=item B<-menuvar>
Scalar reference that will be set to the newly-created sub-menu.
=back
The returned object is currently a blessed reference to an array of two items:
the containing Menu and the 'label'.
Methods C<configure> and C<cget> are mapped onto underlying C<entryconfigure>
and C<entrycget>.
The main purpose of the OO interface is to allow derived item classes to
be defined which pre-set the options used to create a more basic item.
=head1 BUGS
This OO interface is very new. Using the label as the "key" is a problem
for separaror items which don't have one. The alternative would be to
use an index into the menu but that is a problem if items are deleted
(or inserted other than at the end).
There should probably be a PostInit entry point too, or a more widget like
defered 'configure'.
=cut
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