Tk::Menu::Item - Base class for Menu items

- NAME
- SYNOPSIS
- DESCRIPTION
- BUGS

# NAME

Tk::Menu::Item - Base class for Menu items

# 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'};
       }

# 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->`Button(...)` etc. do what you would expect.

The `-label` option is pre-processed allowing ~ to be prefixed to the character to derive a `-underline` value. Thus

        $menu->Button(-label => 'Goto ~Home',...)

        is equivalent to

        $menu->Button(-label => 'Goto Home', -underline => 6, ...)

The `Cascade` menu item creates a sub-menu and accepts these options:

-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],
                        ]

-postcommand
  A callback to be invoked before posting the menu.

-tearoff
  Specifies whether sub-menu can be torn-off or not.

-menuvar
  Scalar reference that will be set to the newly-created sub-menu.

The returned object is currently a blessed reference to an array of two items: the containing Menu and the 'label'. Methods `configure` and `cget` are mapped onto underlying `entryconfigure` and `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.

# 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'.

Tk::Menu::Item - Base class for Menu items