=head1 NAME

UI::Dialog::Screen::Menu - wrapper to screen dialogs.

=head1 SYNOPSIS

  use UI::Dialog::Screen::Menu;

  # $d is an existing instance of UI::Dialog

  my $screen = new UI::Dialog::Screen::Menu ( dialog => $d );
  $screen->add_menu_item("This is the label", sub { print "Hello\n"; });

  # $rv is 0 if the user canceled, 1 if any menu item was selected.
  my $rv = $screen->run();

=head1 ABSTRACT

UI::Dialog::Screen::Menu is a helper class which enables a clean and
modular code flow for menu driven applications using UI::Dialog. Using
callbacks assigned to menu items, a reactionary model to scripting with
UI::Dialog becomes rapidly easy.

=head1 DESCRIPTION

UI::Dialog::Screen::Menu is actually "external" to the UI::Dialog core
usage. The class simply wraps around an existing UI::Dialog instance
for rendering a menu-driven flow of screens.

Using this class, you define a number of screen instances and assign
callbacks to each of the menu items. Once defined, simply call B<run()>
(or B<loop()> to execute B<run()> indefinitely). When a user selects
one of the menu items, the assigned function will be executed. From
within those functions, simply call other UI::Dialog::Screen::Menu
instances and that's how you branch your user's experience from one
screen to the next. See the B<EXAMPLES>

=head1 EXPORT

=over 2

None

=back

=head1 INHERITS

=over 2

None

=back

=head1 CONSTRUCTOR

=head2 new( %options )

=over 4

=item EXAMPLE

=over 6

 # Have UI::Dialog::Screen::Menu use an existing UI::Dialog instance
 # to render the user interface.
 my $s = new( dialog => $d );

 # Also accepts UI::Dialog constructor arguments, so that it can create
 # it's own instance of UI::Dialog if none is provided.
 my $s = new( title => 'Default Title', backtitle => 'Backtitle',
              width => 65, height => 20, listheight => 5,
              order => [ 'zenity', 'xdialog', 'gdialog' ] );

=back

=item DESCRIPTION

=over 6

This is the Class Constructor method. It accepts a list of key => value pairs
and uses them as the defaults when interacting with the various widgets.

=back

=item RETURNS

=over 6

A blessed object reference of the UI::Dialog::Screen::Menu class.

=back

=item OPTIONS

The (...)'s after each option indicate the default for the option. An * denotes
support by all the widget methods on a per-use policy defaulting to the values
decided during object creation.

=over 6

=item B<dialog = UI::Dialog> (undef)

=item B<debug = 0,1,2> (0)

=item B<order = [ zenity, xdialog, gdialog, kdialog, cdialog, whiptail, ascii ]> (as indicated)

=item B<PATH = [ /bin, /usr/bin, /usr/local/bin, /opt/bin ]> (as indicated)

=item B<backtitle = "backtitle"> ('') *

=item B<title = "title"> ('') *

=item B<beepbefore = 0,1> (0) *

=item B<beepafter = 0,1> (0) *

=item B<height = \d+> (20) *

=item B<width = \d+> (65) *

=item B<listheight = \d+> (5) *

=back

=back

=head1 STATE METHODS

=head2 run( )

=over 4

=item EXAMPLE

=over 6

 my $rv = $s->run();

=back

=item DESCRIPTION

=over 6

Render the screen menu immediately. This method blocks until the user
input has been received and acted upon.

=back

=item RETURNS

=over 6

TRUE if the user selected an item from the menu, FALSE otherwise.

=back

=back

=head2 loop( )

=over 4

=item EXAMPLE

=over 6

 $s->loop();

=back

=item DESCRIPTION

=over 6

Calls the B<run()> method immediately. Once B<run()> completes it's
execution, the B<loop()> decides whether or not to display again. If
the return value of run() is TRUE, the B<loop()> will continue. If the
use pressed Cancel (or Escape) or any other action other than one of
the menu items; the B<loop()> will end. The B<loop()> will also end
if the B<break_loop()> method is called.

=back

=item RETURNS

=over 6

TRUE if the user selected an item from the menu, FALSE otherwise.

=back

=back

=head2 is_looping( )

=over 4

=item EXAMPLE

=over 6

 if ($s->is_looping()) {
     print "Currently in a UI::Dialog::Screen::Menu loop\n";
 }

=back

=item DESCRIPTION

=over 6

Returns TRUE if the given screen is in a menu B<loop()>, FALSE
otherwise.

=back

=item RETURNS

=over 6

a single SCALAR.

=back

=back

=head2 break_loop( )

=over 4

=item EXAMPLE

=over 6

 $s->break_loop();

=back

=item DESCRIPTION

=over 6

Flags the screen menu to stop looping. This does not close or
otherwise clear the screen. This simply flags the loop to exit
at the end of it's current run.

=back

=item RETURNS

=over 6

None.

=back

=back

=head1 SCREEN METHODS

=head2 add_menu_item( )

=over 4

=item EXAMPLE

=over 6

 my $index = $s->add_menu_item( "Menu Item Label", \%some_function );

=back

=item DESCRIPTION

=over 6

Append a new item to the menu list.

=back

=item RETURNS

=over 6

Returns the list index (starting from 0) of the item that was just
appended to the list.

=back

=back

=head2 get_menu_items( )

=over 4

=item EXAMPLE

=over 6

 my @items = $s->get_menu_items();

=back

=item DESCRIPTION

=over 6

Returns an array of hashrefs. Each hash contains a "label" and
"func" key/value pairs.

=back

=item RETURNS

=over 6

An ARRAY.

=back

=back

=head2 del_menu_item( )

=over 4

=item EXAMPLE

=over 6

 my $old_item = $d->del_menu_item( $index );

=back

=item DESCRIPTION

=over 6

Remove a specific item from the menu, addressed by it's list index
(starting from 0), and return the menu item as a hashref.

=back

=item RETURNS

=over 6

A HASH containing the 'label' and 'func' of the menu item that was
just removed from the menu list.

=back

=back

=head2 set_menu_item( )

=over 4

=item EXAMPLE

=over 6

 # Modify the 'label' and 'func' for a specific menu item
 my $original_item = $s->set_menu_item( $index, $label, $func );

 # Modify just the label of a menu item
 my $original_item = $s->set_menu_item( $index, $label, undef );

 # Modify just the func of a menu item
 my $original_item = $s->set_menu_item( $index, undef, $func );

 # Effectively do nothing
 my $original_item = $s->set_menu_item( $index, undef, undef );

=back

=item DESCRIPTION

=over 6

Modify the menu item addressed by the given index (starting from 0).
If the 'label' and/or 'func' arguments are undef then the previous
value is kept.

=back

=item RETURNS

=over 6

A HASH of the original values for the modified menu item.

=back

=back

=head1 EXAMPLE USAGE

The below example assumed that $d is an instances of UI::Dialog.

 # Create our first screen
 my $s1 = new UI::Dialog::Screen::Menu ( dialog => $d );
 $s1->add_menu_item( "Just an option", \&some_function );

 # Add a menu item that updates it's own label every time
 # it is selected.
 our $counter = 0;
 $s1->add_menu_item
  ( "Counter: ".$counter,
    sub {
      my ($self,$dialog,$index) = @_;
      $counter++;
      $self->set_menu_item($index,"Counter: ".$counter, undef);
    }
  );

 # Create a second screen
 my $s2 = new UI::Dialog::Screen::Menu ( dialog => $d );
 $s2->add_menu_item( "Another item", \&another_function );

 # Link the second screen to an option of the first
 $s1->add_menu_item( "Goto Screen 2", sub { $s2->loop(); } );

 # Start a menu loop and actually display the first screen
 $s1->loop();

Users can get to second menu from selecting the third item on the first
menu screen. As long as the user continues to select items from the
second menu, it will continue to loop. If the user cancels the second
screen, the will return to the first which will itself continue to loop.

=head1 SEE ALSO

=over 2

=item PERLDOC

 UI::Dialog
 UI::Dialog::GNOME
 UI::Dialog::KDE
 UI::Dialog::Console
 UI::Dialog::Screen::Druid
 UI::Dialog::Backend
 UI::Dialog::Backend::ASCII
 UI::Dialog::Backend::CDialog
 UI::Dialog::Backend::GDialog
 UI::Dialog::Backend::KDialog
 UI::Dialog::Backend::Nautilus
 UI::Dialog::Backend::Whiptail
 UI::Dialog::Backend::XDialog
 UI::Dialog::Backend::XOSD
 UI::Dialog::Backend::Zenity

=back

=over 2

=item MAN FILES

 dialog(1), whiptail(1), zenity(1), gdialog(1), Xdialog(1),
 osd_cat(1), kdialog(1) and nautilus(1)

=back

=head1 BUGS

Please email the author with any bug reports. Include the name of the
module in the subject line.

=head1 AUTHOR

Kevin C. Krinke, E<lt>kevin@krinke.caE<gt>

=head1 COPYRIGHT AND LICENSE

 Copyright (C) 2004-2016  Kevin C. Krinke <kevin@krinke.ca>

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA

=cut
