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Gapp::Manual - An introduction to Gapp programming


Gapp is a framework for creating GUI applications in Perl 5. Gapp is based on Moose and Gtk2-Perl. Moose calls itself a post-modern object system, and relative to Perl 5, it is. Gapp aims to bring that same post-modern feel to developing Gtk+ applications in perl.

Applications maintain a consistent look and feel without hand-configuring every widget. Gapp effectively separates GUI design from application logic and data structures, while keeping your widgets and data up-to-date.

Gapp makes programming complex GUI applications fun and easy.


Gapp uses both Moose and Gtk2 extensively and assumes that the user understands these modules as well. Any of the Gapp documentation that you find lacking is probably covered by these modules.


The documentation for Moose can be found on the CPAN at


The documentation for Gtk2-Perl can be ound at <>.

The documentation for Gtk+ can be found at


  use Gapp;

  $w = Gapp::Window->new(
    properties => {
      title => 'Gapp application',
    signal_connect => [
      [ 'delete-event' => sub { Gapp->quit } ],
    content => [
      Gapp::Label->new( text => 'Hello World!' ),





Any properties you set here will be applied to the Gtk+ widget upon construction. You may find valid parameters by referencing that Gtk+ documentation at

In this example we could have said:

  Gapp::Window->new (
    title => 'Gapp applicaiton'

This is because the title parameter delegates to the title property of the Gtk widget. The documentation for the Gapp widget will provide more information on properties that have been setup for delegation.


You may connect to signals using the signal_connect parameter using the format in the example.


You can add widgets to containers using the content parameter. No formatting options are specified here, just the heirarchy of the widgets. Spacing and other rendering details are resolved by the layout. That will be discussed more later.


As previously mentioned, Gapp is a layer over Gtk2. A Gapp::Widget is used to manage the construction of a Gtk2::Widget.

The Gtk2::Widget is created on the first call to Gapp::gtk_widget. Make all configurations to your widget before this happens; any change you make to the Gapp::Widget will not be reflected in the Gtk widget once it has been constructed.

In our example program, the call to gtk_widget was made implicitly by calling show_all all on the window. This is because show_all is set up to delegate to the Gtk widget's show_all method. The documentation for the Gapp widget will provide more information on methods that have been setup for delegation.


The layout determines how widgets are displayed on the screen. It has control over things like spacing, alignment, borders, etc. By centralizing the code the determines the appearance of widgets, it is is possible to achieve a consistent look GUI. By making changes to the layout, you can affect the appearnce of your whole application. You can subclass layouts too!

Using a Layout

Layouts are referenced using their class names. You can specify which layout to use when constructing your widget. All widgets accept the layout parameter.

  Gapp::Window->new( layout => 'My::Custom::Layout', content => ... );

Creating a Layout

You should see Gapp::Layout for information on creating layouts.


Actions can be performed and know how to display themselves in menu's and on on buttons. You can call them directly or connect them to signals.

  use Gapp::Actions::Basic qw( Quit );

  # call directly

  # connect to signal
  $w = Gapp::Window->new;
  $w->signal_connect( 'delete-event' => Quit );

  # display in menu
  Gapp::MenuItem->new( action => Quit );

You should see Gapp::Actions for information on creatng and using actions.


Apply traits and roles to your widgets to change their behavior!

  Gapp::Entry->new( traits => [qw( MyCustomTrait )] );


Advanced form handling allows you to easily get form data from widgets and vice versa. You don't manually need to update each field in the form.

  $form = Gapp::VBox->new(
    traits => [qw( Form )],
    content => [ Gapp::Entry->new( field => 'user_name' ) ],


Gapp extensions provide added functionality. The GappX:: namespace is the official place to find Gapp extensions. These extensi.ons can be found on the CPAN.


Jeffrey Ray Hallock <jeffrey.hallock at gmail dot com>


    Copyright (c) 2011 Jeffrey Ray Hallock.
    This program is free software; you can redistribute it and/or
    modify it under the same terms as Perl itself.
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