Gtk2::Ex::FormFactory::Layout(3)

NAME
Gtk2::Ex::FormFactory::Layout - Do layout in a FormFactory framework

SYNOPSIS
  package My::Layout;

  use base qw/Gtk2::Ex::FormFactory::Layout/;

  sub build_form         { ... }
  sub add_widget_to_form { ... }
  ...

  package main;

  $ff = Gtk2::Ex::FormFactory->new (
    layouter => My::Layout->new(),
    ...
  );

DESCRIPTION
This class implements the layout of Containers and their Widgets in a Gtk2::Ex::FormFactory framework. "Layout" means, how are the widgets aligned to each other, how much space is between them, how are titles rendered, how labels, etc.

The idea behind Gtk2::Ex::FormFactory::Layout is to have a unique point in a GUI application which actually implements these things. The advantage of this approach is obvious: the implementation is very generic and if you want to change layout things you subclass from Gtk2::Ex::FormFactory::Layout and implement your changes there, and not at hundreds of spots distributed over the source code of your application.

The natural result: a consistent looking GUI.

SUBCLASSING
As described above implementing your own layout module starts with subclassing from Gtk2::Ex::FormFactory::Layout. To use your layout implementation set an object of your class as layouter in your Gtk2::Ex::FormFactory objects.

Gtk2::Ex::FormFactory::Layout mainly defines two sorts of methods.

  BUILD METHODS
The names of the methods are derived from the Widget's short names (which can be retrieved with $widget->get_type), with a prepended build_, e.g.:

  build_form  ( ... )
  build_label ( ... )
  build_table ( ... )

The method prototype looks like this:

$layout->build_TYPE ($widget)
    $widget is the actual Gtk2::Ex::FormFactory::Widget, e.g. Gtk2::Ex::FormFactory::Form for build_form($form).

The build_TYPE method actually creates the necessary Gtk2 widgets, e.g. a Gtk2::Table for a Gtk2::Ex::FormFactory::Form and adds these to the FormFactory's widget instance using the set_gtk_widget() and set_gtk_parent_widget() methods of Gtk2::Ex::FormFactory::Widget.

Call $widget->set_gtk_widget($gtk_widget) for the primary Gtk2 widget which directly displays the value in question, e.g. a Gtk2::Entry if you're dealing with a Gtk2::Ex::FormFactory::Entry.

If you like to do more layout things which require to add the primary Gtk2 widget to a container, e.g. a Gtk2::Frame, you must call $widget->set_gtk_parent_widget($gtk_parent_widget) with the most top level container widget.

Note: the implemenations of all the FormFactory's widgets expect a specific gtk_widget to be set. If you like to change the primary Gtk widget you need to create your own Gtk2::Ex::FormFactory::Widget for this, because the default implemention most probably won't work with a another Gtk2::Widget.

  ADD...TO... METHODS
The second type of methods are so called add-to methods, which place a widget inside a container. The prototye is as follows:

$layout->add_TYPE_to_TYPE ($widget, $container)
    $widget is the actual Gtk2::Ex::FormFactory::Widget, e.g. Gtk2::Ex::FormFactory::Form for build_form($form).

Examples:

  add_form_to_window ( ... )
  add_table_to_form  ( ... )

This way you can adjust layout at a very detailed level, but you need not. E.g. the implementation of these methods is most likely the same:

  add_entry_to_form ( ... )
  add_popup_to_form ( ... )

because the implemenation mainly depends on the form (the container widget) and not on the widget which is added to the form.

That's why Gtk2::Ex::FormFactory::Layout knows a default mechanism: if no add-to method is found for a specific widget/container pair, a generic default implementation is used instead. These are named as follows:

  add_widget_to_window ( ... )
  add_widget_to_form   ( ... )
  add_widget_to_table  ( ... )
  add_widget_to_vbox   ( ... )
  ...

For a new Container you just need to implement the generic add_widget_to_TYPE method, and everything will work. If you want to slightly modify the implementation for specific child widgets, you implement only the methods for these and you're done.

For a example for such a specific add-to message refer to add_menu_to_window() which attaches the menu without any space around it. The default of a Gtk2::Ex::FormFactory::Window is to have some spacing, which looks ugly around a menu.

OBJECT HIERARCHY
  Gtk2::Ex::FormFactory::Layout

ATTRIBUTES
This class has not attributes.

AUTHORS
 Joern Reder <joern at zyn dot de>

COPYRIGHT AND LICENSE
Copyright 2004-2006 by Joern Reder.

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library 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 Library General Public License for more details.

You should have received a copy of the GNU Library 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.