=head1 NAME

Reaction::Manual::RenderPage - Page rendering

=head2 A little overview

  .---------------------------------------.
  |           Controller Action           |
  |---------------------------------------|
  | Decides which logical part to provide |
  '---------------------------------------'
                      |
                      v
      .------------------------------.
      |           ViewPort           |
      |------------------------------|----------.
      | A logical part of the page   |          |
      '------------------------------'          |
                      |                  Inner ViewPorts
                      v                       Data      
   .-------------------------------------.      |
   |              LayoutSet              |      |
   |-------------------------------------|------.
   | A representational part of the page |      |
   '-------------------------------------'      |
                      |                       Looks  
                      v                     Structure
      .-------------------------------.         |
      |            Widget             |         |
      |-------------------------------|---------.
      | A functional part of the page |         |
      '-------------------------------'         |
                                           Preparation
                                            Structure 
      .-------------------------------.         |
      |            Output             |         |
      |-------------------------------|<--------'
      | The rendered part of the page |
      '-------------------------------'

=head2 Or, how to track why your page failed to render

Catalyst's C<begin> and C<end> actions are supplied by
L<Reaction::UI::Controller::Root>, which your C<Root> controller should inherit
from, or at least the root controller of the part of your application that is
using Reaction.

The C<begin> action creates a new L<Reaction::UI::Window> and stores it in $c->stash->{window}.
The C<end> action calls the flush() method on the stashed window object.
L<Reaction::UI::Window/flush> then calls L<Reaction::UI::View/render_window>
on the window's view.

The View first fetches the root ViewPort from the Window's stack and
creates a RenderingContext. The layout is chosen based on the ViewPort name or
though the ViewPort's C<layout> attribute. The Widget is then used to render the
content via the RenderingContext.

Is your head spinning yet?

Ingredients used:

* A Reaction::UI::Skin object built from:

    - The skin_name set on your View
    - The View object
    - The skin_base_dir (MyApp/share/skin)
    - The share/skin/defaults.conf + share/skin/<my_skin>/skin.conf

* A Reaction::UI::LayoutSet object built from:

    - The layoutset file itself, found in the share/skin/<my_skin>/layout directory
      or the share/skin/default/layout directory.
    - The Skin object

* A Reaction::UI::Widget object built from:

    - It's class, determined from the name of the ViewPort or read from the 
      layoutset file, and found in the widget_search_path.
    - The View object
    - The LayoutSet object

* A Reaction::UI::RenderingContext::TT object built from:

    - Nothing

To render the window the correct Reaction::UI::Widget object is
retrieved via the LayoutSet for the root ViewPort of the page. 

The LayoutSet used defaults to the "layout" attribute on the
ViewPort. If there is no layout attribute value set, it takes the
class name of the ViewPort, extracts the parts following
"::ViewPort::" and constructs the layoutset name from converting camel
cased parts of the namespace to lower-case underscored, and namespace
parts into directories.

  ## eg:
  My::ViewPort::Action::UserForm
  ## becomes
  action/user_form

The layoutset file should exist in the skin_base_dir, in the "layout"
directory under the "skin_name" dir set in your View config, or in the
"default/layout" directory. [[ A LayoutSet object is created based on
the layoutset name, skin object, source_file (path to file), top_skin
(skin object), next_skin if exists ]].

The layoutset file is parsed as the LayoutSet object is created, if a
"=widget" line is found, the "widget_type" attribute is set.

The class of the Widget object can be set in the layoutset object
args, or it defaults to being fetched via the Skin. The type of widget
is either specified in the layoutset file via the "=widget" directive
or retrieved by recreating the camelcased name from the layoutset
name. The Widget is assumed to be in the widget search path provided
by defaults.conf or your skin.conf.

The Widget itself is passed the ViewPort to render, and the
RenderingContext. The initial fragment name to render is also passed,
"widget".

The render stack is created using the widget order. The widget order
is fetched for the fragment from the layoutset, this is either the
widget class/layoutset, or retrieved from the extended layouts. As the
render_stack is built, the fragment methods in the Widget are called
to assign values from the ViewPort to arguments for the layout. (Or
other interesting things).

The stack is passed to the RenderingContext to complete.
