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Jifty::Manual::PageRegions - Using page regions


Page regions are a way of doing the new trend of automatic in-page replacement with JavaScript -- while at the same time providing the same user experience for non-JavaScript enabled browsers. Sections are chunked into nestable "page regions", which can be refreshed independently.


Constructing Page Regions

From inside any template, a region may get constructed via something like this:

    <% Jifty->web->region( name     => 'regionname',
                           path     => '/path/of/component',
                           defaults => { argname => 'some value', ... },
                         ) %>

This call will pass all arguments to the new constructor of Jifty::Web::PageRegion. The most often used parameters are:


The mandatory region's name given here is used to embed the region's content into a <div> tag which is marked with a fully qualified name for that region. The qualified name represents the nesting structure of regions inside a page and is automatically built inside. The qualified name for a given Jifty::Web::PageRegion object can be obtained by calling Jifty->web->qualified_region.

path (optional)

If a path is given, the component's rendered result under this path is embedded inside the region. If no path is given, /__jifty/empty will be used resulting in an empty region inside.

defaults (optional)

Every argument given here (as a hash-ref) will be transported to the component that displays the region inside. The values are accessible by building a <%args> block in the component (Mason template) specifying the arguments.

Using Page Regions

Given a template with regions, any region can influence itself or any other region it knows about. Doing this is typically done with JavaScript handlers like onclick. The examples below will demonstrate some typical scenarios:

    %# replace this region with some other component
    <% Jifty->web->link( label   => 'click me',
                         onclick => {
                             replace_with => '/new/path/component',
                             args         => { argname => 'some value' },
                       ) %>

    %# insert a new region in front of a given region
    %# use an HTML-entity as the link-text and a CSS class
    <% Jifty->web->link( label        => '%#9997;',
                         escape_label => 0,
                         class        => 'blue_button',
                         onclick => {
                             region  => 'regionname',
                             prepend => '/new/path/component',
                             args    => { argname => 'some value' },
                       ) %>

    %# insert a new region after a given CSS selector inside $region
    <% Jifty->web->link( label   => 'add something',
                         onclick => {
                             element => $region->parent->get_element('div.list'),
                             append  => '/new/path/component',
                             args    => { argname => 'some value' },
                       ) %>

    %# a button to replace the current region with empty content
    <% Jifty->web->link( label   => 'clear',
                         onclick => {
                             refresh_self => 1,
                             toggle       => 1,
                         as_button => 1,
                       ) %>

    %# a button to delete some region with JavaScript confirmation alert
    <% Jifty->web->link( label   => 'delete',
                         onclick => {
                             delete  => 'regionname',
                             confirm => 'really delete this?',
                         as_button => 1,
                       ) %>

    %# refresh the parent region which holds the current one
    <% $search->button(
        label   => 'Search!',
        onclick => {
            submit  => $search_action,
            refresh => Jifty->web->current_region->parent,
            args    => { page => 1 }
      ) %>


There is a bit of complication involved in making sure that the server-side Perl implementation of page regions, and, more importantly, how they preserve state, interacts with the client-side JavaScript implementation. What follows is an attempt to describe the process.

Regions, when they are created, have a default path and a default set of arguments. These are "defaults" because they can be overridden by the browser -- this is what enables the browser to say "...and that region has this other path, in reality." The same is true for arguments; for example, a paging widget could have a default page argument of 1, but could be actually being rendered with a page of 2.

These overrides are kept track of using state variables. When a region is entered, it peers at the current state variables, and overrides the default path and arguments before rendering the region.

When a Jifty::Web::Form::Clickable object with an onclick is generated, it examines the onclick and determines how to emulate it without JavaScript. It determines which actions need to be run, as well as how to manipulate the future state variables to change the display of the appropriate regions. It encodes all of this in the button or link; since the JavaScript usually returns false, the fallback mode is never seen by the browser.

When a region is output, it is output with a tiny "region wrapper", which serves two purposes: to inform the JavaScript of the existance of the page region and its default path and variables, and to create a unique <div> for the fragment to reside in. The browser reads the JavaScript and creates, on the client-side, a model of the nested PageRegions. This allows the JavaScript to model the state variable changes correctly.

When the JavaScript Update function is called, it is passed a list of fragments that needs to be updated, as well as a list of actions that need to be run. As it does so, it builds up an up-to-date list of state variables, to more closely imitate the state of a non-javascript enabled client. It constructs a JSON request based on that information, and passes it off to the XML web-service endpoint on the server.

When the request comes back, it parses the XML. For each fragment that was requested, it finds the correct bit of the response, and replaces the content of the DOM with the response. As it does so, it re-updates the client-side view of the fragments with the server's information -- this is particularly key for dealing with parameters which were mapped by the request mapper. Finally, it displays any messages and errors from actions.


Hidden information that shows after click on a link

It's ofetn required to hide some extra information, a list of objects or something else under a link. User clicks on the link and the information you're hiding shows up instead of the link. Regions could help you to do this task very easy.

First of all you'll need a region's component templates/additional_info:

    $collapsed => 1
    ... some other arguments required to show correct info ...
    % if ( $collapsed ) {
    <% Jifty->web->link(
        label   => _('text of the link'),
        onclick => {
            refresh_self => 1,
            args         => { %ARGS, collapsed => 0 },
    ) %>
    % } else {
    .... here we show our additional info ...
    % }

In this component we have one argument $collapsed that controls either we show link or information. By default we prefer hidden state and in this case we show only the link with an onclick action that refreshes the current region, however value of the argument is overriden.

You can add any arguments you want to this component that may be required to show the additional information, for example an id of some object, but you should remeber to use this arguments during links generation.

Next thing you should do is to add a region to some page:

    ... and region:
    <% Jifty->web->region(
        name => 'block_name',
        path => '/additional_info',
        defaults => { ... some args required to show the info ... },
    ) %>
    ... other information on the page

That's all. Things should just work.

Smarty ones should mention that the link disappears after click, but may be you want show/hide functionality. This is very easy task when we know how to use links generation. In the component's else branch add:

    % } else {
    <% Jifty->web->link(
        label   => _('text of the link that hides'),
        onclick => {
            refresh_self => 1,
            args         => { %ARGS, collapsed => 1 },
    ) %>
    .... here we show our additional info ...
    % }

Wow! Works again. Enjoy.

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