ResourceLoader/Developing with ResourceLoader

ResourceLoader supports complex client-side web applications in production and development environments. As these different environments have different needs, ResourceLoader offers two distinct modes: production mode and development mode (also known as "debug") mode.

Development mode is designed to make development as easy as possible, prioritizing the ease of identifying and resolving problems in the software over performance. Production mode makes the opposite prioritization, emphasizing performance over ease of development.

It is important to test your code in both development and production modes. In day-to-day development, most developers will find it beneficial to use development mode most of the time, only validating their code's functionality in production mode before committing changes.

Registering

 * See also Manual:$wgResourceModules and ResourceLoader/Migration guide (developers)

@embed

 * See also ResourceLoader/Features

The  annotation triggers the Data URI embedding feature of ResourceLoader. Small images (up to 24kb per image) referenced with this annotation will be automatically embedded by ResourceLoader.

@noflip
For right-to-left languages, Resource Loader changes the direction of most direction-dependent CSS rules. Internally, Mediawiki uses CSS Janus (see below) to accomplish this. However, sometimes it is incorrect to flip some elements -- hence the noflip "attribute". This instructs Resource Loader to not flip the following CSS rule.

For example:

Module structure

 * Work in progress

Two modules for most extensions. A module to be loaded from the containing styles and/or scripts that need to run as soon as possible. This module should generally be a small as possible and be used to:
 * Top module
 * Style output by PHP
 * Insert or modify elements that change the location of anything above the "the fold" (such as inserting a banner that pushes the page down, or a sidebar widgets that pushes another sidebar portlet down, or a content action tab that causes a change in the position of other tabs)


 * Bottom module
 * Insert or modify elements that are not visible right away (e.g. binding autocompletion to a form element or inserting a small absolutely positioned widget)
 * Anything else

Toggle debug mode
As with many other of MediaWiki, ResourceLoader is configured to run in production mode by default. To have ResourceLoader operate in development mode by default, set the  variable to   in LocalSettings.php. For example:

""

Switching modes per-request
ResourceLoader requests, such as those made to load.php, contain a debug parameter in their query string. This parameter controls whether ResourceLoader runs in production or development mode for that particular request. This parameter may also be used with MediaWiki page requests, allowing the default mode set by  to be overridden.

To force ResourceLoader to operate in production mode for a particular request, append debug=false to the query string. For example: " http:// example.org/wiki/An_article?debug=false"

To force ResourceLoader to operate in development mode for a particular request, append debug=true to the query string. For example: " http:// example.org/w/index.php?title=An_article&action=edit&debug=true"

Issues

 * When developing with ResourceLoader debug on, the CSS will not be flipped for right-to-left (RTL) languages. So you should test RTL interface with debug off. (See Bug 30804 - RTL display is broken with ?debug=true.)

Breaking cache
When making frequent changes to code and checking them in a browser, the caching mechanisms designed to improve the performance of web-browsing can quickly become inconvenient. When developing on a system which is not making use of a reverse proxy such as Squid or Varnish, you only need to force your browser to bypass its cache while refreshing. This can be achieved by pressing CTRL+F5 in Internet Explorer, or holding the shift key while clicking the browser's refresh button in most other browsers.

If you are developing behind a reverse proxy, you can either change the values of $wgResourceLoaderMaxage or use ?debug=true to bypass cache since is fixed.

Good examples
The following is a list of MediaWiki extensions which take advantage of ResourceLoader functionality and are known to be a good example of ResourceLoader integration.


 * Extension:ArticleFeedback
 * Extension:Vector
 * Extension:WikiEditor

Server-side
While building the page, if you need a module to be loaded, you need tell the OutputPage object to add one or more modules to the page by calling the  methods and passing one or more (variadic) arguments (such as " ", " " or " ")

adds the given the module name(s) to the load queue of the page. The client side loader will request all of the components for this module (scripts, styles, messages, dependencies, etc.) and load them correctly. If your module contains a stylesheet that styles elements that are outputted by PHP as well as styles and/or scripts that insert content dynamically, then you should split the module into two separate modules. One for styling/enhancing the output, and one for dynamic stuff. The former module should have the "position" property set to "top" (in the module definition in ), so that ResourceLoader will load it before parsing the rest of the HTML, preventing a FOUC (Flash of unstyled content). The other module doesn't need a "position" property and will simply be loaded asynchronously by the client, not blocking further parsing of the page.

Both should be added to the load queue in the same way, without repeating or forcing any particular loading style. This information is already in the module registry and the client will handle it accordingly. Usage of  should be avoided.

Client-side (dynamically)
If you only need a module in a certain scenario of the user interface, you could instead create a small init module (that is loaded server side), and from there use JavaScript to kick-off the load of the rest of the module when necessary. Use the  object for this.

Tip: If you just want to load the module, and don't need the callback, you can use  instead.