Development:Output renderers

Note: This page is a work-in-progress. Feedback and suggested improvements are welcome. Please join the discussion on moodle.org or use the page comments.

Goals

• stable API
• easy to use
• easy to customise via themes

Renderers

Output renderer is a class with collection of methods that handle rendering of visual aspects of Moodle pages, emails, html export, etc. In 1.9 general output related functions were located in weblib.php and modules stored rendering code in lib.php, locallib.php, view.php, etc.

Output renderer instances are obtained through moodle_page::get_renderer($component, $subtype = null, $target = null) method. Current core_renderer is available through the global $OUTPUT variable, please note this global should not be used in low level APIs.

Renderer targets

I most cases we are rendering page output for web browsers, sometimes we need to generate different output for command line scripts, email messages, etc.

renderer_base

Abstract class every other renderer must extend. Renderer base implements basic methods and support for renderer dispatching. The most important method is render(), it is using class name of the widget passed in first parameter to find fine correct protected rendering method (widget rendering methods have render_ prefix.

core_renderer

Core renderer implements:

1. page header and footer related rendering
2. boxes and containers
3. general widget methods - heading, single button, select form, heading, arrows, language selection, user login info
4. error messages, notifications
5. blocks

For example user avatar rendering involves following methods and classes: class core_renderer extends renderer_base {

 // ...

 public function render(widget $widget) {
    // calls $this->render_user_image($widget) when parameter with class user_image submitted 
 }
 protected function render_user_image(user_image $user_image) {
   // returns html markup for user avatar
 }
 public function user_image($userrecord, array $options=null) {
   // helper method that constructs $user_image widget and calls $this->render
 }

 // ...

}

class user_image extends widget {

 public $userrecord;
 public $options;

 public function __construct($userrecord, array $options=null) {
     // ...
 }

}

See also

• Development:Theme_changes