How are Wordpress Dynamic Sidebar Widgets rendered? - wordpress

Question

I have been reading through the Wordpress Source, trying to get a better understanding of how dynamic sidebars are rendered.
However, I am hitting a sticking point...
894 | do_action( 'dynamic_sidebar', $wp_registered_widgets[$id] );
I can't find where add_action('dynamic_sidebar', ... ) is defined. Without that part, I am sort of lost in what happens.
See the code here:
https://github.com/WordPress/WordPress/blob/b7c13e27c255e1fc1f03ab2ab432f1652a0ac212/wp-includes/widgets.php#L894
And to give more context, I am trying to figure out how to grab an array of widgets from a specific sidebar, and from there, I need to know how would you render each widget within that array.
I need finer control than dynamic_sidebar(...); gives me

Answer 1

Well, that specific line permits you to access each registered Widget properties, and it's used like:
<?php
/* Plugin Name: Test registered widgets */
add_action( 'dynamic_sidebar', 'sidebar_widgets_so_18666065' );
/**
* As this is an action hook, we don't return nothing
* use the passed values to do your stuff
*/
function sidebar_widgets_so_18666065( $registered_widget )
{
# Each registered widget passes the following array
/*
$registered_widget = Array
(
[name] => Meta
[id] => meta-2
[callback] => Array
(
[0] => WP_Widget_Meta Object
(
[id_base] => meta
[name] => Meta
[widget_options] => Array
(
[classname] => widget_meta
[description] => Log in/out, admin, feed and WordPress links
)
[control_options] => Array
(
[id_base] => meta
)
[number] => 2
[id] => meta-2
[updated] =>
[option_name] => widget_meta
)
[1] => display_callback
)
[params] => Array
(
[0] => Array
(
[number] => 2
)
)
[classname] => widget_meta
[description] => Log in/out, admin, feed and WordPress links
)
*/
}
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