React to set changes

Icon sets change in many places: the set editor, bulk editing, imports, presets, WP-CLI, client mode, the AI abilities. If your theme or plugin builds something from a set, you need to know when it changed. This tutorial shows the one hook that hears every change, how to keep your own code safe when two saves happen at once, and how to read earlier versions from WordPress revisions.

The one place every change passes

Every path that changes a set's icons ends in the same internal function. It stores the icons and then fires easy_svg_pro_set_icons_written. You never have to hook the editor, the importers and WP-CLI separately.

What you get: the set's post ID and the complete list of icons after the save, each with label and sanitized markup. What you do not get: the previous state or a list of changes.

What does not pass through here: creating an empty set, renaming a set, trashing, restoring and deleting. Those change the post, not its icons.

Step by step: a JSON export per set

A common agency case: a headless frontend or a design system wants the icons of a set as a JSON file. We write one file per set into the uploads folder and keep it current.

add_action(
	'plugins_loaded',
	function () {
		if ( ! defined( 'EASY_SVG_PRO_FILE' ) ) {
			return;
		}
		add_action( 'easy_svg_pro_set_icons_written', 'acme_export_set_json', 10, 2 );
	}
);

function acme_set_collection_slug( $post_id ) {
	$slugs = get_option( 'easy_svg_pro_set_collection_slugs', array() );
	if ( is_array( $slugs ) && ! empty( $slugs[ (string) $post_id ] ) ) {
		return (string) $slugs[ (string) $post_id ];
	}

	// A set created in this request is recorded on the next page load.
	return (string) get_post_field( 'post_name', $post_id );
}

function acme_export_set_json( $post_id, $icons ) {
	if ( 'publish' !== get_post_status( $post_id ) ) {
		return;
	}

	$uploads = wp_upload_dir();
	$dir     = trailingslashit( $uploads['basedir'] ) . 'icon-sets';
	if ( ! wp_mkdir_p( $dir ) ) {
		return;
	}

	$slug = sanitize_file_name( acme_set_collection_slug( $post_id ) );
	$data = array(
		'collection' => $slug,
		'label'      => get_the_title( $post_id ),
		'updated'    => gmdate( 'c' ),
		'icons'      => array(),
	);
	foreach ( $icons as $icon_slug => $icon ) {
		$data['icons'][ $icon_slug ] = array(
			'label'  => (string) ( $icon['label'] ?? $icon_slug ),
			'markup' => (string) ( $icon['markup'] ?? '' ),
		);
	}

	file_put_contents( $dir . '/' . $slug . '.json', wp_json_encode( $data ) );
}

function acme_remove_set_json( $post_id ) {
	if ( 'easy_svg_set' !== get_post_type( $post_id ) ) {
		return;
	}
	$uploads = wp_upload_dir();
	$file    = trailingslashit( $uploads['basedir'] ) . 'icon-sets/' . sanitize_file_name( acme_set_collection_slug( $post_id ) ) . '.json';
	if ( file_exists( $file ) ) {
		wp_delete_file( $file );
	}
}
add_action( 'wp_trash_post', 'acme_remove_set_json' );
add_action( 'before_delete_post', 'acme_remove_set_json' );

Keep slow work out of the save

Your callback runs inside the request that saves the set. A person in the editor, a client in client mode or a CI job waits for it. Anything slow (an HTTP call, image generation, a CDN upload) belongs in a background job:

function acme_queue_set_sync( $post_id, $icons ) {
	if ( ! wp_next_scheduled( 'acme_sync_icon_set', array( (int) $post_id ) ) ) {
		wp_schedule_single_event( time() + 60, 'acme_sync_icon_set', array( (int) $post_id ) );
	}
}
add_action( 'easy_svg_pro_set_icons_written', 'acme_queue_set_sync', 10, 2 );

The check with wp_next_scheduled() folds ten quick saves into one sync. When the job runs, read the set fresh rather than using the $icons from the moment of scheduling.

Writing sets from your own code

If your cron job, admin-post.php handler or webhook changes sets, tell Easy SVG Pro that the request writes, so it takes the set lock first. Without it, two overlapping saves can lose icons.

add_filter(
	'easy_svg_pro_set_write_context',
	function ( $writes ) {
		return $writes || wp_doing_cron();
	}
);

REST requests that are not GET and WP-CLI are already covered. See easy_svg_pro_set_write_context for what the lock does and where it does not reach.

To change sets from code, use the REST routes or the abilities, which run through the sanitizer and the lock. Never write the post meta _easy_svg_set_icons yourself: you skip sanitizing, the lock and this action.

Earlier versions with Icon history

Turn on Icon history under Icons → Features and Easy SVG Pro hooks the same action to ask WordPress for a revision after each save. The revisions carry the _easy_svg_set_icons meta, so you can read what a set looked like before. It keeps the last ten revisions per set, and WordPress skips a new revision when nothing changed.

/**
 * The icons a set held one save ago, or an empty array.
 */
function acme_previous_set_icons( $post_id ) {
	$revisions = wp_get_post_revisions( $post_id, array( 'order' => 'DESC' ) );
	$revisions = array_values( $revisions );

	// [0] is the save that just happened, [1] the one before.
	if ( ! isset( $revisions[1] ) ) {
		return array();
	}

	$raw  = get_post_meta( $revisions[1]->ID, '_easy_svg_set_icons', true );
	$data = is_string( $raw ) ? json_decode( $raw, true ) : null;

	return is_array( $data ) ? $data : array();
}

Call it from a callback at priority 20, so the history callback (priority 10) has already stored the new revision. If the save changed nothing, WordPress made no new revision and [0] is already the state before; compare [0] with the live icons first if that case matters to you.

History starts when the feature is switched on. Saves made before that left no revision.

Checklist

• Accept two arguments: add_action( ..., 10, 2 ).
• Treat $icons as the full new state, not a diff.
• Expect the action even when nothing changed, and on two sets for one bulk move.
• Hook trash, untrash and delete yourself if you build caches.
• Turn the post ID into the collection slug through easy_svg_pro_set_collection_slugs.
• Move slow work into cron.
• Add easy_svg_pro_set_write_context if your own code writes sets outside REST and WP-CLI.

Related

• easy_svg_pro_set_icons_written
• easy_svg_pro_set_write_context
• REST API
• Abilities for AI agents