wp_register_layout_support() │ WP 5.8.0

Registers the layout block attribute for block types that support it.

Internal function — this function is designed to be used by the kernel itself. It is not recommended to use this function in your code.

No Hooks.

Returns

null. Nothing (null).

Usage

wp_register_layout_support( $block_type );
$block_type(WP_Block_Type) (required)
Block Type.

Changelog

Since 5.8.0 Introduced.
Since 6.3.0 Check for layout support via the layout key with fallback to __experimentalLayout.

wp_register_layout_support() code WP 6.9

wp-includes/block-supports/layout.php 
function wp_register_layout_support( $block_type ) {
	$support_layout = block_has_support( $block_type, 'layout', false ) || block_has_support( $block_type, '__experimentalLayout', false );
	if ( $support_layout ) {
		if ( ! $block_type->attributes ) {
			$block_type->attributes = array();
		}

		if ( ! array_key_exists( 'layout', $block_type->attributes ) ) {
			$block_type->attributes['layout'] = array(
				'type' => 'object',
			);
		}
	}
}