A proof of concept for creating a custom translation UI for a Fieldmanager field group utilising repeatable fields

fieldmanager-babble-poc.php

<?php

/*
Plugin Name: A8c VIP Translatable Fields Test
Version: 1.0b1
*/

// Code pasted from Fieldmanager site
// using Fieldmanager for a slideshow - any number of slides,
// with any number of related links
add_action( 'fm_post_post', function() {
	$fm = new Fieldmanager_Group( array(
		'name' => 'slideshow',
		'limit' => 0,
		'label' => __( 'New Slide', 'your-domain' ),
		'label_macro' => array( __( 'Slide: %s', 'your-domain' ), 'title' ),
		'add_more_label' => __( 'Add another slide', 'your-domain' ),
		'collapsed' => true,
		'sortable' => true,
		'children' => array(
			'title' => new Fieldmanager_Textfield( __( 'Slide Title', 'your-domain' ) ),
			'slide' => new Fieldmanager_Media( __( 'Slide', 'your-domain' ) ),
			'description' => new Fieldmanager_RichTextarea( __( 'Description', 'your-domain' ) ),
			'posts' => new Fieldmanager_Autocomplete( array(
				'label' => __( 'Related Posts', 'your-domain' ),
				'limit' => 0,
				'sortable' => true,
				'one_label_per_item' => false,
				'add_more_label' => __( 'Add another related link', 'your-domain' ),
				'datasource' => new Fieldmanager_Datasource_Post( array(
					'query_args' => array(
						'post_status' => 'any',
					),
				) ),
			) ),
		),
	) );
	$fm->add_meta_box( __( 'Slides', 'your-domain' ), 'post' );
} );


class A8c_FM_Bbl_Meta_Field extends Babble_Meta_Field {

	public function get_output() {
		$outputs = '';
		foreach( $this->meta_value as $i => $slide ) {
			$outputs .= '<p>Title ' . absint( $i ) . ': <var>' . esc_html( $slide['title'] )  . '</var></p>';

		}
		return $outputs;
	}

	public function get_input( $name, $value ) {
		$inputs = '';
		foreach( $this->meta_value as $i => $slide ) {
			$translated_value = '';
			if ( isset($value[$i]['title']) ) {
				$translated_value = $value[$i]['title'];
			}
			$inputs .= '<p>Title ' . absint( $i ) . ':' . sprintf( '<input type="text" name="%s" value="%s">',
					esc_attr( $name .'[' . absint($i) . '][title]' ),
					esc_attr( $translated_value )
				) . '</p>';

		}
		return $inputs;
	}

	public function update( $submitted_value, WP_Post $job ) {
		$new_value = array_replace_recursive( $this->meta_value, $submitted_value );
		// At this point we could also find the translation for the related posts referenced
		// in the `posts` array for this slide.
		return $new_value;
	}

}

function fm_bbl_poc_meta_fields( array $fields, WP_Post $post ) {

	$fields[ 'slideshow' ] = new A8c_FM_Bbl_Meta_Field( $post, 'slideshow', __( 'Fieldmanager Slideshow', 'fm_bbl_poc' ) );

	return $fields;
}

add_filter( 'bbl_translated_meta_fields', 'fm_bbl_poc_meta_fields', 10, 2 );