Add a metabox for Gutenberg

Currently the easiest way to make sure the post meta
is added to the Gutenberg editor, since the featured
image metabox hook/filter is no longer available.

Presumably this will eventually be replaced with a true
block, or whatever it will be, but this works for the moment.

includes/class-displayfeaturedimagegenesis-postmeta.php

@@ -10,6 +10,12 @@
  */
 class Display_Featured_Image_Genesis_Post_Meta {
 
+	/**
+	 * ID for our new metabox.
+	 * @var string
+	 */
+	protected $metabox = 'displayfeaturedimagegenesis';
+
 	/**
 	 * Post meta key to disable buttons
 	 * @var string
@@ -22,6 +28,41 @@ class Display_Featured_Image_Genesis_Post_Meta {
 	 */
 	protected $move = '_displayfeaturedimagegenesis_move';
 
+	/**
+	 * For Gutenberg, add a new metabox, since the thumbnail hooks are no longer present.
+	 * Should eventually be replaced with a block.
+	 *
+	 * @since 2.7.0
+	 * @param $post_type
+	 * @param $post
+	 */
+	public function add_metabox( $post_type, $post ) {
+		if ( ! post_type_supports( $post_type, 'thumbnail' ) ) {
+			return;
+		}
+		$classic_editor = filter_input( INPUT_GET, 'classic-editor', FILTER_VALIDATE_BOOLEAN );
+		if ( null !== $classic_editor ) {
+			return;
+		}
+		add_meta_box(
+			$this->metabox,
+			__( 'Display Featured Image', 'display-featured-image-genesis' ),
+			array( $this, 'do_metabox' ),
+			$post_type,
+			'side',
+			'low'
+		);
+	}
+
+	/**
+	 * Output the metabox.
+	 * @param $post
+	 * @param $args
+	 */
+	public function do_metabox( $post, $args ) {
+		echo $this->get_metabox_content( $post->ID );
+	}
+
 	/**
 	 * Build the metabox with the checkbox setting.
 	 * @since 2.5.0
@@ -32,7 +73,17 @@ class Display_Featured_Image_Genesis_Post_Meta {
 	 * @return string
 	 */
 	public function meta_box( $content, $post_id ) {
+		return $this->get_metabox_content( $post_id ) . $content;
+	}
 
+	/**
+	 * Get the metabox content/fields.
+	 *
+	 * @param $post_id
+	 *
+	 * @return string
+	 */
+	protected function get_metabox_content( $post_id ) {
 		$output = wp_nonce_field( 'displayfeaturedimagegenesis_post_save', 'displayfeaturedimagegenesis_post_nonce', true, false );
 		$select = $this->get_select();
 		if ( $select ) {
@@ -47,7 +98,7 @@ class Display_Featured_Image_Genesis_Post_Meta {
 			}
 		}
 
-		return $output . $content;
+		return $output;
 	}
 
 	/**

includes/class-displayfeaturedimagegenesis.php

@@ -102,7 +102,7 @@ class Display_Featured_Image_Genesis {
 	 * @param $settings
 	 * @param $taxonomies
 	 */
-	function __construct( $admin, $author, $common, $customizer, $description, $helptabs, $output, $post_meta, $rss, $settings, $taxonomies, $widgets ) {
+	public function __construct( $admin, $author, $common, $customizer, $description, $helptabs, $output, $post_meta, $rss, $settings, $taxonomies, $widgets ) {
 		$this->admin       = $admin;
 		$this->author      = $author;
 		$this->common      = $common;
@@ -142,10 +142,13 @@ class Display_Featured_Image_Genesis {
 		add_action( 'widgets_init', array( $this->widgets, 'register_shortcodes' ) );
 		add_action( 'admin_enqueue_scripts', array( $this->widgets, 'enqueue_scripts' ) );
 
-		// Taxonomies, Author, Post Meta
+		// Taxonomies, Authors
 		add_filter( 'displayfeaturedimagegenesis_get_taxonomies', array( $this->taxonomies, 'remove_post_status_terms' ) );
 		add_action( 'admin_init', array( $this->taxonomies, 'set_taxonomy_meta' ) );
 		add_action( 'admin_init', array( $this->author, 'set_author_meta' ) );
+
+		// Post Meta
+		add_action( 'add_meta_boxes', array( $this->post_meta, 'add_metabox' ), 10, 2 );
 		add_filter( 'admin_post_thumbnail_html', array( $this->post_meta, 'meta_box' ), 10, 2 );
 		add_action( 'save_post', array( $this->post_meta, 'save_meta' ) );