Add metabox and other functions for subhead

functions.php

@@ -56,6 +56,9 @@
 /** Customizer Additions */
 require_once( 'library/bs-customizer-additions.php' );
 
+/** The "Subhead" metabox and related functions */
+require_once( 'library/metabox-subhead.php' );
+
 /** Required and Recommended Plugins */
 require_once( 'library/class-tgm-plugin-activation.php' );
 require_once( 'library/bs-plugin-activation.php' );
@@ -173,4 +176,4 @@ function calhealth_require_files() {
 		}
 	}
 }
-add_action( 'after_setup_theme', 'calhealth_require_files' ); 
+add_action( 'after_setup_theme', 'calhealth_require_files' ); 

library/metabox-subhead.php

@@ -0,0 +1,108 @@
+<?php
+/**
+ * Functions related to meta boxes
+ */
+
+/**
+ * Register the 'subtitle' post meta
+ */
+function subtitle_meta_box_register_post_meta() {
+	return register_post_meta(
+		'post',
+		'subtitle',
+		array(
+			'object_subtype' => 'post',
+			'type' => 'string',
+			'description' => __( 'The subhead, deck, subtitle, or lead is a preface shown on article pages below the main title.' , 'allonsy' ),
+			'single' => true,
+			'sanitize_callback' => 'sanitize_textarea_field',
+			// 'auth_callback' => '',
+			'show_in_rest' => true,
+		),
+	);
+}
+add_action( 'init', 'subtitle_meta_box_register_post_meta' );
+
+/**
+ * Output the subtitle metabox.
+ *
+ * @link Copied from https://github.com/INN/umbrella-wcij/blob/16247cdd8f03a593633c82f8836c4c1e8aa83987/wp-content/themes/wisconsinwatch/inc/metaboxes.php with improvements
+ */
+function subtitle_meta_box_display() {
+	global $post;
+	$values = get_post_custom( $post->ID );
+	wp_nonce_field( 'subtitle_meta_box_nonce', 'subtitle_meta_box_nonce' );
+	?>
+		<label for="subtitle" class="screen-reader-text"><?php esc_html_e( 'Subtitle', 'largo' ); ?></label>
+		<textarea name="subtitle" id="subtitle" class="widefat" rows="2" cols="20"><?php
+			// PHP open/close are at the textarea boundary so we don't prepend/append this with tabs.
+			if ( isset( $values['subtitle'] ) ) {
+				echo sanitize_text_field( $values['subtitle'][0] );
+			}
+		?></textarea>
+		<p><small><?php esc_html_e( 'Plain text is allowed in the post subtitle.', 'largo' ); ?></small></p>
+	<?php
+}
+
+/**
+ * Save action for the metabox
+ *
+ * @param int     $post_id Post ID.
+ * @param WP_Post $post Post object.
+ * @param bool    $update whether the post is being updated
+ * @return null
+ */
+function subtitle_meta_box_save( $post_id, $post, $update = false ) {
+	if ( ! isset( $_POST['subtitle_meta_box_nonce'] ) ) {
+		error_log(var_export( 'subtitle meta box nonce not set', true));
+		return;
+	}
+
+	if ( ! wp_verify_nonce( $_POST['subtitle_meta_box_nonce'], 'subtitle_meta_box_nonce' ) ) {
+		error_log(var_export( 'subtitle meta box nonce not valid', true));
+		return;
+	}
+
+	if ( ! current_user_can( 'edit_post', $post_id ) ) {
+		return;
+	}
+
+	if ( wp_is_post_autosave( $post_id ) ) {
+		return;
+	}
+
+	if ( wp_is_post_revision( $post_id ) ) {
+		return;
+	}
+
+	$subtitle = wp_kses_post( $_POST['subtitle'] );
+
+	if ( ! empty( $subtitle ) ) {
+		update_post_meta( $post_id, 'subtitle', $subtitle );
+	} else {
+		delete_post_meta( $post_id, 'subtitle' );
+	}
+
+	return $subtitle;
+}
+add_action( 'save_post', 'subtitle_meta_box_save', 10, 3 );
+
+/**
+ * Register our subtitle metabox
+ *
+ * This doesn't have anything special applied to it for Gutenberg.
+ * If Publicsource switches to Gutenberg, read https://developer.wordpress.org/block-editor/developers/backward-compatibility/meta-box/ and update this box as necessary.
+ */
+add_action(
+	'add_meta_boxes',
+	function() {
+		add_meta_box(
+			'subtitle', // id
+			__( 'Subtitle', 'allonsy' ), // title
+			'subtitle_meta_box_display', // callback
+			array( 'post' ), // screen
+			'normal', // context
+			'high' // priority
+		);
+	}
+);

single.php

@@ -28,6 +28,20 @@
 	<section <?php post_class('main-content') ?> id="post-<?php the_ID(); ?>">
     <?php if( get_theme_mod('internal-title-bar') == '' ) { ?>
       <h1 class="entry-title"><?php the_title(); ?></h1>
+      <?php
+        $subtitle = get_post_custom_values( 'subtitle', get_the_ID() );
+        if ( ! empty( $subtitle ) ) {
+          // should be single value post meta, but if it isn't....
+          if ( is_array( $subtitle ) ) {
+            $subtitle = $subtitle[0];
+          }
+
+          printf(
+            '<h2 class="subtitle">%1$s</h2>',
+            esc_html( $subtitle ),
+          );
+        }
+      ?>
       <?php if( get_theme_mod('about-the-author') != '' ): ?>
         <div class="post-meta"><p><span class="author-name author-date">By <a href="<?php echo esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ); ?>" title="<?php echo esc_attr( get_the_author() ); ?>"><?php the_author(); ?></a> • <?php echo get_the_date( 'M j, Y', $post->ID ); ?></span></p></div>
       <?php endif; ?>