PWA: Add 'offline.php' template

header.php

@@ -172,7 +172,7 @@
 
 					<?php
 					// If logo is not centered.
-					if ( false === $header_center_logo ) {
+					if ( false === $header_center_logo && has_nav_menu( 'primary-menu' ) ) {
 						get_template_part( 'template-parts/header/header', 'search' );
 					}
 					?>

offline.php

@@ -0,0 +1,35 @@
+<?php
+/**
+ * The PWA Offline template file
+ *
+ * @package Newspack
+ */
+
+// Prevent showing nav menus.
+add_filter( 'has_nav_menu', '__return_false' );
+
+// Prevent showing widgets.
+add_filter( 'is_active_sidebar', '__return_false' );
+
+// Disable WordAds in the header.
+// See: https://wordads.co/2018/02/07/how-to-control-jetpack-ad-placements-using-hooks/
+add_filter( 'wordads_header_disable', '__return_true' );
+
+get_header();
+?>
+	<section id="primary" class="content-area">
+		<header class="entry-header">
+			<h1 class="entry-title"><?php esc_html_e( 'Offline', 'newspack' ); ?></h1>
+		</header><!-- .entry-header -->
+		<main id="main" class="site-main">
+			<?php
+			if ( function_exists( 'wp_service_worker_error_message_placeholder' ) ) {
+				wp_service_worker_error_message_placeholder();
+			}
+			?>
+		</main><!-- .site-main -->
+	</section><!-- .content-area -->
+<?php
+get_footer();
+
+

sass/layout/_layout.scss

@@ -20,6 +20,7 @@
 }
 
 .site-content {
+	min-height: 30vh;
 	overflow: hidden;
 }