understrap/inc/extras.php

<?php
/**
 * Custom functions that act independently of the theme templates.
 *
 * Eventually, some of the functionality here could be replaced by core features.
 *
 * @package understrap
 */

// Exit if accessed directly.
defined( 'ABSPATH' ) || exit;

add_filter( 'body_class', 'understrap_body_classes' );

if ( ! function_exists( 'understrap_body_classes' ) ) {
	/**
	 * Adds custom classes to the array of body classes.
	 *
	 * @param array $classes Classes for the body element.
	 *
	 * @return array
	 */
	function understrap_body_classes( $classes ) {
		// Adds a class of group-blog to blogs with more than 1 published author.
		if ( is_multi_author() ) {
			$classes[] = 'group-blog';
		}
		// Adds a class of hfeed to non-singular pages.
		if ( ! is_singular() ) {
			$classes[] = 'hfeed';
		}

		return $classes;
	}
}

// Removes tag class from the body_class array to avoid Bootstrap markup styling issues.
add_filter( 'body_class', 'understrap_adjust_body_class' );

if ( ! function_exists( 'understrap_adjust_body_class' ) ) {
	/**
	 * Setup body classes.
	 *
	 * @param string $classes CSS classes.
	 *
	 * @return mixed
	 */
	function understrap_adjust_body_class( $classes ) {

		foreach ( $classes as $key => $value ) {
			if ( 'tag' == $value ) {
				unset( $classes[ $key ] );
			}
		}

		return $classes;

	}
}

// Filter custom logo with correct classes.
add_filter( 'get_custom_logo', 'understrap_change_logo_class' );

if ( ! function_exists( 'understrap_change_logo_class' ) ) {
	/**
	 * Replaces logo CSS class.
	 *
	 * @param string $html Markup.
	 *
	 * @return mixed
	 */
	function understrap_change_logo_class( $html ) {

		$html = str_replace( 'class="custom-logo"', 'class="img-fluid"', $html );
		$html = str_replace( 'class="custom-logo-link"', 'class="navbar-brand custom-logo-link"', $html );
		$html = str_replace( 'alt=""', 'title="Home" alt="logo"', $html );

		return $html;
	}
}

/**
 * Display navigation to next/previous post when applicable.
 */

if ( ! function_exists( 'understrap_post_nav' ) ) {
	function understrap_post_nav() {
		// Don't print empty markup if there's nowhere to navigate.
		$previous = ( is_attachment() ) ? get_post( get_post()->post_parent ) : get_adjacent_post( false, '', true );
		$next     = get_adjacent_post( false, '', false );

		if ( ! $next && ! $previous ) {
			return;
		}
		?>
		<nav class="container navigation post-navigation">
			<h2 class="sr-only"><?php esc_html_e( 'Post navigation', 'understrap' ); ?></h2>
			<div class="row nav-links justify-content-between">
				<?php
				if ( get_previous_post_link() ) {
					previous_post_link( '<span class="nav-previous">%link</span>', _x( '<i class="fa fa-angle-left"></i>&nbsp;%title', 'Previous post link', 'understrap' ) );
				}
				if ( get_next_post_link() ) {
					next_post_link( '<span class="nav-next">%link</span>', _x( '%title&nbsp;<i class="fa fa-angle-right"></i>', 'Next post link', 'understrap' ) );
				}
				?>
			</div><!-- .nav-links -->
		</nav><!-- .navigation -->
		<?php
	}
}

if ( ! function_exists( 'understrap_pingback' ) ) {
	/**
	 * Add a pingback url auto-discovery header for single posts of any post type.
	 */
	function understrap_pingback() {
		if ( is_singular() && pings_open() ) {
			echo '<link rel="pingback" href="' . esc_url( get_bloginfo( 'pingback_url' ) ) . '">' . "\n";
		}
	}
}
add_action( 'wp_head', 'understrap_pingback' );

if ( ! function_exists( 'understrap_mobile_web_app_meta' ) ) {
	/**
	 * Add mobile-web-app meta.
	 */
	function understrap_mobile_web_app_meta() {
		echo '<meta name="mobile-web-app-capable" content="yes">' . "\n";
		echo '<meta name="apple-mobile-web-app-capable" content="yes">' . "\n";
		echo '<meta name="apple-mobile-web-app-title" content="' . esc_attr( get_bloginfo( 'name' ) ) . ' - ' . esc_attr( get_bloginfo( 'description' ) ) . '">' . "\n";
	}
}
add_action( 'wp_head', 'understrap_mobile_web_app_meta' );