functions.php

<?php
/**
 * Welcome to DevDmBootstrap4 a simple to use barebones theme for WordPress theme developers wishing to use the Twitter
 * Bootstrap 4.x frontend framework.
 */

/**
 * Setup the theme defaults.
 */

if (!function_exists( 'devdmbootstrap_setup' ) ) {
    /**
     * Sets up theme defaults and registers support for various WordPress features.
     */
    function devdmbootstrap_setup()
    {

        // Load up the Text domain.
        load_theme_textdomain('devdmbootstrap4', get_template_directory() . '/languages');

        // Add default posts and comments RSS feed links to head.
        add_theme_support('automatic-feed-links');

        // Let WordPress manage the document title.
        add_theme_support('title-tag');

        // Add Theme Support for Custom Background Images and Colors
        add_theme_support( 'custom-background' );

        // Add Theme Support for Customize Selective Refresh Widgets
        add_theme_support( 'customize-selective-refresh-widgets' );

        // Add Theme Support for Custom Header (background) image
        add_theme_support( 'custom-header', array(
            'default-image'          => '',
            'random-default'         => false,
            'width'                  => 1140,
            'height'                 => 150,
            'flex-height'            => true,
            'flex-width'             => true,
            'default-text-color'     => '',
            'header-text'            => false,
            'uploads'                => true,
            'wp-head-callback'       => '',
            'admin-head-callback'    => '',
            'admin-preview-callback' => '',
        ));

        /**
         * Enable support for Post Thumbnails on posts and pages.
         *
         * @link http://codex.wordpress.org/Function_Reference/add_theme_support#Post_Thumbnails
         */
        add_theme_support('post-thumbnails');
        set_post_thumbnail_size(1140, 300, array('center','center'));

        // This theme uses wp_nav_menu() in two locations.
        register_nav_menus(array(
            'main_menu' => esc_html__('Main Menu', 'devdmbootstrap4'),
            'footer_menu' => esc_html__('Footer Menu', 'devdmbootstrap4'),
        ));

        /*
         * Switch default core markup for search form, comment form, and comments
         * to output valid HTML5.
         */
        add_theme_support('html5', array(
            'search-form',
            'comment-form',
            'comment-list',
            'gallery',
            'caption',
        ));

        // Set the max content width
        if ( ! isset( $content_width ) ) {
            $content_width = 1140;
        }

        /* Add custom-logo theme support */
        add_theme_support( 'custom-logo', array(
            'height'      => 150,
            'width'       => 350,
            'flex-height' => true,
            'flex-width'  => true,
            'header-text' => array( 'site-title', 'site-description' ),
            )
        );

    }

}
add_action( 'after_setup_theme', 'devdmbootstrap_setup' );

/**
 * get the custom logo URL
 */
if (!function_exists('devdmbootstrap4_custom_logo')) {
    function devdmbootstrap4_custom_logo() {

        if ( function_exists( 'the_custom_logo' ) ) {
            $custom_logo_id = get_theme_mod( 'custom_logo' );
            $image          = wp_get_attachment_image_src( $custom_logo_id , 'full' );
            return (!empty($image[0]) ? $image[0] : FALSE);
        }
    }
}

/**
 * Register left and right Sidebar
 */
if (!function_exists( 'devdmbootstrap_widgets_init' ) ) {

    function devdmbootstrap_widgets_init()
    {

        register_sidebar(
            array(
            'name'          => __('Right Sidebar', 'devdmbootstrap4'),
            'id'            => 'dmbs-right-sidebar',
            'description'   => __('Widgets in this area will be shown on all posts and pages.', 'devdmbootstrap4'),
            'before_widget' => '<li id="%1$s" class="widget dmbs-widget dmbs-widget-right %2$s">',
            'after_widget'  => '</li>',
            'before_title'  => '<h3 class="widgettitle dmbs-widget-title dmbs-widget-right-title">',
            'after_title'   => '</h3>',
        ));

        register_sidebar(
            array(
            'name'          => __('Left Sidebar', 'devdmbootstrap4'),
            'id'            => 'dmbs-left-sidebar',
            'description'   => __('Widgets in this area will be shown on all posts and pages.', 'devdmbootstrap4'),
            'before_widget' => '<li id="%1$s" class="widget dmbs-widget dmbs-widget-left %2$s">',
            'after_widget'  => '</li>',
            'before_title'  => '<h3 class="widgettitle dmbs-widget-title dmbs-widget-left-title">',
            'after_title'   => '</h3>',
        ));
    }

}
add_action( 'widgets_init', 'devdmbootstrap_widgets_init' );

/**
 * Include the Bootstrap 4.x Stylesheet and JS
 */
if (!function_exists( 'devdmbootstrap_scripts' ) ) {

    function devdmbootstrap_scripts()
    {
        $wpTheme = wp_get_theme();

        // Enqueue the default Bootstrap 4.x CSS with the name devdmbootstrap4-css
        wp_enqueue_style('devdmbootstrap4-css', get_template_directory_uri() . '/assets/css/devdmbootstrap/devdmbootstrap4.min.css');

        // Enqueue the default style.css with the name devdmbootstrap4-stylesheet
        wp_enqueue_style('devdmbootstrap4-stylesheet', get_stylesheet_uri());

        // Enqueue Font Awesome Icon Set with the name devdmbootstrap4-fontawesome.
        if (get_theme_mod('devdmbootstrap4_fontawesome_setting', 1)) {
            wp_enqueue_style('devdmbootstrap4-fontawesome', get_template_directory_uri() . '/assets/fontawesome-free-5.7.2-web/css/all.min.css');
        }

        // Enqueue popper.min.js with the name devdmbootstrap4-popper-js
        wp_enqueue_script('devdmbootstrap4-popper-js', get_template_directory_uri() . '/assets/js/bootstrap4x/popper.min.js', array('jquery'), $wpTheme->get( 'Version' ), true);

        // Enqueue the default Bootstrap 4.x JS with the name devdmbootstrap4-js.
        wp_enqueue_script('devdmbootstrap4-js', get_template_directory_uri() . '/assets/js/bootstrap4x/bootstrap.js', array('jquery'), $wpTheme->get( 'Version' ), true);

        // Enqueue comment-reply
        if ( is_singular() && comments_open() && get_option('thread_comments') ) {
            wp_enqueue_script( 'comment-reply' );
        }
    }
}
add_action( 'wp_enqueue_scripts', 'devdmbootstrap_scripts' );

/**
 * Customizer
 */
require_once( get_template_directory() . '/includes/customizer.php');

/**
 * Calculate Column Sizes and return the value when called
 */
if (!function_exists( 'devdmbootstrap_column_size' ) ) {
    function devdmbootstrap_column_size($column = null) {

        $columnSizes = array(
            'left'  => '',
            'right' => '',
            'main'  => '',
        );

        if ($column != null && array_key_exists($column,$columnSizes)) {

            $columnSizes = array(
                'left' => get_theme_mod('devdmbootstrap4_leftsidebar',0),
                'right' => get_theme_mod('devdmbootstrap4_rightsidebar',3),
            );

            $columnSizes['main'] = 12 - ($columnSizes['right'] + $columnSizes['left']);

            return $columnSizes[$column];

        }

        return;
    }
}

/**
 * Nav Walker
 */
if (!function_exists( 'devdmbootstrap_nav_walker' ) ) {
    function devdmbootstrap_nav_walker()
    {
        $loadEnhancedMenu = get_theme_mod('devdmbootstrap4_enhanced_menu_setting', 1);

        if ($loadEnhancedMenu == 1) {
            $wpTheme = wp_get_theme();

            // Enqueue the Enhanced Menu System JS with the handle devdmbootstrap4-enhanced-menu-js
            wp_enqueue_script('devdmbootstrap4-enhanced-nav-js', get_template_directory_uri() . '/assets/js/devdmbootstrap4_enhanced_nav.js', array('jquery'), $wpTheme->get('Version'), true);

            require get_template_directory() . '/includes/devdmbootstrap_enhanced_nav_walker.php';
        } else {
            wp_dequeue_script('devdmbootstrap4-enhanced-nav');
            require get_template_directory() . '/includes/devdmbootstrap_nav_walker.php';
        }
    }
}
add_action('wp_enqueue_scripts','devdmbootstrap_nav_walker');

/**
 * Custom Comment Walker
 */
require get_template_directory() . '/includes/devdmbootstrap_comment_walker.php';

/**
 * Utilities
 */
require get_template_directory() . '/includes/utilities.php';