Fixed Edit Sidebar

fixed-edit-sidebar.php

<?php
/*
Plugin Name: Fixed Edit Sidebar
Plugin URI:  https://gist.github.com/felixarntz/5b1ad2a72dc22053c07812340daf3274
Description: Allows the sidebar in the post editing screen to scroll along if the screen is large enough.
Version:     1.0.0
Author:      Felix Arntz
Author URI:  https://leaves-and-love.net
License:     GNU General Public License v2
License URI: http://www.gnu.org/licenses/gpl-2.0.html
 */

// Note that jQuery must be loaded on the page.
function fixed_edit_sidebar_print_script_and_style() {
	?>
	<script>
		( function( $ ) {
			'use strict';

			function checkRightContainerOffset() {
				var offset = 0;
				var $postbox = $( '#postbox-container-1' );

				if ( $( 'body' ).hasClass( 'admin-bar' ) ) {
					if ( document.documentElement.clientWidth <= 782 ) {
						offset = 46;
					} else {
						offset = 32;
					}
				}

				if ( $postbox.height() < $( window ).height() - offset ) {
					if ( $( window ).scrollTop() + offset >= $( '#titlediv' ).offset().top - 10 ) {
						$postbox.addClass( 'fixed' );
					} else {
						$postbox.removeClass( 'fixed' );
					}
				} else {
					$postbox.removeClass( 'fixed' );
				}
			}

			checkRightContainerOffset();
			$( window ).on( 'scroll', checkRightContainerOffset );

		}( window.jQuery ) );
	</script>
	<style>
		@media screen and (min-width: 980px) {
			#post-body.columns-2 #postbox-container-1.fixed {
				position: fixed;
				top: 42px;
				right: 20px;
				margin-right: 0;
				float: none;
			}
		}
	</style>
	<?php
}

function fixed_edit_sidebar_add_hook() {
	add_action( 'admin_footer', 'fixed_edit_sidebar_print_script_and_style' );
}
add_action( 'load-post.php', 'fixed_edit_sidebar_add_hook' );
add_action( 'load-post-new.php', 'fixed_edit_sidebar_add_hook' );