From 1345e33a21a322c5918d904b2ac6b93ca446905d Mon Sep 17 00:00:00 2001
From: Peter Wilson <peterwilsoncc@git.wordpress.org>
Date: Sun, 23 Apr 2017 07:15:47 +0000
Subject: [PATCH] Menus: Add filter to sub-menu class in nav menus.

Add new filter `nav_menu_submenu_css_class` to the `Walker_Nav_Menu::start_el()` method, allowing themers to modify the sub menu classes output by `wp_nav_menu()`.

Props: csloisel, darthaud, raisonon.
Fixes: #36163.


git-svn-id: https://develop.svn.wordpress.org/trunk@40537 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/class-walker-nav-menu.php | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/class-walker-nav-menu.php b/src/wp-includes/class-walker-nav-menu.php
index 4c1a1f2c91..c97188b473 100644
--- a/src/wp-includes/class-walker-nav-menu.php
+++ b/src/wp-includes/class-walker-nav-menu.php
@@ -58,7 +58,22 @@ class Walker_Nav_Menu extends Walker {
 			$n = "\n";
 		}
 		$indent = str_repeat( $t, $depth );
-		$output .= "{$n}{$indent}<ul class=\"sub-menu\">{$n}";
+
+		/**
+		 * Filters the CSS class(es) applied to a menu list element.
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array    $classes The CSS classes that are applied to the menu `<ul>` element.
+		 * @param stdClass $args    An object of `wp_nav_menu()` arguments.
+		 * @param int      $depth   Depth of menu item. Used for padding.
+		 */
+
+		$classes = array( 'sub-menu' );
+		$classes = apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth );
+		$class_names = join( ' ', $classes );
+
+		$output .= "{$n}{$indent}<ul class='" . esc_attr( $class_names ) . "'>{$n}";
 	}
 
 	/**