From 7ed04565bb160c3df4629497ce298811dc97fecc Mon Sep 17 00:00:00 2001
From: Lance Willett <nanobar@gmail.com>
Date: Tue, 16 Apr 2013 22:35:55 +0000
Subject: [PATCH] Twenty Thirteen: further performance for functions.js scroll
 event callback, props obenland. See #23875.

git-svn-id: http://core.svn.wordpress.org/trunk@24005 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 .../themes/twentythirteen/functions.php       |  2 +-
 .../themes/twentythirteen/js/functions.js     | 33 ++++++++++---------
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/wp-content/themes/twentythirteen/functions.php b/wp-content/themes/twentythirteen/functions.php
index 03fffcc096..41065405a0 100644
--- a/wp-content/themes/twentythirteen/functions.php
+++ b/wp-content/themes/twentythirteen/functions.php
@@ -223,7 +223,7 @@ function twentythirteen_scripts_styles() {
 		wp_enqueue_script( 'jquery-masonry' );
 
 	// Loads JavaScript file with functionality specific to Twenty Thirteen.
-	wp_enqueue_script( 'twentythirteen-script', get_template_directory_uri() . '/js/functions.js', array( 'jquery' ), '20130211', true );
+	wp_enqueue_script( 'twentythirteen-script', get_template_directory_uri() . '/js/functions.js', array( 'jquery' ), '20130416', true );
 
 	// Loads our main stylesheet.
 	wp_enqueue_style( 'twentythirteen-style', get_stylesheet_uri() );
diff --git a/wp-content/themes/twentythirteen/js/functions.js b/wp-content/themes/twentythirteen/js/functions.js
index d3f8c0e876..0c9a8d1c10 100644
--- a/wp-content/themes/twentythirteen/js/functions.js
+++ b/wp-content/themes/twentythirteen/js/functions.js
@@ -5,12 +5,13 @@
  */
 
 ( function( $ ) {
-	var html          = $( 'html' ),
-	    body          = $( 'body' ),
-	    navbar        = $( '#navbar' ),
-	    _window       = $( window ),
-	    navbarOffset  = -1,
-	    toolbarOffset = body.is( '.admin-bar' ) ? 28 : 0,
+	var html               = $( 'html' ),
+	    body               = $( 'body' ),
+	    navbar             = $( '#navbar' ),
+	    _window            = $( window ),
+	    toolbarOffset      = body.is( '.admin-bar' ) ? 28 : 0,
+	    navbarOffset       = navbar.offset().top - toolbarOffset,
+	    scrollOffsetMethod = ( typeof window.scrollY === 'undefined' ),
 	    adjustFooter,
 	    adjustAnchor;
 
@@ -48,16 +49,16 @@
 	/**
 	 * Displays the fixed navbar based on screen position.
 	 */
-	_window.on( 'scroll.twentythirteen', function() {
-		var scrollOffset = ( typeof window.scrollY === 'undefined' ) ? document.documentElement.scrollTop : window.scrollY;
-		if ( navbarOffset < 0 )
-			navbarOffset = navbar.offset().top - toolbarOffset;
-
-		if ( scrollOffset >= navbarOffset && _window.innerWidth() > 644 )
-			html.addClass( 'navbar-fixed' );
-		else
-			html.removeClass( 'navbar-fixed' );
-	} );
+	if ( _window.innerWidth() > 644 ) {
+		_window.on( 'scroll.twentythirteen', function() {
+			var scrollOffset = scrollOffsetMethod ? document.documentElement.scrollTop : window.scrollY;
+	
+			if ( scrollOffset > navbarOffset )
+				html.addClass( 'navbar-fixed' );
+			else
+				html.removeClass( 'navbar-fixed' );
+		} );
+	}
 
 	/**
 	 * Allows clicking the navbar to scroll to top.