get_custom_header_markup() WordPress Function

function get_custom_header_markup() {
	if ( ! has_custom_header() && ! is_customize_preview() ) {
		return '';
	}

	return sprintf(
		'<div id="wp-custom-header" class="wp-custom-header">%s</div>',
		get_header_image_tag()
	);
}
Uses	Description
wp-includes/theme.php:has_custom_header()	Checks whether a custom header is set or not.
wp-includes/theme.php:get_header_image_tag()	Creates image tag markup for a custom header image.
wp-includes/theme.php:is_customize_preview()	Whether the site is being previewed in the Customizer.