WordPress at a glance
function is not described

_custom_header_background_just_in_time() WP 3.4.0

Registers the internal custom header and background routines.

This is an internal function for using it by WP core itself. It's not recommended to use this function in your code.

No Hooks.

Return

null. Nothing.

Usage

_custom_header_background_just_in_time();

Notes

  • Global. Custom_Image_Header. $custom_image_header
  • Global. Custom_Background. $custom_background

Changelog

Since 3.4.0 Introduced.

Code of _custom_header_background_just_in_time() WP 5.7.2

<?php
function _custom_header_background_just_in_time() {
	global $custom_image_header, $custom_background;

	if ( current_theme_supports( 'custom-header' ) ) {
		// In case any constants were defined after an add_custom_image_header() call, re-run.
		add_theme_support( 'custom-header', array( '__jit' => true ) );

		$args = get_theme_support( 'custom-header' );
		if ( $args[0]['wp-head-callback'] ) {
			add_action( 'wp_head', $args[0]['wp-head-callback'] );
		}

		if ( is_admin() ) {
			require_once ABSPATH . 'wp-admin/includes/class-custom-image-header.php';
			$custom_image_header = new Custom_Image_Header( $args[0]['admin-head-callback'], $args[0]['admin-preview-callback'] );
		}
	}

	if ( current_theme_supports( 'custom-background' ) ) {
		// In case any constants were defined after an add_custom_background() call, re-run.
		add_theme_support( 'custom-background', array( '__jit' => true ) );

		$args = get_theme_support( 'custom-background' );
		add_action( 'wp_head', $args[0]['wp-head-callback'] );

		if ( is_admin() ) {
			require_once ABSPATH . 'wp-admin/includes/class-custom-background.php';
			$custom_background = new Custom_Background( $args[0]['admin-head-callback'], $args[0]['admin-preview-callback'] );
		}
	}
}