Source
File: wp-admin/includes/class-custom-background.php
public function init() {
$page = add_theme_page( __( 'Background' ), __( 'Background' ), 'edit_theme_options', 'custom-background', array( $this, 'admin_page' ) );
if ( ! $page ) {
return;
}
add_action( "load-{$page}", array( $this, 'admin_load' ) );
add_action( "load-{$page}", array( $this, 'take_action' ), 49 );
add_action( "load-{$page}", array( $this, 'handle_upload' ), 49 );
if ( $this->admin_header_callback ) {
add_action( "admin_head-{$page}", $this->admin_header_callback, 51 );
}
}