WordPress at a glance
filter is not described

pre_user_display_name filter-hook . WP 2.0.3

Filters a user's display name before the user is created or updated.

Usage

add_filter( 'pre_user_display_name', 'filter_function_name_472' );
function filter_function_name_472( $display_name ){
	// filter...

	return $display_name;
}
$display_name(string)
The user's display name.

Where the hook is called

wp_insert_user()
wp-includes/user.php 1627
$display_name = apply_filters( 'pre_user_display_name', $display_name );

Where the hook is used (in WP core)

Does not used.