This pipeline, called for every SPIP public page when it is displayed, accepts an array parameter containing the list of page headers. This therefore makes it possible to modify or add to those headers. It is called just before the affichage_final pipeline, which receives the text string output by this function.
This pipeline is called in ecrire/public.php, taking and returning an array parameter containing the various HTTP page headers, or the keys of the array corresponding to the desired header name.
$page['entetes'] = pipeline('affichage_entetes_final', $page['entetes']);
// This array will contain for example:
// $page['entetes']['Content-Language'] ...