printing

Documents printed in the session, on their way to a browser.

The session's print queue, Selkies, is a CUPS scheduler run as this user whose backend writes each job as a PDF into the print spool. The spool is watched, every document that lands whole is announced to the controller pages of the active transport, and a page fetches it once through /api/print/<name>, which takes it out of the spool. The spool therefore holds what no page has taken yet, and a page connecting later is told about that too.