Whether there is a daemon to talk to.
g_paste_daemon_presence_ready once one serves a history; g_paste_daemon_presence_starting while one owns the bus name without serving anything yet, or while a client that follows it ( follow_daemon) has asked for one, or saw one go within the last second or so; g_paste_daemon_presence_absent otherwise.
A client that follows the daemon reports absent about a second after a daemon leaves nobody owning the name, and two minutes into an owner that never serves a history, each new owner getting two minutes of its own. One that does not follow has neither timer: absent the moment nobody owns the name, and starting for as long as an owner serves nothing. Either kind turns ready by itself when a daemon comes back.
A daemon taking the name over straight from another is no exception: the presence leaves ready the moment the bus hands the name over, and comes back once the new daemon serves its history. Whatever was read from the daemon before -- its histories, its items, its version -- is the old one's, and anything still out to it is best given up on that edge.
Calls made while it is not ready start a daemon: the bus activates one on the first call to reach it. A caller that must not do that behind the user's back holds off until it is.