Per-room/space presence

[ara4n]

Our presence API only gives the ability to declare presence on a global basis. From a privacy point of view, this is not ideal: what if i just want to tell users in a given room that i am currently online/offline (or a given space) without telling the world?

For instance, I might want to tell the users in a given room that my client is currently alive, if I've also stated that I'm currently participating in a video conference in that room (for matrix-native confs). I might also want to support richer presence info (eg which conference I am in from which device) - although this could be done by setting room state on a profile-as-room (but it's a bit clunky given it would need to be synced with presence online/offline state to be meaningful).

[ShadowJonathan]

From a usability point of view, global presence is useful as it's unknown who wants to know if i'm online, or if that information would be needed at some point. (This is discord, which cheats this principle a little by always grabbing info for all friends, but then only for the top X users in a memberlist)

Though what could also be interesting is being able to provide only vague info (has been online recently, just now, or "a long time ago", this is telegram's approach), or "tiers" of information disclosure (contacts vs non-contacts).

While above is probably not in-scope for per-spaces presence, maybe it's wise to set up a generic presence system which will only allow broadcasting of certain bits of info for certain users. A thing like being able to tell a server that the presence info is only meant for users A, B, and C, and that users B and C can see property X, and only C property Y, while all can see Z.