The only behaviour that should have changed here is that
presence is also set to online when switching back to the
tab/window.
Presence is not set to unavailable when coming back to the window/tab,
as that might be a bit invasive, but only when timing out.
Before, UserActivitity emitting actions meant that the user had very recently interaction with their hardware.
Now it means they are likely looking at the app.
You can attach a timer that is aborted when we think the user
stops looking at the page
(or hasn't touched their hardware for 2 minutes).
This works better than the previous approach for larger timeouts,
like the 30s we're about to implement for out-of-view RMs
When I was talking to Matthew about this the other day, we couldn't think of a
good reason why we should preserve the HS URL at logout. It introduces the
problem that, if a client is redirected after login as per MSC1730, and then
you log out, you'll then get a login screen for the wrong server.
So basically there's no reason to have an mx_hs_url/mx_is_url without an access
token, and we can remove the stuff which preserves it, and the stuff that
attempts to restore it.
This was noticed as a problem after `Unread.doesRoomHaveUnreadMessages` started being called a lot more frequently. Down the call stack, `shouldHideEvent` is called which used to call into the `SettingsStore` frequently, causing performance issues in many cases. The `SettingsStore` tries to be as fast as possible, however there's still code paths that make it less than desirable to use as the first condition in an AND condition. By not hitting the `SettingsStore` so often, we can shorten those code paths.
As for how much this improves things, I ran some profiling before and after this change. This was done on my massive 1200+ room account. Before it was possible to see nearly 2 seconds spent generating room lists where 20-130ms per room was spent figuring out if the room has unread messages. Afterwards, the room list was generating within ~330ms and each unread check taking 0-2ms. There's still room for improvement on generating the room list, however the significant gains here seem worth it.
They are now independent of each other. If both are specified in the config, the user will see an error and be prevented from logging in. The expected behaviour is that when a default server name is given, we do a .well-known lookup to find the default homeserver (and block the UI while we do this to prevent it from using matrix.org while we go out and find more information). If the config specifies just a default homeserver URL however, we don't do anything special.
