Allow begin observing the keyboard notifications without the view being loaded

[kyleve]

So this is kinda gross, but, no other great solution.

Problem: We receive keyboard frames based on system NSNotifcations. If the keyboard is already visible when a list is created, we previously had no way of knowing what the current keyboard frame was, and thus, we had no way of knowing how to adjust the contentInset of the list view to avoid keyboard overlap.

Solution: On app startup, register for keyboard notifications, and use a single shared observer.

[kylebshr]

Any reason not to use a module initializer (like the second answer here) and set this up automatically?

[kyleve]

@kylebshr: Do you mean the static void __attribute__ ((constructor)) Initer() bit?

[kylebshr]

Yep - won't that get called when the module is loaded? (disclaimer I have no idea what I'm talking about)

[kyleve]

@kylebshr So the C-style constructors should generally be avoided in this kind of case; since this is calling across ObjC types and across frameworks. If you're doing purely local, C-only setup, the constructor call would work, but in this case, we need to wait until the runtime gives us a chance to set things up.

[kyleve]

@kylebshr: Mind giving this a look today? I'd like to merge today to unblock Jason

[kylebshr]

I don't know a ton about exclusive access, but isn't this a non-issue because all these changes would happen on a main thread? I don't see how there are conflicting accesses

[kyleve]

It can happen due to nested accesses as well, eg:

self.things.forEach { thing in
    self.things.append(newThing)
}

Though after testing it, this no longer happens for arrays; I think they're smart about arrays now, likely since they're COW internally (but this was an issue with the original exclusive access implementation). Going to remove this bit!

https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md

[kyleve]

(I ran into this last week with the VisibleContent struct, which is why I did this here, but yeah, seems like arrays are somehow immune, as are im guessing all the stdlib collections.)

[kylebshr]

Do you think the logging is still needed now that set up is automatic? Is there a case where this wouldn't get set up?

[kyleve]

Since I'm doing something that's a little clever to get the registration working, I wanted to add an obvious log statement if it stops working for whatever reason.

[kylebshr]

Reasonable 👍

[kylebshr]

@kyleve totally looked last night and forgot to approve, had some questions but no need to block