What should an app do with an instance of GKGameCenterViewController when the app transitions to the background? Currently, my app just leaves it in place, displayed on top in full screen. Most of the time when my app resumes to the foreground, the GKGameCenterViewController is still displayed and is functional. However, sometimes when the app resumes, the GKGameCenterViewController's view has vanished and, additionally, my app doesn't receive a GK authentication event, so effectively it is "hung". This seems to happen most often when the app has been in the background a while, such as overnight. The app is still in memory, however, not starting cold. I would like to leave the GKGameCenterViewController/view in place when the app is backgrounded since the player may return to the game quickly and be right back where they left off. And most of the time that works. However, I need to solve the problem for the times it doesn't as I described above. Is there any guidance on what to do with a GKGameCenterViewController (or any GK controller for that matter) when an app goes into the background?

I'd like to be able to associate some data with each CapturedRoom scan and maintain those associations when CapturedRooms are combined in a CapturedStructure. For example, in the delegate method captureView(didPresent:error:), I'd like to associate external data with the CapturedRoom. That's easy enough to do with a Swift dictionary, using the CapturedRoom's identifier as the key to the associated data. However, when I assemble a list of CapturedRooms into a CapturedStructure using StructureBuilder.init(from:), the rooms in the output CapturedStructure have different identifiers so their associations to the external data are lost. Is there any way to track or identify CapturedRoom objects that are input into a StructureBuilder to the rooms in the CapturedStructure output? I looked for something like a "userdata" property on a CapturedRoom that might be preserved, but couldn't find one. And since the room identifiers change when they are built into a CapturedStructure, I don't see an obvious way to do this.

Is there any working sample code that demonstrates the 2nd multiroom approach, i.e., capture multiple rooms over more than one scan session using the ARWorldMap approach that's described in the WWDC presentation? I've tried working from the code snippets provided in the transcript but cannot get it working reliably enough.

Recently (I'm not sure exactly when), the "Sign in to Game Center" banner started appearing at the top of my app when the app sets the GC authentication handler and there is no Game Center player currently signed in on the device: So far so good. But if the banner is tapped, a full "Sign In to Game Center" modal view automatically appears and covers the app without notification: This is not the sign-in view controller that the GC authentication handler normally passes when a player is not signed in, which previously gave my app control over when to present it. My app is unaware that it is covered by this new sign-in screen. Is there any way for my app to know when the user taps the "Sign In" banner and causes this new automatic sign-in screen to appear? I need to pause my game while it is covered up. In general, is there a way for my view controller to be notified when it has been covered by a modal view controller that's outside my app's control?