Open Radar

 
Summary:
The "Slide Over and Split View Quick Start" guide states that "Only the primary app [...] is eligible to work with a second physical screen".

If an application is started in slide-over mode, only the main screen is present in the array returned by [UIScreen screens]. If the application is running as the primary application, both the main screen and airplay display are present in the array. This is correct, expected behaviour.

However.. If an application starts as the primary application, returns to the background, and then is brought into slide-over or split mode as the secondary application, [UIScreen screens] returns both displays, implying both are available to the application.

Attempting to display a window on this secondary display fails silently, so the application has no way to determine whether to display alternate content on the main display or not.

Steps to Reproduce:
1) Connect to an Airplay display
2) Start the sample application. Details including "found 2 screens" will be printed
3) Send the application to the background and start another application (e.g. Notes)
4) Bring the sample application back into slide-over mode
5) More details will be printed, including "found 2 screens" again.

And for the expected result:
6) Terminate the sample application
7) Bring the sample application into slide-over mode from a cold start. "Found 1 screen" will be printed.

Expected Results:
[UIScreen screens] should consistently return the accessible screens based on the current application state and not previous states.

Actual Results:
[UIScreen screens] returns differing results on a cold start versus starting as the primary app, backgrounding and re-entering as the secondary app.

Version:
iOS 9.0, iOS 9.0.1, iOS 9.1

Configuration:
iPad Air 2, iOS 9.0. iPad Mini 4, iOS 9.0.1. iPad Mini 4, iOS 9.1. All connected to a 2nd Generation Apple TV.