Stop overlay UIWindow from controlling the status bar - ios

Question

I'm creating a temporary UIWindow, on top of the main window, to show some small amount of data overlaid on the rest of my app. This information should not affect the status bar in any way. Note that the overlay window can be launched from a non-view controller context, meaning that the current view controller at the top of the stack of the main window might not be aware of the existence of the overlay window.
Unfortunately, as soon as I do overlayWindow.isHidden = false, it transfers control of the status bar (its style and whether it's hidden) to the root view controller of my overlay window, and I can't work out how to stop it.
Alternatively, I could just "remember" the previous state of the status bar and have my overlay root view controller output those, but there doesn't seem to be a good method to find out the current state and visibility of the status bar in iOS 13, at least which takes into account modally presented view controllers using the new sheet effect.
How can I have my overlay UIWindow reliably not affect the status bar?
Edit: I've prepared a small test case: https://github.com/Aquilosion/TestWindowView
The test case shows a view controller which changes its status bar appearance every second. You can open the same view controller again in a modal, and despite it also requesting status bar changes, iOS correctly locks the status bar white because the view controller never reaches it in sheet mode. Opening the window overlay currently always shows a black status bar, despite whether there's a modal presented or not. I attempt to set the status bar child to be the main window's root view controller's status bar child. Ideally, iOS would respect this and continue to change the status bar style while the overlay window was visible.

Answer 1

You can override a property childForStatusBarStyle of the root view controller of the overlay window.
class YourRootController { // root of the overlay window
var controllerToInheritStatusAttributesFrom: UIViewController?
override var childForStatusBarStyle: UIViewController? {
return controllerToInheritStatusAttributesFrom
}
}
// Call this from any place of the app, where you show the overlay window
if let controller = overlayWindow.rootViewController as? YourViewController {
controller.controllerToInheritStatusAttributesFrom = // needed controller, which lies underneath
controller.setNeedsStatusBarAppearanceUpdate()
}
I'm not sure it will help, considering that controllers will be in different windows, but it's worth a try.
I made your case work, just update the code:
private func updateStyle() {
styleIndex += 1
setNeedsStatusBarAppearanceUpdate()
overlayWindow?.rootViewController?.setNeedsStatusBarAppearanceUpdate()
}
Add this to MainViewController:
required init?(coder: NSCoder) {
super.init(coder: coder)
modalPresentationCapturesStatusBarAppearance = true
}
override var preferredStatusBarStyle: UIStatusBarStyle {
if self.presentingViewController != nil {
return .lightContent
}
return Self.styles[styleIndex % Self.styles.count]
}