At what stage of the component lifecycle can you safely obtain current information about the window or its frame?

Current information about the window's or its frame's state in iOS can be safely obtained in the viewDidLayoutSubviews method of a view controller (UIViewController). At this stage, all views already have correct sizes and positions, as the layout process has been completed by the system. For example, you can get precise sizes of view.window or view.frame here.

Example:

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    if let window = self.view.window {
        print("Window size: \(window.frame.size)")
    }
    print("View size: \(self.view.frame.size)")
}