Status-bar agnostic UIView.safeAreaInsets API

UIView+TWSafeAreaInsets.swift

extension UIView {
    /// Convenience API to query iOS 11's `UIView.safeAreaInsets`'s insets (also known as "#NotEmbraceTheNotch")
    /// in a backwards compatible API.
    /// It also differs slightly from `UIView.safeAreaInsets` in that it only takes the "Notch" into account
    /// and not the status bar. This allows you to inset content so that the notch doesn't clip it, but you can still
    /// lay it out below the status bar.
    /// Note: This won't be as versitile as the UIKit version because it won't take into account things like navigation bars,
    /// but it should be correct for views in "full-screen" view controllers, where the UIKit `safeAreaInsets` API falls short.
    var twSafeAreaInsets: UIEdgeInsets {
         guard #available(iOS 11.0, *) else {
            return .zero
        }
        
        guard let window = self.window else {
            return .zero
        }
        
        /// We use the window because it only takes the notch into account, and not the status bar.
        let windowSafeAreaInsets = window.safeAreaInsets
        let viewFrameInWindowCoordinateSystem = self.convert(self.bounds, to: window)

        return UIEdgeInsets(
            top: viewFrameInWindowCoordinateSystem.minY < windowSafeAreaInsets.top ? windowSafeAreaInsets.top - viewFrameInWindowCoordinateSystem.minY : 0,
            left: viewFrameInWindowCoordinateSystem.minX < windowSafeAreaInsets.left ? windowSafeAreaInsets.left - viewFrameInWindowCoordinateSystem.minX : 0,
            bottom: viewFrameInWindowCoordinateSystem.maxY > window.frame.height - windowSafeAreaInsets.bottom ? viewFrameInWindowCoordinateSystem.maxY - window.frame.height + windowSafeAreaInsets.bottom : 0,
            right: viewFrameInWindowCoordinateSystem.maxX > window.frame.width - windowSafeAreaInsets.right ? viewFrameInWindowCoordinateSystem.maxX - window.frame.width + windowSafeAreaInsets.right : 0
        )
    }
}