BackgroundWindow.m

UIWindow *window = [[UIWindow alloc] initWithFrame:rootWindow.bounds];
window.hidden = NO;
window.windowLevel = UIWindowLevel_Background;
window.opaque = YES;
window.backgroundColor = UIColor.ows_materialBlueColor;

ScreenLockViewController *viewController = [ScreenLockViewController new];
viewController.delegate = self;
window.rootViewController = viewController;

self.screenBlockingWindow = window;
self.screenBlockingViewController = viewController;