objc code used to show screen properties of iOS device

gistfile1.txt

- (void)viewDidLoad {
    [super viewDidLoad];

    __auto_type appLabel = [UILabel new];
    appLabel.translatesAutoresizingMaskIntoConstraints = NO;
    appLabel.text = NSBundle.mainBundle.executablePath.lastPathComponent;
    [self.view addSubview:appLabel];

    __auto_type createLabel = ^{
        __auto_type l = [UILabel new];
        l.numberOfLines = 0;
        return l;
    };
    __auto_type screen = UIScreen.mainScreen;

    __auto_type scaleLabel = createLabel();
    scaleLabel.text = [NSString stringWithFormat:@"traits scale %.1lf\nscreen scale %.1lf\nscreen nativeScale %.1lf", self.traitCollection.displayScale, screen.scale, screen.nativeScale];

    __auto_type sizeLabel = createLabel();
    sizeLabel.text = [NSString stringWithFormat:@"fixed bounds %@\nnativeBounds %@", NSStringFromCGSize(screen.fixedCoordinateSpace.bounds.size), NSStringFromCGSize(screen.nativeBounds.size)];

    __auto_type verticalStack = [[UIStackView alloc] initWithArrangedSubviews:@[scaleLabel, sizeLabel]];
    verticalStack.axis = UILayoutConstraintAxisVertical;
    verticalStack.spacing = 10;
    verticalStack.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:verticalStack];

    [NSLayoutConstraint activateConstraints:@[[appLabel.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor],
                                              [appLabel.topAnchor constraintEqualToAnchor:self.topLayoutGuide.bottomAnchor],
                                              [verticalStack.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor],
                                              [verticalStack.centerYAnchor constraintEqualToAnchor:self.view.centerYAnchor]]];
}