Orientation issue while presenting Modal ViewController

Question

Current scenario:

Right now I am showing a UIViewController using a segue with the style Modal and presentation Sheet. This Modal gets its superview bounds change, in order to have the dimensions I want, like this:

- (void)viewWillLayoutSubviews
{
    [super viewWillLayoutSubviews];
    self.view.superview.bounds = WHBoundsRect;
}

The only allowed orientations are UIInterfaceOrientationLandscapeLeft and UIInterfaceOrientationLandscapeRight. Since the Modal has some TextFields and the keyboard would be over the Modal itself, I am changing its center so it moves a bit to the top.

The problem:

What I am noticing right now, is that I am unable to work with the Y coordinate. In order for it move vertically (remember it's on landscape) I need to work with the X. The problem is that when it's UIInterfaceOrientationLandscapeLeft I need to come with a negative X. And when it's UIInterfaceOrientationLandscapeRight I need to come with a positive X. So it seems that the X/Y Coordinate System is "glued" to the top left corner while in Portrait and when an orientation occurs, it's still there:

What I have done

So I have something like this:

UIInterfaceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation];
NSInteger newX = 0.0f;

if (orientation == UIInterfaceOrientationLandscapeLeft)
{
  // Logic for calculating the negative X.
}
else
{
  // Logic for calculating the positive X.
}

It works exactly like I want, but it seems a very fragile implementation. Am I missing something? Is this the expected behaviour?

Answer 1

Update

I wrote a test project, you can find it here

Here is the interesting part, the modal view controller subclass code.

- (void)viewDidLoad
{
    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillAppear:) name:UIKeyboardWillShowNotification object:nil];
}

- (void)viewWillLayoutSubviews
{
    [super viewWillLayoutSubviews];
    self.view.superview.bounds = WHBoundsRect;
}

- (void)keyboardWillAppear:(NSNotification*)notification
{
    CGRect keyboardFrame = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];

    // Calculate keyboard frame in superview coordinates.
    // Origin will be in the upper left corner of the superview, so keyboard will have a negative x origin.
    CGRect keyboardFrameInSuperviewCoordinates = [self.view.superview convertRect:keyboardFrame fromView:nil];

    NSLog(@"Superview bounds: %@", NSStringFromCGRect(self.view.superview.bounds));
    NSLog(@"Keyboard frame in screen coordinates: %@", NSStringFromCGRect(keyboardFrame));
    NSLog(@"Keyboard frame in superview coordinates: %@", NSStringFromCGRect(keyboardFrameInSuperviewCoordinates));

    // The keyboard and the superview lay directly in a window, so we should do the math on window coordinates
    // Converting  to the superview system takes account of rotation, so now y is relative to current orientation
    CGRect windowCoordinatesInSuperviewSystem = [self.view.superview convertRect:self.view.superview.window.bounds fromView:nil];

    NSLog(@"Window frame in superview coords: %@", NSStringFromCGRect(windowCoordinatesInSuperviewSystem));


    // We calculate for how much the superview is hidden by the keyboard
    CGFloat hiddenPartHeight = CGRectGetMaxY(self.view.superview.bounds)-CGRectGetMinY(keyboardFrameInSuperviewCoordinates);
    NSLog(@"Superview is hidden by keyboard for %.0f points", hiddenPartHeight);

    // Now we just have to shift the superview frame to the top by 'hiddenPartHeight'.

    // Last step: calculate new superview frame in super-superview coordinate system.
    // To do that, we convert the superview frame relative to its coordinate system to super-superview coordinate system.
    CGRect superviewNewFrameInItsOwnCoordinateSystem = CGRectOffset(self.view.superview.bounds, 0, -hiddenPartHeight);
    CGRect superviewAbsoluteFrame = [self.view.superview convertRect:superviewNewFrameInItsOwnCoordinateSystem toView:self.view.superview.superview];

    NSLog(@"Superview new frame in its own coords: %@", NSStringFromCGRect(superviewNewFrameInItsOwnCoordinateSystem));
    NSLog(@"Superview new frame: %@", NSStringFromCGRect(superviewAbsoluteFrame));

    self.view.superview.frame = superviewAbsoluteFrame;
}