gistfile1.m

- (void)reposition {
  // https://developer.apple.com/library/ios/#qa/qa2010/qa1688.html
  // tl;dr Only the first subview in the window receives orientation changes.
  // So we apply a transform manually to rotate the view, and change the origin of the frame so
  // that it remains in a top-center position for the user.
  UIInterfaceOrientation orientation =
      [UIApplication sharedApplication].statusBarOrientation;
  UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];

  CGAffineTransform viewTransform = CGAffineTransformIdentity;
  CGFloat xPosition = ceilf((keyWindow.frame.size.width - kOverlaySize.width) / 2.0);
  CGFloat yPosition = kTopMargin;
  CGRect frame = CGRectZero;

  CGFloat windowWidth = keyWindow.frame.size.width;
  CGFloat windowHeight = keyWindow.frame.size.height;

  switch (orientation) {
    case UIInterfaceOrientationPortrait:
      frame = CGRectMake(xPosition, yPosition, kOverlaySize.width, kOverlaySize.height);
      break;

    case UIInterfaceOrientationPortraitUpsideDown:
      // Rotate the view 180 degrees, and position on bottomY-centerX of original screen.
      viewTransform = CGAffineTransformMakeRotation(M_PI);
      yPosition = windowHeight - kTopMargin - kOverlaySize.height;
      frame = CGRectMake(xPosition, yPosition, kOverlaySize.width, kOverlaySize.height);
      break;

    case UIInterfaceOrientationLandscapeLeft:  // Home button is on the left
      // Rotate view by -90 degrees, and position on leftX-centerY of original screen.
      viewTransform = CGAffineTransformMakeRotation(-M_PI_2);
      xPosition = kTopMargin;
      yPosition = ceilf((windowHeight - kOverlaySize.width) / 2.0);
      frame = CGRectMake(xPosition, yPosition, kOverlaySize.height, kOverlaySize.width);
      break;

    case UIInterfaceOrientationLandscapeRight:  // Home button is on the right
      // Rotate view by 90 degrees, and position on rightX-centerY of original screen.
      viewTransform = CGAffineTransformMakeRotation(M_PI_2);
      xPosition = windowWidth - kTopMargin - kOverlaySize.height;
      yPosition = ceilf((windowHeight - kOverlaySize.width) / 2.0);
      frame = CGRectMake(xPosition, yPosition, kOverlaySize.height, kOverlaySize.width);
      break;

    default:
      [self hide];
  }

  self.transform = viewTransform;
  self.frame = frame;
}