iOS 6 shouldAutorotate: is NOT being called

See if you are getting the following error when your App starts.

Application windows are expected to have a root view controller at the end of application launch

If so the way to fix it is by making the following change in the AppDelegate.m file (although there seem to be a number of answers how to fix this):

// Replace
[self.window addSubview:[navigationController view]];  //OLD

// With
[self.window setRootViewController:navigationController];  //NEW

After this shouldAutoRotate should be correctly called.

When using UINavigationController as the basis for an app I use the following subclass to give me the flexibility to allow the top most child viewcontroller to decide about rotation.

@interface RotationAwareNavigationController : UINavigationController

@end

@implementation RotationAwareNavigationController

-(NSUInteger)supportedInterfaceOrientations {
    UIViewController *top = self.topViewController;
    return top.supportedInterfaceOrientations;
}

-(BOOL)shouldAutorotate {
    UIViewController *top = self.topViewController;
    return [top shouldAutorotate];
}

@end

That method is not the correct way to determine that. The correct method is willRotateToInterfaceOrientation:duration:

The should rotate to orientation (as opposed to shouldAutorotate) method is deprecated and will no longer be called as of iOS 6, but it was not meant to be used the way you were using it anyway.

EDIT Response to repeated downvotes. Please explain why using the method I indicated is not an (to quote OP) "indication that a rotation is about to occur." The content of the question and the title are mismatched.

It looks that on iOS 6 the container navigations controller doesn't consult child view controllers when rotating:

in iOS 6 release notes :

Now, iOS containers (such as UINavigationController) do not consult their children to determine whether they should autorotate. By default, an app and a view controller’s supported interface orientations are set to UIInterfaceOrientationMaskAll for the iPad idiom and UIInterfaceOrientationMaskAllButUpsideDown for the iPhone idiom.

This behavior is easy to test. What I did is to use the same custom view controller

1. first case as a main view controller
2. second case as a child of a UIPageViewController

In the first case everything is decided in the custom navigation controller by the combination of shouldAutorotate and supportedInterfaceOrientations given that supportedInterfaceOrientations agrees with the supported orientations of the application.

In the second case even if the supportedInterfaceOrientations of the custom view controller is called by the UIPageViewController the return value is not taken in to consideration. It works if the two methods are overwritten in a subclass of the UIPageViewController. I am not sure about the side effects of that as this class is not supposed to be subclassed.