ArgumentNullException on UIApplication.SupportedInterfaceOrientationsForWindow

[MichaelLHerman]

Apple platform

iOS

Framework version

net9.0-*

Affected platform version

MAUI 9.0.21

Description

Getting a crash report with the following stack trace

System.ArgumentNullException: ArgumentNull_Generic Arg_ParamName_Name, window
  ?, in NativeHandle NativeObjectExtensions.GetNonNullHandle(INativeObject, string)
  ?, in UIInterfaceOrientationMask UIApplication.SupportedInterfaceOrientationsForWindow(UIWindow)
  ?, in UIInterfaceOrientationMask AppDelegate.GetSupportedInterfaceOrientations(UIApplication application, UIWindow forWindow)
  ?, in UIInterfaceOrientationMask __Registrar_Callbacks__.callback_11_CadabraMobile_iOS_AppDelegate_GetSupportedInterfaceOrientations(IntPtr pobj, IntPtr sel, IntPtr p0, IntPtr p1, IntPtr* exception_gchandle)

Apple marks the window parameter as nullable, but the generated code seems to be doing a null check.

Steps to Reproduce

My app is overriding supportedInterfaceOrientationsForWindow because we disallow rotation on all but one screen, so this can not be hardcoded in the info.plist

        [Export("application:supportedInterfaceOrientationsForWindow:")]
        public UIInterfaceOrientationMask GetSupportedInterfaceOrientations(UIApplication application,
            UIWindow? forWindow)
        {
            if (forWindow?.WindowScene != null && AllowRotation)
            {
                return UIInterfaceOrientationMask.All;
            }

            return application.SupportedInterfaceOrientationsForWindow(forWindow);
        }

Crash is being reported for iPad Pro (12.9-inch) (3rd generation) running iOS 17.6, app in foreground

Did you find any workaround?

No response

Relevant logs

No response

[rolfbjarne]

According to Apple's documentation, the window parameter to SupportedInterfaceOrientationForWindow can't be null: https://developer.apple.com/documentation/uikit/uiapplication/supportedinterfaceorientations(for:)?language=objc, so this looks correct.

[Export("application:supportedInterfaceOrientationsForWindow:")]
public UIInterfaceOrientationMask GetSupportedInterfaceOrientations(UIApplication application,
    UIWindow? forWindow)
{
    if (forWindow?.WindowScene != null && AllowRotation)
    {
        return UIInterfaceOrientationMask.All;
    }

	if (window is null)
		return UIInterfaceOrientationMask.Portrait; // or whatever is desired for your app when there's no window

    return application.SupportedInterfaceOrientationsForWindow(forWindow);
}

[MichaelLHerman]

@rolfbjarne I'm no iOS expert but I dont think the objective-c documentation has nullability info

See https://developer.apple.com/documentation/uikit/uiapplicationdelegate/application(_:didfinishlaunchingwithoptions:) as another example of a method with a nullable input parameter

launchOptions parameter can be null as shown in the Swift documentation but theres no indication in the Objective-C version of the page (that the pointer can be null).

See https://developer.apple.com/documentation/uikit/uiapplication/supportedinterfaceorientations(for:) (no query string, Swift documentation) that marks window parameter as nullable

The stack trace shows that clearly on some device under some conditions the method is being called with a null window

The xamarin wrapper for GetSupportedInterfaceOrientations is generated with window as not nullable and I assume that means its injecting NativeObjectExtensions.GetNonNullHandle which is throwing

[rolfbjarne]

OK, I see. I've prepared a fix, and this should be fixed in the next minor release.