Fix syncing modal stack when the window is created/recreated

src/Compatibility/Core/src/Android/AppCompat/FormsAppCompatActivity.cs

@@ -294,7 +294,7 @@ protected override void OnNewIntent(Intent intent)
 
 		protected override void OnPause()
 		{
-			_layout.HideKeyboard(true);
+			_layout.HideKeyboard();
 
 			// Stop animations or other ongoing actions that could consume CPU
 			// Commit unsaved changes, build only if users expect such changes to be permanently saved when thy leave such as a draft email

src/Compatibility/Core/src/iOS/Platform.cs

@@ -543,7 +543,7 @@ async Task PresentModal(Page modal, bool animated)
 				SetRenderer(modal, modalRenderer);
 			}
 
-			var wrapper = new ModalWrapper(modalRenderer.Element.Handler as IPlatformViewHandler);
+			var wrapper = new ControlsModalWrapper(modalRenderer.Element.Handler as IPlatformViewHandler);
 
 			if (_modals.Count > 1)
 			{

src/Controls/src/Core/Compatibility/Handlers/NavigationPage/iOS/NavigationRenderer.cs

@@ -150,6 +150,8 @@ public override void ViewWillAppear(bool animated)
 
 		public override void ViewDidDisappear(bool animated)
 		{
+			CompletePendingNavigation(false);
+
 			base.ViewDidDisappear(animated);
 
 			if (!_appeared || Element == null)
@@ -379,9 +381,32 @@ void FindParentFlyoutPage()
 				_parentFlyoutPage = flyoutDetail;
 		}
 
+		TaskCompletionSource<bool> _pendingNavigationRequest;
+		ActionDisposable _removeLifecycleEvents;
+
+		void CompletePendingNavigation(bool success)
+		{
+			if (_pendingNavigationRequest is null)
+				return;
+
+			_removeLifecycleEvents?.Dispose();
+			_removeLifecycleEvents = null;
+
+			var pendingNavigationRequest = _pendingNavigationRequest;
+			_pendingNavigationRequest = null;
+
+			BeginInvokeOnMainThread(() =>
+			{
+				pendingNavigationRequest?.TrySetResult(success);
+				pendingNavigationRequest = null;
+			});
+		}
+
 		Task<bool> GetAppearedOrDisappearedTask(Page page)
 		{
-			var tcs = new TaskCompletionSource<bool>();
+			CompletePendingNavigation(false);
+
+			_pendingNavigationRequest = new TaskCompletionSource<bool>();
 
 			_ = page.ToPlatform(MauiContext);
 			var renderer = (IPlatformViewHandler)page.Handler;
@@ -392,24 +417,24 @@ Task<bool> GetAppearedOrDisappearedTask(Page page)
 			EventHandler appearing = null, disappearing = null;
 			appearing = (s, e) =>
 			{
-				parentViewController.Appearing -= appearing;
-				parentViewController.Disappearing -= disappearing;
-
-				BeginInvokeOnMainThread(() => { tcs.SetResult(true); });
+				CompletePendingNavigation(true);
 			};
 
 			disappearing = (s, e) =>
+			{
+				CompletePendingNavigation(false);
+			};
+
+			_removeLifecycleEvents = new ActionDisposable(() =>
 			{
 				parentViewController.Appearing -= appearing;
 				parentViewController.Disappearing -= disappearing;
-
-				BeginInvokeOnMainThread(() => { tcs.SetResult(false); });
-			};
+			});
 
 			parentViewController.Appearing += appearing;
 			parentViewController.Disappearing += disappearing;
 
-			return tcs.Task;
+			return _pendingNavigationRequest.Task;
 		}
 
 		void HandlePropertyChanged(object sender, PropertyChangedEventArgs e)

src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellSectionRenderer.cs

@@ -156,6 +156,29 @@ internal bool SendPop()
 			return false;
 		}
 
+		public override void ViewDidDisappear(bool animated)
+		{
+			// If this page is removed from the View Hierarchy we need to resolve any
+			// pending navigation operations
+			var sourcesToComplete = new List<TaskCompletionSource<bool>>();
+
+			foreach (var item in _completionTasks.Values)
+			{
+				sourcesToComplete.Add(item);
+			}
+
+			_completionTasks.Clear();
+
+			foreach (var source in sourcesToComplete)
+				source.TrySetResult(false);
+
+			_popCompletionTask?.TrySetResult(false);
+			_popCompletionTask = null;
+
+
+			base.ViewDidDisappear(animated);
+		}
+
 		public override void ViewWillAppear(bool animated)
 		{
 			if (_disposed)

src/Controls/src/Core/Compatibility/Handlers/iOS/DisposeHelpers.cs

@@ -26,7 +26,7 @@ internal static void DisposeModalAndChildHandlers(this Maui.IElement view)
 				{
 					if (renderer.ViewController != null)
 					{
-						if (renderer.ViewController.ParentViewController is Platform.ModalWrapper modalWrapper)
+						if (renderer.ViewController.ParentViewController is Platform.ControlsModalWrapper modalWrapper)
 							modalWrapper.Dispose();
 					}
 

src/Controls/src/Core/HandlerImpl/Window/Window.Impl.cs

@@ -417,16 +417,19 @@ internal void FinishedAddingWindowToApplication(Application application)
 
 		void SendWindowAppearing()
 		{
-			Page?.SendAppearing();
+			if (Navigation.ModalStack.Count == 0)
+				Page?.SendAppearing();
 		}
 
 		void SendWindowDisppearing()
 		{
-			Page?.SendDisappearing();
+			if (Navigation.ModalStack.Count == 0)
+				Page?.SendDisappearing();
+
 			IsActivated = false;
 		}
 
-		void OnModalPopped(Page modalPage)
+		internal void OnModalPopped(Page modalPage)
 		{
 			int index = _visualChildren.IndexOf(modalPage);
 			_visualChildren.Remove(modalPage);
@@ -438,15 +441,15 @@ void OnModalPopped(Page modalPage)
 			VisualDiagnostics.OnChildRemoved(this, modalPage, index);
 		}
 
-		bool OnModalPopping(Page modalPage)
+		internal bool OnModalPopping(Page modalPage)
 		{
 			var args = new ModalPoppingEventArgs(modalPage);
 			ModalPopping?.Invoke(this, args);
 			Application?.NotifyOfWindowModalEvent(args);
 			return args.Cancel;
 		}
 
-		void OnModalPushed(Page modalPage)
+		internal void OnModalPushed(Page modalPage)
 		{
 			_visualChildren.Add(modalPage);
 			var args = new ModalPushedEventArgs(modalPage);
@@ -455,21 +458,25 @@ void OnModalPushed(Page modalPage)
 			VisualDiagnostics.OnChildAdded(this, modalPage);
 		}
 
-		void OnModalPushing(Page modalPage)
+		internal void OnModalPushing(Page modalPage)
 		{
 			var args = new ModalPushingEventArgs(modalPage);
 			ModalPushing?.Invoke(this, args);
 			Application?.NotifyOfWindowModalEvent(args);
 		}
 
-		void OnPopCanceled()
+		internal void OnPopCanceled()
 		{
 			PopCanceled?.Invoke(this, EventArgs.Empty);
 		}
 
 		void IWindow.Created()
 		{
+			if (IsCreated)
+				throw new InvalidOperationException("Window was already created");
+
 			IsCreated = true;
+			IsDestroyed = false;
 
 			Created?.Invoke(this, EventArgs.Empty);
 			OnCreated();
@@ -478,13 +485,19 @@ void IWindow.Created()
 
 		void IWindow.Activated()
 		{
+			if (IsActivated)
+				throw new InvalidOperationException("Window was already activated");
+
 			IsActivated = true;
 			Activated?.Invoke(this, EventArgs.Empty);
 			OnActivated();
 		}
 
 		void IWindow.Deactivated()
 		{
+			if (!IsActivated)
+				throw new InvalidOperationException("Window was already deactivated");
+
 			IsActivated = false;
 			Deactivated?.Invoke(this, EventArgs.Empty);
 			OnDeactivated();
@@ -499,7 +512,12 @@ void IWindow.Stopped()
 
 		void IWindow.Destroying()
 		{
+			if (IsDestroyed)
+				throw new InvalidOperationException("Window was already destroyed");
+
 			IsDestroyed = true;
+			IsCreated = false;
+
 			SendWindowDisppearing();
 			Destroying?.Invoke(this, EventArgs.Empty);
 			OnDestroying();
@@ -613,8 +631,6 @@ void OnPageChanged(Page? oldPage, Page? newPage)
 				_menuBarTracker.Target = newPage;
 			}
 
-			ModalNavigationManager.SettingNewPage();
-
 			if (newPage != null)
 			{
 				newPage.HandlerChanged += OnPageHandlerChanged;
@@ -676,58 +692,14 @@ protected override IReadOnlyList<Page> GetModalStack()
 				return _owner.ModalNavigationManager.ModalStack;
 			}
 
-			protected override async Task<Page?> OnPopModal(bool animated)
+			protected override Task<Page?> OnPopModal(bool animated)
 			{
-				Page modal = _owner.ModalNavigationManager.ModalStack[_owner.ModalNavigationManager.ModalStack.Count - 1];
-				if (_owner.OnModalPopping(modal))
-				{
-					_owner.OnPopCanceled();
-					return null;
-				}
-
-				Page? nextPage;
-				if (modal.NavigationProxy.ModalStack.Count == 1)
-				{
-					nextPage = _owner.Page;
-				}
-				else
-				{
-					nextPage = _owner.ModalNavigationManager.ModalStack[_owner.ModalNavigationManager.ModalStack.Count - 2];
-				}
-
-				Page result = await _owner.ModalNavigationManager.PopModalAsync(animated);
-				result.Parent = null;
-				_owner.OnModalPopped(result);
-
-				modal.SendNavigatedFrom(new NavigatedFromEventArgs(nextPage));
-				nextPage?.SendNavigatedTo(new NavigatedToEventArgs(modal));
-
-				return result;
+				return _owner.ModalNavigationManager.PopModalAsync(animated);
 			}
 
-			protected override async Task OnPushModal(Page modal, bool animated)
+			protected override Task OnPushModal(Page modal, bool animated)
 			{
-				_owner.OnModalPushing(modal);
-
-				modal.Parent = _owner;
-
-				if (modal.NavigationProxy.ModalStack.Count == 0)
-				{
-					modal.NavigationProxy.Inner = this;
-					await _owner.ModalNavigationManager.PushModalAsync(modal, animated);
-					_owner.Page?.SendNavigatedFrom(new NavigatedFromEventArgs(modal));
-					modal.SendNavigatedTo(new NavigatedToEventArgs(_owner.Page));
-				}
-				else
-				{
-					var previousModalPage = modal.NavigationProxy.ModalStack[modal.NavigationProxy.ModalStack.Count - 1];
-					await _owner.ModalNavigationManager.PushModalAsync(modal, animated);
-					modal.NavigationProxy.Inner = this;
-					previousModalPage.SendNavigatedFrom(new NavigatedFromEventArgs(modal));
-					modal.SendNavigatedTo(new NavigatedToEventArgs(previousModalPage));
-				}
-
-				_owner.OnModalPushed(modal);
+				return _owner.ModalNavigationManager.PushModalAsync(modal, animated);
 			}
 		}
 	}

src/Controls/src/Core/Internals/MaybeNullWhenAttribute.cs

@@ -8,7 +8,7 @@
 
 namespace System.Diagnostics.CodeAnalysis
 {
-#if !NETCOREAPP
+#if !NETCOREAPP && !NETSTANDARD2_1_OR_GREATER
 
 	/// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
 	[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]