fix: Ensure iOS NavigationBar renders when inside of AutoLayout (#525)

* fix: Ensure iOS NavigationBar renders when inside of AutoLayout

samples/Uno.Toolkit.Samples/Uno.Toolkit.Samples.Shared/Content/NestedSamples/M3MaterialNavigationBarSample_Primary.xaml.cs

@@ -6,6 +6,7 @@
 using System.Windows.Input;
 using Uno.Toolkit.Samples.Entities;
 using Uno.Toolkit.Samples.ViewModels;
+using Uno.UI;
 using Windows.Foundation;
 using Windows.Foundation.Collections;
 #if IS_WINUI
@@ -26,21 +27,16 @@
 using Windows.UI.Xaml.Navigation;
 #endif
 
-// The Blank Page item template is documented at https://go.microsoft.com/fwlink/?LinkId=234238
-
 namespace Uno.Toolkit.Samples.Content.NestedSamples
 {
-    /// <summary>
-    /// An empty page that can be used on its own or navigated to within a Frame.
-    /// </summary>
-    public sealed partial class M3MaterialNavigationBarSample_Primary : Page
-    {
-        public M3MaterialNavigationBarSample_Primary()
-        {
-            this.InitializeComponent();
-        }
+	public sealed partial class M3MaterialNavigationBarSample_Primary : Page
+	{
+		public M3MaterialNavigationBarSample_Primary()
+		{
+			this.InitializeComponent();
+		}
 
-		private void NavigateBack(object sender, RoutedEventArgs e) => Shell.GetForCurrentView().BackNavigateFromNestedSample();
 
-    }
+		private void NavigateBack(object sender, RoutedEventArgs e) => Shell.GetForCurrentView().BackNavigateFromNestedSample();
+	}
 }

src/Uno.Toolkit.RuntimeTests/Tests/NavigationBarTests.cs

@@ -199,6 +199,50 @@ public async Task MainCommand_In_Popup_With_Page_With_BackStack(MainCommandMode
 				popup.IsOpen = false;
 			}
 		}
+
+#if __IOS__
+		[TestMethod]
+		public async Task NavigationBar_Does_Render()
+		{
+			var frame = new Frame { Width = 200, Height = 200 }; ;
+			await UnitTestUIContentHelperEx.SetContentAndWait(frame);
+
+			frame.Navigate(typeof(NavBarSimplePage));
+
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			AssertNavigationBar(frame);
+		}
+
+		[TestMethod]
+		public async Task NavigationBar_Does_Render_Within_AutoLayout()
+		{
+			var frame = new Frame { Width = 200, Height = 200 };;
+			await UnitTestUIContentHelperEx.SetContentAndWait(frame);
+
+			frame.Navigate(typeof(NavBarAutoLayoutPage));
+
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			AssertNavigationBar(frame);
+		}
+
+		private static void AssertNavigationBar(Frame frame)
+		{
+			var page = frame.Content as Page;
+			var presenter = frame.FindChild<NativeFramePresenter>();
+			var navBar = page?.FindChild<NavigationBar>();
+
+			var renderedNativeNavItem = navBar?.GetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>(null)?.Native;
+			var renderedNativeNavBar = navBar?.GetRenderer<NavigationBar, NavigationBarRenderer>(null)?.Native;
+
+			Assert.IsNotNull(presenter);
+			Assert.IsFalse(presenter!.NavigationController.NavigationBarHidden);
+
+			Assert.AreSame(renderedNativeNavItem, presenter.NavigationController.TopViewController.NavigationItem);
+			Assert.AreSame(renderedNativeNavBar, presenter.NavigationController.NavigationBar);
+		}
+#endif
 	}
 }
 

src/Uno.Toolkit.RuntimeTests/Tests/TestPages/NavBarAutoLayoutPage.xaml

@@ -0,0 +1,14 @@
+<Page x:Class="Uno.Toolkit.RuntimeTests.Tests.TestPages.NavBarAutoLayoutPage"
+	  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	  xmlns:local="using:Uno.Toolkit.RuntimeTests.Tests.TestPages"
+	  xmlns:utu="using:Uno.Toolkit.UI"
+	  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	  mc:Ignorable="d"
+	  Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+	<utu:AutoLayout>
+		<utu:NavigationBar Content="Testing" />
+	</utu:AutoLayout>
+</Page>

src/Uno.Toolkit.RuntimeTests/Tests/TestPages/NavBarAutoLayoutPage.xaml.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Uno.Toolkit.UI;
+
+#if IS_WINUI
+using Microsoft.UI;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
+using Microsoft.UI.Xaml.Data;
+using Microsoft.UI.Xaml.Input;
+using Microsoft.UI.Xaml.Media;
+using Microsoft.UI.Xaml.Navigation;
+#else
+using Windows.UI;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+#endif
+
+namespace Uno.Toolkit.RuntimeTests.Tests.TestPages
+{
+	public sealed partial class NavBarAutoLayoutPage : Page
+	{
+		public NavBarAutoLayoutPage()
+		{
+			this.InitializeComponent();
+		}
+	}
+}

src/Uno.Toolkit.RuntimeTests/Tests/TestPages/NavBarSimplePage.xaml

@@ -0,0 +1,12 @@
+<Page x:Class="Uno.Toolkit.RuntimeTests.Tests.TestPages.NavBarSimplePage"
+	  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	  xmlns:local="using:Uno.Toolkit.RuntimeTests.Tests.TestPages"
+	  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	  xmlns:utu="using:Uno.Toolkit.UI"
+	  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	  mc:Ignorable="d"
+	  Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+	<utu:NavigationBar Content="Testing" />
+</Page>

src/Uno.Toolkit.RuntimeTests/Tests/TestPages/NavBarSimplePage.xaml.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Uno.Toolkit.UI;
+
+#if IS_WINUI
+using Microsoft.UI;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
+using Microsoft.UI.Xaml.Data;
+using Microsoft.UI.Xaml.Input;
+using Microsoft.UI.Xaml.Media;
+using Microsoft.UI.Xaml.Navigation;
+#else
+using Windows.UI;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+#endif
+
+namespace Uno.Toolkit.RuntimeTests.Tests.TestPages
+{
+	public sealed partial class NavBarSimplePage : Page
+	{
+		public NavBarSimplePage()
+		{
+			this.InitializeComponent();
+		}
+	}
+}

src/Uno.Toolkit.UI/Controls/NavigationBar/NativeFramePresenter.iOS.cs

@@ -777,6 +777,20 @@ public PageViewController(Page? page)
 				NavigationBarHelper.PageCreated(this);
 			}
 
+
+			public override void ViewDidAppear(bool animated)
+			{
+				try
+				{
+					base.ViewDidAppear(animated);
+
+					NavigationBarHelper.PageDidAppear(this);
+				}
+				catch (Exception e)
+				{
+					this.Log().Error($"{e.Message}", e);
+				}
+			}
 			public override void ViewWillAppear(bool animated)
 			{
 				try

src/Uno.Toolkit.UI/Controls/NavigationBar/NavigationBarHelper.iOS.cs

@@ -70,6 +70,8 @@ public static void PageWillAppear(UIViewController pageController)
 			var topNavigationBar = pageController.View.FindTopNavigationBar();
 			if (topNavigationBar != null)
 			{
+				EnsureNavigationItem(topNavigationBar, pageController);
+
 				if (topNavigationBar.Visibility == Visibility.Visible)
 				{
 					SetNavigationBar(topNavigationBar, pageController.NavigationController!.NavigationBar);
@@ -97,6 +99,53 @@ public static void PageWillAppear(UIViewController pageController)
 			}
 		}
 
+		// In some cases the NavigationBar may not be rendered yet when PageCreated/PageWillAppear is called
+		// This can be the case when the NavigationBar is part of an AutoLayout
+		// since the AutoLayout is delayed in materializing its Children
+		public static void PageDidAppear(UIViewController pageController)
+		{
+			var topNavigationBar = pageController.View.FindTopNavigationBar();
+			if (topNavigationBar != null)
+			{
+				EnsureNavigationItem(topNavigationBar, pageController);	
+
+				if (topNavigationBar.Visibility == Visibility.Visible)
+				{
+					SetNavigationBar(topNavigationBar, pageController.NavigationController!.NavigationBar);
+
+					// When the NavigationBar is visible, we need to call SetNavigationBarHidden
+					// AFTER it has been rendered. Otherwise, it causes a bug introduced
+					// in iOS 11 in which the BackButtonIcon is not rendered properly.
+					pageController.NavigationController.SetNavigationBarHidden(hidden: false, animated: false);
+				}
+				else
+				{
+					// Even if the NavigationBar should technically be collapsed,
+					// we don't hide it using the NavigationController because it
+					// automatically disables the back gesture.
+					// In order to visually hide it, the NavigationBarRenderer
+					// will hide the native view using the UIView.Hidden property.
+					pageController.NavigationController!.SetNavigationBarHidden(hidden: false, animated: false);
+					SetNavigationBar(topNavigationBar, pageController.NavigationController.NavigationBar);
+				}
+			}
+			else // No NavigationBar
+			{
+				pageController.NavigationController!.SetNavigationBarHidden(true, true);
+			}
+		}
+
+		private static void EnsureNavigationItem(NavigationBar topNavigationBar, UIViewController pageController)
+		{
+			// The Native view from the renderer may have been set to a dummy NavigationItem if we were not able to find
+			// a NavigationBar in the PageCreated method. If that is the case, set it to the pageController's NavigationItem
+			var nativeItem = topNavigationBar.GetRenderer(() => (NavigationBarNavigationItemRenderer?)null)?.Native;
+			if (!ReferenceEquals(nativeItem, pageController.NavigationItem))
+			{
+				SetNavigationItem(topNavigationBar, pageController.NavigationItem);
+			}
+		}
+
 		/// <summary>
 		/// When a page <see cref="UIViewController" /> did disappear, disconnects the <see cref="NavigationBar" /> from the navigation controller.
 		/// </summary>

src/Uno.Toolkit.UI/Controls/NavigationBar/Renderer.cs

@@ -139,12 +139,13 @@ internal static class RendererHelper
 	{
 		private static readonly WeakAttachedDictionary<DependencyObject, Type> _renderers = new WeakAttachedDictionary<DependencyObject, Type>();
 
-		public static TRenderer GetRenderer<TElement, TRenderer>(this TElement element, Func<TRenderer> rendererFactory)
+		public static TRenderer GetRenderer<TElement, TRenderer>(this TElement element, Func<TRenderer>? rendererFactory)
 			where TElement : DependencyObject
 		{
 			return _renderers.GetValue(element, typeof(TRenderer), rendererFactory);
 		}
-		public static TRenderer ResetRenderer<TElement, TRenderer>(this TElement element, Func<TRenderer> rendererFactory)
+
+		public static TRenderer ResetRenderer<TElement, TRenderer>(this TElement element, Func<TRenderer>? rendererFactory)
 			where TElement : DependencyObject
 		{
 			return _renderers.GetValue(element, typeof(TRenderer), rendererFactory);