Shell BackButtonBehavior improvement (#23466)

* Shell BackButtonBehavior improvement (#23424)

* Update ShellPageRendererTracker.cs

* CR comments resolved

* - snapshots

---------

Co-authored-by: Shane Neuville <shneuvil@microsoft.com>

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

@@ -325,6 +325,7 @@ void UpdateLeftToolbarItems()
 			if (!IsRootPage)
 			{
 				NavigationItem.HidesBackButton = !backButtonVisible;
+				image = backButtonVisible ? image : null;
 			}
 
 			image.LoadImage(MauiContext, result =>

src/Controls/tests/TestCases.HostApp/Issues/Issue23424.xaml.cs

@@ -0,0 +1,35 @@
+namespace Maui.Controls.Sample.Issues;
+
+[XamlCompilation(XamlCompilationOptions.Compile)]
+[Issue(IssueTracker.Github, "23424", "BackButtonBehavior IsVisible=False does not hide the back button", PlatformAffected.All)]
+public partial class Issue23424 : Shell
+{
+	public Issue23424()
+	{
+		Items.Add(new ContentPage());
+		Navigation.PushAsync(new DetailPage());
+	}
+
+	public class DetailPage : ContentPage
+	{
+		public DetailPage()
+		{
+			Title = "Detail page";
+			BackButtonBehavior backButtonBehavior = new BackButtonBehavior
+			{
+				IconOverride = "small_dotnet_bot.png"
+			};
+
+			SetBackButtonBehavior(this, backButtonBehavior);
+			Content = new VerticalStackLayout()
+			{
+				new Button() 
+				{
+					AutomationId = "button",
+					Text = "Click to hide the back button",
+					Command = new Command(()=>backButtonBehavior.IsVisible =! backButtonBehavior.IsVisible)
+				}
+			};
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue23424.cs

@@ -0,0 +1,28 @@
+#if !MACCATALYST
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+    public class Issue23424: _IssuesUITest
+	{
+		public Issue23424(TestDevice device) : base(device)
+		{
+		}
+
+		public override string Issue => "BackButtonBehavior IsVisible=False does not hide the back button";
+
+		[Test]
+		[Category(UITestCategories.Shell)]
+		public void BackButtonBehaviorIsVisibleWorksWithCustomIcon()
+		{
+			App.WaitForElement("button");
+			App.Click("button");
+
+			// The test passes if the back button is not visible
+			VerifyScreenshot();
+		}
+	}
+}
+#endif