From e384e2130a7cecea6a481ed625376dcbbd484c07 Mon Sep 17 00:00:00 2001
From: Jakub Florkowski <kubaflo123@gmail.com>
Date: Sun, 25 Aug 2024 18:11:47 +0200
Subject: [PATCH] Update a tabbar with gradient on app theme change

---
 .../Handlers/TabbedPage/iOS/TabbedRenderer.cs | 23 +++++++++++--
 .../Platform/Android/TabbedPageManager.cs     | 22 +++++++++++++
 .../TestCases.HostApp/Issues/Issue24356.xaml  | 23 +++++++++++++
 .../Issues/Issue24356.xaml.cs                 | 11 +++++++
 .../Tests/Issues/Issue24356.cs                | 33 +++++++++++++++++++
 5 files changed, 110 insertions(+), 2 deletions(-)
 create mode 100644 src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml
 create mode 100644 src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml.cs
 create mode 100644 src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue24356.cs

diff --git a/src/Controls/src/Core/Compatibility/Handlers/TabbedPage/iOS/TabbedRenderer.cs b/src/Controls/src/Core/Compatibility/Handlers/TabbedPage/iOS/TabbedRenderer.cs
index 4720766995bc..6256b4d5b115 100644
--- a/src/Controls/src/Core/Compatibility/Handlers/TabbedPage/iOS/TabbedRenderer.cs
+++ b/src/Controls/src/Core/Compatibility/Handlers/TabbedPage/iOS/TabbedRenderer.cs
@@ -29,6 +29,8 @@ public class TabbedRenderer : UITabBarController, IPlatformViewHandler
 		UITabBarAppearance _tabBarAppearance;
 		WeakReference<VisualElement> _element;
 
+		Brush _currentBarBackground;
+
 		IMauiContext MauiContext => _mauiContext;
 		public static IPropertyMapper<TabbedPage, TabbedRenderer> Mapper = new PropertyMapper<TabbedPage, TabbedRenderer>(TabbedViewHandler.ViewMapper);
 		public static CommandMapper<TabbedPage, TabbedRenderer> CommandMapper = new CommandMapper<TabbedPage, TabbedRenderer>(TabbedViewHandler.ViewCommandMapper);
@@ -360,9 +362,26 @@ void UpdateBarBackground()
 			if (Tabbed is not TabbedPage tabbed || TabBar == null)
 				return;
 
-			var barBackground = tabbed.BarBackground;
+			if(_currentBarBackground is GradientBrush oldBarBackground)
+			{
+				oldBarBackground.Parent = null;
+				oldBarBackground.InvalidateGradientBrushRequested -= OnBarBackgroundChanged;
+			}
+			
+			_currentBarBackground = tabbed.BarBackground;
 
-			TabBar.UpdateBackground(barBackground);
+			if(_currentBarBackground is GradientBrush newGradientBrush)
+			{
+				newGradientBrush.Parent = tabbed;
+				newGradientBrush.InvalidateGradientBrushRequested += OnBarBackgroundChanged;
+			}
+
+			TabBar.UpdateBackground(_currentBarBackground);
+		}
+
+		void OnBarBackgroundChanged(object sender, EventArgs e)
+		{
+			TabBar.UpdateBackground(_currentBarBackground);
 		}
 
 		void UpdateBarTextColor()
diff --git a/src/Controls/src/Core/Platform/Android/TabbedPageManager.cs b/src/Controls/src/Core/Platform/Android/TabbedPageManager.cs
index 4fd95c9a6e81..584dcf8b7024 100644
--- a/src/Controls/src/Core/Platform/Android/TabbedPageManager.cs
+++ b/src/Controls/src/Core/Platform/Android/TabbedPageManager.cs
@@ -574,8 +574,30 @@ internal void UpdateBarBackground()
 			if (_currentBarBackground == Element.BarBackground)
 				return;
 
+			if(_currentBarBackground is GradientBrush oldGradientBrush)
+			{
+				oldGradientBrush.Parent = null;
+				oldGradientBrush.InvalidateGradientBrushRequested -= OnBarBackgroundChanged; 
+			}
+
 			_currentBarBackground = Element.BarBackground;
 
+			if(_currentBarBackground is GradientBrush newGradientBrush)
+			{
+				newGradientBrush.Parent = Element;
+				newGradientBrush.InvalidateGradientBrushRequested += OnBarBackgroundChanged; 
+			}
+
+			RefreshBarBackground();
+		}
+
+		void OnBarBackgroundChanged(object sender, EventArgs e)
+		{
+			RefreshBarBackground();
+		}
+
+		void RefreshBarBackground()
+		{
 			if (IsBottomTabPlacement)
 				_bottomNavigationView.UpdateBackground(_currentBarBackground);
 			else
diff --git a/src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml b/src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml
new file mode 100644
index 000000000000..0a79389c32d2
--- /dev/null
+++ b/src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<TabbedPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+       xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+       x:Class="Maui.Controls.Sample.Issues.Issue24356"
+       xmlns:ns="clr-namespace:Maui.Controls.Sample.Issues">
+    <TabbedPage.BarBackground>
+        <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
+        <GradientStop Color="{AppThemeBinding Light=Red, Dark=Brown}"
+                        Offset="0.0" />
+        <GradientStop Color="{AppThemeBinding Light=White, Dark=Black}"
+                        Offset="0.5" />
+        <GradientStop Color="{AppThemeBinding Light=Red, Dark=Brown}"
+                        Offset="1.0" />
+        </LinearGradientBrush>
+    </TabbedPage.BarBackground>
+    <ContentPage Title="Tab 1">
+        <Grid>
+            <Label IsVisible="{AppThemeBinding Light=True, Dark=False}" AutomationId="lightThemeLabel" Text="Light theme"/>
+            <Label IsVisible="{AppThemeBinding Light=False, Dark=True}" AutomationId="darkThemeLabel" Text="Dark theme"/>
+        </Grid>
+    </ContentPage>
+    <ContentPage Title="Tab 2"/>
+</TabbedPage>
\ No newline at end of file
diff --git a/src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml.cs b/src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml.cs
new file mode 100644
index 000000000000..9808f9db5bea
--- /dev/null
+++ b/src/Controls/tests/TestCases.HostApp/Issues/Issue24356.xaml.cs
@@ -0,0 +1,11 @@
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 24356, "AppThemeBinding BarBackground with Brush in NavigationPage and TabbedPage not working", PlatformAffected.All)]
+	public partial class Issue24356 : TabbedPage
+	{	
+		public Issue24356()
+		{
+			InitializeComponent();
+		}
+	}
+}
diff --git a/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue24356.cs b/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue24356.cs
new file mode 100644
index 000000000000..11bd24338f75
--- /dev/null
+++ b/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue24356.cs
@@ -0,0 +1,33 @@
+#if ANDROID || IOS
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue24356 : _IssuesUITest
+	{
+		public Issue24356(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		public override string Issue => "AppThemeBinding BarBackground with Brush in NavigationPage and TabbedPage not working";
+
+		[Test]
+		[Category(UITestCategories.TabbedPage)]
+		public void GradientInTabBarShouldChange()
+		{
+			try {
+				App.WaitForElement("lightThemeLabel");
+				App.SetDarkTheme();
+				App.WaitForElement("darkThemeLabel");
+				VerifyScreenshot();
+			}
+			finally
+			{
+				App.SetLightTheme();
+			}
+		}
+	}
+}
+#endif
\ No newline at end of file