[Windows] Fixed: Setting BackgroundColor for Slider updates the MaximumTrackColor

src/Controls/tests/TestCases.HostApp/Issues/Issue25921.cs

@@ -0,0 +1,46 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 25921, "[Windows] Setting BackgroundColor for Slider updates the Maximum Track Color", PlatformAffected.UWP)]
+public class Issue25921 : ContentPage
+{
+	public Issue25921()
+	{
+		var layout = new VerticalStackLayout();
+		layout.VerticalOptions = LayoutOptions.Center;
+		layout.Spacing = 20;
+		var slider = new Slider()
+		{
+			WidthRequest = 300,
+			Maximum = 100,
+			Minimum = 0,
+			Value = 50,
+			BackgroundColor = Colors.Yellow,
+			MaximumTrackColor = Colors.Red,
+			MinimumTrackColor = Colors.Fuchsia,
+		};
+
+		var secondSlider = new Slider()
+		{
+			WidthRequest = 300,
+			Maximum = 100,
+			Minimum = 0,
+			Value = 50,
+			Background = Colors.Grey,
+			MaximumTrackColor = Colors.SpringGreen,
+			MinimumTrackColor = Colors.BlueViolet,
+		};
+
+		var button = new Button()
+		{
+			Text = "Change Background Color",
+			AutomationId = "ColorChangeButton",
+			Command = new Command(() => secondSlider.Background = Colors.Salmon)
+		};
+
+		layout.Children.Add(slider);
+		layout.Children.Add(secondSlider);
+		layout.Children.Add(button);
+
+		Content = layout;
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Bugzilla/Bugzilla29128.cs

@@ -1,6 +1,4 @@
-#if TEST_FAILS_ON_WINDOWS //Background Color updates on Slider Track
-//For more information : https://github.com/dotnet/maui/issues/25921
-using NUnit.Framework;
+using NUnit.Framework;
 using UITest.Appium;
 using UITest.Core;
 
@@ -23,5 +21,4 @@ public void Bugzilla29128Test()
 			VerifyScreenshot();
 		}
 	}
-}
-#endif
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25921.cs

@@ -0,0 +1,23 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue25921 : _IssuesUITest
+{
+	public override string Issue => "[Windows] Setting BackgroundColor for Slider updates the Maximum Track Color";
+
+	public Issue25921(TestDevice device)
+	: base(device)
+	{ }
+
+	[Test]
+	[Category(UITestCategories.Slider)]
+	public void VerifySliderColors()
+	{
+		App.WaitForElement("ColorChangeButton");
+		App.Tap("ColorChangeButton");
+		VerifyScreenshot();
+	}
+}

src/Core/src/Handlers/Slider/SliderHandler.Windows.cs

@@ -91,6 +91,14 @@ public static void MapThumbImageSource(ISliderHandler handler, ISlider slider)
 			}
 		}
 
+		internal static void MapBackgroundColor(ISliderHandler handler, ISlider slider)
+		{
+			if (handler.PlatformView is MauiSlider mauiSlider)
+			{
+				mauiSlider.UpdateBackgroundColor(slider);
+			}
+		}
+
 		void OnPlatformViewLoaded(object sender, RoutedEventArgs e)
 		{
 			var platformView = sender as Slider;

src/Core/src/Handlers/Slider/SliderHandler.cs

@@ -24,6 +24,9 @@ public partial class SliderHandler : ISliderHandler
 			[nameof(ISlider.ThumbColor)] = MapThumbColor,
 			[nameof(ISlider.ThumbImageSource)] = MapThumbImageSource,
 			[nameof(ISlider.Value)] = MapValue,
+#if WINDOWS
+			[nameof(ISlider.Background)] = MapBackgroundColor
+#endif
 		};
 
 		public static CommandMapper<ISlider, ISliderHandler> CommandMapper = new(ViewCommandMapper)

src/Core/src/Platform/Windows/SliderExtensions.cs

@@ -6,6 +6,7 @@
 using Microsoft.UI.Xaml.Controls;
 using Microsoft.UI.Xaml.Controls.Primitives;
 using Microsoft.UI.Xaml.Media.Imaging;
+using Microsoft.UI.Xaml.Media;
 
 namespace Microsoft.Maui.Platform
 {
@@ -19,7 +20,9 @@ static void UpdateIncrement(this Slider nativeSlider, ISlider slider)
 
 			// Setting the Slider SmallChange property to 0 would throw an System.ArgumentException.
 			if (difference != 0)
+			{
 				stepping = Math.Min((difference) / 1000, 1);
+			}
 
 			nativeSlider.StepFrequency = stepping;
 		}
@@ -39,19 +42,14 @@ public static void UpdateMaximum(this Slider nativeSlider, ISlider slider)
 		public static void UpdateValue(this Slider nativeSlider, ISlider slider)
 		{
 			if (nativeSlider.Value != slider.Value)
+			{
 				nativeSlider.Value = slider.Value;
+			}
 		}
 
 		public static void UpdateMinimumTrackColor(this Slider platformSlider, ISlider slider)
 		{
-			var brush = slider.MinimumTrackColor?.ToPlatform();
-
-			if (brush is null)
-				platformSlider.Resources.RemoveKeys(MinimumTrackColorResourceKeys);
-			else
-				platformSlider.Resources.SetValueForAllKey(MinimumTrackColorResourceKeys, brush);
-
-			platformSlider.RefreshThemeResources();
+			UpdateColor(platformSlider, MinimumTrackColorResourceKeys, slider.MinimumTrackColor?.ToPlatform());
 		}
 
 		static readonly string[] MinimumTrackColorResourceKeys =
@@ -64,14 +62,7 @@ public static void UpdateMinimumTrackColor(this Slider platformSlider, ISlider s
 
 		public static void UpdateMaximumTrackColor(this Slider platformSlider, ISlider slider)
 		{
-			var brush = slider.MaximumTrackColor?.ToPlatform();
-
-			if (brush == null)
-				platformSlider.Resources.RemoveKeys(MaximumTrackColorResourceKeys);
-			else
-				platformSlider.Resources.SetValueForAllKey(MaximumTrackColorResourceKeys, brush);
-
-			platformSlider.RefreshThemeResources();
+			UpdateColor(platformSlider, MaximumTrackColorResourceKeys, slider.MaximumTrackColor?.ToPlatform());
 		}
 
 		static readonly string[] MaximumTrackColorResourceKeys =
@@ -84,14 +75,7 @@ public static void UpdateMaximumTrackColor(this Slider platformSlider, ISlider s
 
 		public static void UpdateThumbColor(this Slider platformSlider, ISlider slider)
 		{
-			var brush = slider.ThumbColor?.ToPlatform();
-
-			if (brush is null)
-				platformSlider.Resources.RemoveKeys(ThumbColorResourceKeys);
-			else
-				platformSlider.Resources.SetValueForAllKey(ThumbColorResourceKeys, brush);
-
-			platformSlider.RefreshThemeResources();
+			UpdateColor(platformSlider, ThumbColorResourceKeys, slider.ThumbColor?.ToPlatform());
 		}
 
 		static readonly string[] ThumbColorResourceKeys =
@@ -144,13 +128,43 @@ void OnImageOpened(object sender, RoutedEventArgs e)
 						}
 
 						if (nativeSlider.Parent is FrameworkElement frameworkElement)
+						{
 							frameworkElement.InvalidateMeasure();
+						}
 					}
-					;
 				}
 
 				nativeSlider.ThumbImageSource = nativeThumbImageSource?.Value;
 			}
 		}
+
+		static readonly string[] BackgroundColorResourceKeys =
+		{
+			"SliderContainerBackground",
+			"SliderContainerBackgroundPointerOver",
+			"SliderContainerBackgroundPressed",
+			"SliderContainerBackgroundDisabled",
+		};
+
+		internal static void UpdateBackgroundColor(this MauiSlider platformSlider, ISlider slider)
+		{
+			UpdateColor(platformSlider, BackgroundColorResourceKeys, slider.Background?.ToPlatform());
+		}
+
+		static void UpdateColor(Slider platformSlider, string[] keys, Brush? brush)
+		{
+			ResourceDictionary resource = platformSlider.Resources;
+
+			if (brush is null)
+			{
+				resource.RemoveKeys(keys);
+			}
+			else
+			{
+				resource.SetValueForAllKey(keys, brush);
+			}
+
+			platformSlider.RefreshThemeResources();
+		}
 	}
 }