[iOS] Thumb image improvements

src/Controls/tests/TestCases.HostApp/Issues/Issue27515.cs

@@ -0,0 +1,31 @@
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 27515, "Slider's thumb image doesn't respect color", PlatformAffected.iOS)]
+	public class Issue27515 : ContentPage
+	{
+		public Issue27515()
+		{
+			var slider = new Slider() { ThumbColor = Colors.Blue };
+			Content = new VerticalStackLayout()
+			{
+				slider,
+				new Button()
+				{
+					AutomationId = "ChangeThumbImageButton",
+					Text = "Click to change image",
+					Command = new Command(() => {
+						slider.ThumbImageSource = "coffee.png";
+					})
+				},
+				new Button()
+				{
+					AutomationId = "ChangeThumbColorButton",
+					Text = "Click to change color",
+					Command = new Command(() => {
+						slider.ThumbColor = Colors.Red;
+					})
+				}
+			};
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue27515.cs

@@ -0,0 +1,27 @@
+#if ANDROID || IOS || MACCATALYST // Slider's thumb image doesn't respect color on Windows
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+    public class Issue27515 : _IssuesUITest
+    {
+        public Issue27515(TestDevice testDevice) : base(testDevice)
+        {
+        }
+
+        public override string Issue => "Slider's thumb image doesn't respect color";
+
+        [Test]
+        [Category(UITestCategories.Slider)]
+        public void SliderThumbImageShouldRespectColor()
+        {
+            App.WaitForElement("ChangeThumbImageButton");
+            App.Click("ChangeThumbImageButton");
+            App.Click("ChangeThumbColorButton");
+            VerifyScreenshot();
+        }
+    }
+}
+#endif

src/Core/src/Platform/iOS/SliderExtensions.cs

@@ -37,8 +37,15 @@ public static void UpdateMaximumTrackColor(this UISlider uiSlider, ISlider slide
 
 		public static void UpdateThumbColor(this UISlider uiSlider, ISlider slider)
 		{
-			if (slider.ThumbColor != null)
+			if (slider.ThumbImageSource is not null && slider.Handler is not null)
+			{
+				var provider = slider.Handler.GetRequiredService<IImageSourceServiceProvider>();
+				uiSlider.UpdateThumbImageSourceAsync(slider, provider).FireAndForget();
+			}
+			else if (slider.ThumbColor is not null)
+			{
 				uiSlider.ThumbTintColor = slider.ThumbColor.ToPlatform();
+			}
 		}
 
 		public static async Task UpdateThumbImageSourceAsync(this UISlider uiSlider, ISlider slider, IImageSourceServiceProvider provider)
@@ -47,11 +54,18 @@ public static async Task UpdateThumbImageSourceAsync(this UISlider uiSlider, ISl
 
 			if (thumbImageSource != null)
 			{
+				// Clear the thumb color if we have a thumb image, so that slider doesn't clear image when sliding
+				uiSlider.ThumbTintColor = null;
 				var service = provider.GetRequiredImageSourceService(thumbImageSource);
 				var scale = uiSlider.GetDisplayDensity();
 				var result = await service.GetImageAsync(thumbImageSource, scale);
 				var thumbImage = result?.Value;
 
+				if (thumbImage is not null && slider.ThumbColor is not null)
+				{
+					thumbImage = thumbImage.ApplyTintColor(slider.ThumbColor.ToPlatform());
+				}
+
 				uiSlider.SetThumbImage(thumbImage, UIControlState.Normal);
 			}
 			else