[Windows] Fix for Picker CharacterSpacing Not Being Applied to Title and Dropdown Items

src/Controls/tests/TestCases.HostApp/Issues/Issue30464.cs

@@ -0,0 +1,71 @@
+namespace Controls.TestCases.HostApp.Issues;
+
+[Issue(IssueTracker.Github, 30464, "The CharacterSpacing property on the Picker control is not applied to the title or the items", PlatformAffected.UWP)]
+public class Issue30464 : ContentPage
+{
+	public Issue30464()
+	{
+		Picker pickerTitleCharacterSpacing = new Picker
+		{
+			Title = "Select an item",
+		};
+		pickerTitleCharacterSpacing.Items.Add("Item 1");
+
+		Picker pickerItemCharacterSpacing = new Picker
+		{
+			ItemsSource = new List<string> { "Item 1", "Item 2" },
+			SelectedIndex = 1
+		};
+
+		Button applyCharacterSpacingBtn = new Button
+		{
+			Text = "Apply character spacing",
+			AutomationId = "Issue30464Btn"
+		};
+
+		applyCharacterSpacingBtn.Clicked += (sender, e) =>
+		{
+			pickerTitleCharacterSpacing.CharacterSpacing = 14;
+			pickerItemCharacterSpacing.CharacterSpacing = 14;
+		};
+
+		Label descriptionLabel = new Label
+		{
+			AutomationId = "Issue30464DescriptionLabel",
+			Text = "The test case passes only if character spacing is correctly applied to both the Picker title and items, and is maintained after selecting a different item; otherwise, it fails.",
+		};
+
+		Picker pickerSelectionChange = new Picker
+		{
+			ItemsSource = new List<string> { "Item 1", "Item 2" },
+			SelectedIndex = 0,
+			CharacterSpacing = 14,
+			AutomationId = "Issue30464SelectionChangePicker"
+		};
+
+		Button changeSelectionBtn = new Button
+		{
+			Text = "Change selection",
+			AutomationId = "Issue30464ChangeSelectionBtn"
+		};
+		changeSelectionBtn.Clicked += (sender, e) =>
+		{
+			pickerSelectionChange.SelectedIndex = 1;
+		};
+
+		Content = new VerticalStackLayout
+		{
+			Spacing = 20,
+			Padding = 20,
+			Children =
+			{
+				pickerTitleCharacterSpacing,
+				pickerItemCharacterSpacing,
+				applyCharacterSpacingBtn,
+				pickerSelectionChange,
+				changeSelectionBtn,
+				descriptionLabel,
+			}
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue30464.cs

@@ -0,0 +1,26 @@
+#if TEST_FAILS_ON_IOS && TEST_FAILS_ON_CATALYST // PR Link - https://github.com/dotnet/maui/pull/34974
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue30464 : _IssuesUITest
+{
+	public Issue30464(TestDevice device) : base(device)
+	{
+	}
+
+	public override string Issue => "The CharacterSpacing property on the Picker control is not applied to the title or the items";
+
+	[Test]
+	[Category(UITestCategories.Picker)]
+	public void ValidatePickerTitleAndItemCharacterSpacing()
+	{
+		App.WaitForElement("Issue30464DescriptionLabel");
+		App.Tap("Issue30464Btn");
+		App.Tap("Issue30464ChangeSelectionBtn");
+		VerifyScreenshot();
+	}
+}
+#endif

src/Core/src/Handlers/Picker/PickerHandler.Windows.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using Microsoft.Maui.Platform;
 using Microsoft.UI.Xaml.Controls;
 using WSelectionChangedEventArgs = Microsoft.UI.Xaml.Controls.SelectionChangedEventArgs;
 
@@ -122,6 +123,13 @@ void OnControlSelectionChanged(object? sender, WSelectionChangedEventArgs e)
 			if (VirtualView != null && !UpdatingItemSource)
 				VirtualView.SelectedIndex = PlatformView.SelectedIndex;
 
+			// Reapply CharacterSpacing to the selected item's TextBlock so it persists
+			// across selection changes (e.g. programmatic SelectedIndex updates).
+			if (VirtualView != null && VirtualView.CharacterSpacing > 0)
+			{
+				PlatformView.ApplyCharacterSpacingToSelectedItem(VirtualView.CharacterSpacing.ToEm());
+			}
+
 			PlatformView.MinWidth = 0;
 		}
 
@@ -134,17 +142,43 @@ void OnMauiComboBoxDropDownOpened(object? sender, object e)
 
 			comboBox.MinWidth = comboBox.ActualWidth;
 
+			// Apply CharacterSpacing to each ComboBoxItem container so dropdown list items
+			// render with the configured spacing. Containers are only realized once the
+			// dropdown is opened, so this is the earliest reliable point to set them.
+			ApplyCharacterSpacingToItems(comboBox);
+
 			if (VirtualView is null)
 				return;
 
 			VirtualView.IsOpen = true;
 		}
 
+		static void ApplyCharacterSpacingToItems(ComboBox comboBox)
+		{
+			var characterSpacing = comboBox.CharacterSpacing;
+
+			for (int i = 0; i < comboBox.Items.Count; i++)
+			{
+				if (comboBox.ContainerFromIndex(i) is ComboBoxItem container)
+				{
+					container.CharacterSpacing = characterSpacing;
+				}
+			}
+		}
+
 		void OnMauiComboBoxDropDownClosed(object? sender, object e)
 		{
 			if (VirtualView is null)
 				return;
 
+			// After a manual dropdown selection, the ContentPresenter's TextBlock is reused
+			// and its rendered text doesn't pick up the CharacterSpacing already set on the
+			// ComboBox. Reapply CharacterSpacing directly to the selected item's TextBlock here.
+			if (sender is ComboBox cb && VirtualView.CharacterSpacing > 0)
+			{
+				cb.ApplyCharacterSpacingToSelectedItem(VirtualView.CharacterSpacing.ToEm());
+			}
+
 			if (sender is ComboBox comboBox && comboBox.MinWidth > 0)
 			{
 				//Reset the MinWidth to allow ComboBox to resize when the parent's size changes

src/Core/src/Platform/Windows/CharacterSpacingConverter.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace Microsoft.Maui.Platform;
+
+internal sealed partial class CharacterSpacingConverter : UI.Xaml.Data.IValueConverter
+{
+	public object Convert(object value, Type targetType, object parameter, string language)
+	{
+		if (value is double characterSpacing)
+		{
+			return characterSpacing.ToEm();
+		}
+
+		return 0;
+	}
+
+	public object ConvertBack(object value, Type targetType, object parameter, string language)
+	{
+		throw new NotSupportedException();
+	}
+}

src/Core/src/Platform/Windows/PickerExtensions.cs

@@ -1,4 +1,5 @@
 #nullable enable
+using System;
 using Microsoft.Maui.Graphics;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
@@ -74,7 +75,31 @@ public static void UpdateSelectedIndex(this ComboBox nativeComboBox, IPicker pic
 
 		public static void UpdateCharacterSpacing(this ComboBox nativeComboBox, IPicker picker)
 		{
-			nativeComboBox.CharacterSpacing = picker.CharacterSpacing.ToEm();
+			var characterSpacing = picker.CharacterSpacing.ToEm();
+			nativeComboBox.CharacterSpacing = characterSpacing;
+
+			// Apply directly to the selected item's TextBlock so the closed picker reflects spacing.
+			// If the control isn't loaded yet, defer until Loaded so the visual tree exists.
+			if (nativeComboBox.IsLoaded)
+			{
+				ApplyCharacterSpacingToSelectedItem(nativeComboBox, characterSpacing);
+			}
+			else
+			{
+				nativeComboBox.OnLoaded(() =>
+					ApplyCharacterSpacingToSelectedItem(nativeComboBox, nativeComboBox.CharacterSpacing));
+			}
+		}
+
+		internal static void ApplyCharacterSpacingToSelectedItem(this ComboBox nativeComboBox, int characterSpacing)
+		{
+			var contentPresenter = nativeComboBox.GetDescendantByName<ContentPresenter>("ContentPresenter");
+			var textBlock = contentPresenter?.GetFirstDescendant<TextBlock>();
+
+			if (textBlock is not null)
+			{
+				textBlock.CharacterSpacing = characterSpacing;
+			}
 		}
 
 		public static void UpdateFont(this ComboBox nativeComboBox, IPicker picker, IFontManager fontManager) =>

src/Core/src/Platform/Windows/Styles/MauiComboBoxStyle.xaml

@@ -6,7 +6,7 @@
     <DataTemplate x:Key="ComboBoxHeader">
         <TextBlock
             Text="{Binding Title}" 
-            CharacterSpacing="{Binding Path=CharacterSpacing, ElementName=HeaderContentPresenter}"
+            CharacterSpacing="{Binding CharacterSpacing, Converter={StaticResource CharacterSpacingConverter}}"
             Foreground="{Binding TitleColor, Converter={StaticResource ColorConverter}, ConverterParameter=DefaultTextForegroundThemeBrush}" />
     </DataTemplate>
 

src/Core/src/Platform/Windows/Styles/Resources.xaml

@@ -14,6 +14,7 @@
   <x:Boolean x:Key="MicrosoftMauiCoreIncluded">true</x:Boolean>
 
   <windows:ColorConverter x:Key="ColorConverter" />
+  <windows:CharacterSpacingConverter x:Key="CharacterSpacingConverter"/>
 
   <x:Double x:Key="FlyoutMinWidth">350</x:Double>