fix: Fix AutoSuggestBox QueryIcon size

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/Given_AutoSuggestBox.cs

@@ -18,13 +18,40 @@
 
 using static Private.Infrastructure.TestServices;
 using static Microsoft.UI.Xaml.Controls.AutoSuggestionBoxTextChangeReason;
+using SamplesApp.UITests;
+using Uno.UI.RuntimeTests.Helpers;
+using Windows.Foundation;
 
 namespace Uno.UI.RuntimeTests.Tests.Windows_UI_Xaml_Controls
 {
 	[TestClass]
 	[RunsOnUIThread]
 	public class Given_AutoSuggestBox
 	{
+		[TestMethod]
+		[UnoWorkItem("https://github.com/unoplatform/uno/issues/15662")]
+		public async Task When_SymbolIcon_Verify_Size()
+		{
+			var SUT = new AutoSuggestBox()
+			{
+				QueryIcon = new SymbolIcon(Symbol.Home),
+			};
+
+			await UITestHelper.Load(SUT);
+
+#if __SKIA__ || __WASM__
+			var tb = SUT.FindChildren<TextBlock>().Single(tb => tb.Text.Length == 1 && tb.Text[0] == (char)Symbol.Home);
+#else
+			var tb = SUT.EnumerateAllChildren(c => c is TextBlock tb && tb.Text.Length == 1 && tb.Text[0] == (char)Symbol.Home).Single();
+#endif
+
+			Assert.AreEqual(12, tb.FontSize);
+
+			var tbBounds = tb.GetAbsoluteBounds();
+
+			Assert.AreEqual(new Size(12, 12), new Size(tbBounds.Width, tbBounds.Height));
+		}
+
 #if !WINAPPSDK // GetTemplateChild is protected in UWP while public in Uno.
 		[TestMethod]
 		public async Task When_Text_Changed_Should_Reflect_In_DataTemplate_TextBox()

src/Uno.UI/UI/Xaml/Controls/AutoSuggestBox/AutoSuggestBox.cs

@@ -349,8 +349,13 @@ private void UpdateQueryButton()
 				return;
 			}
 
-			_queryButton.Content = QueryIcon;
-			_queryButton.Visibility = QueryIcon == null ? Visibility.Collapsed : Visibility.Visible;
+			var queryIcon = QueryIcon;
+			if (queryIcon is SymbolIcon symbolIcon)
+			{
+				symbolIcon.SetFontSize(0);
+			}
+			_queryButton.Content = queryIcon;
+			_queryButton.Visibility = queryIcon == null ? Visibility.Collapsed : Visibility.Visible;
 		}
 
 		private void UpdateTextBox()

src/Uno.UI/UI/Xaml/Controls/Icons/SymbolIcon.cs

@@ -12,7 +12,7 @@ namespace Microsoft.UI.Xaml.Controls;
 /// </summary>
 public sealed partial class SymbolIcon : IconElement
 {
-	private const double DefaultFontSize = 20.0;
+	private double _fontSize = 20.0;
 
 	private readonly TextBlock _textBlock;
 
@@ -63,7 +63,12 @@ private void SynchronizeProperties()
 		_textBlock.TextAlignment = Microsoft.UI.Xaml.TextAlignment.Center;
 		_textBlock.HorizontalAlignment = HorizontalAlignment.Stretch;
 		_textBlock.VerticalAlignment = VerticalAlignment.Center;
-		_textBlock.FontSize = DefaultFontSize;
+
+		if (_fontSize > 0)
+		{
+			_textBlock.FontSize = _fontSize;
+		}
+
 		_textBlock.FontStyle = FontStyle.Normal;
 		_textBlock.FontFamily = GetSymbolFontFamily();
 		_textBlock.IsTextScaleFactorEnabled = false;
@@ -73,6 +78,17 @@ private void SynchronizeProperties()
 		_textBlock.Foreground = Foreground;
 	}
 
+	internal void SetFontSize(double fontSize)
+	{
+		_fontSize = fontSize;
+		if (fontSize == 0)
+		{
+			_textBlock.ClearValue(TextBlock.FontSizeProperty);
+		}
+
+		InvalidateMeasure();
+	}
+
 	private void SetSymbolText() => _textBlock.Text = new string((char)Symbol, 1);
 
 	private static FontFamily GetSymbolFontFamily() =>