Fixed Label Span font property inheritance when applied via Style

src/Controls/src/Core/Platform/Android/Extensions/FormattedStringExtensions.cs

@@ -90,10 +90,10 @@ public static SpannableString ToSpannableString(
 				if (characterSpacing >= 0)
 					spannable.SetSpan(new PlatformFontSpan(characterSpacing.ToEm()), start, end, SpanTypes.InclusiveInclusive);
 
-				// Font
-				var font = span.ToFont(defaultFontSize);
-				if (font.IsDefault && defaultFont.HasValue)
-					font = defaultFont.Value;
+				// Inherit FontFamily from defaultFont if not explicitly set
+				var fontFamily = span.IsSet(Span.FontFamilyProperty) ? span.FontFamily : defaultFont?.Family;
+				var fontSize = span.FontSize >= 0 ? span.FontSize : defaultFontSize;
+				var font = Font.OfSize(fontFamily, fontSize);
 				if (!font.IsDefault)
 					spannable.SetSpan(new PlatformFontSpan(context ?? AAplication.Context, font.ToTypeface(fontManager), font.AutoScalingEnabled, (float)fontManager.GetFontSize(font).Value), start, end, SpanTypes.InclusiveInclusive);
 

src/Controls/src/Core/Platform/Windows/Extensions/FormattedStringExtensions.cs

@@ -127,9 +127,11 @@ public static Tuple<Run, Color, Color> ToRunAndColorsTuple(
 
 			var run = new Run { Text = text ?? string.Empty };
 
-			var font = span.ToFont(defaultFontSize);
-			if (font.IsDefault && defaultFont.HasValue)
-				font = defaultFont.Value;
+
+			// Inherit FontFamily from defaultFont if not explicitly set
+			var fontFamily = span.IsSet(Span.FontFamilyProperty) ? span.FontFamily : defaultFont?.Family;
+			var fontSize = span.FontSize >= 0 ? span.FontSize : defaultFontSize;
+			var font = Font.OfSize(fontFamily, fontSize);
 
 			if (!font.IsDefault)
 			{

src/Controls/src/Core/Platform/iOS/Extensions/FormattedStringExtensions.cs

@@ -91,10 +91,10 @@ public static NSAttributedString ToNSAttributedString(
 				_ => UITextAlignment.Left
 			};
 
-			var font = span.ToFont(defaultFontSize);
-			if (font.IsDefault && defaultFont.HasValue)
-				font = defaultFont.Value;
-
+			// Inherit FontFamily from defaultFont if not explicitly set
+			var fontFamily = span.IsSet(Span.FontFamilyProperty) ? span.FontFamily : defaultFont?.Family;
+			var fontSize = span.FontSize >= 0 ? span.FontSize : defaultFontSize;
+			var font = Font.OfSize(fontFamily, fontSize);
 			var hasUnderline = false;
 			var hasStrikethrough = false;
 			if (span.IsSet(Span.TextDecorationsProperty))

src/Controls/tests/TestCases.HostApp/Issues/Issue21326.cs

@@ -0,0 +1,41 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 21326, "Span does not inherit text styling from Label if that styling is applied using Style", PlatformAffected.All)]
+public partial class Issue21326 : ContentPage
+{
+	public Issue21326()
+	{
+		var Issue21326resourceDictionary = new ResourceDictionary();
+
+		var headingStyle = new Style(typeof(Label));
+		headingStyle.Setters.Add(new Setter { Property = Label.FontFamilyProperty, Value = "MontserratBold" });
+		headingStyle.Setters.Add(new Setter { Property = Label.FontSizeProperty, Value = 20.0 });
+		Issue21326resourceDictionary.Add("HeadingStyle", headingStyle);
+
+		Resources = Issue21326resourceDictionary;
+
+		var Issue21326testLabel = new Label
+		{
+			Style = headingStyle,
+			AutomationId = "Issue21326Label"
+		};
+
+		var formattedString = new FormattedString();
+		formattedString.Spans.Add(new Span
+		{
+			Text = "SHOULD BE MONTSERRATBOLD from Style"
+		});
+		Issue21326testLabel.FormattedText = formattedString;
+
+		Content = new VerticalStackLayout
+		{
+			Padding = 10,
+			Spacing = 20,
+			Children =
+			{
+				new Label { Text = "Test Passes if below label rendered in MontserratBold font from Style" },
+				Issue21326testLabel
+			}
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue21326.cs

@@ -0,0 +1,20 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue21326 : _IssuesUITest
+{
+	public override string Issue => "Span does not inherit text styling from Label if that styling is applied using Style";
+
+	public Issue21326(TestDevice device) : base(device) { }
+
+	[Test]
+	[Category(UITestCategories.Label)]
+	public void SpanShouldInheritStyleFromLabel()
+	{
+		App.WaitForElement("Issue21326Label");
+		VerifyScreenshot();
+	}
+}