[macOS] Fix usage of FormattedText

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue12259.cs

@@ -0,0 +1,34 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.Forms.Core.UITests;
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.ManualReview)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 12259, "App crash when rendering label with FormattedText", PlatformAffected.macOS)]
+	public class Issue12259 : TestContentPage // or TestFlyoutPage, etc ...
+	{
+		protected override void Init()
+		{
+			var label = new Label();
+
+			var fs = new FormattedString();
+
+			fs.Spans.Add(new Span { Text = "Learn more at " });
+
+			fs.Spans.Add(new Span { Text = "https://aka.ms/xamarin-quickstart ", FontAttributes = FontAttributes.Bold });
+
+			label.FormattedText = fs;
+
+			Content = label;
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -1706,6 +1706,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)ShellFlyoutContentOffest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ShellFlyoutContentWithZeroMargin.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue13436.xaml.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue12259.cs" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla22229.xaml">

Xamarin.Forms.Platform.iOS/Renderers/FormattedStringExtensions.cs

@@ -109,14 +109,17 @@ internal static NSAttributedString ToAttributed(this Span span, BindableObject o
 			if (owner is Entry && !fgcolor.IsDefault)
 				fgcolor = defaultForegroundColor;
 
+#if __MOBILE__
 			if (fgcolor.IsDefault)
 				fgcolor = ColorExtensions.LabelColor.ToColor();
-#if __MOBILE__
 			UIColor spanFgColor;
 			UIColor spanBgColor;
 			spanFgColor = fgcolor.ToUIColor();
 			spanBgColor = span.BackgroundColor.ToUIColor();
 #else
+
+			if (fgcolor.IsDefault)
+				fgcolor = ColorExtensions.LabelColor.ToColor(NSColorSpace.GenericRGBColorSpace);
 			NSColor spanFgColor;
 			NSColor spanBgColor;
 			spanFgColor = fgcolor.ToNSColor();