Repro + fix (#10122) fixes #9962

Co-authored-by: Rui Marinho <me@ruimarinho.net>

Xamarin.Forms.ControlGallery.MacOS/NativeServices.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using AppKit;
 using Xamarin.Forms;
 using Xamarin.Forms.ControlGallery.MacOS;
 using Xamarin.Forms.Controls;
@@ -7,6 +8,7 @@ using Xamarin.Forms.Platform.MacOS;
 
 [assembly: Dependency(typeof(TestCloudService))]
 [assembly: Dependency(typeof(CacheService))]
+[assembly: Dependency(typeof(NativeColorService))]
 [assembly: ExportRenderer(typeof(DisposePage), typeof(DisposePageRenderer))]
 [assembly: ExportRenderer(typeof(DisposeLabel), typeof(DisposeLabelRenderer))]
 
@@ -25,6 +27,17 @@ namespace Xamarin.Forms.ControlGallery.MacOS
 		}
 	}
 
+	public class NativeColorService : INativeColorService
+	{
+		public Color GetConvertedColor(bool shouldCrash)
+		{
+			if (shouldCrash)
+				return NSColor.ControlText.ToColor();
+
+			return NSColor.ControlText.ToColor(NSColorSpace.DeviceRGBColorSpace);
+		}
+	}
+
 	public class DisposePageRenderer : PageRenderer
 	{
 		protected override void Dispose(bool disposing)

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

@@ -0,0 +1,7 @@
+namespace Xamarin.Forms.Controls
+{
+	public interface INativeColorService
+	{
+		Color GetConvertedColor(bool shouldCrash); 
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue9962.cs

@@ -0,0 +1,84 @@
+using System;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 9962, "NSException thrown when calling NSColor.ControlBackground.ToColor()", PlatformAffected.macOS)]
+	public class Issue9962 : TestContentPage
+	{
+		public Issue9962()
+		{
+		}
+
+		protected override void Init()
+		{
+			var stackLayout = new StackLayout
+			{
+				HorizontalOptions = LayoutOptions.Center,
+				VerticalOptions = LayoutOptions.Center
+			};
+
+			var debugLabel = new Label
+			{
+				Text = "The first button should show an alert with the exception message, second button should retrieve an actual color and put the value in this label and in the BoxView"
+			};
+
+			var boxView = new BoxView
+			{
+				BackgroundColor = Color.Blue,
+				WidthRequest = 100,
+				HeightRequest = 100
+			};
+
+			var buttonBoom = new Button
+			{
+				Text = "This button should throw an Exception"
+			};
+
+			buttonBoom.Clicked += (_, __) =>
+			{
+				try
+				{
+					var color = DependencyService.Get<INativeColorService>()?.GetConvertedColor(true);
+
+					boxView.BackgroundColor = color ?? Color.Black;
+
+				}
+				catch (InvalidOperationException ex)
+				{
+					DisplayAlert("Exception!", ex.Message, "Gotcha");
+				}
+			};
+
+			var buttonNotBoom = new Button
+			{
+				Text = "This button should NOT throw an Exception"
+			};
+
+			buttonNotBoom.Clicked += (_, __) =>
+			{
+				try
+				{
+					var color = DependencyService.Get<INativeColorService>()?.GetConvertedColor(false);
+
+					debugLabel.Text = color?.ToString();
+					boxView.BackgroundColor = color ?? Color.Black;
+				}
+				catch (Exception ex)
+				{
+					DisplayAlert("Exception!", ex.Message, "Gotcha");
+				}
+			};
+			
+
+			stackLayout.Children.Add(buttonBoom);
+			stackLayout.Children.Add(buttonNotBoom);
+			stackLayout.Children.Add(debugLabel);
+			stackLayout.Children.Add(boxView);
+
+			Content = stackLayout;
+		}
+	}
+}

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

@@ -1342,6 +1342,8 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue8272.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8964.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue9951.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue9962.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Controls\INativeColorService.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue9794.cs" />
   </ItemGroup>
   <ItemGroup>

Xamarin.Forms.Platform.iOS/Extensions/ColorExtensions.cs

@@ -187,11 +187,23 @@ namespace Xamarin.Forms.Platform.MacOS
 #if __MOBILE__
 			color.GetRGBA(out red, out green, out blue, out alpha);
 #else
+			if (color.Type == NSColorType.Catalog)
+				throw new InvalidOperationException("Cannot convert a NSColorType.Catalog color without specifying the color space, use the overload to specify an NSColorSpace");
+
 			color.GetRgba(out red, out green, out blue, out alpha);
 #endif
 			return new Color(red, green, blue, alpha);
 		}
 
+#if __MACOS__
+		public static Color ToColor(this UIColor color, NSColorSpace colorSpace)
+		{
+			var convertedColor = color.UsingColorSpace(colorSpace);
+
+			return convertedColor.ToColor();
+		}
+#endif
+
 #if __MOBILE__
 		public static UIColor ToUIColor(this Color color)
 		{