Fix Linux WebView login hang and User-Agent failure (#2106) (#2108)

- Set NativeWebDialog.UserAgent in AdapterCreated instead of passing a full
  User-Agent header to ApplicationNameForUserAgent (which caused WebKit2GTK
  webkit_settings_set_user_agent assertion failures on Linux).
- Set gtkArgs.ForceX11GdkBackend = true when requesting the GTK WebView
  environment.
- Recognize GTK initialization failures (InvalidOperationException 'Unable to
  initialize GTK', libgtk-3/libgdk-3 DllNotFoundException, and exceptions
  originating from GtkNativeWebViewDialog/AvaloniaGtk) in
  WebView2LoginErrorMessage so async void NativeWebDialog.Show() failures
  fault BrowserLoginAsync instead of leaving tcs.Task waiting forever,
  allowing StartAsyncInternal to fall back to LoginExternalDialog.

Source/LibationAvalonia/Dialogs/Login/AvaloniaLoginChoiceEager.cs

@@ -93,6 +93,15 @@ public class AvaloniaLoginChoiceEager : ILoginChoiceEager
 		};
 		dialog.AdapterCreated += (s, e) =>
 		{
+			try
+			{
+				dialog.UserAgent = Configuration.Instance.GetDeviceRegistrationProfile().UserAgent;
+			}
+			catch (Exception ex)
+			{
+				Serilog.Log.Logger.Warning(ex, "Failed to set WebView User-Agent");
+			}
+
 			if (dialog.TryGetCookieManager() is NativeWebViewCookieManager cookieManager)
 			{
 				foreach (System.Net.Cookie c in shoiceIn.SignInCookies ?? [])
@@ -126,10 +135,13 @@ public class AvaloniaLoginChoiceEager : ILoginChoiceEager
 			return null;
 		}
 
-		// NativeWebDialog can fault on a posted dispatcher job (e.g. missing libwebkit2gtk on Linux), which bypasses a try/catch around Show().
+		// NativeWebDialog.Show() is async void and can fault on a posted dispatcher job (e.g. missing libwebkit2gtk
+		// or GTK initialization failure on Linux), which bypasses a synchronous try/catch around Show() and would
+		// otherwise leave tcs.Task waiting forever.
 		void onUnhandledException(object? sender, DispatcherUnhandledExceptionEventArgs e)
 		{
-			if (!WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(e.Exception))
+			if (!WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(e.Exception)
+				&& !WebView2LoginErrorMessage.TryFindInTree(e.Exception, out _))
 				return;
 			e.Handled = true;
 			try
@@ -166,7 +178,7 @@ public class AvaloniaLoginChoiceEager : ILoginChoiceEager
 				else
 					dialog.Show();
 			}
-			catch (Exception ex) when (WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(ex))
+			catch (Exception ex)
 			{
 				tcs.TrySetException(ex);
 			}
@@ -190,11 +202,10 @@ public class AvaloniaLoginChoiceEager : ILoginChoiceEager
 					break;
 				case AppleWKWebViewEnvironmentRequestedEventArgs appleArgs:
 					appleArgs.NonPersistentDataStore = true;
-					appleArgs.ApplicationNameForUserAgent = userAgent;
 					break;
 				case GtkWebViewEnvironmentRequestedEventArgs gtkArgs:
 					gtkArgs.EphemeralDataManager = true;
-					gtkArgs.ApplicationNameForUserAgent = userAgent;
+					gtkArgs.ForceX11GdkBackend = true;
 					break;
 			}
 		}

Source/LibationUiBase/WebView2LoginErrorMessage.cs

@@ -61,10 +61,15 @@ public static class WebView2LoginErrorMessage
 			if (e is DllNotFoundException dll && IsEmbeddedWebViewNativeDllFailure(dll))
 				return true;
 
+			// AvaloniaGtk.RunTask throws InvalidOperationException("Unable to initialize GTK") when GTK cannot start
+			// (for example on Wayland without X11 backend or when no GTK display is available).
+			if (e is InvalidOperationException && e.Message.Contains("Unable to initialize GTK", StringComparison.OrdinalIgnoreCase))
+				return true;
+
 			if (!StackMentionsEmbeddedSignInBrowser(e))
 				continue;
 
-			if (e is UnauthorizedAccessException)
+			if (e is UnauthorizedAccessException or InvalidOperationException or EntryPointNotFoundException or TypeInitializationException)
 				return true;
 
 			if (e is COMException com
@@ -81,7 +86,9 @@ public static class WebView2LoginErrorMessage
 	private static bool IsEmbeddedWebViewNativeDllFailure(DllNotFoundException e)
 	{
 		if (e.Message.Contains("libwebkit2gtk", StringComparison.OrdinalIgnoreCase)
-			|| e.Message.Contains("webkit2gtk", StringComparison.OrdinalIgnoreCase))
+			|| e.Message.Contains("webkit2gtk", StringComparison.OrdinalIgnoreCase)
+			|| e.Message.Contains("libgtk-3", StringComparison.OrdinalIgnoreCase)
+			|| e.Message.Contains("libgdk-3", StringComparison.OrdinalIgnoreCase))
 			return true;
 
 		return StackMentionsEmbeddedSignInBrowser(e);
@@ -118,7 +125,9 @@ public static class WebView2LoginErrorMessage
 			&& (stack.Contains("WebView2", StringComparison.Ordinal)
 				|| stack.Contains("CoreWebView2", StringComparison.Ordinal)
 				|| stack.Contains("NativeWebDialog", StringComparison.Ordinal)
+				|| stack.Contains("GtkNativeWebViewDialog", StringComparison.Ordinal)
 				|| stack.Contains("GtkWebView", StringComparison.Ordinal)
+				|| stack.Contains("AvaloniaGtk", StringComparison.Ordinal)
 				|| stack.Contains("WebViewControlAvalonia", StringComparison.Ordinal));
 	}
 }

Source/_Tests/LibationUiBase.Tests/WebView2LoginErrorMessageTests.cs

@@ -0,0 +1,69 @@
+using LibationUiBase;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.Runtime.CompilerServices;
+
+namespace LibationUiBase.Tests;
+
+[TestClass]
+public class WebView2LoginErrorMessageTests
+{
+	[TestMethod]
+	public void missing_webkit2gtk_dll_is_recognized_without_stack_trace()
+	{
+		var ex = new DllNotFoundException("Unable to load shared library 'libwebkit2gtk-4.1.so.0'");
+
+		Assert.IsTrue(WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(ex));
+	}
+
+	[TestMethod]
+	public void missing_gtk3_dll_is_recognized_without_stack_trace()
+	{
+		var ex = new DllNotFoundException("Unable to load shared library 'libgtk-3.so.0'");
+
+		Assert.IsTrue(WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(ex));
+	}
+
+	[TestMethod]
+	public void gtk_initialization_failure_is_recognized_without_stack_trace()
+	{
+		var ex = new InvalidOperationException("Unable to initialize GTK");
+
+		Assert.IsTrue(WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(ex));
+	}
+
+	[TestMethod]
+	public void invalid_operation_from_avalonia_gtk_webview_stack_is_recognized()
+	{
+		Exception? caught = null;
+		try
+		{
+			FakeAvaloniaGtkStack.ThrowFromGtkNativeWebViewDialog();
+		}
+		catch (Exception ex)
+		{
+			caught = ex;
+		}
+
+		Assert.IsNotNull(caught);
+		Assert.IsTrue(WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(caught));
+		var agg = new AggregateException(new Exception("outer"), caught);
+		Assert.IsTrue(WebView2LoginErrorMessage.TryFindInTree(agg, out var match));
+		Assert.IsNotNull(match);
+	}
+
+	[TestMethod]
+	public void unrelated_invalid_operation_is_not_treated_as_webview_failure()
+	{
+		var ex = new InvalidOperationException("Something else went wrong");
+
+		Assert.IsFalse(WebView2LoginErrorMessage.IsWebView2SignInInfrastructureFailure(ex));
+	}
+
+	private static class FakeAvaloniaGtkStack
+	{
+		[MethodImpl(MethodImplOptions.NoInlining)]
+		public static void ThrowFromGtkNativeWebViewDialog()
+			=> throw new InvalidOperationException("Avalonia.X11 is not referenced");
+	}
+}