unoplatform/uno · error · NullReferenceException

Couldn't find GLibrary in WebKitGtkSharp

Error message

Couldn't find GLibrary in WebKitGtkSharp

What it means

X11NativeWebView (Skia WebView on Linux/X11) reflects into the WebKitGtkSharp assembly to patch GLibrary so that libwebkit2gtk-4.1.so is pre-loaded before WebKitGtk# dlopens 4.0. It does `Assembly.Load("WebKitGtkSharp").GetType("GLibrary")` and throws NullReferenceException when the type is absent. This is a coupling to a private implementation detail of WebKitGtkSharp: if the package is upgraded/changed so that GLibrary is renamed or removed, the patch can no longer find its anchor.

Solutions

1. Pin the WebKitGtkSharp package version that ships the GLibrary type that X11NativeWebView expects (check the referenced version in the Skia.X11 WebView add-in csproj).
2. Ensure the correct libwebkit2gtk-4.1.so is installed so the patch path still resolves; if 4.1 is missing the code logs an error and proceeds to the 4.0 path instead (no throw here).
3. If you maintain the add-in, update the reflection anchor (type/field/method names) to match the installed WebKitGtkSharp internals.

// Validate the WebKitGtkSharp internals surface before relying on the patch
var asm = AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(a => a.GetName().Name == "WebKitGtkSharp");
bool gLibraryPresent = asm?.GetType("GLibrary") is not null;

static bool WebKitGtkSharpHasGLibrary() => AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(a => a.GetName().Name == "WebKitGtkSharp")?.GetType("GLibrary") is not null;

try { NavigateWithHttpRequest(request); }
catch (NullReferenceException ex) when (ex.Message.Contains("GLibrary")) { /* fall back to URI navigation */ }

When it happens

Trigger: A WebKitGtkSharp version is loaded whose public/internal structure no longer exposes a type literally named 'GLibrary' (the bootstrap class), while libwebkit2gtk-4.1.so IS present (the else-branch is taken).

Common situations: Updating the WebKitGtkSharp NuGet dependency on a distro; running on a Linux distribution whose packaged WebKitGtk# differs; trimming/IL-linking that strips the GLibrary type.

Related errors

• Couldn't find a field named _libraries in GLibrary
• Couldn't read the static field named _libraries in GLibrary
• XLIB ERROR: Cannot connect to X server
• Attempt to set value from read-only property
• Binding to XamlSetMarkupExtensionHandler failed

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/80c4103a77ea1155. Report an issue: GitHub.

Appendix: source

Thrown at src/AddIns/Uno.UI.WebView.Skia.X11/X11NativeWebView.cs:99

				}
			}

			// webkit2gtk-4.1 adds support for exposing libsoup objects, most importantly in webkit_uri_request_get_http_headers.
			// Gtk# by default loads libwebkit2gtk-4.0 (+ libsoup-2.0), but we want libwebkit2gtk-4.1 (+ libsoup-3.0), so what
			// we do is that before WebKitGtk# makes its dlopen calls, we load libwebkit2gtk-4.1 and put it where the handle to
			// libwebkit2gtk-4.0 will be expected to be, so that when WebKitGtk# attempts to dlopen(libwebkit2gtk-4.0), it will
			// find the handle already there and will just use it instead.
			if (!NativeLibrary.TryLoad("libwebkit2gtk-4.1.so", typeof(X11NativeWebView).Assembly, DllImportSearchPath.UserDirectories, out var webkitgtk41handle))
			{
				if (typeof(X11NativeWebView).Log().IsEnabled(LogLevel.Error))
				{
					typeof(X11NativeWebView).Log().Error($"libwebkit2gtk-4.1 was not found. Attempting to call {nameof(ProcessNavigation)} with an {nameof(HttpRequestMessage)} instance will crash the process.");
				}
			}
			else
			{
				Assembly assembly = Assembly.Load("WebKitGtkSharp");
				Type glibraryType = assembly.GetType("GLibrary") ?? throw new NullReferenceException("Couldn't find GLibrary in WebKitGtkSharp");
				Type libraryType = assembly.GetType("Library") ?? throw new NullReferenceException("Couldn't find Library in WebKitGtkSharp");
				object webkitLibraryEnum = Enum.ToObject(libraryType, 11);
				FieldInfo field = glibraryType.GetField("_libraries", BindingFlags.NonPublic | BindingFlags.Static) ?? throw new NullReferenceException("Couldn't find a field named _libraries in GLibrary");
				object libraries = field.GetValue(null) ?? throw new NullReferenceException("Couldn't read the static field named _libraries in GLibrary");
				var setItemMethod = libraries.GetType().GetMethod("set_Item") ?? throw new NullReferenceException("Couldn't find a method named set_Item in _libraries");
				setItemMethod.Invoke(libraries, [webkitLibraryEnum, webkitgtk41handle]);
				_usingWebKit2Gtk41 = true;
			}

			if (!WebKit.Global.IsSupported)
			{
				_initException = new PlatformNotSupportedException("libwebkit2gtk-4.0 is not found. Make sure that WebKit2GTK 4.0 and GTK 3 are installed. See https://aka.platform.uno/webview2 for more information");
				return;
			}

			GLib.ExceptionManager.UnhandledException += args =>
			{
				if (typeof(X11NativeWebView).Log().IsEnabled(LogLevel.Error))

View on GitHub (pinned to 0418340488)