Screw wayland, we aren't dealing with "you can't set window coordinates" right now

src/Gtk/Avalonia.Gtk3/Gtk3Platform.cs

@@ -35,6 +35,9 @@ namespace Avalonia.Gtk3
                     X11.XInitThreads();
                 }catch{}
                 Resolver.Resolve();
+                if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+                    using (var backends = new Utf8Buffer("x11"))
+                        Native.GdkSetAllowedBackends?.Invoke(backends);
                 Native.GtkInit(0, IntPtr.Zero);
                 var disp = Native.GdkGetDefaultDisplay();
                 DisplayClassName =

src/Gtk/Avalonia.Gtk3/Interop/Native.cs

@@ -48,10 +48,13 @@ namespace Avalonia.Gtk3.Interop
             public delegate void gtk_main_iteration();
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
-            public delegate GtkWindow gtk_window_new(GtkWindowType windowType);
+            public delegate GtkWindow gtk_window_new(GtkWindowType windowType);           
-
+            
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate IntPtr gtk_init(int argc, IntPtr argv);
+            
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gdk, optional: true)]
+            public delegate IntPtr gdk_set_allowed_backends (Utf8Buffer backends);
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate void gtk_window_present(GtkWindow gtkWindow);
@@ -393,6 +396,7 @@ namespace Avalonia.Gtk3.Interop
         public static D.gtk_window_new GtkWindowNew;
         public static D.gtk_window_set_icon GtkWindowSetIcon;
         public static D.gtk_window_set_modal GtkWindowSetModal;
+        public static D.gdk_set_allowed_backends GdkSetAllowedBackends;
         public static D.gtk_init GtkInit;
         public static D.gtk_window_present GtkWindowPresent;
         public static D.gtk_widget_hide GtkWidgetHide;