[X11] For now use GtkFileChooser on a separate thread

src/Avalonia.X11/Avalonia.X11.csproj

@@ -7,6 +7,7 @@
 
     <ItemGroup>
         <ProjectReference Include="..\..\packages\Avalonia\Avalonia.csproj" />
+        <ProjectReference Include="..\Gtk\Avalonia.Gtk3\Avalonia.Gtk3.csproj" />
     </ItemGroup>
 
 </Project>

src/Avalonia.X11/X11Platform.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using Avalonia.Controls;
 using Avalonia.Controls.Platform;
+using Avalonia.Gtk3;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.OpenGL;
@@ -41,7 +42,8 @@ namespace Avalonia.X11
                 .Bind<IClipboard>().ToConstant(new X11Clipboard(this))
                 .Bind<IPlatformSettings>().ToConstant(new PlatformSettingsStub())
                 .Bind<ISystemDialogImpl>().ToConstant(new SystemDialogsStub())
-                .Bind<IPlatformIconLoader>().ToConstant(new IconLoaderStub());
+                .Bind<IPlatformIconLoader>().ToConstant(new IconLoaderStub())
+                .Bind<ISystemDialogImpl>().ToConstant(new Gtk3ForeignX11SystemDialog());
             X11Screens.Init(this);
             if (Info.XInputVersion != null)
             {

src/Gtk/Avalonia.Gtk3/Gtk3ForeignX11SystemDialog.cs

@@ -0,0 +1,115 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Controls.Platform;
+using Avalonia.Gtk3.Interop;
+using Avalonia.Platform;
+using Avalonia.Platform.Interop;
+
+namespace Avalonia.Gtk3
+{
+    public class Gtk3ForeignX11SystemDialog : ISystemDialogImpl
+    {
+        private Task<bool> _initialized;
+        private SystemDialogBase _inner = new SystemDialogBase();
+
+
+        public async Task<string[]> ShowFileDialogAsync(FileDialog dialog, IWindowImpl parent)
+        {
+            await EnsureInitialized();
+            var xid = parent.Handle.Handle;
+            return await await RunOnGtkThread(
+                () => _inner.ShowFileDialogAsync(dialog, GtkWindow.Null, chooser => UpdateParent(chooser, xid)));
+        }
+
+        public async Task<string> ShowFolderDialogAsync(OpenFolderDialog dialog, IWindowImpl parent)
+        {
+            await EnsureInitialized();
+            var xid = parent.Handle.Handle;
+            return await await RunOnGtkThread(
+                () => _inner.ShowFolderDialogAsync(dialog, GtkWindow.Null, chooser => UpdateParent(chooser, xid)));
+        }
+
+        void UpdateParent(GtkFileChooser chooser, IntPtr xid)
+        {
+            Native.GtkWidgetRealize(chooser);
+            var window = Native.GtkWidgetGetWindow(chooser);
+            var parent = Native.GdkWindowForeignNewForDisplay(GdkDisplay, xid);
+            if (window != IntPtr.Zero && parent != IntPtr.Zero)
+                Native.GdkWindowSetTransientFor(window, parent);
+        }
+        
+        async Task EnsureInitialized()
+        {
+            if (_initialized == null)
+            {
+                var tcs = new TaskCompletionSource<bool>();
+                _initialized = tcs.Task;
+                new Thread(() => GtkThread(tcs))
+                {
+                    IsBackground = true
+                }.Start();
+            }
+
+            if (!(await _initialized))
+                throw new Exception("Unable to initialize GTK on separate thread");
+
+        }
+        
+        Task<T> RunOnGtkThread<T>(Func<T> action)
+        {
+            var tcs = new TaskCompletionSource<T>();
+            GlibTimeout.Add(0, 0, () =>
+            {
+
+                try
+                {
+                    tcs.SetResult(action());
+                }
+                catch (Exception e)
+                {
+                    tcs.TrySetException(e);
+                }
+
+                return false;
+            });
+            return tcs.Task;
+        }
+        
+
+        void GtkThread(TaskCompletionSource<bool> tcs)
+        {
+            try
+            {
+                X11.XInitThreads();
+            }catch{}
+            Resolver.Resolve();
+            if (Native.GdkWindowForeignNewForDisplay == null)
+                throw new Exception("gdk_x11_window_foreign_new_for_display is not found in your libgdk-3.so");
+            using (var backends = new Utf8Buffer("x11"))
+                Native.GdkSetAllowedBackends?.Invoke(backends);
+            if (!Native.GtkInitCheck(0, IntPtr.Zero))
+            {
+                tcs.SetResult(false);
+                return;
+            }
+
+            using (var utf = new Utf8Buffer($"avalonia.app.a{Guid.NewGuid().ToString("N")}"))
+                App = Native.GtkApplicationNew(utf, 0);
+            if (App == IntPtr.Zero)
+            {
+                tcs.SetResult(false);
+                return;
+            }
+            GdkDisplay = Native.GdkGetDefaultDisplay();
+            tcs.SetResult(true);
+            while (true)
+                Native.GtkMainIteration();
+        }
+
+        private IntPtr GdkDisplay { get; set; }
+        private IntPtr App { get; set; }
+    }
+}

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

@@ -50,6 +50,9 @@ namespace Avalonia.Gtk3.Interop
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate IntPtr gtk_init(int argc, IntPtr argv);
             
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
+            public delegate bool gtk_init_check(int argc, IntPtr argv);
+            
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gdk, optional: true)]
             public delegate IntPtr gdk_set_allowed_backends (Utf8Buffer backends);
 
@@ -288,6 +291,12 @@ namespace Avalonia.Gtk3.Interop
             
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gdk)]
             public delegate void gdk_window_end_paint(IntPtr window);
+            
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gdk, optional: true)]
+            public delegate IntPtr gdk_x11_window_foreign_new_for_display(IntPtr display, IntPtr xid);
+            
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gdk)]
+            public delegate void gdk_window_set_transient_for(IntPtr window, IntPtr parent);
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gdk)]
             public delegate void gdk_event_request_motions(IntPtr ev);
@@ -414,6 +423,7 @@ namespace Avalonia.Gtk3.Interop
         public static D.gtk_window_set_transient_for GtkWindowSetTransientFor;
         public static D.gdk_set_allowed_backends GdkSetAllowedBackends;
         public static D.gtk_init GtkInit;
+        public static D.gtk_init_check GtkInitCheck;
         public static D.gtk_window_present GtkWindowPresent;
         public static D.gtk_widget_hide GtkWidgetHide;
         public static D.gtk_widget_show GtkWidgetShow;
@@ -483,8 +493,9 @@ namespace Avalonia.Gtk3.Interop
         public static D.gdk_window_process_updates GdkWindowProcessUpdates;
         public static D.gdk_window_begin_paint_rect GdkWindowBeginPaintRect;
         public static D.gdk_window_end_paint GdkWindowEndPaint;
+        public static D.gdk_x11_window_foreign_new_for_display GdkWindowForeignNewForDisplay;
+        public static D.gdk_window_set_transient_for GdkWindowSetTransientFor;
         
-
         public static D.gdk_pixbuf_new_from_file GdkPixbufNewFromFile;
         public static D.gtk_icon_theme_get_default GtkIconThemeGetDefault;
         public static D.gtk_icon_theme_load_icon GtkIconThemeLoadIcon;

src/Gtk/Avalonia.Gtk3/SystemDialogs.cs

@@ -11,16 +11,17 @@ using Avalonia.Platform.Interop;
 
 namespace Avalonia.Gtk3
 {
-    class SystemDialog : ISystemDialogImpl
+    class SystemDialogBase
     {
 
-        unsafe static Task<string[]> ShowDialog(string title, GtkWindow parent, GtkFileChooserAction action,
-            bool multiselect, string initialFileName)
+        public unsafe static Task<string[]> ShowDialog(string title, GtkWindow parent, GtkFileChooserAction action,
+            bool multiselect, string initialFileName, Action<GtkFileChooser> modify)
         {
             GtkFileChooser dlg;
             parent = parent ?? GtkWindow.Null;
             using (var name = new Utf8Buffer(title))
                 dlg = Native.GtkFileChooserDialogNew(name, parent, action, IntPtr.Zero);
+            modify?.Invoke(dlg);
             if (multiselect)
                 Native.GtkFileChooserSetSelectMultiple(dlg, true);
 
@@ -42,7 +43,7 @@ namespace Avalonia.Gtk3
                     dispose();
                     return false;
                 }),
-                Signal.Connect<Native.D.signal_dialog_response>(dlg, "response", (_, resp, __)=>
+                Signal.Connect<Native.D.signal_dialog_response>(dlg, "response", (_, resp, __) =>
                 {
                     string[] result = null;
                     if (resp == GtkResponseType.Accept)
@@ -56,9 +57,11 @@ namespace Avalonia.Gtk3
                                 rlst.Add(Utf8Buffer.StringFromPtr(cgs->Data));
                             cgs = cgs->Next;
                         }
+
                         Native.GSlistFree(gs);
                         result = rlst.ToArray();
                     }
+
                     Native.GtkWidgetHide(dlg);
                     dispose();
                     tcs.TrySetResult(result);
@@ -70,27 +73,38 @@ namespace Avalonia.Gtk3
                 Native.GtkDialogAddButton(dlg, open, GtkResponseType.Accept);
             using (var open = new Utf8Buffer("Cancel"))
                 Native.GtkDialogAddButton(dlg, open, GtkResponseType.Cancel);
-            if(initialFileName!=null)
+            if (initialFileName != null)
                 using (var fn = new Utf8Buffer(initialFileName))
                     Native.GtkFileChooserSetFilename(dlg, fn);
             Native.GtkWindowPresent(dlg);
             return tcs.Task;
         }
 
-        public Task<string[]> ShowFileDialogAsync(FileDialog dialog, IWindowImpl parent)
+        public Task<string[]> ShowFileDialogAsync(FileDialog dialog, GtkWindow parent,
+            Action<GtkFileChooser> modify = null)
         {
-            return ShowDialog(dialog.Title, ((WindowBaseImpl)parent)?.GtkWidget,
+            return ShowDialog(dialog.Title, parent,
                 dialog is OpenFileDialog ? GtkFileChooserAction.Open : GtkFileChooserAction.Save,
                 (dialog as OpenFileDialog)?.AllowMultiple ?? false,
                 Path.Combine(string.IsNullOrEmpty(dialog.InitialDirectory) ? "" : dialog.InitialDirectory,
-                string.IsNullOrEmpty(dialog.InitialFileName) ? "" : dialog.InitialFileName));
+                    string.IsNullOrEmpty(dialog.InitialFileName) ? "" : dialog.InitialFileName), modify);
         }
 
-        public async Task<string> ShowFolderDialogAsync(OpenFolderDialog dialog, IWindowImpl parent)
+        public async Task<string> ShowFolderDialogAsync(OpenFolderDialog dialog, GtkWindow parent,
+            Action<GtkFileChooser> modify = null)
         {
-            var res = await ShowDialog(dialog.Title, ((WindowBaseImpl) parent)?.GtkWidget,
-                GtkFileChooserAction.SelectFolder, false, dialog.InitialDirectory);
+            var res = await ShowDialog(dialog.Title, parent,
+                GtkFileChooserAction.SelectFolder, false, dialog.InitialDirectory, modify);
             return res?.FirstOrDefault();
         }
     }
+
+    class SystemDialog : SystemDialogBase, ISystemDialogImpl
+    {
+        public Task<string> ShowFolderDialogAsync(OpenFolderDialog dialog, IWindowImpl parent)
+            => ShowFolderDialogAsync(dialog, ((WindowBaseImpl)parent)?.GtkWidget);
+
+        public Task<string[]> ShowFileDialogAsync(FileDialog dialog, IWindowImpl parent)
+            => ShowFileDialogAsync(dialog, ((WindowBaseImpl)parent)?.GtkWidget);
+    }
 }