Abstract linux DBus and GTK storage providers, use async initialization

Avalonia.sln

@@ -559,6 +559,7 @@ Global
 		{2B390431-288C-435C-BB6B-A374033BD8D1} = {4ED8B739-6F4E-4CD4-B993-545E6B5CE637}
 		{EABE2161-989B-42BF-BD8D-1E34B20C21F1} = {C5A00AC3-B34C-4564-9BDD-2DA473EF4D8B}
 		{1BBFAD42-B99E-47E0-B00A-A4BC6B6BB4BB} = {4ED8B739-6F4E-4CD4-B993-545E6B5CE637}
+		{4D36CEC8-53F2-40A5-9A37-79AAE356E2DA} = {86C53C40-57AA-45B8-AD42-FAE0EFDF0F2B}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {87366D66-1391-4D90-8999-95A620AD786A}

src/Avalonia.FreeDesktop/DBusHelper.cs

@@ -24,8 +24,7 @@ namespace Avalonia.FreeDesktop
                     if (_ctx is not null)
                         _ctx?.Post(d, state);
                     else
-                        lock (_lock)
-                            d(state);
+                        d(state);
                 }
             }
 

src/Avalonia.FreeDesktop/DBusSystemDialog.cs

@@ -15,27 +15,26 @@ namespace Avalonia.FreeDesktop
 {
     internal class DBusSystemDialog : BclStorageProvider
     {
-        private static readonly Lazy<IFileChooser?> s_fileChooser = new(() =>
+        private static readonly Lazy<IFileChooser?> s_fileChooser = new(() => DBusHelper.Connection?
+            .CreateProxy<IFileChooser>("org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop"));
+
+        internal static async Task<DBusSystemDialog?> TryCreate(IPlatformHandle handle)
         {
-            var fileChooser = DBusHelper.Connection?.CreateProxy<IFileChooser>("org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop");
-            if (fileChooser is null)
-                return null;
-            try
+            if (handle.HandleDescriptor == "XID" && s_fileChooser.Value is { } fileChooser)
             {
-                _ = fileChooser.GetVersionAsync();
-                return fileChooser;
-            }
-            catch (Exception e)
-            {
-                Logger.TryGet(LogEventLevel.Error, LogArea.X11Platform)?.Log(null, $"Unable to connect to org.freedesktop.portal.Desktop: {e.Message}");
-                return null;
+                try
+                {
+                    await fileChooser.GetVersionAsync();
+                    return new DBusSystemDialog(fileChooser, handle);
+                }
+                catch (Exception e)
+                {
+                    Logger.TryGet(LogEventLevel.Error, LogArea.X11Platform)?.Log(null, $"Unable to connect to org.freedesktop.portal.Desktop: {e.Message}");
+                    return null;
+                }
             }
-        });
 
-        internal static DBusSystemDialog? TryCreate(IPlatformHandle handle)
-        {
-            return handle.HandleDescriptor == "XID" && s_fileChooser.Value is { } fileChooser
-                ? new DBusSystemDialog(fileChooser, handle) : null;
+            return null;
         }
 
         private readonly IFileChooser _fileChooser;

src/Avalonia.X11/NativeDialogs/Gtk.cs

@@ -264,8 +264,6 @@ namespace Avalonia.X11.NativeDialogs
         public static Task<bool> StartGtk()
         {
             return StartGtkCore();
-            lock (s_startGtkLock)
-                return s_startGtkTask ??= StartGtkCore();
         }
 
         private static void GtkThread(TaskCompletionSource<bool> tcs)

src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs

@@ -17,10 +17,10 @@ namespace Avalonia.X11.NativeDialogs
 {
     internal class GtkSystemDialog : BclStorageProvider
     {
-        private Task<bool>? _initialized;
+        private static Task<bool>? _initialized;
         private readonly X11Window _window;
 
-        public GtkSystemDialog(X11Window window)
+        private GtkSystemDialog(X11Window window)
         {
             _window = window;
         }
@@ -31,10 +31,15 @@ namespace Avalonia.X11.NativeDialogs
 
         public override bool CanPickFolder => true;
 
-        public override async Task<IReadOnlyList<IStorageFile>> OpenFilePickerAsync(FilePickerOpenOptions options)
+        internal static async Task<GtkSystemDialog?> TryCreate(X11Window window)
         {
-            await EnsureInitialized();
+            _initialized ??= StartGtk();
+
+            return await _initialized ? new GtkSystemDialog(window) : null;
+        }
 
+        public override async Task<IReadOnlyList<IStorageFile>> OpenFilePickerAsync(FilePickerOpenOptions options)
+        {
             return await await RunOnGlibThread(async () =>
             {
                 var res = await ShowDialog(options.Title, _window, GtkFileChooserAction.Open,
@@ -46,8 +51,6 @@ namespace Avalonia.X11.NativeDialogs
 
         public override async Task<IReadOnlyList<IStorageFolder>> OpenFolderPickerAsync(FolderPickerOpenOptions options)
         {
-            await EnsureInitialized();
-
             return await await RunOnGlibThread(async () =>
             {
                 var res = await ShowDialog(options.Title, _window, GtkFileChooserAction.SelectFolder,
@@ -59,8 +62,6 @@ namespace Avalonia.X11.NativeDialogs
 
         public override async Task<IStorageFile?> SaveFilePickerAsync(FilePickerSaveOptions options)
         {
-            await EnsureInitialized();
-
             return await await RunOnGlibThread(async () =>
             {
                 var res = await ShowDialog(options.Title, _window, GtkFileChooserAction.Save,
@@ -225,19 +226,6 @@ namespace Avalonia.X11.NativeDialogs
             return tcs.Task;
         }
 
-        private async Task EnsureInitialized()
-        {
-            if (_initialized == null)
-            {
-                _initialized = StartGtk();
-            }
-
-            if (!(await _initialized))
-            {
-                throw new Exception("Unable to initialize GTK on separate thread");
-            }
-        }
-
         private static void UpdateParent(IntPtr chooser, IWindowImpl parentWindow)
         {
             var xid = parentWindow.Handle.Handle;

src/Avalonia.X11/NativeDialogs/LinuxStorageProvider.cs

@@ -0,0 +1,72 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Avalonia.FreeDesktop;
+using Avalonia.Platform.Storage;
+
+namespace Avalonia.X11.NativeDialogs;
+
+internal class LinuxStorageProvider : IStorageProvider
+{
+    private readonly X11Window _window;
+    public LinuxStorageProvider(X11Window window)
+    {
+        _window = window;
+    }
+
+    public bool CanOpen => true;
+    public bool CanSave => true;
+    public bool CanPickFolder => true;
+
+    private async Task<IStorageProvider> EnsureStorageProvider()
+    {
+        var options = AvaloniaLocator.Current.GetService<X11PlatformOptions>() ?? new X11PlatformOptions();
+
+        if (options.UseDBusFilePicker)
+        {
+            var dBusDialog = await DBusSystemDialog.TryCreate(_window.Handle);
+            if (dBusDialog is not null)
+            {
+                return dBusDialog;
+            }
+        }
+        
+        var gtkDialog = await GtkSystemDialog.TryCreate(_window);
+        if (gtkDialog is not null)
+        {
+            return gtkDialog;
+        }
+
+        throw new InvalidOperationException("Neither DBus nor GTK are available on the system");
+    }
+
+    public async Task<IReadOnlyList<IStorageFile>> OpenFilePickerAsync(FilePickerOpenOptions options)
+    {
+        var provider = await EnsureStorageProvider().ConfigureAwait(false);
+        return await provider.OpenFilePickerAsync(options).ConfigureAwait(false);
+    }
+
+    public async Task<IStorageFile> SaveFilePickerAsync(FilePickerSaveOptions options)
+    {
+        var provider = await EnsureStorageProvider().ConfigureAwait(false);
+        return await provider.SaveFilePickerAsync(options).ConfigureAwait(false);
+    }
+
+    public async Task<IReadOnlyList<IStorageFolder>> OpenFolderPickerAsync(FolderPickerOpenOptions options)
+    {
+        var provider = await EnsureStorageProvider().ConfigureAwait(false);
+        return await provider.OpenFolderPickerAsync(options).ConfigureAwait(false);
+    }
+
+    public async Task<IStorageBookmarkFile> OpenFileBookmarkAsync(string bookmark)
+    {
+        var provider = await EnsureStorageProvider().ConfigureAwait(false);
+        return await provider.OpenFileBookmarkAsync(bookmark).ConfigureAwait(false);
+    }
+
+    public async Task<IStorageBookmarkFolder> OpenFolderBookmarkAsync(string bookmark)
+    {
+        var provider = await EnsureStorageProvider().ConfigureAwait(false);
+        return await provider.OpenFolderBookmarkAsync(bookmark).ConfigureAwait(false);
+    }
+}

src/Avalonia.X11/X11Platform.cs

@@ -216,16 +216,16 @@ namespace Avalonia
         public bool OverlayPopups { get; set; }
 
         /// <summary>
-        /// Enables native file dialogs as well as global menu support on Linux desktop environments where it's supported (e. g. XFCE and MATE with plugin, KDE, etc).
+        /// Enables global menu support on Linux desktop environments where it's supported (e. g. XFCE and MATE with plugin, KDE, etc).
         /// The default value is true.
         /// </summary>
         public bool UseDBusMenu { get; set; } = true;
 
         /// <summary>
-        /// Enables GTK file picker instead of default FreeDesktop.
-        /// The default value is true. And FreeDesktop file picker is used instead if available.
+        /// Enables DBus file picker instead of GTK.
+        /// The default value is true.
         /// </summary>
-        public bool UseGtkFilePicker { get; set; } = false;
+        public bool UseDBusFilePicker { get; set; } = true;
 
         /// <summary>
         /// Deferred renderer would be used when set to true. Immediate renderer when set to false. The default value is true.

src/Avalonia.X11/X11Window.cs

@@ -215,9 +215,7 @@ namespace Avalonia.X11
                     _x11.Atoms.XA_CARDINAL, 32, PropertyMode.Replace, ref _xSyncCounter, 1);
             }
 
-            var canUseFreeDekstopPicker = !platform.Options.UseGtkFilePicker && platform.Options.UseDBusMenu;
-            StorageProvider = canUseFreeDekstopPicker && DBusSystemDialog.TryCreate(Handle) is {} dBusStorage
-                ? dBusStorage : new NativeDialogs.GtkSystemDialog(this);
+            StorageProvider = new NativeDialogs.LinuxStorageProvider(this);
         }
 
         class SurfaceInfo  : EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo