Add xdg-desktop-portal file chooser

src/Avalonia.FreeDesktop/DBusFileChooser.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+using Tmds.DBus;
+
+[assembly: InternalsVisibleTo(Connection.DynamicAssemblyName)]
+namespace Avalonia.FreeDesktop
+{
+    [DBusInterface("org.freedesktop.portal.FileChooser")]
+    public interface IFileChooser : IDBusObject
+    {
+        Task<ObjectPath> OpenFileAsync(string ParentWindow, string Title, IDictionary<string, object> Options);
+        Task<ObjectPath> SaveFileAsync(string ParentWindow, string Title, IDictionary<string, object> Options);
+        Task<ObjectPath> SaveFilesAsync(string ParentWindow, string Title, IDictionary<string, object> Options);
+        Task<T> GetAsync<T>(string prop);
+        Task<FileChooserProperties> GetAllAsync();
+        Task SetAsync(string prop, object val);
+        Task<IDisposable> WatchPropertiesAsync(Action<PropertyChanges> handler);
+    }
+
+    [Dictionary]
+    public class FileChooserProperties
+    {
+        public uint Version { get; set; }
+    }
+
+    public static class FileChooserExtensions
+    {
+        public static Task<uint> GetVersionAsync(this IFileChooser o) => o.GetAsync<uint>("version");
+    }
+}

src/Avalonia.FreeDesktop/DBusRequest.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+using Tmds.DBus;
+
+[assembly: InternalsVisibleTo(Connection.DynamicAssemblyName)]
+namespace Avalonia.FreeDesktop
+{
+    [DBusInterface("org.freedesktop.portal.Request")]
+    internal interface IRequest : IDBusObject
+    {
+        Task CloseAsync();
+        Task<IDisposable> WatchResponseAsync(Action<(uint response, IDictionary<string, object> results)> handler, Action<Exception> onError = null);
+    }
+}

src/Avalonia.FreeDesktop/DBusSystemDialog.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Controls.Platform;
+using Tmds.DBus;
+
+namespace Avalonia.FreeDesktop
+{
+    public class DBusSystemDialog : ISystemDialogImpl
+    {
+        private readonly IFileChooser _fileChooser;
+
+        public DBusSystemDialog()
+        {
+            _fileChooser = DBusHelper.Connection.CreateProxy<IFileChooser>("org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop");
+        }
+
+        public async Task<string[]> ShowFileDialogAsync(FileDialog dialog, Window parent)
+        {
+            var parentWindow = $"x11:{parent.PlatformImpl!.Handle.Handle.ToString("X")}";
+            ObjectPath objectPath;
+            var options = new Dictionary<string, object>();
+            if (dialog.Filters is not null)
+                options.Add("filters", ParseFilters(dialog));
+
+            switch (dialog)
+            {
+                case OpenFileDialog openFileDialog:
+                    options.Add("multiple", openFileDialog.AllowMultiple);
+                    objectPath = await _fileChooser.OpenFileAsync(parentWindow, openFileDialog.Title ?? string.Empty, options);
+                    break;
+                case SaveFileDialog saveFileDialog:
+                    if (saveFileDialog.InitialFileName is not null)
+                        options.Add("current_name", saveFileDialog.InitialFileName);
+                    if (saveFileDialog.Directory is not null)
+                        options.Add("current_folder", Encoding.UTF8.GetBytes(saveFileDialog.Directory));
+                    objectPath = await _fileChooser.SaveFileAsync(parentWindow, saveFileDialog.Title ?? string.Empty, options);
+                    break;
+            }
+
+            var request = DBusHelper.Connection.CreateProxy<IRequest>("org.freedesktop.portal.Request", objectPath);
+            var tsc = new TaskCompletionSource<string[]>();
+            using var disposable = await request.WatchResponseAsync(x => tsc.TrySetResult(x.results["uris"] as string[]));
+            var uris = await tsc.Task;
+            for (var i = 0; i < uris.Length; i++)
+                uris[i] = new Uri(uris[i]).AbsolutePath;
+            return uris;
+        }
+
+        public async Task<string> ShowFolderDialogAsync(OpenFolderDialog dialog, Window parent)
+        {
+            var parentWindow = $"x11:{parent.PlatformImpl!.Handle.Handle.ToString("X")}";
+            var options = new Dictionary<string, object>
+            {
+                { "directory", true }
+            };
+            var objectPath = await _fileChooser.OpenFileAsync(parentWindow, dialog.Title ?? string.Empty, options);
+            var request = DBusHelper.Connection.CreateProxy<IRequest>("org.freedesktop.portal.Request", objectPath);
+            var tsc = new TaskCompletionSource<string[]>();
+            using var disposable = await request.WatchResponseAsync(x => tsc.TrySetResult(x.results["uris"] as string[]));
+            var uris = await tsc.Task;
+            return uris.Length != 1 ? string.Empty : new Uri(uris[0]).AbsolutePath;
+        }
+
+        private static (string name, (uint style, string extension)[])[] ParseFilters(FileDialog dialog)
+        {
+            var filters = new (string name, (uint style, string extension)[])[dialog.Filters!.Count];
+            for (var i = 0; i < filters.Length; i++)
+            {
+                var extensions = dialog.Filters[i].Extensions.Select(static x => (0u, x)).ToArray();
+                filters[i] = (dialog.Filters[i].Name, extensions);
+            }
+
+            return filters;
+        }
+    }
+}