feat: Initial implementation of FolderPicker for Gtk

chore: Update picker docs to indicate newly supported target

doc/articles/features/windows-storage-pickers.md

@@ -13,7 +13,7 @@ Legend
 |----------------|-----|-------------|---------|-----|-------|-----|-----|
 | FileOpenPicker | ✅   | ✅      (1)     | ✅       | ✅   | ✅     | ✅   | ✅  |
 | FileSavePicker | ✅   | ✅  (1)         | ✅       | ✅   | ✅     | ✅   | 🚫  |
-| FolderPicker   | ✅   | ✅           | ✅       | ⏸️ (2)|✅     | 🚫  | 🚫  |
+| FolderPicker   | ✅   | ✅           | ✅       | ⏸️ (2)|✅     | 🚫  | ✅  |
 
 (1) - Multiple implementations supported - see WebAssembly section below
 (2) - See iOS section below

src/SamplesApp/UITests.Shared/Windows_Storage/Pickers/FolderPickerTests.xaml.cs

@@ -12,7 +12,7 @@
 namespace UITests.Windows_Storage.Pickers
 {
 	[Sample("Windows.Storage", ViewModelType = typeof(FolderPickerTestsViewModel), IsManualTest = true,
-		Description = "Allows testing all features of FolderPicker. Currently not supported on Android, iOS, macOS and GTK. Not selecting a folder should not cause an exception")]
+		Description = "Allows testing all features of FolderPicker. Currently not supported on Android, iOS, and macOS. Not selecting a folder should not cause an exception")]
 	public sealed partial class FolderPickerTests : Page
 	{
 		public FolderPickerTests()

src/Uno.UI.Runtime.Skia.Gtk/Extensions/Storage/Pickers/FileOpenPickerExtension.cs

@@ -4,11 +4,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Uno.UI.Runtime.Skia;
-using Windows.ApplicationModel.Resources;
 using Windows.Storage;
 using Windows.Storage.Pickers;
 

src/Uno.UI.Runtime.Skia.Gtk/Extensions/Storage/Pickers/FolderPickerExtension.cs

@@ -0,0 +1,56 @@
+#nullable enable
+
+using Gtk;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Uno.UI.Runtime.Skia;
+using Windows.Storage;
+using Windows.Storage.Pickers;
+
+namespace Uno.Extensions.Storage.Pickers
+{
+	internal class FolderPickerExtension : IFolderPickerExtension
+	{
+		private readonly FolderPicker _picker;
+
+		public FolderPickerExtension(FolderPicker owner)
+		{
+			_picker = owner ?? throw new ArgumentNullException(nameof(owner));
+		}
+
+		public async Task<StorageFolder?> PickSingleFolderAsync(CancellationToken token)
+		{
+			string commitText = "Select Folder";
+			if (!string.IsNullOrWhiteSpace(_picker.CommitButtonText))
+			{
+				commitText = _picker.CommitButtonText;
+			}
+
+			FileChooserDialog dialog = new FileChooserDialog(
+				"Select Folder",
+				GtkHost.Window,
+				FileChooserAction.SelectFolder,
+				"Cancel", ResponseType.Cancel,
+				commitText, ResponseType.Accept);
+
+			dialog.SelectMultiple = false;
+
+			if (!_picker.FileTypeFilter.Contains("*"))
+			{
+				throw new ArgumentNullException();
+			}
+
+			dialog.SetCurrentFolder(PickerHelpers.GetInitialDirectory(_picker.SuggestedStartLocation));
+
+			StorageFolder folder = null;
+			if (dialog.Run() == (int)ResponseType.Accept)
+			{
+				folder = await StorageFolder.GetFolderFromPathAsync(dialog.Filename);
+			}
+
+			dialog.Destroy();
+			return folder;
+		}
+	}
+}

src/Uno.UI.Runtime.Skia.Gtk/GtkHost.cs

@@ -58,6 +58,7 @@ public void Run()
 			ApiExtensibility.Register<TextBoxView>(typeof(ITextBoxViewExtension), o => new TextBoxViewExtension(o, _window));
 			ApiExtensibility.Register(typeof(ILauncherExtension), o => new LauncherExtension(o));
 			ApiExtensibility.Register<FileOpenPicker>(typeof(IFileOpenPickerExtension), o => new FileOpenPickerExtension(o));
+			ApiExtensibility.Register<FolderPicker>(typeof(IFolderPickerExtension), o => new FolderPickerExtension(o));
 
 			_isDispatcherThread = true;
 			_window = new Gtk.Window("Uno Host");