feat: Initial implementation of FileOpenPicker for Skia.Gtk

Add PickerHelpers to Skia.Gtk

Update docs for pickers

Use strongly typed extension registration

Change test description to include Gtk

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

@@ -11,7 +11,7 @@ Legend
 
 | Picker         | UWP | WebAssembly | Android | iOS | macOS | WPF | GTK |
 |----------------|-----|-------------|---------|-----|-------|-----|-----|
-| FileOpenPicker | ✅   | ✅      (1)     | ✅       | ✅   | ✅     | ✅   | 🚫  |
+| FileOpenPicker | ✅   | ✅      (1)     | ✅       | ✅   | ✅     | ✅   | ✅  |
 | FileSavePicker | ✅   | ✅  (1)         | ✅       | ✅   | ✅     | ✅   | 🚫  |
 | FolderPicker   | ✅   | ✅           | ✅       | ⏸️ (2)|✅     | 🚫  | 🚫  |
 

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

@@ -14,7 +14,7 @@
 namespace UITests.Shared.Windows_Storage.Pickers
 {
 	[Sample("Windows.Storage", ViewModelType = typeof(FileOpenPickerTestsViewModel), IsManualTest = true,
-		Description = "Allows testing all features of FileOpenPicker. Currently not supported on Android, iOS, macOS and GTK. Not selecting a file should not cause an exception")]
+		Description = "Allows testing all features of FileOpenPicker. Currently not supported on Android, iOS, and macOS. Not selecting a file should not cause an exception")]
 	public sealed partial class FileOpenPickerTests : Page
 	{
 		public FileOpenPickerTests()

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

@@ -0,0 +1,86 @@
+#nullable enable
+
+using Gtk;
+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;
+
+namespace Uno.Extensions.Storage.Pickers
+{
+	internal class FileOpenPickerExtension : IFileOpenPickerExtension
+	{
+		private readonly FileOpenPicker _picker;
+
+		public FileOpenPickerExtension(FileOpenPicker owner)
+		{
+			_picker = owner ?? throw new ArgumentNullException(nameof(owner));
+		}
+
+		public async Task<StorageFile?> PickSingleFileAsync(CancellationToken token)
+		{
+			var files = await OpenPickerAsync(false);
+			return files.FirstOrDefault();
+		}
+
+		public async Task<IReadOnlyList<StorageFile>> PickMultipleFilesAsync(CancellationToken token)
+		{
+			var files = await OpenPickerAsync(true);
+			return new FilePickerSelectedFilesArray(files);
+		}
+
+		private async Task<StorageFile[]> OpenPickerAsync(bool multiple)
+		{
+			string commitText = "Open";
+			if (!string.IsNullOrWhiteSpace(_picker.CommitButtonText))
+			{
+				commitText = _picker.CommitButtonText;
+			}
+
+			FileChooserDialog dialog = new FileChooserDialog(
+				"Open",
+				GtkHost.Window,
+				FileChooserAction.Open,
+				"Cancel", ResponseType.Cancel,
+				commitText, ResponseType.Accept);
+
+			dialog.SelectMultiple = multiple;
+
+			if (!_picker.FileTypeFilter.Contains("*"))
+			{
+				FileFilter filter = new FileFilter();
+
+				foreach (string pattern in _picker.FileTypeFilter)
+				{
+					// Pattern is already validated to start with a period, so prepend star
+					filter.AddPattern("*" + pattern);
+				}
+
+				if (_picker.FileTypeFilter.Count > 0)
+				{
+					dialog.AddFilter(filter);
+				}
+			}
+
+			dialog.SetCurrentFolder(PickerHelpers.GetInitialDirectory(_picker.SuggestedStartLocation));
+
+			var files = new List<StorageFile>();
+			if (dialog.Run() == (int)ResponseType.Accept)
+			{
+				foreach (var fileName in dialog.Filenames)
+				{
+					files.Add(await StorageFile.GetFileFromPathAsync(fileName));
+				}
+			}
+
+			dialog.Destroy();
+			return files.ToArray();
+		}
+	}
+}

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

@@ -0,0 +1,31 @@
+#nullable enable
+
+using Windows.Storage.Pickers;
+using static System.Environment;
+
+namespace Uno.Extensions.Storage.Pickers
+{
+	internal static class PickerHelpers
+    {
+		public static string GetInitialDirectory(PickerLocationId location)
+		{
+			switch (location)
+			{
+				case PickerLocationId.DocumentsLibrary:
+					return GetFolderPath(SpecialFolder.MyDocuments);
+				case PickerLocationId.ComputerFolder:
+					return @"/";
+				case PickerLocationId.Desktop:
+					return GetFolderPath(SpecialFolder.Desktop);
+				case PickerLocationId.MusicLibrary:
+					return GetFolderPath(SpecialFolder.MyMusic);
+				case PickerLocationId.PicturesLibrary:
+					return GetFolderPath(SpecialFolder.MyPictures);
+				case PickerLocationId.VideosLibrary:
+					return GetFolderPath(SpecialFolder.MyVideos);
+				default:
+					return string.Empty;
+			}
+		}
+    }
+}

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

@@ -16,6 +16,8 @@
 using Uno.Extensions.System;
 using Uno.UI.Runtime.Skia.GTK.Extensions.System;
 using Uno.UI.Runtime.Skia.GTK.UI.Core;
+using Uno.Extensions.Storage.Pickers;
+using Windows.Storage.Pickers;
 
 namespace Uno.UI.Runtime.Skia
 {
@@ -55,6 +57,7 @@ public void Run()
 			ApiExtensibility.Register(typeof(Windows.Graphics.Display.IDisplayInformationExtension), o => _displayInformationExtension ??= new GtkDisplayInformationExtension(o, _window));
 			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));
 
 			_isDispatcherThread = true;
 			_window = new Gtk.Window("Uno Host");