Make FileDialog.FileName consistent across platforms

Mac: Fix setting FileName to null
Mac/Gtk: Remember set value before/after dialog is shown
Added test to ensure things work as expected

src/Eto.Gtk/Forms/GtkFileDialog.cs

@@ -10,14 +10,26 @@ public abstract class GtkFileDialog<TControl, TWidget> : WidgetHandler<TControl,
 		where TControl: Gtk.FileChooserDialog
 		where TWidget: FileDialog
 	{
-		public string FileName
+		public virtual string FileName
 		{
-			get { return Control.Filename; }
+			get { return Control.Filename ?? Control.CurrentName; }
 			set
 			{
-				Control.SetCurrentFolder(Path.GetDirectoryName(value));
-				Control.SetFilename(value);
-				Control.CurrentName = Path.GetFileName(value);
+				if (string.IsNullOrEmpty(value))
+				{
+					Control.UnselectAll();
+					if (!string.IsNullOrEmpty(Control.Filename))
+						Control.UnselectFilename(Control.Filename);
+				}
+				else
+				{
+					var dir = Path.GetDirectoryName(value);
+					if (!string.IsNullOrEmpty(dir))
+						Control.SetCurrentFolder(dir);
+					if (File.Exists(value))
+						Control.SetFilename(value);
+				}
+				Control.CurrentName = Path.GetFileName(value) ?? string.Empty;
 			}
 		}
 
@@ -79,7 +91,7 @@ public string Title
 		}
 
 
-		public DialogResult ShowDialog(Window parent)
+		public virtual DialogResult ShowDialog(Window parent)
 		{
 			SetFilters();
 			if (parent != null) Control.TransientFor = (Gtk.Window)parent.ControlObject;

src/Eto.Gtk/Forms/OpenFileDialog.cs → src/Eto.Gtk/Forms/OpenFileDialogHandler.cs

@@ -1,15 +1,18 @@
 using Eto.Forms;
 using System.Collections.Generic;
+using System.IO;
 
 namespace Eto.GtkSharp.Forms
 {
 	public class OpenFileDialogHandler : GtkFileDialog<Gtk.FileChooserDialog, OpenFileDialog>, OpenFileDialog.IHandler
 	{
+		string fileName;
+
 		public OpenFileDialogHandler()
 		{
 			Control = new Gtk.FileChooserDialog(string.Empty, null, Gtk.FileChooserAction.Open);
 			Control.SetCurrentFolder(System.IO.Directory.GetCurrentDirectory());
-			
+
 			Control.AddButton(Gtk.Stock.Cancel, Gtk.ResponseType.Cancel);
 			Control.AddButton(Gtk.Stock.Open, Gtk.ResponseType.Ok);
 			Control.DefaultResponse = Gtk.ResponseType.Ok;
@@ -18,13 +21,32 @@ public OpenFileDialogHandler()
 		public bool MultiSelect
 		{
 			get { return Control.SelectMultiple; }
-			set { Control.SelectMultiple = value; }	
+			set { Control.SelectMultiple = value; }
 		}
 
 		public IEnumerable<string> Filenames
 		{
 			get { return Control.Filenames; }
 		}
 
+		public override string FileName
+		{
+			get => base.FileName ?? fileName;
+			set => base.FileName = fileName = value;
+		}
+
+		public override DialogResult ShowDialog(Window parent)
+		{
+			var result = base.ShowDialog(parent);
+
+			// When cancelling, Control.Filename all of the sudden returns a value but is just the folder.
+			// so, combine it with the desired file name, if one was set.
+			if (result == DialogResult.Ok)
+				fileName = null;
+			else if (!string.IsNullOrEmpty(fileName) && string.IsNullOrEmpty(Path.GetDirectoryName(fileName)))
+				Control.SetFilename(Path.Combine(base.FileName, fileName));
+			return result;
+		}
+
 	}
 }

src/Eto.Mac/Forms/MacFileDialog.cs

@@ -92,25 +92,18 @@ void Create()
 				Control.AccessoryView = null;
 		}
 
+		string fileName;
+
 		public virtual string FileName
 		{
-			get
-			{ 
-				return Control.Url.Path;
-			}
-			set { }
+			get => Control.Url?.Path ?? fileName;
+			set => fileName = value;
 		}
 
 		public Uri Directory
 		{
-			get
-			{
-				return new Uri(Control.DirectoryUrl.AbsoluteString);
-			}
-			set
-			{
-				Control.DirectoryUrl = new NSUrl(value.AbsoluteUri);
-			}
+			get => new Uri(Control.DirectoryUrl.AbsoluteString);
+			set => Control.DirectoryUrl = new NSUrl(value.AbsoluteUri);
 		}
 
 		public string GetDefaultExtension()
@@ -173,15 +166,18 @@ public string Title
 			get { return Control.Message; }
 			set { Control.Message = value ?? string.Empty; }
 		}
-
-		public DialogResult ShowDialog(Window parent)
+		
+		public virtual DialogResult ShowDialog(Window parent)
 		{
 			//Control.AllowsOtherFileTypes = false;
 			Control.Delegate = new SavePanelDelegate{ Handler = this };
 			Create();
 
 			int ret = MacModal.Run(Control, parent);
-
+
+			if (ret == 1)
+				fileName = null;
+
 			return ret == 1 ? DialogResult.Ok : DialogResult.Cancel;
 		}
 

src/Eto.Mac/Forms/SaveFileDialogHandler.cs

@@ -5,15 +5,15 @@ namespace Eto.Mac.Forms
 {
 	public class SaveFileDialogHandler : MacFileDialog<NSSavePanel, SaveFileDialog>, SaveFileDialog.IHandler
 	{
+		bool hasShown;
+
 		public override string FileName
 		{
-			get
-			{
-				return base.FileName;
-			}
+			get => hasShown ? base.FileName : Control.NameFieldStringValue;
 			set
 			{
-				Control.NameFieldStringValue = value;
+				Control.NameFieldStringValue = value ?? string.Empty;
+				hasShown = false;
 			}
 		}
 
@@ -30,5 +30,14 @@ protected override void Initialize()
 			Control.CanSelectHiddenExtension = true;
 			base.Initialize();
 		}
+
+		public override DialogResult ShowDialog(Window parent)
+		{
+			hasShown = true;
+			var result = base.ShowDialog(parent);
+			if (result != DialogResult.Ok)
+				hasShown = false;
+			return result;
+		}
 	}
 }

test/Eto.Test/UnitTests/Forms/FileDialogTests.cs

@@ -0,0 +1,55 @@
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using Eto.Drawing;
+using Eto.Forms;
+using NUnit.Framework;
+
+namespace Eto.Test.UnitTests.Forms
+{
+	[TestFixture]
+	public class OpenFileDialogTests : FileDialogTests<OpenFileDialog>
+	{
+	}
+
+	[TestFixture]
+	public class SaveFileDialogTests : FileDialogTests<SaveFileDialog>
+	{
+	}
+
+	public class FileDialogTests<T> : TestBase
+		where T: FileDialog, new()
+	{
+		[Test, InvokeOnUI, ManualTest]
+		public void FileNameShouldHaveConsistentValues()
+		{
+			var fd = new T();
+			fd.Filters.Add(new FileFilter("Text Files (*.txt)", ".txt"));
+
+			Assert.That(fd.FileName, Is.Null.Or.Empty.Or.EqualTo("Untitled"), "#1");
+
+			fd.FileName = null;
+			Assert.That(fd.FileName, Is.Null.Or.Empty.Or.EqualTo("Untitled"), "#2");
+
+			fd.FileName = "SomeFile.txt";
+
+			Assert.AreEqual("SomeFile.txt", Path.GetFileName(fd.FileName), "#3");
+
+			var result = fd.ShowDialog(null);
+
+			if (result == DialogResult.Cancel || typeof(T) == typeof(SaveFileDialog))
+				Assert.AreEqual("SomeFile.txt", Path.GetFileName(fd.FileName), "#4");
+
+			if (result == DialogResult.Ok)
+			{
+				var directoryName = Path.GetDirectoryName(fd.FileName);
+				Assert.IsNotNull(directoryName, "#5.1");
+				Assert.IsNotEmpty(directoryName, "#5.2");
+				Console.WriteLine($"Directory: {directoryName}");
+			}
+
+			Console.WriteLine($"FileName: {fd.FileName}");
+
+		}
+	}
+}