Add FilesSelected event

Allows user to do things like confirm dialogs on selecting existing file(s)

Terminal.Gui/Windows/FileDialog.cs

@@ -234,6 +234,12 @@ namespace Terminal.Gui {
 		private MenuBarItem allowedTypeMenu;
 		private MenuItem [] allowedTypeMenuItems;
 
+		/// <summary>
+		/// Event fired when user attempts to confirm a selection (or multi selection).
+		/// Allows you to cancel the selection or undertake alternative behavior e.g.
+		/// open a dialog "File already exists, Overwrite? yes/no".
+		/// </summary>
+		public event EventHandler<FilesSelectedEventArgs> FilesSelected;
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="FileDialog"/> class.
@@ -850,9 +856,11 @@ namespace Terminal.Gui {
 
 			this.MultiSelected = toMultiAccept.Select (s => s.FileSystemInfo.FullName).ToList ().AsReadOnly ();
 			this.tbPath.Text = this.MultiSelected.Count == 1 ? this.MultiSelected [0] : string.Empty;
-			this.Canceled = false;
-			Application.RequestStop ();
+
+			FinishAccept ();
 		}
+
+
 		private void Accept (FileInfo f)
 		{
 			if (!this.IsCompatibleWithOpenMode (f.FullName, out var reason)) {
@@ -866,8 +874,8 @@ namespace Terminal.Gui {
 			if (AllowsMultipleSelection) {
 				this.MultiSelected = new List<string> { f.FullName }.AsReadOnly ();
 			}
-			this.Canceled = false;
-			Application.RequestStop ();
+
+			FinishAccept ();
 		}
 
 		private void Accept ()
@@ -880,6 +888,18 @@ namespace Terminal.Gui {
 				return;
 			}
 
+			FinishAccept ();
+		}
+
+		private void FinishAccept ()
+		{
+			var e = new FilesSelectedEventArgs (this);
+
+			this.FilesSelected?.Invoke (this, e);
+			
+			if(e.Cancel) {
+				return;
+			}
 
 			this.Canceled = false;
 			Application.RequestStop ();

Terminal.Gui/Windows/FilesSelectedEventArgs.cs

@@ -0,0 +1,31 @@
+using System;
+
+namespace Terminal.Gui {
+	/// <summary>
+	/// Event args for the <see cref="FileDialog.FilesSelected"/> event
+	/// </summary>
+	public class FilesSelectedEventArgs : EventArgs
+	{
+		/// <summary>
+		/// Set to true if you want to prevent the selection
+		/// going ahead (this will leave the <see cref="FileDialog"/>
+		/// still showing).
+		/// </summary>
+		public bool Cancel { get; set; }
+
+		/// <summary>
+		/// The dialog where the choice is being made.  Use <see cref="FileDialog.Path"/>
+		/// and/or <see cref="FileDialog.MultiSelected"/> to evaluate the users choice.
+		/// </summary>
+		public FileDialog Dialog { get; }
+
+		/// <summary>
+		/// Creates a new instance of the <see cref="FilesSelectedEventArgs"/>
+		/// </summary>
+		/// <param name="dialog"></param>
+		public FilesSelectedEventArgs (FileDialog dialog)
+		{
+			Dialog = dialog;
+		}
+	}
+}

UICatalog/Scenarios/FileDialogExamples.cs

@@ -118,6 +118,11 @@ namespace UICatalog.Scenarios {
 
 				fd.Style.OkButtonText = rgCaption.RadioLabels [rgCaption.SelectedItem].ToString ();
 
+				// If Save style dialog then give them an overwrite prompt
+				if(rgCaption.SelectedItem == 2) {
+					fd.FilesSelected += ConfirmOverwrite;
+				}
+
 				if (cbIcons.Checked ?? false) {
 					fd.IconGetter = GetIcon;
 				}
@@ -170,6 +175,16 @@ namespace UICatalog.Scenarios {
 			};
 		}
 
+		private void ConfirmOverwrite (object sender, FilesSelectedEventArgs e)
+		{
+			if (!string.IsNullOrWhiteSpace (e.Dialog.Path)) {
+				if(File.Exists(e.Dialog.Path)) {
+					int result = MessageBox.Query ("Overwrite?", "File already exists", "Yes", "No");
+					e.Cancel = result == 1;
+				}
+			}
+		}
+
 		private class CaseSensitiveSearchMatcher : FileDialog.ISearchMatcher {
 			private string terms;
 

UnitTests/FileDialogTests.cs

@@ -118,6 +118,25 @@ namespace Terminal.Gui.Core {
 			Assert.False(dlg.Canceled);
 		}
 
+		[Theory, AutoInitShutdown]
+		[InlineData(true)]
+		[InlineData (false)]
+		public void CancelSelection (bool cancel)
+		{
+			var dlg = GetInitializedFileDialog ();
+			var openIn = Path.Combine (Environment.CurrentDirectory, "zz");
+			Directory.CreateDirectory (openIn);
+			dlg.Path = openIn + Path.DirectorySeparatorChar;
+
+			dlg.FilesSelected += (s, e) => e.Cancel = cancel;
+
+			//pressing enter will complete the current selection
+			// unless the event cancels the confirm
+			Send ('\n', ConsoleKey.Enter, false);
+			
+			Assert.Equal(cancel,dlg.Canceled);
+		}
+
 		private void Send (char ch, ConsoleKey ck, bool shift = false, bool alt = false, bool control=false)
 		{
 			Application.Driver.SendKeys (ch, ck, shift, alt, control);