Add Support for Overwrite Prompt option in save dialog (#7531)

Add support for overwrite prompt option

src/Avalonia.Controls/SystemDialog.cs

@@ -52,6 +52,11 @@ namespace Avalonia.Controls
         /// </summary>
         public string? DefaultExtension { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether to display a warning if the user specifies the name of a file that already exists.
+        /// </summary>
+        public bool? ShowOverwritePrompt { get; set; }
+
         /// <summary>
         /// Shows the save file dialog.
         /// </summary>

src/Avalonia.Dialogs/ManagedFileChooserViewModel.cs

@@ -17,6 +17,7 @@ namespace Avalonia.Dialogs
         private readonly ManagedFileDialogOptions _options;
         public event Action CancelRequested;
         public event Action<string[]> CompleteRequested;
+        public event Action<string> OverwritePrompt;
 
         public AvaloniaList<ManagedFileChooserItemViewModel> QuickLinks { get; } =
             new AvaloniaList<ManagedFileChooserItemViewModel>();
@@ -39,6 +40,7 @@ namespace Avalonia.Dialogs
         private bool _scheduledSelectionValidation;
         private bool _alreadyCancelled = false;
         private string _defaultExtension;
+        private bool _overwritePrompt;
         private CompositeDisposable _disposables;
 
         public string Location
@@ -167,6 +169,7 @@ namespace Avalonia.Dialogs
             {
                 _savingFile = true;
                 _defaultExtension = sfd.DefaultExtension;
+                _overwritePrompt = sfd.ShowOverwritePrompt ?? true;
                 FileName = sfd.InitialFileName;
             }
 
@@ -360,7 +363,16 @@ namespace Avalonia.Dialogs
                         FileName = Path.ChangeExtension(FileName, _defaultExtension);
                     }
 
-                    CompleteRequested?.Invoke(new[] { Path.Combine(Location, FileName) });
+                    var fullName = Path.Combine(Location, FileName);
+
+                    if (_overwritePrompt && File.Exists(fullName))
+                    {
+                        OverwritePrompt?.Invoke(fullName);
+                    }
+                    else
+                    {
+                        CompleteRequested?.Invoke(new[] { fullName });
+                    }
                 }
             }
             else

src/Avalonia.Dialogs/ManagedFileDialogExtensions.cs

@@ -1,3 +1,4 @@
+using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
@@ -31,6 +32,75 @@ namespace Avalonia.Dialogs
                     dialog.Close();
                 };
 
+                model.OverwritePrompt += async (filename) =>
+                {
+                    Window overwritePromptDialog = new Window()
+                    {
+                        Title = "Confirm Save As",
+                        SizeToContent = SizeToContent.WidthAndHeight,
+                        WindowStartupLocation = WindowStartupLocation.CenterOwner,
+                        Padding = new Thickness(10),
+                        MinWidth = 270
+                    };
+
+                    string name = Path.GetFileName(filename);
+
+                    var panel = new DockPanel()
+                    {
+                        HorizontalAlignment = Layout.HorizontalAlignment.Stretch
+                    };
+
+                    var label = new Label()
+                    {
+                        Content = $"{name} already exists.\nDo you want to replace it?"
+                    };
+
+                    panel.Children.Add(label);
+                    DockPanel.SetDock(label, Dock.Top);
+
+                    var buttonPanel = new StackPanel()
+                    {
+                        HorizontalAlignment = Layout.HorizontalAlignment.Right,
+                        Orientation = Layout.Orientation.Horizontal,
+                        Spacing = 10
+                    };
+
+                    var button = new Button()
+                    {
+                        Content = "Yes",
+                        HorizontalAlignment = Layout.HorizontalAlignment.Right
+                    };
+
+                    button.Click += (sender, args) =>
+                    {
+                        result = new string[1] { filename };
+                        overwritePromptDialog.Close();
+                        dialog.Close();
+                    };
+
+                    buttonPanel.Children.Add(button);
+
+                    button = new Button()
+                    {
+                        Content = "No",
+                        HorizontalAlignment = Layout.HorizontalAlignment.Right
+                    };
+
+                    button.Click += (sender, args) =>
+                    {
+                        overwritePromptDialog.Close();
+                    };
+
+                    buttonPanel.Children.Add(button);
+
+                    panel.Children.Add(buttonPanel);
+                    DockPanel.SetDock(buttonPanel, Dock.Bottom);
+
+                    overwritePromptDialog.Content = panel;
+
+                    await overwritePromptDialog.ShowDialog(dialog);
+                };
+
                 model.CancelRequested += dialog.Close;
 
                 await dialog.ShowDialog<object>(parent);

src/Avalonia.X11/NativeDialogs/Gtk.cs

@@ -179,6 +179,9 @@ namespace Avalonia.X11.NativeDialogs
 
         [DllImport(GtkName)]
         public static extern void gtk_file_chooser_set_select_multiple(IntPtr chooser, bool allow);
+        
+        [DllImport(GtkName)]
+        public static extern void gtk_file_chooser_set_do_overwrite_confirmation(IntPtr chooser, bool do_overwrite_confirmation);
 
         [DllImport(GtkName)]
         public static extern void

src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs

@@ -16,7 +16,7 @@ namespace Avalonia.X11.NativeDialogs
     {
         private Task<bool> _initialized;
         private unsafe  Task<string[]> ShowDialog(string title, IWindowImpl parent, GtkFileChooserAction action,
-            bool multiSelect, string initialFileName, IEnumerable<FileDialogFilter> filters, string defaultExtension)
+            bool multiSelect, string initialFileName, IEnumerable<FileDialogFilter> filters, string defaultExtension, bool overwritePrompt)
         {
             IntPtr dlg;
             using (var name = new Utf8Buffer(title))
@@ -109,6 +109,8 @@ namespace Avalonia.X11.NativeDialogs
                         gtk_file_chooser_set_filename(dlg, fn);
                 }
 
+            gtk_file_chooser_set_do_overwrite_confirmation(dlg, overwritePrompt);
+            
             gtk_window_present(dlg);
             return tcs.Task;
         }
@@ -148,7 +150,7 @@ namespace Avalonia.X11.NativeDialogs
                     (dialog as OpenFileDialog)?.AllowMultiple ?? false,
                     Path.Combine(string.IsNullOrEmpty(dialog.Directory) ? "" : dialog.Directory,
                         string.IsNullOrEmpty(dialog.InitialFileName) ? "" : dialog.InitialFileName), dialog.Filters,
-                    (dialog as SaveFileDialog)?.DefaultExtension));
+                    (dialog as SaveFileDialog)?.DefaultExtension, (dialog as SaveFileDialog)?.ShowOverwritePrompt ?? false));
         }
 
         public async Task<string> ShowFolderDialogAsync(OpenFolderDialog dialog, Window parent)
@@ -160,7 +162,7 @@ namespace Avalonia.X11.NativeDialogs
             return await await RunOnGlibThread(async () =>
             {
                 var res = await ShowDialog(dialog.Title, platformImpl,
-                    GtkFileChooserAction.SelectFolder, false, dialog.Directory, null, null);
+                    GtkFileChooserAction.SelectFolder, false, dialog.Directory, null, null, false);
                 return res?.FirstOrDefault();
             });
         }

src/Windows/Avalonia.Win32/SystemDialogImpl.cs

@@ -40,6 +40,16 @@ namespace Avalonia.Win32
                     {
                         options |= FILEOPENDIALOGOPTIONS.FOS_ALLOWMULTISELECT;
                     }
+
+                    if (dialog is SaveFileDialog saveFileDialog)
+                    {
+                        var overwritePrompt = saveFileDialog.ShowOverwritePrompt ?? true;
+
+                        if (!overwritePrompt)
+                        {
+                            options &= ~FILEOPENDIALOGOPTIONS.FOS_OVERWRITEPROMPT;
+                        }
+                    }
                     frm.SetOptions(options);
 
                     var defaultExtension = (dialog as SaveFileDialog)?.DefaultExtension ?? "";