fix: crash when enabling TShellListView.MultiSelect in OnFormShow, now sets options per setter method, before FormShow

ansgarbecker · ansgarbecker · commit 2acce3520684 · 2026-02-20T12:37:13.000+01:00
Closes #2410
diff --git a/source/extfiledialog.pas b/source/extfiledialog.pas
@@ -71,6 +71,7 @@   TfrmExtFileDialog = class(TExtForm)
     procedure SetInitialDir(const AValue: String);
     procedure SetFilterIndex(AValue: Integer);
     function GetPathPartAt(X: Integer): String;
+    procedure SetOptions(AValue: TOpenOptions);
   public
     property OnTypeChange: TNotifyEvent read FOnTypeChange write FOnTypeChange;
     property Title: String write SetTitle;
@@ -79,7 +80,7 @@   TfrmExtFileDialog = class(TExtForm)
     property FileName: String read GetFileName write SetFileName;
     property InitialDir: String read FInitialDir write SetInitialDir;
     property DefaultExt: String read FDefaultExt write FDefaultExt;
-    property Options: TOpenOptions read FOptions write FOptions;
+    property Options: TOpenOptions read FOptions write SetOptions;
     property Files: TStringList read FFiles;
     property FilterIndex: Integer read FFilterIndex write SetFilterIndex;
   end;
@@ -157,7 +158,6 @@ procedure TfrmExtFileDialog.FormShow(Sender: TObject);
   LineBreakIndexInt: Integer;
   PreviousDir: String;
 begin
-  ShellListView.MultiSelect := ofAllowMultiSelect in FOptions;
   PreviousDir := AppSettings.ReadString(asFileDialogPreviousDir);
   if not FInitialDir.IsEmpty then
     SetInitialDir(FInitialDir)
@@ -237,6 +237,17 @@ function TfrmExtFileDialog.GetPathPartAt(X: Integer): String;
   end;
 end;
 
+procedure TfrmExtFileDialog.SetOptions(AValue: TOpenOptions);
+begin
+  if FOptions = AValue then
+    Exit;
+  FOptions := AValue;
+  if (ofAllowMultiSelect in FOptions) <> ShellListView.MultiSelect then begin
+    // This would crash if we would do it in FormShow. See issue #2410
+    ShellListView.MultiSelect := ofAllowMultiSelect in FOptions;
+  end;
+end;
+
 procedure TfrmExtFileDialog.lblPathMouseMove(Sender: TObject;
   Shift: TShiftState; X, Y: Integer);
 begin
