Delphi 2007 - Allowing a Read-only file to be selected in a TSaveDialog

Question

I have a need for a user to be able to select an existing read-only file from a save dialog. I thought you could do this with a judicious selection of the TSaveDialog options but I can't make it happen. If I select a R/O file, as soon as I hit the Save button I get the message:

    Read-only.txt
    This file is set to read-only.
    Try again with a different file name.

I imagined the option bit ofNoReadOnlyReturn would control this, but it seems to have no effect.

What am I missing?

program Project1;

uses
  Forms,
  Unit1 in 'Unit1.pas' {Form1};

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

-

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    SaveDialog1: TSaveDialog;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
if SaveDialog1.Execute then
    begin
    Windows.Beep (1000, 300) ;
    end ;
end ;

end.

-

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 69
  ClientWidth = 195
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 56
    Top = 18
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object SaveDialog1: TSaveDialog
    FileName = 'Read-only.txt'
    InitialDir = 'C:\Users\Ross\Documents\RAD Studio\Projects'
    Options = [ofHideReadOnly, ofNoReadOnlyReturn, ofEnableSizing]
    Left = 16
    Top = 16
  end
end

If the file is read-only, you can't choose it in a **save** dialog, because you can't overwrite the file (it's read-only). If you want the user to be able to overwrite the file, then remove the readonly attribute first before displaying the dialog.. (Hardly makes sense to make the file read-only in the first place when you know you want the user to be able to overwrite it. *I'll make this file read-only to prevent the user from overwriting it. Wait, how do I let the user overwrite the file?*) — Ken White, Jan 17 '18 at 23:09
The intention was to reset the R/O flag, allow the overwrite, then set the R/O flag again. The issue is that the files are marked read-only because we want to prevent "general" users overwriting them, but these files occasionally need to be updated by supervisors (using a program that only they have access to) and I wanted to make that process as painless as possible. — rossmcm, Jan 17 '18 at 23:16
A little playing around shows that TOpenDialog allows selection of a read-only file, while TSaveDialog does not (regardless of the flags you use in Options). Apparently it's something in the VCL wrapper that's interfering with the ability to choose read-only files with TSaveDialog. Don't know if that's something that will help, but... Also not sure you're aware, so I"ll mention it: You can experiment with the dialogs at design time by setting the options you want in the OI and then double-click the component, which will open the dialog with the current options. It makes testing pretty quick. — Ken White, Jan 17 '18 at 23:43
Thanks Ken. No, I wasn't aware of the design-time preview by double-clicking - very useful, especially if the project takes a while to build and startup. Eventually, I did use `TOpenDialog`, with code in the `OnShow` event to bend the `Open` button caption to read `Save` — rossmcm, Jan 18 '18 at 01:12
Yeah, the design-time preview even allows testing file masks and initial directories and the other stuff, not just the options settings. Not everyone is aware, which I thought I'd mention it. It's an extremely useful feature, and works with all of the dialog components (TSaveDialog, TFileSaveDialog, etc.). — Ken White, Jan 18 '18 at 01:16

score 2 · Accepted Answer · answered Jan 18 '18 at 01:58

The issue is not with TSaveDialog itself, but with the underlying Win32 GetSaveFileName()/IFileSaveDialog APIs that TSaveDialog uses internally. They simply do not allow a read/only file to be the result of a "save" dialog.

That being said, IFileSaveDialog does provide a possible (albeit ugly) workaround. If you enable the dialog's FOS_OVERWRITEPROMPT flag, then selecting an existing file will prompt the user if the file can be overwritten before closing the dialog. The IFileDialogEvents interface has an OnOverwrite event, which is fired before that prompt appears (and can return FDESVR_ACCEPT to skip the prompt completely). So, in that event, you could remove the file's FILE_ATTRIBUTE_READONLY attribute before the dialog is closed. However, the dialog will still display the same "This file is set to read-only" error message and refuse to close (presumably because it has checked the attribute before firing the OnOverwrite event), but if you then select the same file again, the attribute will have been cleared and the dialog will accept the file (that is the ugly part - you would have to train your managers to ignore that error and retry).

GetSaveFileName() has an ofOverwritePrompt flag, but no event for overwrite prompting.

That being said, TSaveDialog does not expose access to the IFileSaveDialog.OnOverwrite event when it uses IFileSaveDialog internally, but you can use TFileSaveDialog instead, which does.

Delphi 2007 - Allowing a Read-only file to be selected in a TSaveDialog

1 Answers1