Show message to user while Delphi program terminating

Question

In some cases I should terminate application with

Application.Terminate;

In that case I want to show some message to user inside destructor of some TFrame.

I have tryed to use MessageBox, MessageBoxIndirect, ShowMessage functions with no success. Message box isn't appears on screen and application closes.

Is there any way to show some message to user while Application terminating?

Btw, Delphi XE used.

Answer 1

Like comments indicate for showing messages with e.g. MessageBox, MessageBoxIndirect or ShowMessage, your process needs to still run.

Delphi for .NET would have a suiting OnShutdown event, but when not compiling with the conditional CLR it is absent.

One can however use an exit procedure, like TApplication does itself with DoneApplication. This procedure is called at a point where the process still lives, before System.Halt is called. It is added by calling AddExitProc(Proc: TProcedure) in System.SysUtils. In code commentary for this is following:

{ AddExitProc adds the given procedure to the run-time library's exit procedure list. When an application terminates, its exit procedures are executed in reverse order of definition, i.e. the last procedure passed to AddExitProc is the first one to get executed upon termination. }

I would personally decide to use this, despite the warning from the documentation, as TApplication itself is still using it in Tokyo to have DoneApplication called. Excerpt from documentation:

[...]AddExitProc is not compatible with ULX package support and is provided for backward compatibility only. Do not use AddExitProc in new applications.[...]

The small code example of a VCL project will show a message on application termination:

program Project1;

uses
  Vcl.Forms,
  Vcl.Dialogs,
  System.SysUtils,
  Unit2 in 'Unit2.pas' {Form2};

{$R *.res}

procedure AppTerminated;
begin
  MessageDlg('Message', mtInformation, [mbOk], 0);
end;

begin
  AddExitProc(AppTerminated);
  Application.Initialize;
  Application.MainFormOnTaskbar := True;
  Application.CreateForm(TForm2, Form2);
  Application.Run;
end.