Why doesn't WINWORD.EXE quit after Closing the document from Delphi?

Question

I managed to distill one of the underlying issues rooted in my question How to trace _AddRef / _Release calls for OLE Automation objects in the unit below.

I'll answer this answer too, just in case anyone else bumps into this.

The question: with the below code, why doesn't WINWORD.EXE always quit (sometimes it does quit).

The unit can probably be trimmed down even more.

unit Unit2;

interface

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

type
  TForm2 = class(TForm)
    WordXPFailsToQuitButton: TButton;
    procedure WordXPFailsToQuitButtonClick(Sender: TObject);
  private
    FWordApplication: TWordApplication;
  strict protected
    function GetWordApplication: TWordApplication; virtual;
    function GetWordApplication_Documents: Documents; virtual;
    procedure WordApplication_DocumentBeforeClose(ASender: TObject; const Doc: _Document; var Cancel: WordBool); virtual;
    procedure WordApplication_Quit(Sender: TObject); virtual;
    property WordApplication: TWordApplication read GetWordApplication;
    property WordApplication_Documents: Documents read GetWordApplication_Documents;
  end;

var
  Form2: TForm2;

implementation

uses
  Vcl.OleServer;

{$R *.dfm}

function TForm2.GetWordApplication: TWordApplication;
begin
  if not Assigned(FWordApplication) then
  begin
    FWordApplication := TWordApplication.Create(nil);

    FWordApplication.AutoConnect := False;
    FWordApplication.AutoQuit := False;
    FWordApplication.ConnectKind := ckNewInstance;
    FWordApplication.OnDocumentBeforeClose := WordApplication_DocumentBeforeClose;
    FWordApplication.OnQuit := WordApplication_Quit;
    FWordApplication.Connect;
  end;
  Result := FWordApplication;
end;

function TForm2.GetWordApplication_Documents: Documents;
begin
  Result := WordApplication.Documents;
  if not Assigned(Result) then
    raise EAccessViolation.Create('WordApplication.Documents');
end;

procedure TForm2.WordXPFailsToQuitButtonClick(Sender: TObject);
begin
  try
    WordApplication_Documents.Add(EmptyParam, EmptyParam, EmptyParam, EmptyParam);
    WordApplication.Visible := True;
    WordApplication.ActiveDocument.Close(False, EmptyParam, EmptyParam);
  finally
    WordApplication.OnQuit := nil;
    WordApplication.OnDocumentBeforeClose := nil;
    WordApplication.AutoQuit := True;
    WordApplication.Disconnect;
    WordApplication.Free;
    FWordApplication := nil;
  end;
end;

procedure TForm2.WordApplication_DocumentBeforeClose(ASender: TObject; const Doc: _Document; var Cancel: WordBool);
begin
  FWordApplication.Disconnect;
end;

procedure TForm2.WordApplication_Quit(Sender: TObject);
begin
  FWordApplication.Disconnect;
end;

end.

Answer 1

Answer part 1:

Comment out the disconnect in the below event:

procedure TForm2.WordApplication_DocumentBeforeClose(ASender: TObject; const Doc: _Document; var Cancel: WordBool);
begin
//  FWordApplication.Disconnect;
end;

The event will be called during the DocumentClose(...) method, then disconnect and delete the OLE interface from the FWordApplication instance.

I have not yet figured out which reference is dangling, but this effectively keeps WINWORD.EXE alive most of the times.

Answer part 2:

Sometimes WINWORD.EXE does quit because toe WordApplication_DocumentBeforeClose event is not called. The reason is that the code runs so fast that Word is not fully initialized yet to perform the event.