How to shell to another app and have it appear in a delphi form

Question

In Delphi I've used ShellExecute for years to launch (and optionally wait for) other applications. Now though, I need to have one of these applications appear in one of my Delphi app forms. I've tried the code below as a simple test to open notepad (which it does) and to display the result within PAnel1 on my form (which it doesnt). Can some kind person put me on the right track? Thanks

var
  Rec          : TShellExecuteInfo;
  wnd : HWnd;
const
  AVerb = 'open';
  AParams = '';
  AFileName = 'Notepad.exe';
  ADir = '';
begin
  FillChar(Rec, SizeOf(Rec), #0);

  Rec.cbSize       := SizeOf(Rec);
  Rec.fMask        := SEE_MASK_NOCLOSEPROCESS;
  Rec.lpVerb       := PChar( AVerb );
  Rec.lpFile       := PChar( AfileName );
  Rec.lpParameters := PChar( AParams );
  Rec.lpDirectory  := PChar( Adir );
  Rec.nShow        := sw_Show;

  ShellExecuteEx(@Rec);

  wnd := Windows.FindWindow( 'Notepad', nil );
  Windows.SetParent( Wnd, PAnel1.Handle );

end;

Answer 1

That will be a tricky one, if it's even possible.

I've seen approaches that will work for text-based applications - they generally capture the standard output of the process as it happens and put it into a text control.

But what you're talking about is a fully fledged graphical application (Notepad, despite working on text, display pixels, not character codes).

So, unless Notepad provides an interface where you can:

• request arbitrary characters in the buffer; and
• send arbitrary keystrokes to the program, I'd say you're flat out of luck.

Definitely a kludge, but one option is to continuously monitor the Notepad windows and ensure it's always superimposed over your forms client area. That's pretty horrible since you have to stop it moving, resizing, minimizing and so on, and maintain its z-order to be just above your applications. I wouldn't wish those requirements on my worst enemy.

Have you thought of using an editor control built specifically for Delphi (or an ActiveX editor that you could embed)? That might be a better approach.

Answer 2

All error checking omitted, but this should get you started:

procedure TForm1.Button1Click(Sender: TObject);
var
  Rec: TShellExecuteInfo;
const
  AVerb = 'open';
  AParams = '';
  AFileName = 'Notepad.exe';
  ADir = '';
begin
  FillChar(Rec, SizeOf(Rec), #0);

  Rec.cbSize       := SizeOf(Rec);
  Rec.fMask        := SEE_MASK_NOCLOSEPROCESS;
  Rec.lpVerb       := PChar( AVerb );
  Rec.lpFile       := PChar( AfileName );
  Rec.lpParameters := PChar( AParams );
  Rec.lpDirectory  := PChar( Adir );
  Rec.nShow        := SW_HIDE;

  ShellExecuteEx(@Rec);
  WaitForInputIdle(Rec.hProcess, 5000);

  fNotepadHandle := Windows.FindWindow( 'Notepad', nil );
  Windows.SetParent( fNotepadHandle, Handle );

  Resize;
  ShowWindow(fNotepadHandle, SW_SHOW);
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  if IsWindow(fNotepadHandle) then begin
    SetWindowPos(fNotepadHandle, 0, 0, 0, ClientWidth, ClientHeight,
      SWP_ASYNCWINDOWPOS);
  end;
end;

What you should definitely do is enumerate the windows of the new process, instead of simply using any window handle that FindWindow() returns.