The background: My form has a TWebBrowser. I want to close the form with ESC but the TWebBrowser eats the keystrokes - so I decided to go with a keyboard hook.

The problem is that the Form can be open in multiple instances at the same time.

No matter what I do, in some situations, if there are two instances open of my form, closing one of them closes the other as well.

I've attached some sample code. Any ideas on what causes the issue?

var
  EmailDetailsForm: TEmailDetailsForm;
  KeyboardHook: HHook;

implementation

function KeyboardHookProc(Code: Integer; wParam, lParam: LongInt): LongInt; stdcall;
var
  hWnd: THandle;
  I: Integer;
  F: TForm;
begin
  if Code < 0 then
    Result := CallNextHookEx(KeyboardHook, Code, wParam, lParam)
  else begin
    case wParam of
      VK_ESCAPE:  
        if (lParam and $80000000) <> $00000000 then
        begin
          hWnd := GetForegroundWindow;
          for I := 0 to Screen.FormCount - 1 do
          begin
            F := Screen.Forms[I];
            if F.Handle = hWnd then
              if F is TEmailDetailsForm then
              begin
                PostMessage(hWnd, WM_CLOSE, 0, 0);
                Result := HC_SKIP;
                break;
              end;
          end; //for
        end; //if
      else
        Result := CallNextHookEx(KeyboardHook, Code, wParam, lParam);
    end;  //case
  end;  //if
end;

function TEmailDetailsForm.CheckInstance: Boolean;
var
  I, J: Integer;
  F: TForm;
begin
  Result := false;

  J := 0;

  for I := 0 to Screen.FormCount - 1 do
  begin
    F := Screen.Forms[I];
    if F is TEmailDetailsForm then
    begin
      J := J + 1;
      if J = 2 then
      begin
        Result := true;
        break;
      end;
    end;
  end;
end;

procedure TEmailDetailsForm.FormCreate(Sender: TObject);
begin
    if not CheckInstance then    
      KeyboardHook := SetWindowsHookEx(WH_KEYBOARD, @KeyboardHookProc, 0, GetCurrentThreadId());
end;

procedure TEmailDetailsForm.FormDestroy(Sender: TObject);
begin
    if not CheckInstance then
      UnHookWindowsHookEx(KeyboardHook);
end;