Ещё правки VCL (12)

procedure TCustomForm.Activate;
var
 ActChild : TCustomForm; {V}
begin
  {V}
  if (FormStyle = fsMDIForm) and (FActiveControl <> nil) and
     (GetParentForm(FActiveControl).FormStyle = fsMDIChild)
   then
    Begin
     ActChild := GetActiveMDIChild;
     If ActChild <> nil then PostMessage(ActChild.Handle, CM_ACTIVATE, 0, 0);
    end;
  {^V}
  DoNestedActivation(CM_ACTIVATE, ActiveControl, Self);
  if Assigned(FOnActivate) then FOnActivate(Self);
end;