MDI切换到上次显示的子窗口

void __fastcall TMainBuilder::mnuWindow_LastVisitedClick(TObject *Sender)
{
 const HWND hwnd = m_hLastActiveChild;

 if (IsWindow(hwnd))
  {
   bool bmaximized;
   HWND hwndactivechild = (HWND)SendMessage(g_hMDIClient, WM_MDIGETACTIVE, 0, (LPARAM)&bmaximized);
   if (bmaximized)
    {
     SendMessage(g_hMDIClient, WM_MDINEXT, (WPARAM)GetWindow(hwnd, GW_HWNDPREV), 0);
    }
   else
    {
     if (IsIconic(hwnd))
      ShowWindow(hwnd, SW_RESTORE);
     else
      SetWindowPos(hwnd, HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE|SWP_NOSIZE|SWP_SHOWWINDOW);
    }
  }
}