重写DoModal，让窗口隐藏

INT_PTR CxDlg::DoModal()
{
  // can be constructed with a resource template or InitModalIndirect
  ASSERT(m_lpszTemplateName != NULL || m_hDialogTemplate != NULL ||
    m_lpDialogTemplate != NULL);
 
  // load resource as necessary
  LPCDLGTEMPLATE lpDialogTemplate = m_lpDialogTemplate;
  HGLOBAL hDialogTemplate = m_hDialogTemplate;
  HINSTANCE hInst = AfxGetResourceHandle();
  if (m_lpszTemplateName != NULL)
  {
    hInst = AfxFindResourceHandle(m_lpszTemplateName, RT_DIALOG);
    HRSRC hResource = ::FindResource(hInst, m_lpszTemplateName, RT_DIALOG);
    hDialogTemplate = LoadResource(hInst, hResource);
  }
  if (hDialogTemplate != NULL)
    lpDialogTemplate = (LPCDLGTEMPLATE)LockResource(hDialogTemplate);
 
  // return -1 in case of failure to load the dialog template resource
  if (lpDialogTemplate == NULL)
    return -1;
 
  // disable parent (before creating dialog)
  HWND hWndParent = PreModal();
  AfxUnhookWindowCreate();
  BOOL bEnableParent = FALSE;
#ifndef _AFX_NO_OLE_SUPPORT
  CWnd* pMainWnd = NULL;
  BOOL bEnableMainWnd = FALSE;
#endif
  if (hWndParent && hWndParent != ::GetDesktopWindow() && ::IsWindowEnabled(hWndParent))
  {
    ::EnableWindow(hWndParent, FALSE);
    bEnableParent = TRUE;
#ifndef _AFX_NO_OLE_SUPPORT
    pMainWnd = AfxGetMainWnd();
    if (pMainWnd && pMainWnd->IsFrameWnd() && pMainWnd->IsWindowEnabled())
    {
      //
      // We are hosted by non-MFC container
      // 
      pMainWnd->EnableWindow(FALSE);
      bEnableMainWnd = TRUE;
    }
#endif
  }
 
  TRY
  {
    // create modeless dialog
    AfxHookWindowCreate(this);
    if (CreateDlgIndirect(lpDialogTemplate,
      CWnd::FromHandle(hWndParent), hInst))
    {
      if (m_nFlags & WF_CONTINUEMODAL)
      {
        // enter modal loop
        DWORD dwFlags = 0; //MLF_SHOWONIDLE;
        if (GetStyle() & DS_NOIDLEMSG)
          dwFlags |= MLF_NOIDLEMSG;
        VERIFY(RunModalLoop(dwFlags) == m_nModalResult);
      }
 
      // hide the window before enabling the parent, etc.
      if (m_hWnd != NULL)
        SetWindowPos(NULL, 0, 0, 0, 0, SWP_HIDEWINDOW|
        SWP_NOSIZE|SWP_NOMOVE|SWP_NOACTIVATE|SWP_NOZORDER);
    }
  }
  CATCH_ALL(e)
  {
    { e->Delete(); } // DELETE_EXCEPTION(e);
    m_nModalResult = -1;
  }
  END_CATCH_ALL
 
#ifndef _AFX_NO_OLE_SUPPORT
    if (bEnableMainWnd)
      pMainWnd->EnableWindow(TRUE);
#endif
  if (bEnableParent)
    ::EnableWindow(hWndParent, TRUE);
  if (hWndParent != NULL && ::GetActiveWindow() == m_hWnd)
    ::SetActiveWindow(hWndParent);
 
  // destroy modal window
  DestroyWindow();
  PostModal();
 
  // unlock/free resources as necessary
  if (m_lpszTemplateName != NULL || m_hDialogTemplate != NULL)
    UnlockResource(hDialogTemplate);
  if (m_lpszTemplateName != NULL)
    FreeResource(hDialogTemplate);
 
  return m_nModalResult;
}

参考自：https://blog.youkuaiyun.com/viggirl/article/details/43269317