Aero effect Shadow, and transparency goes away if Rgn APIs are used

hello,

i have a Default MFC Application, and i have an imaginary Rectangle(larger then MFC Apps) in the Desktops,
i want to clip the MFC applications when it moves beyond that rectangle. here is what i have been doing
i used SetWindowRgn() with the offset rects, and i am able to clip it.

Code:

---

if ( pRect->right > 800)
        {
               
                int delta = pRect->right - 800;

                HRGN  hgn = CreateRectRgn(0,0, rc.Width() -delta, rc.Height());

                HRGN hrgntemp = CreateRectRgn(0,0,0,0);
                int regionType = GetWindowRgn(hrgntemp);
                if (regionType != ERROR)
                {
                        DeleteObject(hrgntemp);
                        SetWindowRgn(hgn, TRUE);
                }
                else
                {
                        SetWindowRgn(hgn, TRUE);
                }
               

        }

---

but for some unknown reason, the tranperency and shadow effect goes away when i am using SetWindowRgn, is there any way to keep transperance and Shodow effect.

then i dug more that found that there is a message(WM_DWMNCRENDERINGCHANGED fRenderingEnabled:False) that is sent to my widnow when i apply region API, and when i delete it same message with true (WM_DWMNCRENDERINGCHANGED fRenderingEnabled:True) is sent. looks windows itself is doing it, is there any way to prevent it?

i added a message handle on WM_DWMNCRENDERINGCHANGED message and then try to re-enable it, but strangly for the first time it works multiple tries it does not work.

Code:

---

LRESULT CMonitorTestAppDlg::OndwmncRenderingChanged(WPARAM wp, LPARAM lp)
{
        if(wp == TRUE)
        {
                OutputDebugString(L"Nc Rendereing Enabled\n");
        }
        else
        {
                OutputDebugString(L"Nc Rendereing disabled\n");
                EnableNCRendering(m_hWnd);
        }

        return 0;
}

HRESULT EnableNCRendering(HWND hwnd)
{
  HRESULT hr = S_OK;
  DWMNCRENDERINGPOLICY ncrp = DWMNCRP_ENABLED;

  // Disable non-client area rendering on the window.
  hr = DwmSetWindowAttribute(hwnd, DWMWA_NCRENDERING_POLICY, &ncrp, sizeof(ncrp));

  if (SUCCEEDED(hr))
  {
      // Do work here.
  }
 
  return hr;
}

---

Any clue when using region deactivates Aero Effects, is there any way to fix it

regards
Deepak

more update with screen shot. i am using this code in default MFC application.

Code:

---

void CMonitorTestAppDlg::OnMoving(UINT fwSide, LPRECT pRect)
{
        CRect rc(*pRect);

       
        if ( pRect->right > 800)
        {
               
                OutputDebugString(L"In the Range\n");
                int delta = pRect->right - 800;

                HRGN  hgn = CreateRectRgn(0,0, rc.Width() -delta, rc.Height());

                HRGN hrgntemp = CreateRectRgn(0,0,0,0);
                int regionType = GetWindowRgn(hrgntemp);
                if (regionType != ERROR)
                {
                        DeleteObject(hrgntemp);
                        SetWindowRgn(hgn, TRUE);
                }
                else
                {
                        SetWindowRgn(hgn, TRUE);
                }
               

        }
        else
        {
                OutputDebugString(L" out of Range\n");
                HRGN hrgntemp = CreateRectRgn(0,0,0,0);
                int regionType = GetWindowRgn(hrgntemp);
                if (regionType != ERROR)
                {
                        DeleteObject(hrgntemp);
                        SetWindowRgn(NULL, TRUE);
                }       
               

        }

        CDialogEx::OnMoving(fwSide, pRect);
       
}

---

i have attached the image also.

Regards
DS