[MFC] how to get screen width, height

GetWindowRect(), GetDesktopWindow()

CRect rc;
::GetWindowRect(GetDesktopWindow()->m_hWnd, &rc);
int nWidth = rc.right - rc.left;
int nHeight = rc.bottom - rc.top;

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GetSystemMetrics()

int nWidth = GetSystemMetrics(SM_CXSCREEN);
int nHeight = GetSystemMetrics(SM_CYSCREEN);

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GetDeviceCaps()

HDC hDC = GetDC();
int nWidth = GetDeviceCaps(hDC, HORZRES);
int nHeight = GetDeviceCaps(hDC, VERTRES);