The GetViewportExtEx function retrieves the x-extents and y-extents of the current viewport for the specified device context.
BOOL GetViewportExtEx(
  HDC hdc,  // handle of device context
  LPSIZE lpSize 
            // address of structure receiving viewport dimensions
);
 
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero.
Windows NT: To get extended error information, call GetLastError.
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in wingdi.h.
  Import Library: Use gdi32.lib.
Coordinate Spaces and Transformations Overview, Coordinate Space and Transformation Functions, GetWindowExtEx, SetViewportExtEx, SetWindowExtEx