title: What is RIDI_PREPARSEDDATA in GetRawInputDeviceInfo?
body: <p>Windows API function <a href="http://msdn.microsoft.com/en-us/library/ms645597(VS.85).aspx" rel="nofollow noreferrer">GetRawInputDeviceInfo</a> has a parameter <code>uiCommand</code>. One of the options is <code>RIDI_PREPARSEDDATA</code>. It says "pData points to the previously parsed data".</p>
  
  <p>I don't get what previously parsed data they are referring to. Is it the data that was last sent with <code>WM_INPUT</code>? Or is it data that was returned by any of the functions? Or something else? Also in what format is that data?</p>