SetFocus( hWnd )-> <hWndPrev>
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 PARAMETER:

  <hWnd>        Is the handle that identifies the window to receive the
                Input Focus. If this parameter is 0, keystrokes are ignored 


 RETURNS:

 <hWndPrev> Identifies the window that previously had the focus. 


 DESCRIPTION:

  The SetFocus function sets the input focus to the given window. All 
  subsequent keyboard input is directed to this window. The window that
  previously had the input focus looses it.
  SetFocus() sends a WM_KILLFOCUS message to the window that loses 
  the input focus and a WM_SETFOCUS message to the window that receives 
  the input focus. It also activates either the window that receives the
  focus or the parent of the window that receives the focus. 

  If a window is active but does not have the focus (that is, no window 
  has the focus), any key pressed will produce a WM_SYSCHAR, WM_SYSKEYDOWN
  or WM_SYSKEYUP message. 

 SOURCE:

  SOURCE\WINAPI\SETFOCUS.C