int pascal GetClientRect(HWND hWnd, LPRECT r)
 <MS-WINDOWS equivalent>

  This function returns the rectangle which a window's client area
encompasses. The client area of a window is the area which the
windows encompasses not including the borders and the menubar. If the
window has no borders, then the client rectangle is the same as the
window's rectangle. If a window has a menubar, then the top of the
client area starts at the next row under the menubar.

Parameters
  hWnd is the handle of the window to query.
  r a far pointer to a RECT structure which will be filled with the
      window's client rectangle.

Returns
  Nothing