Function DefFrameProc 

pub unsafe extern "system" fn DefFrameProc(
    hwnd: *mut c_void,
    hwndmdiclient: *mut c_void,
    umsg: u32,
    wparam: usize,
    lparam: isize,
) -> isize

#31 DefFrameProc

performs default processing for any messages that the window procedure of an MDI frame window does not process