@brief Send GetProperty request to get _NET_ACTIVE_WINDOW root
window property
@see xcb_ewmh_get_active_window_unchecked
@param ewmh The information relative to EWMH
@param screen_nbr The screen number
@return The _NET_ACTIVE_WINDOW cookie of the GetProperty request
@brief Send GetProperty request to get _NET_ACTIVE_WINDOW root window property
@see xcb_ewmh_get_active_window_unchecked @param ewmh The information relative to EWMH @param screen_nbr The screen number @return The _NET_ACTIVE_WINDOW cookie of the GetProperty request