@brief Send GetProperty request to get _NET_VIRTUAL_ROOTS root window property
@param ewmh The information relative to EWMH @param screen_nbr The screen number @return The _NET_VIRTUAL_ROOTS cookie of the GetProperty request
See Implementation
@brief Send GetProperty request to get _NET_VIRTUAL_ROOTS root window property
@param ewmh The information relative to EWMH @param screen_nbr The screen number @return The _NET_VIRTUAL_ROOTS cookie of the GetProperty request