Function parse_net_wm_state_fullscreen 

pub(super) fn parse_net_wm_state_fullscreen(text: &str) -> bool

True iff _NET_WM_STATE_FULLSCREEN appears in xprop output for _NET_WM_STATE. Crucially, _NET_WM_STATE_MAXIMIZED_* must NOT match — a maximised window with the taskbar visible is the exact case we want to exclude.