Focus in/out handling?

[Bill Gray]

   You can tell xterm to provide focus in/out data :

https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-FocusIn_FocusOut

   Short of emitting CSI ?1004h and using define_key(),  is there a way 
in ncurses to access this?  I'm envisioning something like

int focus_state( void);

   returning (say) -1 if the state can't be determined or is 
meaningless,  1 if you've got the focus,  0 if you don't.  Or a function 
to say "I want to receive focus events",  and they're returned as 
KEY_FOCUS_IN and KEY_FOCUS_OUT by getch().  Or maybe you'd call

mousemask( REPORT_FOCUS_EVENTS | other events, NULL);

   and get notified via mouse events (though the KEY_FOCUS_* seems more 
appealing to me).

Thanks!         -- Bill