32 constant MAX_EVENTHANDLERS

0
  cell +field eventhandler.eventid
  cell +field eventhandler.xt
constant /EVENTHANDLER

MAX_EVENTHANDLERS /EVENTHANDLER * constant EVENTHANDLERS_SIZE
create eventhandlers EVENTHANDLERS_SIZE allot
eventhandlers EVENTHANDLERS_SIZE erase

: (translate) ( index-u -- eventhandler-addr ) /EVENTHANDLER * eventhandlers + ;
: (eventhandler-set?) ( eventhandler-addr -- flag ) eventhandler.xt @ 0<> ;
: (set-eventhandler) ( handler-xt eventid-u eventhandler-addr -- )
  tuck eventhandler.eventid ! eventhandler.xt ! ;
: eventhandlers.remove ( index-u -- )
  (translate) /EVENTHANDLER erase ;
: eventhandlers.append ( handler-xt eventid-u -- index-u )
  MAX_EVENTHANDLERS 0 DO
    I (translate) dup (eventhandler-set?) invert IF
      (set-eventhandler) UNLOOP EXIT
    ELSE
      drop
    THEN
  LOOP
  true abort" no free eventhandler slots!" ;