# facts.ludic - what happened to a Thing, pushed on the package's queue for the game to drain
# a fact's record is one kept for it, not a new one: the halves swap whenever a fact finds the queue
# empty (everything before it drained or cleared), so a record comes back two drains after it was
# handed out - a reader placing a Thing while it reads the last drain's list never sees one change
function th_fact(things_st: mut ThingsState, what: int, t: Thing) -> void {
  if q_len(things_st.th_facts) == 0 and things_st.th_fact_n > 0 {
    things_st.th_fact_on_b = not things_st.th_fact_on_b
    things_st.th_fact_n = 0
  }
  var pool = things_st.th_fact_a
  if things_st.th_fact_on_b { pool = things_st.th_fact_b }
  if things_st.th_fact_n >= len(pool) {
    @alloc_ok("a pool miss: past the most facts in one drain only, then kept")
    push(pool, new ThingFact)
  }
  let f = pool[things_st.th_fact_n]
  things_st.th_fact_n += 1
  f.what = what
  f.uid = t.uid
  f.kind = t.kind
  f.id = t.id
  f.owner = t.owner
  f.x = t.x
  f.z = t.z
  q_push(things_facts(things_st), f)
}