show method

String? show(String id)

Shows id on the next frame, and reports what is on screen after the call.

Neither an id this program does not hold nor a call that beat the first frame is an error to raise. The host's recovery for both is the compile and the reload it would have done anyway — which is also its recovery for a guest too old to have this at all — so answering with whatever is actually showing lets it tell "switched" from "could not" by comparison, with no exception path to get right on either side.

Implementation

String? show(String id) {
  var state = _state;
  if (state != null && id != state.entryId && _ids().contains(id)) {
    state.show(id);
  }
  return _state?.entryId;
}