markDisplaying method

void markDisplaying()

Moves the presentation to displaying and emits DisplayedSignal.

A no-op once displaying or settled, so a renderer that reports visibility twice cannot produce two impressions.

Implementation

void markDisplaying() {
  if (_state != PresentationState.pending) return;
  _state = PresentationState.displaying;
  _displayedEmitted = true;
  _emit(const DisplayedSignal());
}