describePanel method

@override void describePanel(Panel panel)

Declares feeds, states, knobs and actions onto panel, each with the code that serves it.

Called once per mount. The plugin keeps panel if it has anything to emit or announce later.

Implementation

@override
void describePanel(Panel panel) {
  _panel = panel;
  panel.action(presetAction, _preset);
  _mirror();
  // The set is not fixed: a variable appears when the widget declaring it
  // builds and goes when that widget unmounts, so the panel has to follow
  // rather than snapshot.
  _variablesSubscription = _variables.stream.listen((_) => _mirror());
}