A sketch for a FlutterView focus API

flutter_view_focus.dart

abstract interface class FlutterView {
  FlutterViewFocusState get focusState;
  
  /// The timing of these events relative to keyboard events
  /// is such and such.
  FlutterViewFocusStateChanged get onFocusStateChanged;
  set onFocusStateChanged(FlutterViewFocusStateChanged callback);
}

typedef FlutterViewFocusStateChanged = Function(
  FlutterViewFocusStateChangedNotification notification,
);

final class FlutterViewFocusState {
  FlutterViewFocusState({
    required this.hasFocus,
  });

  final bool hasFocus;
}

final class FlutterViewFocusStateChangedNotification {
  FlutterViewFocusStateChangedNotification({
    required this.oldState,
    required this.newState,
    required this.direction,
  });
  
  final FlutterViewFocusState oldState;
  final FlutterViewFocusState newState;
  final FocusChangeDirection direction;
}

enum FocusChangeDirection {
  // TAB
  forward,
  // Shift TAB
  backward,
  // Alt+TAB, or focus lost
  unknown,
}