app-flutter/lib/shell_scope.dart

// What a page needs from the shell (lib/shell.dart), without importing it: open the
// menu, switch view. Pages import this; the shell imports the pages.

import 'package:flutter/material.dart';

/// Every view the menu offers. Tools are the rarely used ones (pirate-station-aide's pattern).
enum ShellView { dash, signals, captures, camera, linkTest, settings }

/// The landing view, set at build time: `--dart-define=YUKART_HOME=dash` for the car,
/// `signals` (the default, for now) while developing.
ShellView get landingView => switch (const String.fromEnvironment(
  'YUKART_HOME',
  defaultValue: 'signals',
)) {
  'dash' => ShellView.dash,
  _ => ShellView.signals,
};

/// The view on screen. The shell listens to it; anything may set it (the link-test hook does).
final shellView = ValueNotifier<ShellView>(landingView);

class ShellScope extends InheritedWidget {
  const ShellScope({super.key, required this.openMenu, required super.child});

  final VoidCallback openMenu;

  static ShellScope? maybeOf(BuildContext context) =>
      context.dependOnInheritedWidgetOfExactType<ShellScope>();

  @override
  bool updateShouldNotify(ShellScope old) => false;
}

/// The menu button every page puts where a back arrow would be. The menu also opens
/// with a swipe in from the left edge.
class MenuButton extends StatelessWidget {
  const MenuButton({super.key, this.color});

  final Color? color;

  @override
  Widget build(BuildContext context) => IconButton(
    tooltip: 'Menu',
    icon: Icon(Icons.menu, color: color),
    onPressed: ShellScope.maybeOf(context)?.openMenu,
  );
}