Reland iOS 16 context menu

[justinmc]

This is a reland of #115805, which had a bug where the button text color used the wrong brightness in some cases (reverted in #116312). This fixes that problem by using the right brightness value.

Platform	Native iOS 16 light mode	Native iOS 16 dark mode
Flutter (this branch)
Native iOS 16

Test app

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

void main() {
  debugDefaultTargetPlatformOverride = TargetPlatform.iOS;
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  Brightness _brightness = Brightness.light;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    _brightness = WidgetsBinding.instance.window.platformBrightness;
  }

  @override
  void didChangePlatformBrightness() {
    if (mounted) {
      setState(() {
        _brightness = WidgetsBinding.instance.window.platformBrightness;
      });
    }

    super.didChangePlatformBrightness();
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return CupertinoApp(
      debugShowCheckedModeBanner: false,
      theme: CupertinoThemeData(
        brightness: _brightness,
      ),
      home: const CupertinoPageScaffold(
        navigationBar: CupertinoNavigationBar(
          middle: Text('Flutter Forward 2023'),
        ),
        child: _MyPage(),
      ),
    );
  }
}

class _MyPage extends StatelessWidget {
  const _MyPage();

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Icon(
            CupertinoTheme.of(context).brightness == Brightness.light
                ? Icons.light_mode
                : Icons.dark_mode,
            color: const CupertinoDynamicColor.withBrightness(
              color: CupertinoColors.black,
              darkColor: CupertinoColors.white,
            ).resolveFrom(context),
            size: 100.0,
          ),
          Text(
            'Im using CupertinoDynamicColor',
            style: TextStyle(
              color: const CupertinoDynamicColor.withBrightness(
                color: Color(0xFFFF0000),
                darkColor: Color(0xFF00FF00),
              ).resolveFrom(context),
            ),
          ),
          CupertinoTextField(
            contextMenuBuilder: (BuildContext context, EditableTextState editableTextState) {
              return AdaptiveTextSelectionToolbar(
                anchors: editableTextState.contextMenuAnchors,
                children: <Widget>[
                  ...AdaptiveTextSelectionToolbar.getAdaptiveButtons(context, editableTextState.contextMenuButtonItems),
                  CupertinoTextSelectionToolbarButton.text(
                    text: 'I am disabled',
                    onPressed: null,
                  ),
                ],
              );
            },
          ),
        ],
      ),
    );
  }
}

[MitchellGoodwin]

LGTM