settings [nfc]: Split out a GlobalSettingsStore, and GlobalStoreWidget.settingsOf

This allows widgets to listen separately for changes to settings or
to the rest of the global store's data, which is a bit nice.

More fundamentally, as a matter of code organization, it gives us a
place to put code related to the store of global settings where
there's more room to spread out than if we kept it in GlobalStore,
and where the namespace is already specific to global settings.

Those two points in turn will also help us adjust the API the rest
of the app uses for interacting with these settings, so as to make
it more ergonomic.

The TODO comments added in this commit mark places where this API
will be more coherent after upcoming commits in this series.

Author: gnprice

lib/model/settings.dart

@@ -85,3 +85,18 @@ extension GlobalSettingsHelpers on GlobalSettingsData {
     }
   }
 }
+
+/// Store for the user's account-independent settings.
+///
+/// From UI code, use [GlobalStoreWidget.settingsOf] to get hold of
+/// the settings data.
+///
+/// (At the moment the actual settings data lives on [GlobalStore];
+/// but when the settings change, the notification goes to listeners
+/// of this class, not [GlobalStore].  Soon the actual data will
+/// move to this class too.)
+class GlobalSettingsStore extends ChangeNotifier {
+  // TODO move the actual settings content to this class
+
+  void markUpdated() => notifyListeners();
+}

lib/model/store.dart

@@ -29,6 +29,7 @@ import 'message_list.dart';
 import 'recent_dm_conversations.dart';
 import 'recent_senders.dart';
 import 'channel.dart';
+import 'settings.dart';
 import 'typing_status.dart';
 import 'unreads.dart';
 import 'user.dart';
@@ -60,15 +61,22 @@ abstract class GlobalStore extends ChangeNotifier {
     : _globalSettings = globalSettings,
       _accounts = Map.fromEntries(accounts.map((a) => MapEntry(a.id, a)));
 
+  // TODO use this as the actual store
+  final GlobalSettingsStore settingsNotifier = GlobalSettingsStore();
+
   /// A cache of the [GlobalSettingsData] singleton in the underlying data store.
+  ///
+  /// To be notified for changes to this value, subscribe to [settingsNotifier]
+  /// (usually by calling [GlobalStoreWidget.settingsOf]).
+  /// The [GlobalStore] itself will not notify its own listeners.
   GlobalSettingsData get globalSettings => _globalSettings;
   GlobalSettingsData _globalSettings;
 
   /// Update the global settings in the store.
   Future<void> updateGlobalSettings(GlobalSettingsCompanion data) async {
     await doUpdateGlobalSettings(data);
     _globalSettings = _globalSettings.copyWithCompanion(data);
-    notifyListeners();
+    settingsNotifier.markUpdated();
   }
 
   /// Update the global settings in the underlying data store.

lib/widgets/content.dart

@@ -1439,7 +1439,7 @@ void _launchUrl(BuildContext context, String urlString) async {
     return;
   }
 
-  final globalSettings = GlobalStoreWidget.of(context).globalSettings;
+  final globalSettings = GlobalStoreWidget.settingsOf(context);
   bool launched = false;
   String? errorMessage;
   try {

lib/widgets/settings.dart

@@ -40,7 +40,7 @@ class _ThemeSetting extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final zulipLocalizations = ZulipLocalizations.of(context);
-    final globalStore = GlobalStoreWidget.of(context);
+    final globalSettings = GlobalStoreWidget.settingsOf(context);
     return Column(
       children: [
         ListTile(title: Text(zulipLocalizations.themeSettingTitle)),
@@ -50,7 +50,7 @@ class _ThemeSetting extends StatelessWidget {
               themeSetting: themeSettingOption,
               zulipLocalizations: zulipLocalizations)),
             value: themeSettingOption,
-            groupValue: globalStore.globalSettings.themeSetting,
+            groupValue: globalSettings.themeSetting,
             onChanged: (newValue) => _handleChange(context, newValue)),
       ]);
   }
@@ -69,9 +69,9 @@ class _BrowserPreferenceSetting extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final zulipLocalizations = ZulipLocalizations.of(context);
+    final globalSettings = GlobalStoreWidget.settingsOf(context);
     final openLinksWithInAppBrowser =
-      GlobalStoreWidget.of(context).globalSettings.effectiveBrowserPreference
-      == BrowserPreference.inApp;
+      globalSettings.effectiveBrowserPreference == BrowserPreference.inApp;
     return SwitchListTile.adaptive(
       title: Text(zulipLocalizations.openLinksWithInAppBrowser),
       value: openLinksWithInAppBrowser,

lib/widgets/store.dart

@@ -2,6 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart';
 
 import '../model/binding.dart';
+import '../model/database.dart';
+import '../model/settings.dart';
 import '../model/store.dart';
 import 'page.dart';
 
@@ -51,6 +53,28 @@ class GlobalStoreWidget extends StatefulWidget {
     return widget!.store;
   }
 
+  /// The user's [GlobalSettings] data, from the app's global data store.
+  ///
+  /// The given build context will be registered as a dependency and
+  /// subscribed to changes in the [GlobalSettingsStore].
+  /// This means that when the setting values in the store change,
+  /// the element at that build context will be rebuilt.
+  ///
+  /// This method is typically called near the top of a build method or a
+  /// [State.didChangeDependencies] method, like so:
+  /// ```
+  ///   @override
+  ///   Widget build(BuildContext context) {
+  ///     final globalSettings = GlobalStoreWidget.settingsOf(context);
+  /// ```
+  ///
+  /// See [of] for further discussion of how to use this kind of method.
+  static GlobalSettingsData settingsOf(BuildContext context) {
+    final widget = context.dependOnInheritedWidgetOfExactType<_GlobalSettingsStoreInheritedWidget>();
+    assert(widget != null, 'No GlobalStoreWidget ancestor');
+    return widget!.store.globalSettings;
+  }
+
   @override
   State<GlobalStoreWidget> createState() => _GlobalStoreWidgetState();
 }
@@ -81,14 +105,27 @@ class _GlobalStoreWidgetState extends State<GlobalStoreWidget> {
 // a [StatefulWidget] to get hold of the store, and an [InheritedWidget] to
 // provide it to descendants, and one widget can't be both of those.
 class _GlobalStoreInheritedWidget extends InheritedNotifier<GlobalStore> {
-  const _GlobalStoreInheritedWidget({
+  _GlobalStoreInheritedWidget({
     required GlobalStore store,
-    required super.child,
-  }) : super(notifier: store);
+    required Widget child,
+  }) : super(notifier: store,
+         child: _GlobalSettingsStoreInheritedWidget(store: store, child: child));
 
   GlobalStore get store => notifier!;
 }
 
+// This is like [_GlobalStoreInheritedWidget] except it subscribes to the
+// [GlobalSettingsStore] instead of the overall [GlobalStore].
+// That enables [settingsOf] to do the same.
+class _GlobalSettingsStoreInheritedWidget extends InheritedNotifier<GlobalSettingsStore> {
+  _GlobalSettingsStoreInheritedWidget({
+    required this.store,
+    required super.child,
+  }) : super(notifier: store.settingsNotifier);
+
+  final GlobalStore store;
+}
+
 /// Provides access to the user's data for a particular Zulip account.
 ///
 /// Widgets that need information that comes from the Zulip server, or need to

lib/widgets/theme.dart

@@ -13,7 +13,7 @@ import 'text.dart';
 ThemeData zulipThemeData(BuildContext context) {
   final DesignVariables designVariables;
   final List<ThemeExtension> themeExtensions;
-  final globalSettings = GlobalStoreWidget.of(context).globalSettings;
+  final globalSettings = GlobalStoreWidget.settingsOf(context);
   Brightness brightness = switch (globalSettings.themeSetting) {
     null => MediaQuery.platformBrightnessOf(context),
     ThemeSetting.light => Brightness.light,

test/model/store_test.dart

@@ -45,7 +45,7 @@ void main() {
     test('should notify listeners', () async {
       int notifyCount = 0;
       final globalStore = eg.globalStore();
-      globalStore.addListener(() => notifyCount++);
+      globalStore.settingsNotifier.addListener(() => notifyCount++);
       check(notifyCount).equals(0);
 
       await globalStore.updateGlobalSettings(

test/widgets/store_test.dart

@@ -5,6 +5,8 @@ import 'package:flutter/material.dart';
 import 'package:flutter_checks/flutter_checks.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:zulip/model/actions.dart';
+import 'package:zulip/model/database.dart';
+import 'package:zulip/model/settings.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/widgets/app.dart';
 import 'package:zulip/widgets/inbox.dart';
@@ -102,6 +104,28 @@ void main() {
     check(accountIds).isNotNull().deepEquals([eg.selfAccount.id]);
   });
 
+  testWidgets('GlobalStoreWidget.settingsOf updates on settings update', (tester) async {
+    addTearDown(testBinding.reset);
+    await testBinding.globalStore.updateGlobalSettings(
+      GlobalSettingsCompanion(themeSetting: Value(ThemeSetting.dark)));
+
+    ThemeSetting? themeSetting;
+    await tester.pumpWidget(
+      GlobalStoreWidget(
+        child: Builder(
+          builder: (context) {
+            themeSetting = GlobalStoreWidget.settingsOf(context).themeSetting;
+            return const SizedBox.shrink();
+          })));
+    await tester.pump();
+    check(themeSetting).equals(ThemeSetting.dark);
+
+    await testBinding.globalStore.updateGlobalSettings(
+      GlobalSettingsCompanion(themeSetting: Value(ThemeSetting.light)));
+    await tester.pump();
+    check(themeSetting).equals(ThemeSetting.light);
+  });
+
   testWidgets('PerAccountStoreWidget basic', (tester) async {
     await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
     addTearDown(testBinding.reset);