store: Move PerAccountStoreWidget down into individual routes

lib/widgets/app.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import '../model/store.dart';
 import 'compose_box.dart';
 import 'message_list.dart';
+import 'page.dart';
 import 'store.dart';
 
 class ZulipApp extends StatelessWidget {
@@ -11,23 +12,23 @@ class ZulipApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final theme = ThemeData(
-        // This applies Material 3's color system to produce a palette of
-        // appropriately matching and contrasting colors for use in a UI.
-        // The Zulip brand color is a starting point, but doesn't end up as
-        // one that's directly used.  (After all, we didn't design it for that
-        // purpose; we designed a logo.)  See docs:
-        //   https://api.flutter.dev/flutter/material/ColorScheme/ColorScheme.fromSeed.html
-        // Or try this tool to see the whole palette:
-        //   https://m3.material.io/theme-builder#/custom
-        colorScheme: ColorScheme.fromSeed(seedColor: kZulipBrandColor));
+      // This applies Material 3's color system to produce a palette of
+      // appropriately matching and contrasting colors for use in a UI.
+      // The Zulip brand color is a starting point, but doesn't end up as
+      // one that's directly used.  (After all, we didn't design it for that
+      // purpose; we designed a logo.)  See docs:
+      //   https://api.flutter.dev/flutter/material/ColorScheme/ColorScheme.fromSeed.html
+      // Or try this tool to see the whole palette:
+      //   https://m3.material.io/theme-builder#/custom
+      colorScheme: ColorScheme.fromSeed(seedColor: kZulipBrandColor));
     return GlobalStoreWidget(
-      child: PerAccountStoreWidget(
-        // Just one account for now.
-        accountId: LiveGlobalStore.fixtureAccountId,
-        child: MaterialApp(
-          title: 'Zulip',
-          theme: theme,
-          home: const HomePage())));
+      child: MaterialApp(
+        title: 'Zulip',
+        theme: theme,
+        home: const PerAccountStoreWidget(
+          // Just one account for now.
+          accountId: LiveGlobalStore.fixtureAccountId,
+          child: HomePage())));
   }
 }
 
@@ -45,36 +46,34 @@ class HomePage extends StatelessWidget {
     final store = PerAccountStoreWidget.of(context);
 
     InlineSpan bold(String text) => TextSpan(
-        text: text, style: const TextStyle(fontWeight: FontWeight.bold));
+      text: text, style: const TextStyle(fontWeight: FontWeight.bold));
 
     return Scaffold(
-        appBar: AppBar(title: const Text("Home")),
-        body: Center(
-            child:
-                Column(mainAxisAlignment: MainAxisAlignment.center, children: [
+      appBar: AppBar(title: const Text("Home")),
+      body: Center(
+        child: Column(mainAxisAlignment: MainAxisAlignment.center, children: [
           DefaultTextStyle.merge(
-              style: const TextStyle(fontSize: 18),
-              child: Column(children: [
-                const Text('🚧 Under construction 🚧'),
-                const SizedBox(height: 12),
-                Text.rich(TextSpan(
-                    text: 'Connected to: ',
-                    children: [bold(store.account.realmUrl)])),
-                Text.rich(TextSpan(
-                    text: 'Zulip server version: ',
-                    children: [bold(store.zulip_version)])),
-                Text.rich(TextSpan(text: 'Subscribed to ', children: [
-                  bold(store.subscriptions.length.toString()),
-                  const TextSpan(text: ' streams'),
-                ])),
+            style: const TextStyle(fontSize: 18),
+            child: Column(children: [
+              const Text('🚧 Under construction 🚧'),
+              const SizedBox(height: 12),
+              Text.rich(TextSpan(
+                text: 'Connected to: ',
+                children: [bold(store.account.realmUrl)])),
+              Text.rich(TextSpan(
+                text: 'Zulip server version: ',
+                children: [bold(store.zulip_version)])),
+              Text.rich(TextSpan(text: 'Subscribed to ', children: [
+                bold(store.subscriptions.length.toString()),
+                const TextSpan(text: ' streams'),
               ])),
+            ])),
           const SizedBox(height: 16),
           ElevatedButton(
-              onPressed: () => Navigator.push(
-                  context,
-                  MaterialPageRoute(
-                      builder: (context) => const MessageListPage())),
-              child: const Text("All messages"))
+            onPressed: () => Navigator.push(context,
+              MaterialAccountPageRoute(context: context, builder: (context) =>
+                const MessageListPage())),
+            child: const Text("All messages")),
         ])));
   }
 }
@@ -85,21 +84,22 @@ class MessageListPage extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-        appBar: AppBar(title: const Text("All messages")),
-        body: Builder(
-            builder: (BuildContext context) => Center(
-                child: Column(children: [
-                  MediaQuery.removePadding(
-                      // Scaffold knows about the app bar, and so has run this
-                      // BuildContext, which is under `body`, through
-                      // MediaQuery.removePadding with `removeTop: true`.
-                      context: context,
+      appBar: AppBar(title: const Text("All messages")),
+      body: Builder(
+        builder: (BuildContext context) => Center(
+          child: Column(children: [
+            MediaQuery.removePadding(
+              // Scaffold knows about the app bar, and so has run this
+              // BuildContext, which is under `body`, through
+              // MediaQuery.removePadding with `removeTop: true`.
+              context: context,
 
-                      // The compose box pads the bottom inset.
-                      removeBottom: true,
+              // The compose box pads the bottom inset.
+              removeBottom: true,
 
-                      child: const Expanded(
-                          child: MessageList())),
-                  const StreamComposeBox()]))));
+              child: const Expanded(
+                child: MessageList())),
+            const StreamComposeBox(),
+          ]))));
   }
 }

lib/widgets/page.dart

@@ -0,0 +1,50 @@
+
+import 'package:flutter/material.dart';
+
+import 'store.dart';
+
+mixin AccountPageRouteMixin<T> on PageRoute<T> {
+  int get accountId;
+
+  @override
+  Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
+    return PerAccountStoreWidget(
+      accountId: accountId,
+      child: super.buildPage(context, animation, secondaryAnimation));
+  }
+}
+
+class MaterialAccountPageRoute<T> extends MaterialPageRoute<T> with AccountPageRouteMixin<T> {
+  MaterialAccountPageRoute({
+    required BuildContext context,
+    required super.builder,
+    super.settings,
+    super.maintainState,
+    super.fullscreenDialog,
+    super.allowSnapshotting,
+  }) : accountId = PerAccountStoreWidget.accountIdOf(context);
+
+  @override
+  final int accountId;
+}
+
+class AccountPageRouteBuilder<T> extends PageRouteBuilder<T> with AccountPageRouteMixin<T> {
+  AccountPageRouteBuilder({
+    required BuildContext context,
+    super.settings,
+    required super.pageBuilder,
+    super.transitionsBuilder,
+    super.transitionDuration,
+    super.reverseTransitionDuration,
+    super.opaque,
+    super.barrierDismissible,
+    super.barrierColor,
+    super.barrierLabel,
+    super.maintainState,
+    super.fullscreenDialog,
+    super.allowSnapshotting,
+  }) : accountId = PerAccountStoreWidget.accountIdOf(context);
+
+  @override
+  final int accountId;
+}

lib/widgets/store.dart

@@ -132,16 +132,38 @@ class PerAccountStoreWidget extends StatefulWidget {
   /// [BuildContext.dependOnInheritedWidgetOfExactType].
   ///
   /// See also:
-  ///  * [InheritedNotifier], which provides the "dependency" mechanism.
+  ///  * [accountIdOf], for the account ID corresponding to the same data.
   ///  * [GlobalStoreWidget.of], for the app's data beyond that of a
   ///    particular account.
+  ///  * [InheritedNotifier], which provides the "dependency" mechanism.
   static PerAccountStore of(BuildContext context) {
     final widget = context
         .dependOnInheritedWidgetOfExactType<_PerAccountStoreInheritedWidget>();
     assert(widget != null, 'No PerAccountStoreWidget ancestor');
     return widget!.store;
   }
 
+  /// Our account ID for the relevant account for this widget.
+  ///
+  /// As with [of], the data is taken from the closest [PerAccountStoreWidget]
+  /// that encloses the given context.  Throws an error if there is no enclosing
+  /// [PerAccountStoreWidget].
+  ///
+  /// Unlike [of], this method does not create a dependency relationship, and
+  /// updates to the [PerAccountStoreWidget] will not cause the calling widget
+  /// to be rebuilt.  As a result, this should not be called from build methods,
+  /// but is appropriate to use in interaction event handlers.  For more, see
+  /// [BuildContext.findAncestorWidgetOfExactType].
+  ///
+  /// Like [of], the cost of this method is O(1) with a small constant factor.
+  static int accountIdOf(BuildContext context) {
+    final element = context.getElementForInheritedWidgetOfExactType<_PerAccountStoreInheritedWidget>();
+    assert(element != null, 'No PerAccountStoreWidget ancestor');
+    final widget = element!.findAncestorWidgetOfExactType<PerAccountStoreWidget>();
+    assert(widget != null);
+    return widget!.accountId;
+  }
+
   @override
   State<PerAccountStoreWidget> createState() => _PerAccountStoreWidgetState();
 }

pubspec.lock

@@ -29,10 +29,10 @@ packages:
     dependency: transitive
     description:
       name: async
-      sha256: bfe67ef28df125b7dddcea62755991f807aa39a2492a23e1550161692950bbe0
+      sha256: "947bfcf187f74dbc5e146c9eb9c0f10c9f8b30743e341481c1e2ed3ecc18c20c"
       url: "https://pub.dev"
     source: hosted
-    version: "2.10.0"
+    version: "2.11.0"
   boolean_selector:
     dependency: transitive
     description: