app_bar [nfc]: Move ZulipAppBar.isLoading to within widget

This keeps call sites simpler.

Author: gnprice

lib/widgets/app.dart

@@ -253,9 +253,7 @@ class HomePage extends StatelessWidget {
     }
 
     return Scaffold(
-      appBar: ZulipAppBar(
-        title: const Text("Home"),
-        isLoading: store.isLoading),
+      appBar: ZulipAppBar(title: const Text("Home")),
       body: Center(
         child: Column(mainAxisAlignment: MainAxisAlignment.center, children: [
           DefaultTextStyle.merge(

lib/widgets/app_bar.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/material.dart';
 
+import 'store.dart';
+
 /// A custom [AppBar] with a loading indicator.
 ///
 /// This should be used for most of the pages with access to [PerAccountStore].
@@ -12,11 +14,21 @@ class ZulipAppBar extends AppBar {
     super.backgroundColor,
     super.shape,
     super.actions,
-    required bool isLoading,
-  }) : super(
-    bottom: PreferredSize(
-      preferredSize: const Size.fromHeight(4.0),
-      child: (isLoading)
-        ? LinearProgressIndicator(backgroundColor: backgroundColor, minHeight: 4.0)
-        : const SizedBox.shrink()));
+  }) : super(bottom: _ZulipAppBarBottom(backgroundColor: backgroundColor));
+}
+
+class _ZulipAppBarBottom extends StatelessWidget implements PreferredSizeWidget {
+  const _ZulipAppBarBottom({this.backgroundColor});
+
+  final Color? backgroundColor;
+
+  @override
+  Size get preferredSize => const Size.fromHeight(4.0);
+
+  @override
+  Widget build(BuildContext context) {
+    final store = PerAccountStoreWidget.of(context);
+    if (!store.isLoading) return const SizedBox.shrink();
+    return LinearProgressIndicator(minHeight: 4.0, backgroundColor: backgroundColor);
+  }
 }

lib/widgets/inbox.dart

@@ -161,9 +161,7 @@ class _InboxPageState extends State<InboxPage> with PerAccountStoreAwareStateMix
     }
 
     return Scaffold(
-      appBar: ZulipAppBar(
-        title: const Text('Inbox'),
-        isLoading: store.isLoading),
+      appBar: ZulipAppBar(title: const Text('Inbox')),
       body: SafeArea(
         // Don't pad the bottom here; we want the list content to do that.
         bottom: false,

lib/widgets/message_list.dart

@@ -271,7 +271,6 @@ class _MessageListPageState extends State<MessageListPage> implements MessageLis
     return Scaffold(
       appBar: ZulipAppBar(
         title: MessageListAppBarTitle(narrow: narrow),
-        isLoading: store.isLoading,
         backgroundColor: appBarBackgroundColor,
         shape: removeAppBarBottomBorder
           ? const Border()

lib/widgets/profile.dart

@@ -103,9 +103,7 @@ class ProfilePage extends StatelessWidget {
     ];
 
     return Scaffold(
-      appBar: ZulipAppBar(
-        title: Text(user.fullName),
-        isLoading: store.isLoading),
+      appBar: ZulipAppBar(title: Text(user.fullName)),
       body: SingleChildScrollView(
         child: Center(
           child: ConstrainedBox(
@@ -123,11 +121,8 @@ class _ProfileErrorPage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final store = PerAccountStoreWidget.of(context);
     return Scaffold(
-      appBar: ZulipAppBar(
-        title: const Text('Error'),
-        isLoading: store.isLoading),
+      appBar: ZulipAppBar(title: const Text('Error')),
       body: const SingleChildScrollView(
         child: Padding(
           padding: EdgeInsets.symmetric(horizontal: 16, vertical: 32),

lib/widgets/recent_dm_conversations.dart

@@ -56,13 +56,11 @@ class _RecentDmConversationsPageState extends State<RecentDmConversationsPage> w
 
   @override
   Widget build(BuildContext context) {
-    final store = PerAccountStoreWidget.of(context);
     final zulipLocalizations = ZulipLocalizations.of(context);
     final sorted = model!.sorted;
     return Scaffold(
       appBar: ZulipAppBar(
-        title: Text(zulipLocalizations.recentDmConversationsPageTitle),
-        isLoading: store.isLoading),
+        title: Text(zulipLocalizations.recentDmConversationsPageTitle)),
       body: SafeArea(
         // Don't pad the bottom here; we want the list content to do that.
         bottom: false,

lib/widgets/subscription_list.dart

@@ -90,9 +90,7 @@ class _SubscriptionListPageState extends State<SubscriptionListPage> with PerAcc
     _sortSubs(unpinned);
 
     return Scaffold(
-      appBar: ZulipAppBar(
-        title: const Text("Channels"),
-        isLoading: store.isLoading),
+      appBar: ZulipAppBar(title: const Text("Channels")),
       body: SafeArea(
         // Don't pad the bottom here; we want the list content to do that.
         bottom: false,