perf: prevent expensive blurring when the current page is hidden

lib/model/settings/defaults.dart

@@ -27,7 +27,7 @@ class SettingsDefaults {
   static const mustBackTwiceToExit = true;
   static const keepScreenOn = KeepScreenOn.viewerOnly;
   static const homePage = HomePageSetting.collection;
-  static const showBottomNavigationBar = false;
+  static const showBottomNavigationBar = true;
   static const confirmDeleteForever = true;
   static const confirmMoveToBin = true;
   static const confirmMoveUndatedItems = true;

lib/widgets/aves_app.dart

@@ -44,6 +44,10 @@ class AvesApp extends StatefulWidget {
 
   static final GlobalKey<NavigatorState> navigatorKey = GlobalKey(debugLabel: 'app-navigator');
 
+  // do not monitor all `ModalRoute`s, which would include popup menus,
+  // so that we can react to fullscreen `PageRoute`s only
+  static final RouteObserver<PageRoute> pageRouteObserver = RouteObserver<PageRoute>();
+
   const AvesApp({
     super.key,
     required this.flavor,
@@ -62,7 +66,7 @@ class _AvesAppState extends State<AvesApp> with WidgetsBindingObserver {
 
   // observers are not registered when using the same list object with different items
   // the list itself needs to be reassigned
-  List<NavigatorObserver> _navigatorObservers = [];
+  List<NavigatorObserver> _navigatorObservers = [AvesApp.pageRouteObserver];
   final EventChannel _mediaStoreChangeChannel = const EventChannel('deckers.thibault/aves/media_store_change');
   final EventChannel _newIntentChannel = const EventChannel('deckers.thibault/aves/intent');
   final EventChannel _analysisCompletionChannel = const EventChannel('deckers.thibault/aves/analysis_events');
@@ -284,6 +288,7 @@ class _AvesAppState extends State<AvesApp> with WidgetsBindingObserver {
       'time_zone': '${now.timeZoneName} (${now.timeZoneOffset})',
     });
     _navigatorObservers = [
+      AvesApp.pageRouteObserver,
       ReportingRouteTracker(),
     ];
   }

lib/widgets/common/identity/aves_app_bar.dart

@@ -1,5 +1,6 @@
 import 'package:aves/model/settings/settings.dart';
 import 'package:aves/theme/durations.dart';
+import 'package:aves/widgets/aves_app.dart';
 import 'package:aves/widgets/common/fx/blurred.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
@@ -35,9 +36,11 @@ class AvesAppBar extends StatelessWidget {
             child: SafeArea(
               bottom: false,
               child: AvesFloatingBar(
-                builder: (context, backgroundColor) => Material(
+                builder: (context, backgroundColor, child) => Material(
                   color: backgroundColor,
                   textStyle: Theme.of(context).appBarTheme.titleTextStyle,
+                  child: child,
+                ),
                 child: Column(
                   children: [
                     SizedBox(
@@ -69,7 +72,6 @@ class AvesAppBar extends StatelessWidget {
               ),
             ),
           ),
-          ),
         );
       },
     );
@@ -100,39 +102,75 @@ class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
   bool shouldRebuild(covariant _SliverAppBarDelegate oldDelegate) => true;
 }
 
-class AvesFloatingBar extends StatelessWidget {
-  final Widget Function(BuildContext context, Color backgroundColor) builder;
+class AvesFloatingBar extends StatefulWidget {
+  final Widget Function(BuildContext context, Color backgroundColor, Widget? child) builder;
+  final Widget? child;
+
+  static const margin = EdgeInsets.all(8);
+  static const borderRadius = BorderRadius.all(Radius.circular(8));
 
   const AvesFloatingBar({
     super.key,
     required this.builder,
+    this.child,
   });
 
-  static const margin = EdgeInsets.all(8);
-  static const borderRadius = BorderRadius.all(Radius.circular(8));
+  @override
+  State<AvesFloatingBar> createState() => _AvesFloatingBarState();
+}
+
+class _AvesFloatingBarState extends State<AvesFloatingBar> with RouteAware {
+  // prevent expensive blurring when the current page is hidden
+  final ValueNotifier<bool> _isBlurAllowedNotifier = ValueNotifier(true);
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    final route = ModalRoute.of(context);
+    if (route is PageRoute) {
+      AvesApp.pageRouteObserver.subscribe(this, route);
+    }
+  }
+
+  @override
+  void dispose() {
+    AvesApp.pageRouteObserver.unsubscribe(this);
+    super.dispose();
+  }
+
+  @override
+  void didPopNext() => _isBlurAllowedNotifier.value = true;
+
+  @override
+  void didPushNext() => _isBlurAllowedNotifier.value = false;
 
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
     final backgroundColor = theme.appBarTheme.backgroundColor!;
-    final blurred = context.select<Settings, bool>((s) => s.enableOverlayBlurEffect);
-
+    return ValueListenableBuilder<bool>(
+      valueListenable: _isBlurAllowedNotifier,
+      builder: (context, isBlurAllowed, child) {
+        final blurred = isBlurAllowed && context.select<Settings, bool>((s) => s.enableOverlayBlurEffect);
         return Container(
           foregroundDecoration: BoxDecoration(
             border: Border.all(
               color: theme.dividerColor,
             ),
-        borderRadius: borderRadius,
+            borderRadius: AvesFloatingBar.borderRadius,
           ),
-      margin: margin,
+          margin: AvesFloatingBar.margin,
           child: BlurredRRect(
             enabled: blurred,
-        borderRadius: borderRadius,
-        child: builder(
+            borderRadius: AvesFloatingBar.borderRadius,
+            child: widget.builder(
               context,
               blurred ? backgroundColor.withOpacity(.85) : backgroundColor,
+              widget.child,
             ),
           ),
         );
+      },
+    );
   }
 }

lib/widgets/navigation/nav_bar/nav_bar.dart

@@ -75,7 +75,7 @@ class _AppBottomNavBarState extends State<AppBottomNavBar> {
     ];
 
     Widget child = AvesFloatingBar(
-      builder: (context, backgroundColor) => BottomNavigationBar(
+      builder: (context, backgroundColor, child) => BottomNavigationBar(
         items: items
             .map((item) => BottomNavigationBarItem(
                   icon: item.icon(context),

test_driver/driver_screenshots.dart

@@ -20,6 +20,7 @@ Future<void> configureAndLaunch() async {
     ..isErrorReportingAllowed = false
     ..keepScreenOn = KeepScreenOn.always
     ..homePage = HomePageSetting.collection
+    ..showBottomNavigationBar = true
     ..setTileExtent(CountryListPage.routeName, 112)
     ..setTileLayout(CountryListPage.routeName, TileLayout.grid)
     // collection