Changes WidgetInspector to use valuenotifier instead of a force rebuild for (#131634)

![](https://media.giphy.com/media/qriH9W51oLsL6/giphy.gif)
Fixes https://github.com/flutter/devtools/issues/6014

Change the forceRebuild behaviour of the WidgetInspector to use
ValueListenableBuilders instead. This should help resolve heavy rebuilds
when the widgetInspectorOverride value changes.

packages/flutter/lib/src/widgets/app.dart

@@ -31,6 +31,7 @@ import 'shortcuts.dart';
 import 'tap_region.dart';
 import 'text.dart';
 import 'title.dart';
+import 'value_listenable_builder.dart';
 import 'widget_inspector.dart';
 
 export 'dart:ui' show Locale;
@@ -1189,13 +1190,22 @@ class WidgetsApp extends StatefulWidget {
 
   /// If true, forces the widget inspector to be visible.
   ///
+  /// Overrides the `debugShowWidgetInspector` value set in [WidgetsApp].
+  ///
   /// Used by the `debugShowWidgetInspector` debugging extension.
   ///
-  /// The inspector allows you to select a location on your device or emulator
+  /// The inspector allows the selection of a location on your device or emulator
   /// and view what widgets and render objects associated with it. An outline of
   /// the selected widget and some summary information is shown on device and
   /// more detailed information is shown in the IDE or DevTools.
-  static bool debugShowWidgetInspectorOverride = false;
+  static bool get debugShowWidgetInspectorOverride {
+    return _debugShowWidgetInspectorOverrideNotifier.value;
+  }
+  static set debugShowWidgetInspectorOverride(bool value) {
+    _debugShowWidgetInspectorOverrideNotifier.value = value;
+  }
+
+  static final ValueNotifier<bool> _debugShowWidgetInspectorOverrideNotifier = ValueNotifier<bool>(false);
 
   /// If false, prevents the debug banner from being visible.
   ///
@@ -1743,12 +1753,19 @@ class _WidgetsAppState extends State<WidgetsApp> with WidgetsBindingObserver {
     }
 
     assert(() {
-      if (widget.debugShowWidgetInspector || WidgetsApp.debugShowWidgetInspectorOverride) {
-        result = WidgetInspector(
-          selectButtonBuilder: widget.inspectorSelectButtonBuilder,
-          child: result,
-        );
-      }
+      result = ValueListenableBuilder<bool>(
+        valueListenable: WidgetsApp._debugShowWidgetInspectorOverrideNotifier,
+        builder: (BuildContext context, bool debugShowWidgetInspectorOverride, Widget? child) {
+          if (widget.debugShowWidgetInspector || debugShowWidgetInspectorOverride) {
+            return WidgetInspector(
+              selectButtonBuilder: widget.inspectorSelectButtonBuilder,
+              child: child!,
+            );
+          }
+          return child!;
+        },
+        child: result,
+      );
       if (widget.debugShowCheckedModeBanner && WidgetsApp.debugAllowBannerOverride) {
         result = CheckedModeBanner(
           child: result,

packages/flutter/lib/src/widgets/widget_inspector.dart

@@ -1078,11 +1078,10 @@ mixin WidgetInspectorService {
       name: WidgetInspectorServiceExtensions.show.name,
       getter: () async => WidgetsApp.debugShowWidgetInspectorOverride,
       setter: (bool value) {
-        if (WidgetsApp.debugShowWidgetInspectorOverride == value) {
-          return Future<void>.value();
+        if (WidgetsApp.debugShowWidgetInspectorOverride != value) {
+          WidgetsApp.debugShowWidgetInspectorOverride = value;
         }
-        WidgetsApp.debugShowWidgetInspectorOverride = value;
-        return forceRebuild();
+        return Future<void>.value();
       },
       registerExtension: registerExtension,
     );

packages/flutter/test/widgets/widget_inspector_test.dart

@@ -4115,6 +4115,28 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
     testWidgetsWithLeakTracking('ext.flutter.inspector.show', (WidgetTester tester) async {
       final Iterable<Map<Object, Object?>> extensionChangedEvents = service.getServiceExtensionStateChangedEvents('ext.flutter.inspector.show');
       Map<Object, Object?> extensionChangedEvent;
+      int debugShowChangeCounter = 0;
+
+      final GlobalKey key = GlobalKey();
+      await tester.pumpWidget(
+        WidgetsApp(
+          key: key,
+          builder: (BuildContext context, Widget? child) {
+            return const Placeholder();
+          },
+          color: const Color(0xFF123456),
+        ),
+      );
+
+      final ValueListenableBuilder<bool> valueListenableBuilderWidget = tester.widget(
+        find.byType(ValueListenableBuilder<bool>),
+      );
+      void debugShowWidgetInspectorOverrideCallback() {
+        debugShowChangeCounter++;
+      }
+
+      WidgetsApp.debugShowWidgetInspectorOverride = false;
+      valueListenableBuilderWidget.valueListenable.addListener(debugShowWidgetInspectorOverrideCallback);
 
       service.rebuildCount = 0;
       expect(extensionChangedEvents, isEmpty);
@@ -4129,7 +4151,8 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       extensionChangedEvent = extensionChangedEvents.last;
       expect(extensionChangedEvent['extension'], equals('ext.flutter.inspector.show'));
       expect(extensionChangedEvent['value'], isTrue);
-      expect(service.rebuildCount, equals(1));
+      expect(service.rebuildCount, equals(0)); // Should not be force rebuilt.
+      expect(debugShowChangeCounter, equals(1));
       expect(
         await service.testBoolExtension(
           WidgetInspectorServiceExtensions.show.name,
@@ -4139,6 +4162,8 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       );
       expect(WidgetsApp.debugShowWidgetInspectorOverride, isTrue);
       expect(extensionChangedEvents.length, equals(1));
+      expect(service.rebuildCount, equals(0)); // Should not be force rebuilt.
+      expect(debugShowChangeCounter, equals(1));
       expect(
         await service.testBoolExtension(
           WidgetInspectorServiceExtensions.show.name,
@@ -4150,7 +4175,8 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       extensionChangedEvent = extensionChangedEvents.last;
       expect(extensionChangedEvent['extension'], equals('ext.flutter.inspector.show'));
       expect(extensionChangedEvent['value'], isTrue);
-      expect(service.rebuildCount, equals(1));
+      expect(service.rebuildCount, equals(0)); // Should not be force rebuilt.
+      expect(debugShowChangeCounter, equals(1));
       expect(
         await service.testBoolExtension(
           WidgetInspectorServiceExtensions.show.name,
@@ -4162,6 +4188,8 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       extensionChangedEvent = extensionChangedEvents.last;
       expect(extensionChangedEvent['extension'], equals('ext.flutter.inspector.show'));
       expect(extensionChangedEvent['value'], isFalse);
+      expect(service.rebuildCount, equals(0)); // Should not be force rebuilt.
+      expect(debugShowChangeCounter, equals(2));
       expect(
         await service.testBoolExtension(
           WidgetInspectorServiceExtensions.show.name,
@@ -4170,7 +4198,8 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
         equals('false'),
       );
       expect(extensionChangedEvents.length, equals(3));
-      expect(service.rebuildCount, equals(2));
+      expect(service.rebuildCount, equals(0)); // Should not be force rebuilt.
+      expect(debugShowChangeCounter, equals(2));
       expect(WidgetsApp.debugShowWidgetInspectorOverride, isFalse);
     });