Support brightness override in a11y page

packages/devtools_app/lib/src/screens/accessibility/accessibility_controller.dart

@@ -2,11 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file or at https://developers.google.com/open-source/licenses/bsd.
 
+import 'dart:async';
+
+import 'package:devtools_app_shared/service.dart';
 import 'package:devtools_app_shared/utils.dart';
 import 'package:flutter/foundation.dart';
 
+import '../../service/service_extensions.dart' as extensions;
 import '../../shared/framework/screen.dart';
 import '../../shared/framework/screen_controllers.dart';
+import '../../shared/globals.dart';
 
 /// Modes for brightness override in the accessibility controls.
 enum BrightnessOverride {
@@ -26,6 +31,12 @@ class AccessibilityController extends DevToolsScreenController
     _initListeners();
   }
 
+  @override
+  void init() {
+    super.init();
+    _initServiceExtensionStates();
+  }
+
   void _initListeners() {
     addAutoDisposeListener(brightness, _onBrightnessChanged);
     addAutoDisposeListener(textScale, _onTextScaleChanged);
@@ -34,9 +45,50 @@ class AccessibilityController extends DevToolsScreenController
     addAutoDisposeListener(highContrast, _onHighContrastChanged);
   }
 
+  void _initServiceExtensionStates() {
+    final state = serviceConnection.serviceManager.serviceExtensionManager
+        .getServiceExtensionState(extensions.brightnessMode.extension);
+
+    void updateFromDeviceState(ServiceExtensionState s) {
+      final newBrightness = !s.enabled || s.value == null
+          ? BrightnessOverride.system
+          : switch (s.value) {
+              'Brightness.light' => BrightnessOverride.light,
+              'Brightness.dark' => BrightnessOverride.dark,
+              _ => BrightnessOverride.system,
+            };
+      if (brightness.value != newBrightness) {
+        brightness.value = newBrightness;
+      }
+    }
+
+    updateFromDeviceState(state.value);
+    addAutoDisposeListener(
+      state,
+      () => updateFromDeviceState(state.value),
+    );
+  }
+
   void _onBrightnessChanged() {
-    // TODO(hannah-hyj): Implement VM service extension call for brightness override.
-    // e.g. using 'ext.flutter.brightnessOverride'.
+    final value = brightness.value;
+    // Values expected by Flutter framework's 'ext.flutter.brightnessOverride':
+    // - 'Brightness.light': forces light mode
+    // - 'Brightness.dark': forces dark mode
+    // - '': any value other than 'Brightness.light' or 'Brightness.dark' clears
+    //   the override and resets to system default.
+    final paramValue = switch (value) {
+      BrightnessOverride.light => 'Brightness.light',
+      BrightnessOverride.dark => 'Brightness.dark',
+      BrightnessOverride.system => '',
+    };
+    unawaited(
+      serviceConnection.serviceManager.serviceExtensionManager
+          .setServiceExtensionState(
+        extensions.brightnessMode.extension,
+        enabled: value != BrightnessOverride.system,
+        value: paramValue,
+      ),
+    );
   }
 
   void _onTextScaleChanged() {

packages/devtools_app/lib/src/service/service_extensions.dart

@@ -379,6 +379,16 @@ final togglePlatformMode = ServiceExtensionDescription<String>.from(
   tooltip: 'Override Target Platform',
 );
 
+/// Service extension description for overriding brightness in accessibility controls.
+final brightnessMode = ServiceExtensionDescription<String>.from(
+  extensions.brightnessMode,
+  title: 'Override brightness',
+  iconData: Icons.brightness_6,
+  gaScreenName: gac.accessibility,
+  gaItem: gac.brightnessOverride,
+  tooltip: 'Override Brightness',
+);
+
 final disableClipLayers = ToggleableServiceExtensionDescription<bool>.from(
   extensions.disableClipLayers,
   title: 'Render Clip layers',

packages/devtools_app/lib/src/shared/analytics/constants.dart

@@ -44,6 +44,7 @@ final vmTools = ScreenMetaData.vmTools.id;
 const console = 'console';
 final simple = ScreenMetaData.simple.id;
 final deeplink = ScreenMetaData.deepLinks.id;
+final accessibility = ScreenMetaData.accessibility.id;
 
 // GA events not associated with a any screen e.g., hotReload, hotRestart, etc
 const devToolsMain = 'main';
@@ -86,6 +87,7 @@ const repaintRainbow = 'repaintRainbow';
 const repaintRainbowDocs = 'repaintRainbowDocs';
 const debugBanner = 'debugBanner';
 const togglePlatform = 'togglePlatform';
+const brightnessOverride = 'brightnessOverride';
 const highlightOversizedImages = 'highlightOversizedImages';
 const highlightOversizedImagesDocs = 'highlightOversizedImagesDocs';
 const selectWidgetMode = 'selectWidgetMode';

packages/devtools_app/test/screens/accessibility/accessibility_screen_test.dart

@@ -181,5 +181,36 @@ void main() {
         expect(controller.highContrast.value, isTrue);
       },
     );
+
+    testWidgetsWithWindowSize(
+      'service extension state change updates controller brightness state',
+      windowSize,
+      (WidgetTester tester) async {
+        final fakeServiceExtensionManager =
+            serviceConnection.serviceManager.serviceExtensionManager
+                as FakeServiceExtensionManager;
+
+        await pumpAccessibilityScreen(tester);
+        await tester.pumpAndSettle();
+
+        expect(controller.brightness.value, BrightnessOverride.system);
+
+        // Simulate service extension state change from device to dark mode
+        fakeServiceExtensionManager.fakeServiceExtensionStateChanged(
+          brightnessMode.extension,
+          'Brightness.dark',
+        );
+        await tester.pumpAndSettle();
+        expect(controller.brightness.value, BrightnessOverride.dark);
+
+        // Simulate service extension state change from device to light mode
+        fakeServiceExtensionManager.fakeServiceExtensionStateChanged(
+          brightnessMode.extension,
+          'Brightness.light',
+        );
+        await tester.pumpAndSettle();
+        expect(controller.brightness.value, BrightnessOverride.light);
+      },
+    );
   });
 }

packages/devtools_app_shared/lib/src/service/service_extensions.dart

@@ -201,6 +201,13 @@ final togglePlatformMode = ServiceExtension<String>(
   values: ['iOS', 'android', 'fuchsia', 'macOS', 'linux'],
 );
 
+/// Override the platform brightness (light mode, dark mode, or system default).
+final brightnessMode = ServiceExtension<String>(
+  extension:
+      '$flutterExtensionPrefix${FoundationServiceExtensions.brightnessOverride.name}',
+  values: ['system', 'Brightness.light', 'Brightness.dark'],
+);
+
 /// Toggle whether interacting with the device selects widgets or triggers
 /// normal interactions.
 final toggleSelectWidgetMode = ToggleableServiceExtension<bool>(
@@ -259,6 +266,7 @@ final _extensionDescriptions = <ServiceExtension<Object>>[
   toggleSelectWidgetMode,
   countWidgetBuilds,
   profilePlatformChannels,
+  brightnessMode,
 ];
 
 /// Service extensions that are not safe to call unless a frame has already
@@ -281,6 +289,7 @@ final _unsafeBeforeFirstFrameFlutterExtensions = Set.of(
     enableOnDeviceInspector,
     togglePlatformMode,
     slowAnimations,
+    brightnessMode,
   ].map((extension) => extension.extension),
 );
 

packages/devtools_app_shared/test/service/service_extensions_test.dart

@@ -0,0 +1,32 @@
+// Copyright 2026 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file or at https://developers.google.com/open-source/licenses/bsd.
+
+import 'package:devtools_app_shared/service_extensions.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('ServiceExtensions', () {
+    test('brightnessMode is properly configured', () {
+      expect(
+        brightnessMode.extension,
+        equals('ext.flutter.brightnessOverride'),
+      );
+      expect(
+        brightnessMode.values,
+        equals(['system', 'Brightness.light', 'Brightness.dark']),
+      );
+      expect(
+        serviceExtensionsAllowlist[brightnessMode.extension],
+        equals(brightnessMode),
+      );
+    });
+
+    test('brightnessMode is in unsafe before first frame set', () {
+      expect(
+        isUnsafeBeforeFirstFlutterFrame('ext.flutter.brightnessOverride'),
+        isTrue,
+      );
+    });
+  });
+}