Add assistiveTechnologyEnabled flag to window (#5740)

lib/ui/hooks.dart

@@ -70,6 +70,11 @@ void _updateSemanticsEnabled(bool enabled) {
   _invoke(window.onSemanticsEnabledChanged, window._onSemanticsEnabledChangedZone);
 }
 
+void _updateAssistiveTechnologyEnabled(bool enabled) {
+  window._assistiveTechnologyEnabled = enabled;
+  _invoke(window._onAssistiveTechnologyEnabled, window._onAssistiveTechnologyEnabledZone);
+}
+
 void _dispatchPlatformMessage(String name, ByteData data, int responseId) {
   if (window.onPlatformMessage != null) {
     _invoke3<String, ByteData, PlatformMessageResponseCallback>(

lib/ui/window.dart

@@ -637,6 +637,30 @@ class Window {
   bool get semanticsEnabled => _semanticsEnabled;
   bool _semanticsEnabled = false;
 
+  /// Whether the user is using assitive technologies to interact with the
+  /// application.
+  /// 
+  /// This includes screen readers such as TalkBack on Android and VoiceOVer
+  /// on iOS, as well as hardware switches, and more.
+  /// 
+  /// The [onAssistiveTechnologyEnabled] callback is called whenever this value
+  /// changes.
+  bool get assistiveTechnologyEnabled => _assistiveTechnologyEnabled;
+  bool _assistiveTechnologyEnabled = false;
+
+  /// A callback that is invoked when the value of [assistiveTechnologyEnabled]
+  /// changes.
+  /// 
+  /// The framework invokes this callback in the same zone in which the callback
+  /// was set.
+  VoidCallback get onAssistiveTechnologyEnabled => _onAssistiveTechnologyEnabled;
+  VoidCallback _onAssistiveTechnologyEnabled;
+  Zone _onAssistiveTechnologyEnabledZone;
+  set onAssistiveTechnologyEnabled(VoidCallback callback) {
+     _onAssistiveTechnologyEnabled = callback;
+    _onAssistiveTechnologyEnabledZone = Zone.current;
+  }
+
   /// A callback that is invoked when the value of [semanticsEnabled] changes.
   ///
   /// The framework invokes this callback in the same zone in which the

lib/ui/window/window.cc

@@ -199,6 +199,16 @@ void Window::UpdateSemanticsEnabled(bool enabled) {
                   {ToDart(enabled)});
 }
 
+void Window::UpdateAssistiveTechnologyEnabled(bool enabled) {
+  tonic::DartState* dart_state = library_.dart_state().get();
+  if (!dart_state)
+    return;
+  tonic::DartState::Scope scope(dart_state);
+
+  DartInvokeField(library_.value(), "_updateAssistiveTechnologyEnabled",
+                   {ToDart(enabled)});
+}
+
 void Window::DispatchPlatformMessage(fxl::RefPtr<PlatformMessage> message) {
   tonic::DartState* dart_state = library_.dart_state().get();
   if (!dart_state)

lib/ui/window/window.h

@@ -54,6 +54,7 @@ class Window final {
                     const std::string& country_code);
   void UpdateUserSettingsData(const std::string& data);
   void UpdateSemanticsEnabled(bool enabled);
+  void UpdateAssistiveTechnologyEnabled(bool enabled);
   void DispatchPlatformMessage(fxl::RefPtr<PlatformMessage> message);
   void DispatchPointerDataPacket(const PointerDataPacket& packet);
   void DispatchSemanticsAction(int32_t id,

runtime/runtime_controller.cc

@@ -122,7 +122,8 @@ std::unique_ptr<RuntimeController> RuntimeController::Clone() const {
 bool RuntimeController::FlushRuntimeStateToIsolate() {
   return SetViewportMetrics(window_data_.viewport_metrics) &&
          SetLocale(window_data_.language_code, window_data_.country_code) &&
-         SetSemanticsEnabled(window_data_.semantics_enabled);
+         SetSemanticsEnabled(window_data_.semantics_enabled) &&
+         SetAssistiveTechnologyEnabled(window_data_.assistive_technology_enabled);
 }
 
 bool RuntimeController::SetViewportMetrics(const ViewportMetrics& metrics) {
@@ -170,6 +171,16 @@ bool RuntimeController::SetSemanticsEnabled(bool enabled) {
   return false;
 }
 
+bool RuntimeController::SetAssistiveTechnologyEnabled(bool enabled) {
+  window_data_.assistive_technology_enabled = enabled;
+  if (auto window = GetWindowIfAvailable()) {
+    window->UpdateAssistiveTechnologyEnabled(window_data_.assistive_technology_enabled);
+    return true;
+  }
+
+  return false;
+}
+
 bool RuntimeController::BeginFrame(fxl::TimePoint frame_time) {
   if (auto window = GetWindowIfAvailable()) {
     window->BeginFrame(frame_time);

runtime/runtime_controller.h

@@ -47,6 +47,8 @@ class RuntimeController final : public WindowClient {
 
   bool SetSemanticsEnabled(bool enabled);
 
+  bool SetAssistiveTechnologyEnabled(bool enabled);
+
   bool BeginFrame(fxl::TimePoint frame_time);
 
   bool NotifyIdle(int64_t deadline);
@@ -80,6 +82,7 @@ class RuntimeController final : public WindowClient {
     std::string country_code;
     std::string user_settings_data = "{}";
     bool semantics_enabled = false;
+    bool assistive_technology_enabled = false;
   };
 
   RuntimeDelegate& client_;

shell/common/engine.cc

@@ -339,6 +339,10 @@ void Engine::SetSemanticsEnabled(bool enabled) {
   runtime_controller_->SetSemanticsEnabled(enabled);
 }
 
+void Engine::SetAssistiveTechnologyEnabled(bool enabled) {
+  runtime_controller_->SetAssistiveTechnologyEnabled(enabled);
+}
+
 void Engine::StopAnimator() {
   animator_->Stop();
 }

shell/common/engine.h

@@ -99,6 +99,8 @@ class Engine final : public blink::RuntimeDelegate {
 
   void SetSemanticsEnabled(bool enabled);
 
+  void SetAssistiveTechnologyEnabled(bool enabled);
+
   void ScheduleFrame(bool regenerate_layer_tree = true) override;
 
   // |blink::RuntimeDelegate|

shell/common/platform_view.cc

@@ -52,6 +52,10 @@ void PlatformView::SetSemanticsEnabled(bool enabled) {
   delegate_.OnPlatformViewSetSemanticsEnabled(*this, enabled);
 }
 
+void PlatformView::SetAssistiveTechnologyEnabled(bool enabled) {
+  delegate_.OnPlatformViewSetAssistiveTechnologyEnabled(*this, enabled);
+}
+
 void PlatformView::SetViewportMetrics(const blink::ViewportMetrics& metrics) {
   delegate_.OnPlatformViewSetViewportMetrics(*this, metrics);
 }

shell/common/platform_view.h

@@ -58,6 +58,9 @@ class PlatformView {
     virtual void OnPlatformViewSetSemanticsEnabled(const PlatformView& view,
                                                    bool enabled) = 0;
 
+    virtual void OnPlatformViewSetAssistiveTechnologyEnabled(const PlatformView& view,
+                                                             bool enabled) = 0;
+
     virtual void OnPlatformViewRegisterTexture(
         const PlatformView& view,
         std::shared_ptr<flow::Texture> texture) = 0;
@@ -84,6 +87,8 @@ class PlatformView {
 
   virtual void SetSemanticsEnabled(bool enabled);
 
+  virtual void SetAssistiveTechnologyEnabled(bool enabled);
+
   void SetViewportMetrics(const blink::ViewportMetrics& metrics);
 
   void NotifyCreated();

shell/common/shell.cc

@@ -574,6 +574,20 @@ void Shell::OnPlatformViewSetSemanticsEnabled(const PlatformView& view,
       });
 }
 
+void Shell::OnPlatformViewSetAssistiveTechnologyEnabled(const PlatformView& view,
+                                                        bool enabled) {
+  FXL_DCHECK(is_setup_);
+  FXL_DCHECK(&view == platform_view_.get());
+  FXL_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
+
+  task_runners_.GetUITaskRunner()->PostTask(
+      [engine = engine_->GetWeakPtr(), enabled] {
+        if (engine) {
+          engine->SetAssistiveTechnologyEnabled(enabled);
+        }
+      });
+}
+
 // |shell::PlatformView::Delegate|
 void Shell::OnPlatformViewRegisterTexture(
     const PlatformView& view,

shell/common/shell.h

@@ -149,6 +149,10 @@ class Shell final : public PlatformView::Delegate,
   void OnPlatformViewSetSemanticsEnabled(const PlatformView& view,
                                          bool enabled) override;
 
+  // |shell::PlatformView::Delegate|
+  void OnPlatformViewSetAssistiveTechnologyEnabled(const PlatformView& view,
+                                                   bool enabled) override;
+
   // |shell::PlatformView::Delegate|
   void OnPlatformViewRegisterTexture(
       const PlatformView& view,

shell/platform/android/io/flutter/view/FlutterView.java

@@ -669,6 +669,9 @@ public class FlutterView extends SurfaceView
 
     private static native void nativeSetSemanticsEnabled(long nativePlatformViewAndroid,
         boolean enabled);
+    
+    private static native void nativeSetAssistiveTechnologyEnabled(long nativePlatformViewAndroid,
+        boolean enabled);
 
     private static native boolean nativeGetIsSoftwareRenderingEnabled();
 
@@ -812,11 +815,13 @@ public class FlutterView extends SurfaceView
             if (enabled) {
                 mTouchExplorationEnabled = true;
                 ensureAccessibilityEnabled();
+                nativeSetAssistiveTechnologyEnabled(mNativeView.get(), true);
             } else {
                 mTouchExplorationEnabled = false;
                 if (mAccessibilityNodeProvider != null) {
                     mAccessibilityNodeProvider.handleTouchExplorationExit();
                 }
+                nativeSetAssistiveTechnologyEnabled(mNativeView.get(), false);
             }
             resetWillNotDraw();
         }

shell/platform/android/platform_view_android_jni.cc

@@ -429,6 +429,13 @@ static void SetSemanticsEnabled(JNIEnv* env,
   ANDROID_SHELL_HOLDER->GetPlatformView()->SetSemanticsEnabled(enabled);
 }
 
+static void SetAssistiveTechnologyEnabled(JNIEnv* env,
+                                          jobject jcaller,
+                                          jlong shell_holder,
+                                          jboolean enabled) {
+  ANDROID_SHELL_HOLDER->GetPlatformView()->SetAssistiveTechnologyEnabled(enabled);
+}
+
 static jboolean GetIsSoftwareRendering(JNIEnv* env, jobject jcaller) {
   return FlutterMain::Get().GetSettings().enable_software_rendering;
 }
@@ -600,6 +607,11 @@ bool PlatformViewAndroid::Register(JNIEnv* env) {
           .signature = "(JZ)V",
           .fnPtr = reinterpret_cast<void*>(&shell::SetSemanticsEnabled),
       },
+      {
+          .name = "nativeSetAssistiveTechnologyEnabled",
+          .signature = "(JZ)V",
+          .fnPtr = reinterpret_cast<void*>(&shell::SetAssistiveTechnologyEnabled),
+      },
       {
           .name = "nativeGetIsSoftwareRenderingEnabled",
           .signature = "()Z",

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -792,16 +792,18 @@ static inline blink::PointerData::DeviceKind DeviceKindFromTouchType(UITouch* to
 #pragma mark - Accessibility
 
 - (void)onAccessibilityStatusChanged:(NSNotification*)notification {
+  auto platformView =  _shell->GetPlatformView();
 #if TARGET_OS_SIMULATOR
   // There doesn't appear to be any way to determine whether the accessibility
   // inspector is enabled on the simulator. We conservatively always turn on the
-  // accessibility bridge in the simulator.
-  bool enabled = true;
+  // accessibility bridge in the simulator, but never assistive technology.
+  platformView->SetSemanticsEnabled(true);
+  platformView->SetAssistiveTechnologyEnabled(false);
 #else
-  bool enabled = UIAccessibilityIsVoiceOverRunning() || UIAccessibilityIsSwitchControlRunning() ||
-                 UIAccessibilityIsSpeakScreenEnabled();
+  bool enabled = UIAccessibilityIsVoiceOverRunning() || UIAccessibilityIsSwitchControlRunning();
+  platformView->SetSemanticsEnabled(enabled || UIAccessibilityIsSpeakScreenEnabled());
+  platformView->SetAssistiveTechnologyEnabled(enabled);
 #endif
-  _shell->GetPlatformView()->SetSemanticsEnabled(enabled);
 }
 
 #pragma mark - Memory Notifications

shell/platform/darwin/ios/platform_view_ios.h

@@ -57,6 +57,12 @@ class PlatformViewIOS final : public HeadlessPlatformViewIOS {
   // |shell::PlatformView|
   void SetSemanticsEnabled(bool enabled) override;
 
+  // |shell::PlatformView|
+  void SetAssistiveTechnologyEnabled(bool enabled) override;
+
+  // |shell::PlatformView|
+  void HandlePlatformMessage(
+      fxl::RefPtr<blink::PlatformMessage> message) override;
 
   // |shell::PlatformView|
   void UpdateSemantics(blink::SemanticsNodeUpdates update,

shell/platform/darwin/ios/platform_view_ios.mm

@@ -67,6 +67,17 @@ void PlatformViewIOS::SetSemanticsEnabled(bool enabled) {
   PlatformView::SetSemanticsEnabled(enabled);
 }
 
+// |shell:PlatformView|
+void PlatformViewIOS::SetAssistiveTechnologyEnabled(bool enabled) {
+  if (enabled && !accessibility_bridge_) {
+    accessibility_bridge_ = std::make_unique<AccessibilityBridge>(owner_view_, this);
+  }
+  // Note: since the accessibility bridge is needed for both semantics and
+  // assistive technologies, but you cannot have the latter without the
+  // former, we only destroy the bridge in SetSemanticsEnabled and not here.
+  PlatformView::SetAssistiveTechnologyEnabled(enabled);
+}
+
 // |shell::PlatformView|
 void PlatformViewIOS::UpdateSemantics(blink::SemanticsNodeUpdates update,
                                       blink::CustomAccessibilityActionUpdates actions) {