refactor tab bar behaviour; respect scroll preferences of websites;

packages/flutter_mozilla_components/lib/src/domain/services/gecko_viewport.dart

@@ -30,6 +30,7 @@ class GeckoViewportService extends GeckoViewportEvents {
     isVisible: false,
     isAnimating: false,
   ));
+  final _browserHandlingScrollSubject = BehaviorSubject<bool>.seeded(false);
 
   /// Stream of keyboard visibility changes.
   ///
@@ -46,6 +47,17 @@ class GeckoViewportService extends GeckoViewportEvents {
   /// Whether the keyboard is currently visible.
   bool get isKeyboardVisible => _keyboardSubject.value.isVisible;
 
+  /// Stream of browser scroll-handling eligibility.
+  ///
+  /// Emits true when GeckoView reports that browser content can handle
+  /// scrolling for dynamic toolbar behavior.
+  ValueStream<bool> get browserHandlingScrollEvents =>
+      _browserHandlingScrollSubject.stream;
+
+  /// Current browser scroll-handling eligibility.
+  bool get isBrowserHandlingScrollEnabled =>
+      _browserHandlingScrollSubject.value;
+
   /// Creates a new viewport service.
   ///
   /// Call [setUp] to register the event handlers after construction.
@@ -113,8 +125,14 @@ class GeckoViewportService extends GeckoViewportEvents {
     ));
   }
 
+  @override
+  void onBrowserHandlingScrollChanged(int sequence, bool isHandling) {
+    _browserHandlingScrollSubject.addWhenMoreRecent(sequence, null, isHandling);
+  }
+
   /// Disposes the service and closes all streams.
   Future<void> dispose() async {
     await _keyboardSubject.close();
+    await _browserHandlingScrollSubject.close();
   }
 }

packages/flutter_mozilla_components/lib/src/pigeons/gecko.g.dart

@@ -1735,6 +1735,7 @@ class TabContentState {
     required this.isPrivate,
     required this.isFullScreen,
     required this.isLoading,
+    required this.showToolbarAsExpanded,
   });
 
   String id;
@@ -1755,6 +1756,8 @@ class TabContentState {
 
   bool isLoading;
 
+  bool showToolbarAsExpanded;
+
   List<Object?> _toList() {
     return <Object?>[
       id,
@@ -1766,6 +1769,7 @@ class TabContentState {
       isPrivate,
       isFullScreen,
       isLoading,
+      showToolbarAsExpanded,
     ];
   }
 
@@ -1784,6 +1788,7 @@ class TabContentState {
       isPrivate: result[6]! as bool,
       isFullScreen: result[7]! as bool,
       isLoading: result[8]! as bool,
+      showToolbarAsExpanded: result[9]! as bool,
     );
   }
 
@@ -8133,6 +8138,14 @@ abstract class GeckoViewportEvents {
   /// [isAnimating] Whether the keyboard is currently animating.
   void onKeyboardVisibilityChanged(int sequence, int heightPx, bool isVisible, bool isAnimating);
 
+  /// Called when GeckoView scroll-handling eligibility changes.
+  ///
+  /// [sequence] Event sequence number for ordering.
+  /// [isHandling] True when browser content can consume scrolling for
+  /// dynamic toolbar behavior. False when content is not scrollable or
+  /// the page consumed touch input.
+  void onBrowserHandlingScrollChanged(int sequence, bool isHandling);
+
   static void setUp(GeckoViewportEvents? api, {BinaryMessenger? binaryMessenger, String messageChannelSuffix = '',}) {
     messageChannelSuffix = messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
     {
@@ -8169,6 +8182,34 @@ abstract class GeckoViewportEvents {
         });
       }
     }
+    {
+      final pigeonVar_channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.flutter_mozilla_components.GeckoViewportEvents.onBrowserHandlingScrollChanged$messageChannelSuffix', pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (api == null) {
+        pigeonVar_channel.setMessageHandler(null);
+      } else {
+        pigeonVar_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+          'Argument for dev.flutter.pigeon.flutter_mozilla_components.GeckoViewportEvents.onBrowserHandlingScrollChanged was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final int? arg_sequence = (args[0] as int?);
+          assert(arg_sequence != null,
+              'Argument for dev.flutter.pigeon.flutter_mozilla_components.GeckoViewportEvents.onBrowserHandlingScrollChanged was null, expected non-null int.');
+          final bool? arg_isHandling = (args[1] as bool?);
+          assert(arg_isHandling != null,
+              'Argument for dev.flutter.pigeon.flutter_mozilla_components.GeckoViewportEvents.onBrowserHandlingScrollChanged was null, expected non-null bool.');
+          try {
+            api.onBrowserHandlingScrollChanged(arg_sequence!, arg_isHandling!);
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          }          catch (e) {
+            return wrapResponse(error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
   }
 }