Change default value for headingLevel to 0

lib/ui/semantics.dart

@@ -913,8 +913,8 @@ base class _NativeSemanticsUpdateBuilder extends NativeFieldWrapperClass1 implem
   }) {
     assert(_matrix4IsValid(transform));
     assert (
-      headingLevel == -1 || (headingLevel >= 1 && headingLevel <= 6),
-      'Heading level must be between 1 and 6, or -1 to indicate that this node is not a heading.'
+      headingLevel >= 0 && headingLevel <= 6,
+      'Heading level must be between 1 and 6, or 0 to indicate that this node is not a heading.'
     );
     _updateNode(
       id,
@@ -1033,7 +1033,8 @@ base class _NativeSemanticsUpdateBuilder extends NativeFieldWrapperClass1 implem
       Float64List transform,
       Int32List childrenInTraversalOrder,
       Int32List childrenInHitTestOrder,
-      Int32List additionalActions);
+      Int32List additionalActions,
+      int headingLevel,);
 
   @override
   void updateCustomAction({required int id, String? label, String? hint, int overrideId = -1}) {
@@ -1183,6 +1184,7 @@ abstract class SemanticsUpdateBuilderNew {
     required Int32List childrenInTraversalOrder,
     required Int32List childrenInHitTestOrder,
     required Int32List additionalActions,
+    required int headingLevel,
   });
 
   /// Update the custom semantics action associated with the given `id`.
@@ -1253,6 +1255,7 @@ base class _NativeSemanticsUpdateBuilderNew extends NativeFieldWrapperClass1 imp
     required Int32List childrenInTraversalOrder,
     required Int32List childrenInHitTestOrder,
     required Int32List additionalActions,
+    required int headingLevel,
   }) {
     assert(_matrix4IsValid(transform));
     _updateNode(
@@ -1292,6 +1295,7 @@ base class _NativeSemanticsUpdateBuilderNew extends NativeFieldWrapperClass1 imp
       childrenInTraversalOrder,
       childrenInHitTestOrder,
       additionalActions,
+      headingLevel,
     );
   }
   @Native<
@@ -1332,7 +1336,8 @@ base class _NativeSemanticsUpdateBuilderNew extends NativeFieldWrapperClass1 imp
           Handle,
           Handle,
           Handle,
-          Handle)>(symbol: 'SemanticsUpdateBuilder::updateNode')
+          Handle,
+          Int32)>(symbol: 'SemanticsUpdateBuilder::updateNode')
   external void _updateNode(
       int id,
       int flags,

lib/ui/semantics/semantics_node.h

@@ -142,7 +142,7 @@ struct SemanticsNode {
   std::vector<int32_t> childrenInTraversalOrder;
   std::vector<int32_t> childrenInHitTestOrder;
   std::vector<int32_t> customAccessibilityActions;
-  int32_t headingLevel = -1;
+  int32_t headingLevel = 0;
 };
 
 // Contains semantic nodes that need to be updated.

lib/web_ui/lib/semantics.dart

@@ -322,6 +322,7 @@ class SemanticsUpdateBuilderNew {
       childrenInHitTestOrder: childrenInHitTestOrder,
       additionalActions: additionalActions,
       platformViewId: platformViewId,
+      headingLevel: headingLevel,
     ));
   }
 
@@ -379,6 +380,7 @@ class SemanticsUpdateBuilder {
     required Int32List childrenInTraversalOrder,
     required Int32List childrenInHitTestOrder,
     required Int32List additionalActions,
+    required int headingLevel,
   }) {
     if (transform.length != 16) {
       throw ArgumentError('transform argument must have 16 entries.');

lib/web_ui/lib/src/engine/semantics/heading.dart

@@ -23,7 +23,7 @@ class Heading extends PrimaryRoleManager {
       return;
     }
 
-    if (semanticsObject.headingLevel != -1) {
+    if (semanticsObject.headingLevel != 0) {
       addHeadingLevel(semanticsObject.headingLevel);
     } else {
       addHeadingLevel(defaultHeadingLevel);

lib/web_ui/lib/src/engine/semantics/semantics.dart

@@ -1027,7 +1027,7 @@ class SemanticsObject {
 
   /// See [ui.SemanticsUpdateBuilder.updateNode].
   int get headingLevel => _headingLevel;
-  int _headingLevel = -1;
+  int _headingLevel = 0;
 
   static const int _headingLevelIndex = 1 << 24;
 
@@ -1143,7 +1143,7 @@ class SemanticsObject {
   bool get isTextField => hasFlag(ui.SemanticsFlag.isTextField);
 
   /// Whether this object represents a heading element.
-  bool get isHeading => headingLevel != -1;
+  bool get isHeading => headingLevel != 0;
 
     /// Whether this object represents an editable text field.
   bool get isLink => hasFlag(ui.SemanticsFlag.isLink);

lib/web_ui/test/engine/semantics/semantics_test.dart

@@ -3092,7 +3092,7 @@ void updateNode(
   Int32List? childrenInTraversalOrder,
   Int32List? childrenInHitTestOrder,
   Int32List? additionalActions,
-  int headingLevel = -1,
+  int headingLevel = 0,
 }) {
   transform ??= Float64List.fromList(Matrix4.identity().storage);
   childrenInTraversalOrder ??= Int32List(0);

lib/web_ui/test/engine/semantics/semantics_tester.dart

@@ -317,7 +317,7 @@ class SemanticsTester {
       childrenInTraversalOrder: childIds,
       childrenInHitTestOrder: childIds,
       additionalActions: additionalActions ?? Int32List(0),
-      headingLevel: headingLevel ?? -1,
+      headingLevel: headingLevel ?? 0,
     );
     _nodeUpdates.add(update);
     return update;

shell/platform/embedder/fixtures/main.dart

@@ -167,7 +167,7 @@ Future<void> a11y_main() async {
       decreasedValueAttributes: <StringAttribute>[],
       tooltip: 'tooltip',
       additionalActions: Int32List(0),
-      headingLevel: -1
+      headingLevel: 0
     )
     ..updateNode(
       id: 84,
@@ -201,7 +201,7 @@ Future<void> a11y_main() async {
       additionalActions: Int32List(0),
       childrenInHitTestOrder: Int32List(0),
       childrenInTraversalOrder: Int32List(0),
-      headingLevel: -1
+      headingLevel: 0
     )
     ..updateNode(
       id: 96,
@@ -269,7 +269,7 @@ Future<void> a11y_main() async {
       tooltip: 'tooltip',
       childrenInHitTestOrder: Int32List(0),
       childrenInTraversalOrder: Int32List(0),
-      headingLevel: -1
+      headingLevel: 0
     )
     ..updateCustomAction(
       id: 21,
@@ -364,7 +364,7 @@ Future<void> a11y_string_attributes() async {
       decreasedValueAttributes: <StringAttribute>[],
       tooltip: 'tooltip',
       additionalActions: Int32List(0),
-      headingLevel: -1,
+      headingLevel: 0,
     );
 
   PlatformDispatcher.instance.views.first.updateSemantics(builder.build());

testing/scenario_app/lib/src/locale_initialization.dart

@@ -77,7 +77,7 @@ class LocaleInitialization extends Scenario {
         childrenInTraversalOrder: Int32List(0),
         childrenInHitTestOrder: Int32List(0),
         additionalActions: Int32List(0),
-        headingLevel: -1,
+        headingLevel: 0,
       );
 
     final SemanticsUpdate semanticsUpdate = semanticsUpdateBuilder.build();
@@ -136,7 +136,7 @@ class LocaleInitialization extends Scenario {
         childrenInTraversalOrder: Int32List(0),
         childrenInHitTestOrder: Int32List(0),
         additionalActions: Int32List(0),
-        headingLevel: -1,
+        headingLevel: 0,
       );
 
     final SemanticsUpdate semanticsUpdate = semanticsUpdateBuilder.build();