more tests for enabling semantics (flutter/engine#14060)

* more tests for enabling semantics

* addressing pr comments

engine/src/flutter/lib/web_ui/lib/src/engine/dom_renderer.dart

@@ -390,7 +390,7 @@ flt-glass-pane * {
     _glassPaneElement.append(_sceneHostElement);
 
     final html.Element _accesibilityPlaceholder = EngineSemanticsOwner
-        .instance.enableSemantics
+        .instance.semanticsHelper
         .prepareAccesibilityPlaceholder();
 
     // Insert the semantics placeholder after the scene host. For all widgets

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

@@ -1198,7 +1198,7 @@ class EngineSemanticsOwner {
     _now = () => DateTime.now();
   }
 
-  final SemanticsHelper enableSemantics = SemanticsHelper();
+  final SemanticsHelper semanticsHelper = SemanticsHelper();
 
   /// Whether the user has requested that [updateSemantics] be called when
   /// the semantic contents of window changes.
@@ -1346,7 +1346,7 @@ class EngineSemanticsOwner {
       _temporarilyDisableBrowserGestureMode();
     }
 
-    return enableSemantics.shouldEnableSemantics(event);
+    return semanticsHelper.shouldEnableSemantics(event);
   }
 
   /// Callbacks called when the [GestureMode] changes.

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

@@ -36,19 +36,25 @@ String placeholderMessage = 'Enable accessibility';
 ///
 /// See [DesktopSemanticsEnabler], [MobileSemanticsEnabler].
 class SemanticsHelper {
-  final _SemanticsEnabler _enableSemantics =
+  SemanticsEnabler _semanticsEnabler =
       isDesktop ? DesktopSemanticsEnabler() : MobileSemanticsEnabler();
 
+  @visibleForTesting
+  set semanticsEnabler(SemanticsEnabler semanticsEnabler) {
+    this._semanticsEnabler = semanticsEnabler;
+  }
+
   bool shouldEnableSemantics(html.Event event) {
-    return _enableSemantics.shouldEnableSemantics(event);
+    return _semanticsEnabler.shouldEnableSemantics(event);
   }
 
   html.Element prepareAccesibilityPlaceholder() {
-    return _enableSemantics.prepareAccesibilityPlaceholder();
+    return _semanticsEnabler.prepareAccesibilityPlaceholder();
   }
 }
 
-abstract class _SemanticsEnabler {
+@visibleForTesting
+abstract class SemanticsEnabler {
   /// Whether to enable semantics.
   ///
   /// Semantics should be enabled if the web engine is no longer waiting for
@@ -89,7 +95,7 @@ abstract class _SemanticsEnabler {
 }
 
 @visibleForTesting
-class DesktopSemanticsEnabler extends _SemanticsEnabler {
+class DesktopSemanticsEnabler extends SemanticsEnabler {
   /// We do not immediately enable semantics when the user requests it, but
   /// instead wait for a short period of time before doing it. This is because
   /// the request comes as an event targeted on the [_semanticsPlaceholder].
@@ -212,7 +218,7 @@ class DesktopSemanticsEnabler extends _SemanticsEnabler {
 }
 
 @visibleForTesting
-class MobileSemanticsEnabler extends _SemanticsEnabler {
+class MobileSemanticsEnabler extends SemanticsEnabler {
   /// We do not immediately enable semantics when the user requests it, but
   /// instead wait for a short period of time before doing it. This is because
   /// the request comes as an event targeted on the [_semanticsPlaceholder].

engine/src/flutter/lib/web_ui/pubspec.yaml

@@ -10,6 +10,7 @@ dependencies:
 dev_dependencies:
   http: 0.12.0+2
   image: 2.1.4
+  mockito: 4.1.1
   path: 1.6.4
   test: 1.6.5
   quiver: 2.0.5

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

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:html' as html;
 import 'dart:typed_data';
 
+import 'package:mockito/mockito.dart';
 import 'package:quiver/testing/async.dart';
 import 'package:test/test.dart';
 
@@ -190,8 +191,30 @@ void _testEngineSemanticsOwner() {
       semantics().semanticsEnabled = false;
     });
   });
+  test('checks shouldEnableSemantics for every global event', () {
+    final MockSemanticsEnabler mockSemanticsEnabler = MockSemanticsEnabler();
+    semantics().semanticsHelper.semanticsEnabler = mockSemanticsEnabler;
+    final html.Event pointerEvent = html.Event('pointermove');
+
+    semantics().receiveGlobalEvent(pointerEvent);
+
+    // Verify the interactions.
+    verify(mockSemanticsEnabler.shouldEnableSemantics(pointerEvent));
+  });
+
+  test('Forward events to framewors if shouldEnableSemantics', () {
+    final MockSemanticsEnabler mockSemanticsEnabler = MockSemanticsEnabler();
+    semantics().semanticsHelper.semanticsEnabler = mockSemanticsEnabler;
+    final html.Event pointerEvent = html.Event('pointermove');
+    when(mockSemanticsEnabler.shouldEnableSemantics(pointerEvent))
+        .thenReturn(true);
+
+    expect(semantics().receiveGlobalEvent(pointerEvent), isTrue);
+  });
 }
 
+class MockSemanticsEnabler extends Mock implements SemanticsEnabler {}
+
 void _testHeader() {
   test('renders heading role for headers', () {
     semantics()