fix selectable text selections are not announced in voice over (#24933)

Author: chunhtai

shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMacTest.mm

@@ -59,6 +59,80 @@
   [engine shutDownEngine];
 }
 
+TEST(FlutterPlatformNodeDelegateMac, SelectableTextHasCorrectSemantics) {
+  FlutterEngine* engine = CreateTestEngine();
+  engine.semanticsEnabled = YES;
+  auto bridge = engine.accessibilityBridge.lock();
+  // Initialize ax node data.
+  FlutterSemanticsNode root;
+  root.id = 0;
+  root.flags =
+      static_cast<FlutterSemanticsFlag>(FlutterSemanticsFlag::kFlutterSemanticsFlagIsTextField |
+                                        FlutterSemanticsFlag::kFlutterSemanticsFlagIsReadOnly);
+  root.actions = static_cast<FlutterSemanticsAction>(0);
+  root.text_selection_base = 1;
+  root.text_selection_extent = 3;
+  root.label = "";
+  root.hint = "";
+  // Selectable text store its text in value
+  root.value = "selectable text";
+  root.increased_value = "";
+  root.decreased_value = "";
+  root.child_count = 0;
+  root.custom_accessibility_actions_count = 0;
+  bridge->AddFlutterSemanticsNodeUpdate(&root);
+
+  bridge->CommitUpdates();
+
+  auto root_platform_node_delegate = bridge->GetFlutterPlatformNodeDelegateFromID(0).lock();
+  // Verify the accessibility attribute matches.
+  NSAccessibilityElement* native_accessibility =
+      root_platform_node_delegate->GetNativeViewAccessible();
+  std::string value = [native_accessibility.accessibilityValue UTF8String];
+  EXPECT_EQ(value, "selectable text");
+  EXPECT_EQ(native_accessibility.accessibilityRole, NSAccessibilityStaticTextRole);
+  EXPECT_EQ([native_accessibility.accessibilityChildren count], 0u);
+  NSRange selection = native_accessibility.accessibilitySelectedTextRange;
+  EXPECT_EQ(selection.location, 1u);
+  EXPECT_EQ(selection.length, 2u);
+  std::string selected_text = [native_accessibility.accessibilitySelectedText UTF8String];
+  EXPECT_EQ(selected_text, "el");
+}
+
+TEST(FlutterPlatformNodeDelegateMac, SelectableTextWithoutSelectionReturnZeroRange) {
+  FlutterEngine* engine = CreateTestEngine();
+  engine.semanticsEnabled = YES;
+  auto bridge = engine.accessibilityBridge.lock();
+  // Initialize ax node data.
+  FlutterSemanticsNode root;
+  root.id = 0;
+  root.flags =
+      static_cast<FlutterSemanticsFlag>(FlutterSemanticsFlag::kFlutterSemanticsFlagIsTextField |
+                                        FlutterSemanticsFlag::kFlutterSemanticsFlagIsReadOnly);
+  root.actions = static_cast<FlutterSemanticsAction>(0);
+  root.text_selection_base = -1;
+  root.text_selection_extent = -1;
+  root.label = "";
+  root.hint = "";
+  // Selectable text store its text in value
+  root.value = "selectable text";
+  root.increased_value = "";
+  root.decreased_value = "";
+  root.child_count = 0;
+  root.custom_accessibility_actions_count = 0;
+  bridge->AddFlutterSemanticsNodeUpdate(&root);
+
+  bridge->CommitUpdates();
+
+  auto root_platform_node_delegate = bridge->GetFlutterPlatformNodeDelegateFromID(0).lock();
+  // Verify the accessibility attribute matches.
+  NSAccessibilityElement* native_accessibility =
+      root_platform_node_delegate->GetNativeViewAccessible();
+  NSRange selection = native_accessibility.accessibilitySelectedTextRange;
+  EXPECT_TRUE(selection.location == NSNotFound);
+  EXPECT_EQ(selection.length, 0u);
+}
+
 TEST(FlutterPlatformNodeDelegateMac, CanPerformAction) {
   FlutterEngine* engine = CreateTestEngine();
   engine.semanticsEnabled = YES;

third_party/accessibility/ax/platform/ax_platform_node_mac.mm

@@ -600,8 +600,19 @@ - (id)AXValueInternal {
   if (role == ax::mojom::Role::kTab)
     return [self AXSelectedInternal];
 
-  if (ui::IsNameExposedInAXValueForRole(role))
+  if (ui::IsNameExposedInAXValueForRole(role)) {
+    if (role == ax::mojom::Role::kStaticText) {
+      // Static texts may store their texts in the value attributes. For
+      // example, the selectable text stores its text in value instead of
+      // name.
+      NSString* value = [self getName];
+      if (value.length == 0) {
+        value = [self getStringAttribute:ax::mojom::StringAttribute::kValue];
+      }
+      return value;
+    }
     return [self getName];
+  }
 
   if (_node->IsPlatformCheckable()) {
     // Mixed checkbox state not currently supported in views, but could be.
@@ -699,6 +710,11 @@ - (NSValue*)AXSelectedTextRangeInternal {
     start = _node->GetIntAttribute(ax::mojom::IntAttribute::kTextSelStart);
     end = _node->GetIntAttribute(ax::mojom::IntAttribute::kTextSelEnd);
   }
+  NSAssert((start >= 0 && end >= 0) || (start == -1 && end == -1), @"selection is invalid");
+
+  if (start == -1 && end == -1) {
+    return [NSValue valueWithRange:{NSNotFound, 0}];
+  }
 
   // NSRange cannot represent the direction the text was selected in.
   return [NSValue valueWithRange:{static_cast<NSUInteger>(std::min(start, end)),