Emit an ATK text-caret-moved signal on anchor navigation

This will ensure that Orca knows to properly move the text caret after
anchor navigation even when Chromium-based text caret navigation is
disabled. Normally, this is handled by the sequential focus navigation
starting point, but this value is not propagated to the accessibility
layer.

Bug: 1011942
Change-Id: I21d2cde59e12f8aff212b2d9bf3700dad27242c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1871887
Commit-Queue: Martin Robinson <mrobinson@igalia.com>
Commit-Queue: Joanmarie Diggs <jdiggs@igalia.com>
Auto-Submit: Martin Robinson <mrobinson@igalia.com>
Reviewed-by: Joanmarie Diggs <jdiggs@igalia.com>
Cr-Commit-Position: refs/heads/master@{#708185}

content/browser/accessibility/browser_accessibility_manager_auralinux.cc

@@ -106,7 +106,14 @@ void BrowserAccessibilityManagerAuraLinux::FireBlinkEvent(
     ax::mojom::Event event_type,
     BrowserAccessibility* node) {
   BrowserAccessibilityManager::FireBlinkEvent(event_type, node);
-  // Need to implement.
+
+  switch (event_type) {
+    case ax::mojom::Event::kScrolledToAnchor:
+      ToBrowserAccessibilityAuraLinux(node)->GetNode()->OnScrolledToAnchor();
+      break;
+    default:
+      break;
+  }
 }
 
 void BrowserAccessibilityManagerAuraLinux::FireNameChangedEvent(

ui/accessibility/platform/ax_platform_node_auralinux.cc

@@ -3186,6 +3186,12 @@ void AXPlatformNodeAuraLinux::OnWindowVisibilityChanged() {
   atk_object_notify_state_change(atk_object, ATK_STATE_ICONIFIED, minimized);
 }
 
+void AXPlatformNodeAuraLinux::OnScrolledToAnchor() {
+  AtkObject* atk_object = GetOrCreateAtkObject();
+  DCHECK(ATK_IS_TEXT(atk_object));
+  g_signal_emit_by_name(atk_object, "text-caret-moved", 0);
+}
+
 void AXPlatformNodeAuraLinux::OnFocused() {
   AtkObject* atk_object = GetOrCreateAtkObject();
 

ui/accessibility/platform/ax_platform_node_auralinux.h

@@ -167,6 +167,7 @@ class AX_EXPORT AXPlatformNodeAuraLinux : public AXPlatformNodeBase {
   void OnSubtreeWillBeDeleted();
   void OnParentChanged();
   void OnWindowVisibilityChanged();
+  void OnScrolledToAnchor();
 
   bool SupportsSelectionWithAtkSelection();
   bool SelectionAndFocusAreTheSame();

ui/accessibility/platform/ax_platform_node_auralinux_unittest.cc

@@ -2338,4 +2338,32 @@ TEST_F(AXPlatformNodeAuraLinuxTest, TestAtkObjectParentChanged) {
   ASSERT_TRUE(saw_parent_changed);
 }
 
+TEST_F(AXPlatformNodeAuraLinuxTest, TestScrolledToAnchorEvent) {
+  AXNodeData root_data;
+  root_data.id = 1;
+  root_data.role = ax::mojom::Role::kListBox;
+  root_data.child_ids.push_back(2);
+
+  AXNodeData item_1_data;
+  item_1_data.id = 2;
+  item_1_data.role = ax::mojom::Role::kListBoxOption;
+
+  Init(root_data, item_1_data);
+
+  AXNode* item_1 = GetRootNode()->children()[0];
+  AtkObject* atk_object = AtkObjectFromNode(item_1);
+
+  bool saw_caret_moved = false;
+  g_signal_connect(
+      atk_object, "text-caret-moved",
+      G_CALLBACK(+[](AtkObject*, int position, bool* saw_caret_moved) {
+        *saw_caret_moved = true;
+      }),
+      &saw_caret_moved);
+
+  GetPlatformNode(item_1)->OnScrolledToAnchor();
+
+  ASSERT_TRUE(saw_caret_moved);
+}
+
 }  // namespace ui