[a11y] Implement support for atk_text_get_offset_at_point()

This CL implements GetOffsetAtPoint which returns the offset of the
character located at the position and adds the unittest for the API.

AX-Relnotes: It supports atk_text_get_offset_at_point() on Linux.
Bug: 1070742
Change-Id: Iff075f3e4f95cc746b67819b9426300c250ff485
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2280805
Commit-Queue: Julie Kim <jkim@igalia.com>
Reviewed-by: Martin Robinson <mrobinson@igalia.com>
Cr-Commit-Position: refs/heads/master@{#785740}

content/browser/accessibility/browser_accessibility_auralinux_unittest.cc

@@ -763,4 +763,59 @@ TEST_F(BrowserAccessibilityAuraLinuxTest, TextAtkStaticTextChange) {
   EXPECT_STREQ(base::UTF16ToUTF8(div_node->GetHypertext()).c_str(), "Text2");
 }
 
+TEST_F(BrowserAccessibilityAuraLinuxTest, TestAtkTextGetOffesetAtPoint) {
+  ui::AXNodeData static_text1;
+  static_text1.id = 1;
+  static_text1.role = ax::mojom::Role::kStaticText;
+  static_text1.SetName("Hello");
+  static_text1.child_ids = {2};
+
+  ui::AXNodeData inline_box1;
+  inline_box1.id = 2;
+  inline_box1.role = ax::mojom::Role::kInlineTextBox;
+  inline_box1.SetName("Hello");
+  inline_box1.relative_bounds.bounds = gfx::RectF(0, 50, 25, 30);
+  std::vector<int32_t> character_offsets1;
+  // The width of each character is 5px.
+  character_offsets1.push_back(5);
+  character_offsets1.push_back(10);
+  character_offsets1.push_back(15);
+  character_offsets1.push_back(20);
+  character_offsets1.push_back(25);
+  inline_box1.AddIntListAttribute(
+      ax::mojom::IntListAttribute::kCharacterOffsets, character_offsets1);
+  inline_box1.AddIntListAttribute(ax::mojom::IntListAttribute::kWordStarts,
+                                  std::vector<int32_t>{0});
+  inline_box1.AddIntListAttribute(ax::mojom::IntListAttribute::kWordEnds,
+                                  std::vector<int32_t>{5});
+
+  std::unique_ptr<BrowserAccessibilityManager> manager(
+      BrowserAccessibilityManager::Create(
+          MakeAXTreeUpdate(static_text1, inline_box1),
+          test_browser_accessibility_delegate_.get()));
+
+  ASSERT_NE(nullptr, manager->GetRoot());
+  BrowserAccessibilityAuraLinux* ax_root =
+      ToBrowserAccessibilityAuraLinux(manager->GetRoot());
+  ASSERT_NE(nullptr, ax_root);
+
+  AtkObject* root_atk_object = ax_root->GetNode()->GetNativeViewAccessible();
+  g_object_ref(root_atk_object);
+  AtkText* atk_text = ATK_TEXT(root_atk_object);
+  ASSERT_TRUE(ATK_IS_TEXT(atk_text));
+
+  int x, y, width, height;
+  char* text = atk_text_get_text(atk_text, 0, -1);
+  int root_text_length = g_utf8_strlen(text, -1);
+  g_free(text);
+  for (int offset = 0; offset < root_text_length; offset++) {
+    atk_text_get_character_extents(atk_text, offset, &x, &y, &width, &height,
+                                   ATK_XY_SCREEN);
+    int result = atk_text_get_offset_at_point(atk_text, x, y, ATK_XY_SCREEN);
+    ASSERT_EQ(offset, result);
+  }
+  g_object_unref(root_atk_object);
+  manager.reset();
+}
+
 }  // namespace content

ui/accessibility/platform/ax_platform_node_auralinux.cc

@@ -1024,6 +1024,18 @@ gunichar GetCharacterAtOffset(AtkText* atk_text, int offset) {
   return code_point;
 }
 
+gint GetOffsetAtPoint(AtkText* text, gint x, gint y, AtkCoordType coords) {
+  g_return_val_if_fail(ATK_IS_TEXT(text), -1);
+
+  AtkObject* atk_object = ATK_OBJECT(text);
+  AXPlatformNodeAuraLinux* obj =
+      AXPlatformNodeAuraLinux::FromAtkObject(atk_object);
+  if (!obj)
+    return -1;
+
+  return obj->GetTextOffsetAtPoint(x, y, coords);
+}
+
 // This function returns a single character as a UTF-8 encoded C string because
 // the character may be encoded into more than one byte.
 char* GetCharacter(AtkText* atk_text,
@@ -1447,6 +1459,7 @@ void Init(AtkTextIface* iface) {
   iface->get_text = GetText;
   iface->get_character_count = GetCharacterCount;
   iface->get_character_at_offset = GetCharacterAtOffset;
+  iface->get_offset_at_point = GetOffsetAtPoint;
   iface->get_text_after_offset = GetTextAfterOffset;
   iface->get_text_before_offset = GetTextBeforeOffset;
   iface->get_text_at_offset = GetTextAtOffset;
@@ -4115,6 +4128,28 @@ size_t AXPlatformNodeAuraLinux::UnicodeToUTF16OffsetInText(int unicode_offset) {
   return utf16_offset;
 }
 
+int AXPlatformNodeAuraLinux::GetTextOffsetAtPoint(int x,
+                                                  int y,
+                                                  AtkCoordType atk_coord_type) {
+  if (!GetExtentsRelativeToAtkCoordinateType(atk_coord_type).Contains(x, y))
+    return -1;
+
+  AtkObject* atk_object = GetOrCreateAtkObject();
+  if (!atk_object)
+    return -1;
+
+  int count = atk_text::GetCharacterCount(ATK_TEXT(atk_object));
+  for (int i = 0; i < count; i++) {
+    int out_x, out_y, out_width, out_height;
+    atk_text::GetCharacterExtents(ATK_TEXT(atk_object), i, &out_x, &out_y,
+                                  &out_width, &out_height, atk_coord_type);
+    gfx::Rect rect(out_x, out_y, out_width, out_height);
+    if (rect.Contains(x, y))
+      return i;
+  }
+  return -1;
+}
+
 gfx::Vector2d AXPlatformNodeAuraLinux::GetParentOriginInScreenCoordinates()
     const {
   AtkObject* parent = GetParent();

ui/accessibility/platform/ax_platform_node_auralinux.h

@@ -245,6 +245,7 @@ class AX_EXPORT AXPlatformNodeAuraLinux : public AXPlatformNodeBase {
   const base::OffsetAdjuster::Adjustments& GetHypertextAdjustments();
   size_t UTF16ToUnicodeOffsetInText(size_t utf16_offset);
   size_t UnicodeToUTF16OffsetInText(int unicode_offset);
+  int GetTextOffsetAtPoint(int x, int y, AtkCoordType atk_coord_type);
 
   // Called on a toplevel frame to set the document parent, which is the parent
   // of the toplevel document. This is used to properly express the ATK embeds