Test setting and retrieving selection with ignored nodes on ATK

In https://crrev.com/c/2205400/ a fix was made to the
selection offsets that might be necessary whenever there are
nodes in the internal accessibility tree that are ignored, i.e.,
they are not exposed to the platform tree.
This patch adds a test for Linux ATK which checks
whether either setting or retrieving the selection works properly
in such a tree.
A helper method is added to the test fixture that searches the ATK tree
for a node with a specific role.
Also took the opportunity to clean up the test fixture by adding comments,
moving methods to be in declaration order, adding const, and renaming
erroneously named variables.

Example:
<p>
  <div></div> <!-- ignored -->
  <span>Selected</span>
</p>

The anchor offset points to the second child of the paragraph
and the focus offset to the third.
However, the first child, the div, is not exposed to the platform tree because it is empty.
The offsets should be adjusted accordingly, i.e.,
in ATK text, the anchor offset should be equal to 0 and
the focus offset should equal the text's length.

AX-Relnotes: n/a.

R=dmazzoni@chromium.org

Change-Id: I22fabbbdc3eea1648c088f35ee898ff307a97d24
Bug: 1082814
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218042Reviewed-by: Joanmarie Diggs <jdiggs@igalia.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773743}

content/browser/accessibility/accessibility_auralinux_browsertest.cc

@@ -60,6 +60,8 @@ class AccessibilityAuraLinuxBrowserTest : public AccessibilityBrowserTest {
     return false;
   }
 
+  // Ensures that the text and the start and end offsets retrieved using
+  // get_textAtOffset match the expected values.
   static void CheckTextAtOffset(AtkText* text_object,
                                 int offset,
                                 AtkTextBoundary boundary_type,
@@ -67,54 +69,69 @@ class AccessibilityAuraLinuxBrowserTest : public AccessibilityBrowserTest {
                                 int expected_end_offset,
                                 const char* expected_text);
 
+  // Loads a page with  an input text field and places sample text in it.
+  // Returns a pointer to the field's AtkText interface.
   AtkText* SetUpInputField();
+
+  // Loads a page with  a textarea text field, places sample text in it, and
+  // places the caret after the last character.
+  //  Returns a pointer to the field's AtkText interface.
   AtkText* SetUpTextareaField();
+
+  // Loads a page with a paragraph of sample text and returns its AtkText
+  // interface.
   AtkText* SetUpSampleParagraph();
-  AtkText* SetUpSampleParagraphInScrollableDocument();
 
+  // Retrieves a pointer to the already loaded paragraph's AtkText interface.
   AtkText* GetSampleParagraph();
-  AtkText* GetAtkTextForChild(AtkRole expected_role);
+
+  // Searches the accessibility tree in pre-order debth-first traversal for a
+  // node with the given role and returns its AtkText interface if found,
+  // otherwise returns nullptr.
+  AtkText* FindNode(const AtkRole role);
 
  private:
+  // Searches the accessibility tree in pre-order debth-first traversal starting
+  // at a given node and for a node with the given role and returns its AtkText
+  // interface if found, otherwise returns nullptr.
+  AtkText* FindNode(AtkObject* root, const AtkRole role) const;
+
   DISALLOW_COPY_AND_ASSIGN(AccessibilityAuraLinuxBrowserTest);
 };
 
-AtkText* AccessibilityAuraLinuxBrowserTest::GetAtkTextForChild(
-    AtkRole expected_role) {
-  AtkObject* document = GetRendererAccessible();
-  EXPECT_EQ(1, atk_object_get_n_accessible_children(document));
-
-  AtkObject* parent_element = atk_object_ref_accessible_child(document, 0);
-  int number_of_children = atk_object_get_n_accessible_children(parent_element);
-  EXPECT_LT(0, number_of_children);
-
-  // The input field is always the last child.
-  AtkObject* input =
-      atk_object_ref_accessible_child(parent_element, number_of_children - 1);
-  EXPECT_EQ(expected_role, atk_object_get_role(input));
-
-  EXPECT_TRUE(ATK_IS_TEXT(input));
-  AtkText* atk_text = ATK_TEXT(input);
-
-  g_object_unref(parent_element);
+void AccessibilityAuraLinuxBrowserTest::CheckTextAtOffset(
+    AtkText* text_object,
+    int offset,
+    AtkTextBoundary boundary_type,
+    int expected_start_offset,
+    int expected_end_offset,
+    const char* expected_text) {
+  testing::Message message;
+  message << "While checking at index \'" << offset << "\' for \'"
+          << expected_text << "\' at " << expected_start_offset << '-'
+          << expected_end_offset << '.';
+  SCOPED_TRACE(message);
 
-  return atk_text;
+  int start_offset = 0;
+  int end_offset = 0;
+  char* text = atk_text_get_text_at_offset(text_object, offset, boundary_type,
+                                           &start_offset, &end_offset);
+  EXPECT_EQ(expected_start_offset, start_offset);
+  EXPECT_EQ(expected_end_offset, end_offset);
+  EXPECT_STREQ(expected_text, text);
+  g_free(text);
 }
 
-// Loads a page with  an input text field and places sample text in it.
 AtkText* AccessibilityAuraLinuxBrowserTest::SetUpInputField() {
   LoadInputField();
-  return GetAtkTextForChild(ATK_ROLE_ENTRY);
+  return FindNode(ATK_ROLE_ENTRY);
 }
 
-// Loads a page with  a textarea text field and places sample text in it. Also,
-// places the caret before the last character.
 AtkText* AccessibilityAuraLinuxBrowserTest::SetUpTextareaField() {
   LoadTextareaField();
-  return GetAtkTextForChild(ATK_ROLE_ENTRY);
+  return FindNode(ATK_ROLE_ENTRY);
 }
 
-// Loads a page with a paragraph of sample text.
 AtkText* AccessibilityAuraLinuxBrowserTest::SetUpSampleParagraph() {
   LoadSampleParagraph();
 
@@ -139,37 +156,48 @@ AtkText* AccessibilityAuraLinuxBrowserTest::GetSampleParagraph() {
   int number_of_children = atk_object_get_n_accessible_children(document);
   EXPECT_LT(0, number_of_children);
 
-  // The input field is always the last child.
-  AtkObject* input = atk_object_ref_accessible_child(document, 0);
-  EXPECT_EQ(ATK_ROLE_PARAGRAPH, atk_object_get_role(input));
+  // The paragraph is the last child.
+  AtkObject* paragraph = atk_object_ref_accessible_child(document, 0);
+  EXPECT_EQ(ATK_ROLE_PARAGRAPH, atk_object_get_role(paragraph));
 
-  EXPECT_TRUE(ATK_IS_TEXT(input));
-  return ATK_TEXT(input);
+  EXPECT_TRUE(ATK_IS_TEXT(paragraph));
+  return ATK_TEXT(paragraph);
 }
 
-// Ensures that the text and the start and end offsets retrieved using
-// get_textAtOffset match the expected values.
-void AccessibilityAuraLinuxBrowserTest::CheckTextAtOffset(
-    AtkText* text_object,
-    int offset,
-    AtkTextBoundary boundary_type,
-    int expected_start_offset,
-    int expected_end_offset,
-    const char* expected_text) {
-  testing::Message message;
-  message << "While checking at index \'" << offset << "\' for \'"
-          << expected_text << "\' at " << expected_start_offset << '-'
-          << expected_end_offset << '.';
-  SCOPED_TRACE(message);
+AtkText* AccessibilityAuraLinuxBrowserTest::FindNode(const AtkRole role) {
+  AtkObject* document = GetRendererAccessible();
+  EXPECT_NE(nullptr, document);
+  return FindNode(document, role);
+}
 
-  int start_offset = 0;
-  int end_offset = 0;
-  char* text = atk_text_get_text_at_offset(text_object, offset, boundary_type,
-                                           &start_offset, &end_offset);
-  EXPECT_EQ(expected_start_offset, start_offset);
-  EXPECT_EQ(expected_end_offset, end_offset);
-  EXPECT_STREQ(expected_text, text);
-  g_free(text);
+AtkText* AccessibilityAuraLinuxBrowserTest::FindNode(AtkObject* root,
+                                                     const AtkRole role) const {
+  EXPECT_NE(nullptr, root);
+  if (atk_object_get_role(root) == role) {
+    EXPECT_TRUE(ATK_IS_TEXT(root));
+    g_object_ref(root);
+    AtkText* root_text = ATK_TEXT(root);
+    return root_text;
+  }
+
+  for (int i = 0; i < atk_object_get_n_accessible_children(root); ++i) {
+    AtkObject* child = atk_object_ref_accessible_child(root, i);
+    EXPECT_NE(nullptr, child);
+    if (atk_object_get_role(child) == role) {
+      EXPECT_TRUE(ATK_IS_TEXT(child));
+      AtkText* child_text = ATK_TEXT(child);
+      return child_text;
+    }
+
+    if (AtkText* descendant_text = FindNode(child, role)) {
+      g_object_unref(child);
+      return descendant_text;
+    }
+
+    g_object_unref(child);
+  }
+
+  return nullptr;
 }
 
 IN_PROC_BROWSER_TEST_F(AccessibilityAuraLinuxBrowserTest,
@@ -1142,6 +1170,126 @@ IN_PROC_BROWSER_TEST_F(AccessibilityAuraLinuxBrowserTest,
   g_object_unref(atk_text);
 }
 
+IN_PROC_BROWSER_TEST_F(AccessibilityAuraLinuxBrowserTest,
+                       SetSelectionWithIgnoredObjects) {
+  LoadInitialAccessibilityTreeFromHtml(R"HTML(<!DOCTYPE html>
+      <html>
+        <body>
+          <ul>
+            <li>
+              <div role="presentation"></div>
+              <p role="presentation">
+                <span>Banana</span>
+              </p>
+              <span>fruit.</span>
+            </li>
+          </ul>
+        </body>
+      </html>)HTML");
+
+  AtkText* atk_list_item = FindNode(ATK_ROLE_LIST_ITEM);
+  ASSERT_NE(nullptr, atk_list_item);
+
+  // The hypertext expose by "list_item_text" includes an embedded object
+  // character for the list bullet and the joined word "Bananafruit.". The word
+  // "Banana" is exposed as text because its container paragraph is ignored.
+  int n_characters = atk_text_get_character_count(atk_list_item);
+  ASSERT_EQ(13, n_characters);
+
+  AccessibilityNotificationWaiter waiter(
+      shell()->web_contents(), ui::kAXModeComplete,
+      ax::mojom::Event::kDocumentSelectionChanged);
+
+  // First select the whole of the text found in the hypertext.
+  int start_offset = 0;
+  int end_offset = n_characters;
+  std::string embedded_character;
+  ASSERT_TRUE(
+      base::UTF16ToUTF8(&ui::AXPlatformNodeAuraLinux::kEmbeddedCharacter, 1,
+                        &embedded_character));
+  char* selected_text = nullptr;
+
+  EXPECT_TRUE(
+      atk_text_set_selection(atk_list_item, 0, start_offset, end_offset));
+  waiter.WaitForNotification();
+
+  selected_text =
+      atk_text_get_selection(atk_list_item, 0, &start_offset, &end_offset);
+  ASSERT_NE(nullptr, selected_text);
+  EXPECT_EQ(0, start_offset);
+  EXPECT_EQ(n_characters, end_offset);
+  // The list bullet should be represented by an embedded object character.
+  EXPECT_STREQ((embedded_character + std::string("Bananafruit.")).c_str(),
+               selected_text);
+  g_free(selected_text);
+
+  // Select only the list bullet.
+  start_offset = 0;
+  end_offset = 1;
+  EXPECT_TRUE(
+      atk_text_set_selection(atk_list_item, 0, start_offset, end_offset));
+  waiter.WaitForNotification();
+
+  selected_text =
+      atk_text_get_selection(atk_list_item, 0, &start_offset, &end_offset);
+  ASSERT_NE(nullptr, selected_text);
+  EXPECT_EQ(0, start_offset);
+  EXPECT_EQ(1, end_offset);
+  // The list bullet should be represented by an embedded object character.
+  EXPECT_STREQ(embedded_character.c_str(), selected_text);
+  g_free(selected_text);
+
+  // Select the word "Banana" in the ignored paragraph.
+  start_offset = 1;
+  end_offset = 7;
+  EXPECT_TRUE(
+      atk_text_set_selection(atk_list_item, 0, start_offset, end_offset));
+  waiter.WaitForNotification();
+
+  selected_text =
+      atk_text_get_selection(atk_list_item, 0, &start_offset, &end_offset);
+  ASSERT_NE(nullptr, selected_text);
+  EXPECT_EQ(1, start_offset);
+  EXPECT_EQ(7, end_offset);
+  EXPECT_STREQ("Banana", selected_text);
+  g_free(selected_text);
+
+  // Select both the list bullet and the word "Banana" in the ignored paragraph.
+  start_offset = 0;
+  end_offset = 7;
+  EXPECT_TRUE(
+      atk_text_set_selection(atk_list_item, 0, start_offset, end_offset));
+  waiter.WaitForNotification();
+
+  selected_text =
+      atk_text_get_selection(atk_list_item, 0, &start_offset, &end_offset);
+  ASSERT_NE(nullptr, selected_text);
+  EXPECT_EQ(0, start_offset);
+  EXPECT_EQ(7, end_offset);
+  // The list bullet should be represented by an embedded object character.
+  EXPECT_STREQ((embedded_character + std::string("Banana")).c_str(),
+               selected_text);
+  g_free(selected_text);
+
+  // Select the joined word "Bananafruit." both in the ignored paragraph and in
+  // the unignored span.
+  start_offset = 1;
+  end_offset = n_characters;
+  EXPECT_TRUE(
+      atk_text_set_selection(atk_list_item, 0, start_offset, end_offset));
+  waiter.WaitForNotification();
+
+  selected_text =
+      atk_text_get_selection(atk_list_item, 0, &start_offset, &end_offset);
+  ASSERT_NE(nullptr, selected_text);
+  EXPECT_EQ(1, start_offset);
+  EXPECT_EQ(n_characters, end_offset);
+  EXPECT_STREQ("Bananafruit.", selected_text);
+  g_free(selected_text);
+
+  g_object_unref(atk_list_item);
+}
+
 IN_PROC_BROWSER_TEST_F(AccessibilityAuraLinuxBrowserTest, TestAtkTextListItem) {
   LoadInitialAccessibilityTreeFromHtml(
       R"HTML(<!DOCTYPE html>