[Sh-Blink] Fix for non text node positions

Fix by replacing the non text node position by its child text node,
if possible. Otherwise, skip the word-completion logic, which assumes,
the position is in text node.

Bug: 1165317
Change-Id: Iafb82eb1f1f7e5b6644cc07034166e6f0344d184
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2622987
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843765}

third_party/blink/renderer/core/page/scrolling/text_fragment_selector_generator.cc

@@ -28,9 +28,10 @@ namespace {
 bool IsFirstVisiblePosition(Node* node, unsigned pos_offset) {
   auto range_start = Position::FirstPositionInNode(*node);
   auto range_end = Position(node, pos_offset);
-  return pos_offset == 0 || PlainText(EphemeralRange(range_start, range_end))
-                                .StripWhiteSpace()
-                                .IsEmpty();
+  return node->getNodeType() == Node::kElementNode || pos_offset == 0 ||
+         PlainText(EphemeralRange(range_start, range_end))
+             .StripWhiteSpace()
+             .IsEmpty();
 }
 
 // Returns true if text from |pos_offset| until end of |node| can be considered
@@ -38,7 +39,8 @@ bool IsFirstVisiblePosition(Node* node, unsigned pos_offset) {
 bool IsLastVisiblePosition(Node* node, unsigned pos_offset) {
   auto range_start = Position(node, pos_offset);
   auto range_end = Position::LastPositionInNode(*node);
-  return pos_offset == node->textContent().length() ||
+  return node->getNodeType() == Node::kElementNode ||
+         pos_offset == node->textContent().length() ||
          PlainText(EphemeralRange(range_start, range_end))
              .StripWhiteSpace()
              .IsEmpty();
@@ -152,6 +154,19 @@ String GetWordsFromStart(String text, int word_num) {
   return text.Substring(0, pos).StripWhiteSpace();
 }
 
+// For Element-based Position returns the node that its pointing to, otherwise
+// returns the container node.
+Node* ResolvePositionToNode(const PositionInFlatTree& position) {
+  Node* node = position.ComputeContainerNode();
+  int offset = position.ComputeOffsetInContainerNode();
+
+  if (node->getNodeType() == Node::kElementNode && node->hasChildren() &&
+      node->childNodes()->item(offset)) {
+    return node->childNodes()->item(offset);
+  }
+  return node;
+}
+
 }  // namespace
 
 constexpr int kExactTextMaxChars = 300;
@@ -195,13 +210,23 @@ void TextFragmentSelectorGenerator::AdjustSelection() {
       ephemeral_range.StartPosition().ComputeContainerNode();
   Node* end_container = ephemeral_range.EndPosition().ComputeContainerNode();
 
+  Node* corrected_start =
+      ResolvePositionToNode(ephemeral_range.StartPosition());
+  int corrected_start_offset =
+      (corrected_start->isSameNode(start_container))
+          ? ephemeral_range.StartPosition().ComputeOffsetInContainerNode()
+          : 0;
+
+  Node* corrected_end = ResolvePositionToNode(ephemeral_range.EndPosition());
+  int corrected_end_offset =
+      (corrected_end->isSameNode(end_container))
+          ? ephemeral_range.EndPosition().ComputeOffsetInContainerNode()
+          : 0;
+
   // If start node has no text or given start position point to the last visible
   // text in its containiner node, use the following visible node for selection
   // start. This has to happen before generation, so that selection is correctly
   // classified as same block or not.
-  Node* corrected_start = start_container;
-  int corrected_start_offset =
-      ephemeral_range.StartPosition().ComputeOffsetInContainerNode();
   if (IsLastVisiblePosition(corrected_start, corrected_start_offset)) {
     corrected_start = FirstNonEmptyVisibleTextNode(
         FlatTreeTraversal::NextSkippingChildren(*corrected_start));
@@ -220,9 +245,6 @@ void TextFragmentSelectorGenerator::AdjustSelection() {
   // text in its containiner node, use the previous visible node for selection
   // end. This has to happen before generation, so that selection is correctly
   // classified as same block or not.
-  Node* corrected_end = end_container;
-  int corrected_end_offset =
-      ephemeral_range.EndPosition().ComputeOffsetInContainerNode();
   if (IsFirstVisiblePosition(corrected_end, corrected_end_offset)) {
     // Here, |Previous()| already skips the children of the given node,
     // because we're doing pre-order traversal.

third_party/blink/renderer/core/page/scrolling/text_fragment_selector_generator_test.cc

@@ -947,6 +947,72 @@ TEST_F(TextFragmentSelectorGeneratorTest, RangeSelector_SameNode_Interrupted) {
   VerifySelector(start, end, "First,paragraph");
 }
 
+// Checks the case when selection end position is a non text node.
+TEST_F(TextFragmentSelectorGeneratorTest, SelectionEndsWithNonText) {
+  SimRequest request("https://example.com/test.html", "text/html");
+  LoadURL("https://example.com/test.html");
+  request.Complete(R"HTML(
+  <!DOCTYPE html>
+  <div id='div'>
+    <p id='start'>First paragraph</p>
+    <p id='second'>Second paragraph</p>
+  </div>
+  )HTML");
+  GetDocument().UpdateStyleAndLayoutTree();
+  Node* first_paragraph = GetDocument().getElementById("start")->firstChild();
+  Node* div = GetDocument().getElementById("div");
+  const auto& start = Position(first_paragraph, 0);
+  const auto& end = Position(div, 2);
+  ASSERT_EQ("First paragraph\n\n", PlainText(EphemeralRange(start, end)));
+
+  VerifySelector(start, end, "First%20paragraph,-Second");
+}
+
+// Checks the case when selection end position is a non text node which doesn't
+// have text child node.
+TEST_F(TextFragmentSelectorGeneratorTest,
+       SelectionEndsWithNonTextWithNoTextChild) {
+  SimRequest request("https://example.com/test.html", "text/html");
+  LoadURL("https://example.com/test.html");
+  request.Complete(R"HTML(
+    <!DOCTYPE html>
+  <div id='div'><p id='start'>First paragraph</p><p id='second'>Second paragraph</p><img id="img">
+  </div>
+  )HTML");
+  GetDocument().UpdateStyleAndLayoutTree();
+  Node* first_paragraph = GetDocument().getElementById("start")->firstChild();
+  Node* div = GetDocument().getElementById("div");
+  const auto& start = Position(first_paragraph, 0);
+  const auto& end =
+      Position(div, 3);  // Points to the 3rd child of the div, which is <img>
+  ASSERT_EQ("First paragraph\n\nSecond paragraph\n\n",
+            PlainText(EphemeralRange(start, end)));
+
+  VerifySelector(start, end, "First%20paragraph,Second%20paragraph");
+}
+
+// Checks the case when selection end position is a non text node which doesn't
+// have text child node.
+TEST_F(TextFragmentSelectorGeneratorTest, SelectionEndsWithImageDiv) {
+  SimRequest request("https://example.com/test.html", "text/html");
+  LoadURL("https://example.com/test.html");
+  request.Complete(R"HTML(
+    <!DOCTYPE html>
+  <div id='div'><p id='start'>First paragraph</p><p id='second'>Second paragraph</p><div id='div_img'><img id="img"></div>
+  </div>
+  )HTML");
+  GetDocument().UpdateStyleAndLayoutTree();
+  Node* first_paragraph = GetDocument().getElementById("start")->firstChild();
+  Node* div = GetDocument().getElementById("div");
+  const auto& start = Position(first_paragraph, 0);
+  const auto& end =
+      Position(div, 3);  // Points to the 3rd child of the div, which is div_img
+  ASSERT_EQ("First paragraph\n\nSecond paragraph\n\n",
+            PlainText(EphemeralRange(start, end)));
+
+  VerifySelector(start, end, "First%20paragraph,Second%20paragraph");
+}
+
 // Basic test case for |GetNextTextBlock|.
 TEST_F(TextFragmentSelectorGeneratorTest, GetPreviousTextBlock) {
   SimRequest request("https://example.com/test.html", "text/html");