Fixed bugs with finding line boundaries using IA2 get_textAtOffset and AXPosition::AtStartOfLine.

ui/accessibility/ax_position.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_ACCESSIBILITY_AX_POSITION_H_
 #define UI_ACCESSIBILITY_AX_POSITION_H_
 
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 258 matching lines @@
 
   bool AtStartOfLine() const {
     AXPositionInstance text_position = AsLeafTextPosition();
     switch (text_position->kind_) {
       case AXPositionKind::NULL_POSITION:
         return false;
       case AXPositionKind::TREE_POSITION:
         NOTREACHED();
         return false;
       case AXPositionKind::TEXT_POSITION:
-        return !text_position->IsInLineBreak() &&
-               GetPreviousOnLineID(text_position->anchor_id_) ==
+        // Special case, when the caret is right after a line break and the next
+        // position is not another line break. We should return |true| because
+        // visually the caret is at the beginning of a new line.
+        if (text_position->IsInLineBreak()) {
+          return text_position->AtEndOfAnchor() &&
+                 !text_position->CreateNextTextAnchorPosition()
+                      ->IsInLineBreak();
+        }
+        return GetPreviousOnLineID(text_position->anchor_id_) ==
                    INVALID_ANCHOR_ID &&
                text_position->AtStartOfAnchor();
     }
     return false;
   }
 
   bool AtEndOfLine() const {
     AXPositionInstance text_position = AsLeafTextPosition();
     switch (text_position->kind_) {
       case AXPositionKind::NULL_POSITION:
@@ skipping 287 matching lines @@
   }
 
   // The following methods work across anchors.
 
   AXPositionInstance CreateNextCharacterPosition() const {
     bool was_tree_position = IsTreePosition();
     AXPositionInstance text_position = AsTextPosition();
     if (text_position->IsNullPosition())
       return text_position;
 
     if ((text_position->text_offset_ + 1) < text_position->MaxTextOffset()) {

[dmazzoni, 2017/05/25 21:28:41]

David noticed that this +1 isn't safe because the
string is unicode. I think the correct thing to
do is use base/i18n/break_iterator.h like we do in
ui/accessibility/ax_text_utils.cc.

Not needed in this change, but ASAP it'd be great
to write a test that iterates over a string with
a non-ASCII character and fix it.

       text_position->text_offset_ += 1;
       // Even if our affinity was upstream, moving to the next character should
       // inevitably reset it to downstream.
       text_position->affinity_ = AX_TEXT_AFFINITY_DOWNSTREAM;
     } else {
       // Moving to the end of the current anchor first is essential. Otherwise
       // |CreateNextAnchorPosition| might return our deepest left-most child
       // because we are using pre-order traversal.
       text_position = text_position->CreatePositionAtEndOfAnchor();
       text_position = text_position->CreateNextTextAnchorPosition();
@@ skipping 587 matching lines @@
 
 template <class AXPositionType, class AXNodeType>
 bool operator>=(const AXPosition<AXPositionType, AXNodeType>& first,
                 const AXPosition<AXPositionType, AXNodeType>& second) {
   return first == second || first > second;
 }
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_AX_POSITION_H_