Switched to using |AXPosition| for calculating word and line boundaries on Windows.

content/browser/accessibility/browser_accessibility_win.cc

Index: content/browser/accessibility/browser_accessibility_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_win.cc b/content/browser/accessibility/browser_accessibility_win.cc
index 01b5e28fd78e4782c85ca438de5f67de756504b0..48e7395f3400ad286dc8051f8512452ec6341cf8 100644
--- a/content/browser/accessibility/browser_accessibility_win.cc
+++ b/content/browser/accessibility/browser_accessibility_win.cc
@@ -2486,11 +2486,11 @@ STDMETHODIMP BrowserAccessibilityWin::get_textAtOffset(
   if (!start_offset || !end_offset || !text)
     return E_INVALIDARG;
 
-  const base::string16& text_str = GetText();
   HandleSpecialTextOffset(&offset);
   if (offset < 0)
     return E_INVALIDARG;
 
+  const base::string16& text_str = GetText();
   LONG text_len = text_str.length();
   if (offset > text_len)
     return E_INVALIDARG;
@@ -3889,8 +3889,9 @@ void BrowserAccessibilityWin::ComputeStylesIfNeeded() {
 
 // |offset| could either be a text character or a child index in case of
 // non-text objects.
+// TODO(nektar): Remove this function once selection bugs are fixed in Blink.
 BrowserAccessibilityWin::AXPlatformPositionInstance
-BrowserAccessibilityWin::CreatePositionAt(int offset) const {
+BrowserAccessibilityWin::CreatePositionForSelectionAt(int offset) const {
   if (!IsNativeTextControl() && !IsTextOnlyObject()) {
     DCHECK(manager_);
     const BrowserAccessibilityWin* child = this;
@@ -3920,7 +3921,7 @@ BrowserAccessibilityWin::CreatePositionAt(int offset) const {
     }
     return position;
   }
-  return BrowserAccessibility::CreatePositionAt(offset);
+  return CreatePositionAt(offset);
 }
 
 base::string16 BrowserAccessibilityWin::GetText() const {
@@ -4577,9 +4578,9 @@ void BrowserAccessibilityWin::SetIA2HypertextSelection(LONG start_offset,
   HandleSpecialTextOffset(&start_offset);
   HandleSpecialTextOffset(&end_offset);
   AXPlatformPositionInstance start_position =
-      CreatePositionAt(static_cast<int>(start_offset));
+      CreatePositionForSelectionAt(static_cast<int>(start_offset));
   AXPlatformPositionInstance end_position =
-      CreatePositionAt(static_cast<int>(end_offset));
+      CreatePositionForSelectionAt(static_cast<int>(end_offset));
   manager_->SetSelection(AXPlatformRange(start_position->AsTextPosition(),
                                          end_position->AsTextPosition()));
 }
@@ -4987,13 +4988,61 @@ LONG BrowserAccessibilityWin::FindBoundary(
                                     : ui::AX_TEXT_AFFINITY_DOWNSTREAM;
 
   HandleSpecialTextOffset(&start_offset);
-  if (ia2_boundary == IA2_TEXT_BOUNDARY_WORD)
-    return GetWordStartBoundary(static_cast<int>(start_offset), direction);
+  if (ia2_boundary == IA2_TEXT_BOUNDARY_WORD) {
+    switch (direction) {
+      case ui::FORWARDS_DIRECTION: {
+        AXPlatformPositionInstance position =
+            CreatePositionAt(static_cast<int>(start_offset), affinity);
+        AXPlatformPositionInstance next_word =
+            position->CreateNextWordStartPosition();
+        if (next_word->IsNullPosition())
+          next_word = position->CreatePositionAtEndOfAnchor();
+        return next_word->text_offset();
+      }
+      case ui::BACKWARDS_DIRECTION: {
+        AXPlatformPositionInstance position =
+            CreatePositionAt(static_cast<int>(start_offset), affinity);
+        AXPlatformPositionInstance previous_word;
+        if (!position->AtStartOfWord()) {
+          previous_word = position->CreatePreviousWordStartPosition();

[dmazzoni, 2017/04/10 22:39:49]

Just curious, should CreatePreviousWordStartPosition and
CreateNextWordStartPosition always return the start or end of anchor if there's
no previous or next word?

I'm just thinking that might be better default behavior. But if another platform
needs this current behavior that's fine.

+          if (previous_word->IsNullPosition())
+            previous_word = position->CreatePositionAtStartOfAnchor();
+        } else {
+          previous_word = std::move(position);
+        }
+        return previous_word->text_offset();
+      }
+    }

[dmazzoni, 2017/04/10 22:39:49]

Maybe add a NOTREACHED() after the switch since there shouldn't be
anything other than FORWARDS or BACKWARDS

+  }
+
   if (ia2_boundary == IA2_TEXT_BOUNDARY_LINE) {
-    return GetLineStartBoundary(
-        static_cast<int>(start_offset), direction, affinity);
+    switch (direction) {
+      case ui::FORWARDS_DIRECTION: {
+        AXPlatformPositionInstance position =
+            CreatePositionAt(static_cast<int>(start_offset), affinity);
+        AXPlatformPositionInstance next_line =
+            position->CreateNextLineStartPosition();
+        if (next_line->IsNullPosition())
+          next_line = position->CreatePositionAtEndOfAnchor();
+        return next_line->text_offset();
+      }
+      case ui::BACKWARDS_DIRECTION: {
+        AXPlatformPositionInstance position =
+            CreatePositionAt(static_cast<int>(start_offset), affinity);
+        AXPlatformPositionInstance previous_line;
+        if (!position->AtStartOfLine()) {
+          previous_line = position->CreatePreviousLineStartPosition();
+          if (previous_line->IsNullPosition())
+            previous_line = position->CreatePositionAtStartOfAnchor();
+        } else {
+          previous_line = std::move(position);
+        }
+        return previous_line->text_offset();
+      }
+    }

[dmazzoni, 2017/04/10 22:39:49]

NOTREACHED

   }
 
+  // TODO(nektar): |AXPosition| can handle other types of boundaries as well.
   ui::TextBoundaryType boundary = IA2TextBoundaryToTextBoundary(ia2_boundary);
   return ui::FindAccessibleTextBoundary(text, GetLineStartOffsets(), boundary,
                                         start_offset, direction, affinity);