Make computeInlineBoxPosition() to handle unicode-bidi:isolate correctly

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1953 matching lines @@
 PositionTemplate<Strategy> upstreamIgnoringEditingBoundaries(PositionTemplate<Strategy> position)
 {
     PositionTemplate<Strategy> lastPosition;
     while (position != lastPosition) {
         lastPosition = position;
         position = mostBackwardCaretPosition(position, CanCrossEditingBoundary);
     }
     return position;
 }
 
+// Returns true if |inlineBox| starts different direction of embedded text ru.
+// See [1] for details.
+// [1] UNICODE BIDIRECTIONAL ALGORITHM, http://unicode.org/reports/tr9/
+static bool isStartOfDifferentDirection(const InlineBox* inlineBox)
+{
+    InlineBox* prevBox = inlineBox->prevLeafChild();
+    if (!prevBox)
+        return true;
+    if (prevBox->direction() == inlineBox->direction())
+        return true;
+    DCHECK_NE(prevBox->bidiLevel(), inlineBox->bidiLevel());
+    return prevBox->bidiLevel() > inlineBox->bidiLevel();
+}
+
 template <typename Strategy>
 static InlineBoxPosition computeInlineBoxPositionTemplate(const PositionTemplate<Strategy>& position, TextAffinity affinity, TextDirection primaryDirection)
 {
     InlineBox* inlineBox = nullptr;
     int caretOffset = position.computeEditingOffset();
     Node* const anchorNode = position.anchorNode();
     LayoutObject* layoutObject = anchorNode->isShadowRoot() ? toShadowRoot(anchorNode)->host().layoutObject() : anchorNode->layoutObject();
 
     DCHECK(layoutObject) << position;
 
@@ skipping 73 matching lines @@
 
             // For example, abc 123 ^ CBA
             while (InlineBox* nextBox = inlineBox->nextLeafChild()) {
                 if (nextBox->bidiLevel() < level)
                     break;
                 inlineBox = nextBox;
             }
             return InlineBoxPosition(inlineBox, inlineBox->caretRightmostOffset());
         }
 
-        InlineBox* prevBox = inlineBox->prevLeafChild();
-        if (!prevBox || prevBox->bidiLevel() >= level)
+        if (isStartOfDifferentDirection(inlineBox))
             return InlineBoxPosition(inlineBox, caretOffset);
 
-        level = prevBox->bidiLevel();
+        level = inlineBox->prevLeafChild()->bidiLevel();
         InlineBox* nextBox = inlineBox;
         do {
             nextBox = nextBox->nextLeafChild();
         } while (nextBox && nextBox->bidiLevel() > level);
 
         if (nextBox && nextBox->bidiLevel() == level)
             return InlineBoxPosition(inlineBox, caretOffset);
 
         while (InlineBox* prevBox = inlineBox->prevLeafChild()) {
             if (prevBox->bidiLevel() < level)
@@ skipping 1225 matching lines @@
 {
     return previousPositionOfAlgorithm<EditingStrategy>(visiblePosition, rule);
 }
 
 VisiblePositionInFlatTree previousPositionOf(const VisiblePositionInFlatTree& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     return previousPositionOfAlgorithm<EditingInFlatTreeStrategy>(visiblePosition, rule);
 }
 
 } // namespace blink