Handle surrogates in BidiResolver::determineParagraphDirectionality

Source/platform/text/BidiResolver.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008 Apple Inc.  All right reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 530 matching lines @@
 template <class Iterator, class Run>
 TextDirection BidiResolver<Iterator, Run>::determineParagraphDirectionality(bool* hasStrongDirectionality)
 {
     while (!m_current.atEnd()) {
         if (inIsolate()) {
             increment();
             continue;
         }
         if (m_current.atParagraphSeparator())
             break;
-        if (UChar current = m_current.current()) {
-            WTF::Unicode::Direction charDirection = WTF::Unicode::direction(current);
-            if (charDirection == WTF::Unicode::LeftToRight) {
-                if (hasStrongDirectionality)
-                    *hasStrongDirectionality = true;
-                return LTR;
-            }
-            if (charDirection == WTF::Unicode::RightToLeft || charDirection == WTF::Unicode::RightToLeftArabic) {
-                if (hasStrongDirectionality)
-                    *hasStrongDirectionality = true;
-                return RTL;
-            }
+        UChar32 current = m_current.current();
+        if (UNLIKELY(U16_IS_SURROGATE(current))) {
+            increment();
+            // If this not the high part of the surrogate pair, then drop it and move to the next.
+            if (!U16_IS_SURROGATE_LEAD(current))
+                continue;
+            UChar high = static_cast<UChar>(current);
+            if (m_current.atEnd())
+                continue;
+            UChar low = m_current.current();
+            // Verify the low part. If invalid, then assume an invalid surrogate pair and retry.
+            if (!U16_IS_TRAIL(low))
+                continue;
+            current = U16_GET_SUPPLEMENTARY(high, low);
+        }
+        WTF::Unicode::Direction charDirection = WTF::Unicode::direction(current);
+        if (charDirection == WTF::Unicode::LeftToRight) {
+            if (hasStrongDirectionality)
+                *hasStrongDirectionality = true;
+            return LTR;
+        }
+        if (charDirection == WTF::Unicode::RightToLeft || charDirection == WTF::Unicode::RightToLeftArabic) {
+            if (hasStrongDirectionality)
+                *hasStrongDirectionality = true;
+            return RTL;
         }
         increment();
     }
     if (hasStrongDirectionality)
         *hasStrongDirectionality = false;
     return LTR;
 }
 
 template <class Iterator, class Run>
 void BidiResolver<Iterator, Run>::createBidiRunsForLine(const Iterator& end, VisualDirectionOverride override, bool hardLineBreak)
@@ skipping 408 matching lines @@
 template<class Iterator, class Run>
 MidpointState<Iterator> BidiResolver<Iterator, Run>::midpointStateForIsolatedRun(Run* run)
 {
     return m_midpointStateForIsolatedRun.take(run);
 }
 
 
 } // namespace WebCore
 
 #endif // BidiResolver_h