Provide user friendly messages for OTS parsing of fonts

Source/platform/fonts/opentype/OpenTypeSanitizer.h

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef OpenTypeSanitizer_h
 #define OpenTypeSanitizer_h
 
 #include "opentype-sanitiser.h"
 #include "wtf/Forward.h"
+#include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class SharedBuffer;
 
 class OpenTypeSanitizer {
 public:
     explicit OpenTypeSanitizer(SharedBuffer* buffer)
         : m_buffer(buffer)
+        , m_otsErrorString("")
     {
     }
 
     PassRefPtr<SharedBuffer> sanitize();
 
     static bool supportsFormat(const String&);
+    String getErrorString() const { return static_cast<String>(m_otsErrorString); }
+
+    void setErrorString(const String& errorString) { m_otsErrorString = errorString; }
+
+    bool isParsingError() const { return m_parsingError; }
+    void setParsingError(bool parsingError) { m_parsingError = parsingError; }
 
 private:
     SharedBuffer* const m_buffer;
+    String m_otsErrorString;
+    bool m_parsingError;
 };
 
 class BlinkOTSContext: public ots::OTSContext {
 public:
-        // TODO: Implement "Message" to support user friendly messages
+        BlinkOTSContext()
+            : m_errorString("")
+        {
+        }
+
+        virtual void Message(int level, const char *format, ...)

[jungshik at Google, 2015/05/12 20:22:48]

Just wondering if there's a reason to have this inlined in *h file. Not a big
deal. 

[h.joshi, 2015/05/14 04:52:15]

Moved methods to CPP file, normally all methods were in header file to kept the
same way.

+        {
+            va_list args;
+            va_start(args, format);
+
+#if COMPILER(MSVC)
+            int result = _vscprintf(format, args);
+#else
+            char ch;
+            int result = vsnprintf(&ch, 1, format, args);
+#endif
+            va_end(args);
+
+            if (result <= 0) {
+                m_errorString = String("OTS Error");
+            } else {
+                Vector<char, 256> buffer;
+                unsigned len = result;
+                buffer.grow(len + 1);
+
+                va_start(args, format);
+                vsnprintf(buffer.data(), buffer.size(), format, args);
+                va_end(args);
+                m_errorString = StringImpl::create(reinterpret_cast<const LChar*>(buffer.data()), len);
+            }
+        }
+
         virtual ots::TableAction GetTableAction(uint32_t tag)
         {
 #define TABLE_TAG(c1, c2, c3, c4) ((uint32_t)((((uint8_t)(c1)) << 24) | (((uint8_t)(c2)) << 16) | (((uint8_t)(c3)) << 8) | ((uint8_t)(c4))))
 
             const uint32_t cbdtTag = TABLE_TAG('C', 'B', 'D', 'T');
             const uint32_t cblcTag = TABLE_TAG('C', 'B', 'L', 'C');
             const uint32_t colrTag = TABLE_TAG('C', 'O', 'L', 'R');
             const uint32_t cpalTag = TABLE_TAG('C', 'P', 'A', 'L');
 
             switch (tag) {
             // Google Color Emoji Tables
             case cbdtTag:
             case cblcTag:
             // Windows Color Emoji Tables
             case colrTag:
             case cpalTag:
                 return ots::TABLE_ACTION_PASSTHRU;
             default:
                 return ots::TABLE_ACTION_DEFAULT;
             }
 #undef TABLE_TAG
         }
+
+        String getErrorString() const { return static_cast<String>(m_errorString); }
+private:
+        String m_errorString;
 };
 
 } // namespace blink
 
 #endif // OpenTypeSanitizer_h