Provide user friendly messages for OTS parsing of fonts

Source/platform/fonts/opentype/OpenTypeSanitizer.h

Index: Source/platform/fonts/opentype/OpenTypeSanitizer.h
diff --git a/Source/platform/fonts/opentype/OpenTypeSanitizer.h b/Source/platform/fonts/opentype/OpenTypeSanitizer.h
index 460dd0262ee3a89e3ce70e8ffb96b7c2b3698e91..8799d51e37d4af96bcd91144b7f17d449b951aff 100644
--- a/Source/platform/fonts/opentype/OpenTypeSanitizer.h
+++ b/Source/platform/fonts/opentype/OpenTypeSanitizer.h
@@ -33,6 +33,7 @@
 
 #include "opentype-sanitiser.h"
 #include "wtf/Forward.h"
+#include "wtf/text/WTFString.h"
 
 namespace blink {
 
@@ -42,20 +43,60 @@ 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))))
@@ -78,6 +119,10 @@ public:
             }
 #undef TABLE_TAG
         }
+
+        String getErrorString() const { return static_cast<String>(m_errorString); }
+private:
+        String m_errorString;
 };
 
 } // namespace blink