Re: Multi language application

Hi,

I think that if you want to correctly display Unicode characters in
Windows, you must use UTF-16 (which is the Unicode encoding used
internally by Windows).

However, if for some reasons you do want to use UTF-8 inside your
application, I think that you can do that (e.g. storing your strings in
CStringA or std::string), and then you can just convert your UTF-8 strings
to UTF-16 just before passing them to Windows controls (like edit control)
for display.

You can use ::MultiByteToWideChar Win32 API to convert from UTF-8 to
UTF-16, and pass the UTF-16 string to Windows controls.

e.g.

<code>

 // Your UTF-8 string
 CStringA utf8;
 ... process your utf8 string ...
 ...

 // Convert UTF-8 string to Unicode UTF-16
 // to be used by Windows
 CStringW utf16 = ConvertUtf8ToUtf16( utf8 );

 // Pass the UTF-16 string to Windows
 ... e.g.
 pSomeEditCtrl->SetWindowText( utf16 );

</code>

I can share a function I developed to convert strings from UTF-8 to
UTF-16, feel free to use that in your code, if you need:

<code>

// ======================================================================
//
// FUNCTION: ConvertUtf8ToUtf16
// AUTHOR: Giovanni Dicanio
//
// Converts from Unicode UTF-8 string to UTF-16.
//
// On error: ASSERTs in debug builds; in release builds throws using
// AtlThrow or AtlThrowLastWin32 (see documentations of these functions
// for more details).
//
// This function should work since VS2003 (VC++7.1), but not on VC6,
// because of lack of newer ATL-MFC shared classes and functions like
// CStringA/W in VC6.
//
// ======================================================================
CStringW ConvertUtf8ToUtf16( const CStringA & utf8 )
{
   //
   // Special case of empty string
   //
   if ( utf8.IsEmpty() )
   {
       return L"";
   }

   //
   // Consider byte count corresponding to total string length,
   // including end-of-string (\0) character
   //
   const int utf8ByteCount = utf8.GetLength() + 1;

   //
   // Get size of destination UTF-16 buffer, in wchar_t's
   //
   int utf16Size = ::MultiByteToWideChar(
       CP_UTF8, // convert from UTF-8
       MB_ERR_INVALID_CHARS, // error on invalid chars
       static_cast<const char *>(utf8), // source UTF-8 string
       utf8ByteCount, // total length of source UTF-8 string,
                               // in bytes, including end-of-string \0
       NULL, // unused - no conversion done in this step
       0 // request size of destination buffer, in wchar_t's
   );
   ATLASSERT( utf16Size != 0 );
   if ( utf16Size == 0 )
   {
       AtlThrowLastWin32();
   }

   //
   // Allocate destination buffer to store UTF-16 string
   //
   std::vector< wchar_t > utf16Buffer( utf16Size );

   //
   // Do the conversion from UTF-8 to UTF-16
   //
   int result = ::MultiByteToWideChar(
       CP_UTF8, // convert from UTF-8
       MB_ERR_INVALID_CHARS, // error on invalid chars
       static_cast< const char *>(utf8), // source UTF-8 string
       utf8ByteCount, // total length of source UTF-8 string,
                               // in bytes, including end-of-string \0
       &utf16Buffer[0], // destination buffer
       utf16Size // size of destination buffer, in wchar_t's
   );
   ATLASSERT( result != 0 );
   if ( result == 0 )
   {
       AtlThrowLastWin32();
   }

   //
   // Build UTF-16 string from conversion buffer
   //
   return CStringW( &utf16Buffer[0] );
}

</code>

HTH,
Giovanni

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