If you mean you need to handle the case where STROBJ->flAccel has SO_GLYPHINDEX_TEXTOUT set, then see this answer here from Microsoft's Bobby Mattappally:

http://www.winvistatips.com/glyph-handles-drvtextout-t183048.html

There is not always a 1:1 mapping between glyph indices and character codes and vice versa. This is expecially true with international character sets like Hebrew, Arabic etc.

So once you get this as SO_GLYPHINDEX_TEXTOUT, your driver should handle the glyph itself instead of trying to convert it back to Unicode.