In Delphi 2007 you can store a UTF8 string in a WideString and then pass that onto a Win32 function, e.g.

var
  UnicodeStr: WideString;
  UTF8Str: WideString;
begin
  UnicodeStr:='some unicode text';
  UTF8Str:=UTF8Encode(UnicodeStr);
  Windows.SomeFunction(PWideChar(UTF8Str), ...)
end;

Delphi 2007 does not interfere with the contents of UTF8Str, i.e. it is left as a UTF8 encoded string stored in a WideString.

But in Delphi 2010 I'm struggling to find a way to do the same thing, i.e. store a UTF8 encoded string in a WideString without it being automatically converted from UTF8. I cannot pass a pointer to UTF8 string (or RawByteString), e.g. the following will obviously not work:

var
  UnicodeStr: WideString;
  UTF8Str: UTF8String;
begin
  UnicodeStr:='some unicode text';
  UTF8Str:=UTF8Encode(UnicodeStr);
  Windows.SomeFunction(PWideChar(UTF8Str), ...)
end;

Any help appreciated. Thanks.