How to set chinese language??

Hello, I am programming a gtk application on win32.
But I don't know how to set the language to chinese if I want to open 
a chinese document and let it show in gtk_buffer.

ifstream file("version.txt"); // it is a chinese document
  stringstream tmp;
  tmp << file.rdbuf();
  string content = tmp.str();
  const gchar *pBuffer = content.c_str();  

   gtk_text_buffer_set_text (buffer, g_locale_to_utf8(pBuffer, -1, 
NULL, NULL, NULL), -1

It will not properly shown in the buffer , I only can see quadrangles.

Can somebody help me