code: func (v *Editable) InsertText(newText string, position int) int {
  	cstr := C.CString(newText)
  	defer C.free(unsafe.Pointer(cstr))
  	pos := new(C.gint)
  	*pos = C.gint(position)
  	C.gtk_editable_insert_text(v.native(), (*C.gchar)(cstr),
  		C.gint(len(newText)), pos)
  	return int(*pos)
  }
docs: // InsertText is a wrapper around gtk_editable_insert_text(). The returned
  // int is the position after the inserted text.