code: def ch_handler(offset=0, length=-1, **kw):
      
      global _lastSel
  
      offset = int(offset)
      length = int(length)
      if length < 0: length = len(_lastSel)
      return _lastSel[offset:offset+length]
docs: Handle standard PRIMARY clipboard access.  Note that offset and length
      are passed as strings.  This differs from CLIPBOARD.