rem: inline const QString &key() const { return mKey; }
add: virtual QString key( int column, bool  ) const {   const char req_col = (char)column; if(mKey.isEmpty() || mKey.left(1) != &req_col) { KMHeaders *headers = static_cast<KMHeaders*>(listView()); return ((KMHeaderItem *)this)->mKey = generate_key(mMsgId, headers->folder()->getMsgBase( mMsgId ), headers->paintInfo(), column); } return mKey; }
context:     inline const QString &key() const { return mKey; }