Replace const char * based connect statements by modern API and remove '_q_' slot prefixes. This requires explicit disconnection in the destructor -> add. Replace bool traps for layouting and removing buttons by enum classes. Replace if/elseif event handler by switch. Replace iterator typedef with auto. Encapsulate logic to ensure defaulting to first accept button in a member function for better readability. Remove dead code. Move private header declaration from cpp to a new _p.h. Task-number: QTBUG-114377 Pick-to: 6.6 6.5 Change-Id: I8a2bc355e3816c3c826c10cd96194c89bf0ae510 Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>