//=============================================================================
//  MuseScore
//  Music Composition & Notation
//
//  Copyright (C) 2010-2011 Werner Schweer
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License version 2
//  as published by the Free Software Foundation and appearing in
//  the file LICENCE.GPL
//=============================================================================
 
#ifndef __STAFFSTATE_H__
#define __STAFFSTATE_H__
 
#include "element.h"
#include "elementlayout.h"
#include "instrument.h"
 
namespace Ms {
 
enum class StaffStateType : char {
      INSTRUMENT,
      TYPE,
      VISIBLE,
      INVISIBLE
      };
 
//---------------------------------------------------------
//   @@ StaffState
//---------------------------------------------------------
 
class StaffState : public Element {
      Q_GADGET
 
      StaffStateType _staffStateType;
      qreal lw;
      QPainterPath path;
 
      Instrument* _instrument;
 
      virtual void draw(QPainter*) const;
      virtual void layout();
 
   public:
      StaffState(Score*);
      StaffState(const StaffState&);
      ~StaffState();
 
      virtual StaffState* clone() const  { return new StaffState(*this); }
      virtual ElementType type() const { return ElementType::STAFF_STATE; }
 
      void setStaffStateType(const QString&);
      void setStaffStateType(StaffStateType st) { _staffStateType = st; }
      StaffStateType staffStateType() const     { return _staffStateType; }
      QString staffStateTypeName() const;
 
      virtual bool acceptDrop(EditData&) const override;
      virtual Element* drop(EditData&);
      virtual void write(XmlWriter&) const;
      virtual void read(XmlReader&);
      Instrument* instrument() const           { return _instrument; }
      void setInstrument(const Instrument* i)  { *_instrument = *i;    }
      void setInstrument(const Instrument&& i) { *_instrument = i;    }
      Segment* segment()                       { return (Segment*)parent(); }
      };
 
 
}     // namespace Ms
#endif

V690 The 'StaffState' class implements a copy constructor, but lacks the '=' operator. It is dangerous to use such a class.