rightclick event in Qt to open a context menu

Question

I have a segment of code that calls a mousePressEvent. I have the left-click output the coordinates of the cursor, and I have rightclick do the same, but I also want to have the rightclick open a context menu. The code I have so far is:

void plotspace::mousePressEvent(QMouseEvent*event) {     double trange = _timeonright - _timeonleft;     int twidth = width();     double tinterval = trange/twidth;      int xclicked = event->x();      _xvaluecoordinate = _timeonleft+tinterval*xclicked;        double fmax = Data.plane(X,0).max();     double fmin = Data.plane(X,0).min();     double fmargin = (fmax-fmin)/40;     int fheight = height();     double finterval = ((fmax-fmin)+4*fmargin)/fheight;      int yclicked = event->y();      _yvaluecoordinate = (fmax+fmargin)-finterval*yclicked;      cout<<"Time(s): "<<_xvaluecoordinate<<endl;     cout<<"Flux: "<<_yvaluecoordinate<<endl;     cout << "timeonleft= " << _timeonleft << "\n";      returncoordinates();      emit updateCoordinates();      if (event->button()==Qt::RightButton)     {             contextmenu->setContextMenuPolicy(Qt::CustomContextMenu);              connect(contextmenu, SIGNAL(customContextMenuRequested(const QPoint&)),             this, SLOT(ShowContextMenu(const QPoint&)));              void A::ShowContextMenu(const QPoint &pos)              {                 QMenu *menu = new QMenu;                 menu->addAction(tr("Remove Data Point"), this,                   SLOT(test_slot()));                  menu->exec(w->mapToGlobal(pos));             }      }     } 

I know that my problem is very fundamental in nature, and that 'contextmenu' is not properly declared. I have pieced together this code from many sources, and do not know how to declare something in c++. Any advice would be greatly appreciated.

Answer 1

customContextMenuRequested is emitted when the widget's contextMenuPolicy is Qt::CustomContextMenu, and the user has requested a context menu on the widget. So in the constructor of your widget you can call setContextMenuPolicy and connect customContextMenuRequested to a slot to make a custom context menu.

In the constructor of plotspace :

this->setContextMenuPolicy(Qt::CustomContextMenu);  connect(this, SIGNAL(customContextMenuRequested(const QPoint &)),          this, SLOT(ShowContextMenu(const QPoint &))); 

ShowContextMenu slot should be a class member of plotspace like :

void plotspace::ShowContextMenu(const QPoint &pos)  {    QMenu contextMenu(tr("Context menu"), this);     QAction action1("Remove Data Point", this);    connect(&action1, SIGNAL(triggered()), this, SLOT(removeDataPoint()));    contextMenu.addAction(&action1);     contextMenu.exec(mapToGlobal(pos)); }