More like this. You must test for the objects you're installing the filter for.
Qt Code: 
  1. bool MWin::eventFilter(QObject* object, QEvent* event) {
  2.           if(event->type() == QEvent::ContextMenu && 
  3.            ( object == fileToolbar || object == modeToolBar ... ) ) {
  4.               QContextMenuEvent* mevent = static_cast<QContextMenuEvent *>(event);
  5.               if(mevent->reason() == QContextMenuEvent::Mouse) {
  6.                   qDebug("I have blocked the context menu.");
  7.                   return true;
  8.               } else 
  9.                  return false;
  10.           }
  11.           else 
  12.                 return QObject::eventFilter(object, event);
  13.       }
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Regards