Managing the escape key to quit a program - c++

Question

I don't know how to implement the managing of the escape key to quit the program. I don't know either where to put it in my code, because if I put it in a method, how can it quit anywhere?
This is my actual code :
#include <iostream>
#include <QApplication>
#include <QPushButton>
#include <QLineEdit>
#include <QFormLayout>
#include <QDebug>
#include "LibQt.hpp"
LibQt::LibQt() : QWidget()
{
this->size_x = 500;
this->size_y = 500;
QWidget::setWindowTitle("The Plazza");
setFixedSize(this->size_x, this->size_y);
manageOrder();
}
LibQt::~LibQt()
{
}
void LibQt::manageOrder()
{
this->testline = new QLineEdit;
this->m_button = new QPushButton("Send Order");
QFormLayout *converLayout = new QFormLayout;
this->m_button->setCursor(Qt::PointingHandCursor);
this->m_button->setFont(QFont("Comic Sans MS", 14));
converLayout->addRow("Order : ", this->testline);
converLayout->addWidget(this->m_button);
this->setLayout(converLayout);
QObject::connect(m_button, SIGNAL(clicked()), this, SLOT(ClearAndGetTxt()));
}
std::string LibQt::ClearAndGetTxt()
{
QString txt = this->testline->text();
this->usertxt = txt.toStdString();
std::cout << this->usertxt << std::endl;
this->testline->clear();
return (this->usertxt);
}
std::string LibQt::getUsertxt()
{
return (this->usertxt);
}
and this is my .hpp
#ifndef _LIBQT_HPP_
#define _LIBQT_HPP_
#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLineEdit>
#include <QKeyEvent>
#include <QCheckBox>
#include <QPlainTextEdit>
class LibQt : public QWidget
{
Q_OBJECT
public:
LibQt();
~LibQt();
void manageOrder();
std::string getUsertxt();
public slots:
std::string ClearAndGetTxt();
protected:
int size_x;
int size_y;
QPushButton *m_button;
QLineEdit *testline;
std::string usertxt;
};
#endif /* _LIBQT_HPP_ */

Answer 1

You need to override the method void QWidget::keyPressEvent(QKeyEvent *event). It will look like this for you :
void LibQt::keyPressEvent(QKeyEvent* event)
{
if(event->key() == Qt::Key_Escape)
{
QCoreApplication::quit();
}
else
QWidget::keyPressEvent(event)
}

Answer 2

I know you solved this issue, and my solution is in Python, but other people may find this useful. Essentially, you can implement this feature as an action:
w = LibQt() # QWidget().
escape = QAction('Escape', w)
escape.setShortcut(QKeySequence('Esc'))
escape.setShortcutContext(Qt.WidgetWithChildrenShortcut) # acts as an event filter.
escape.triggered.connect(w.close)
w.addAction(escape)
Obviously, with first line removed, this code may be added to class constructor.