show confirmation message and block screen before leave(close or loose focus) main window[SOLVED]

[Giorgi]

I want to show confirmation messagebox and block the screen before user leaves(alt + tab (close or loose focus) ) MainWindow. how to do this?

here is my code

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QMainWindow::showFullScreen();
    this->installEventFilter(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

bool MainWindow::eventFilter(QObject *obj, QEvent *event){
    if(event->type() == 128){
        QMessageBox::information(this, "title", "text", QMessageBox::Ok | QMessageBox::Cancel);

        return true;
    }

    return true;
}

[Hamed]

if you have QMainWindow you can subclass closeEvent
if you have QDialog then you should subclass reject

QMainWindow example :

void MainWindow::closeEvent (QCloseEvent *event)
{
    QMessageBox::StandardButton resBtn = 
    QMessageBox::question( this, APP_NAME,tr("You sure?\n"),
    QMessageBox::Cancel | QMessageBox::No | QMessageBox::Yes,
    QMessageBox::Yes);
    if (resBtn != QMessageBox::Yes)
    {
        event->ignore();
    } 
   else
    {
        event->accept();
    }
}

QDialog example :

void MyDialog::reject()
{
    QMessageBox::StandardButton resBtn = QMessageBox::Yes;
    if (changes)
    {
        resBtn = QMessageBox::question( this, APP_NAME,
                 tr("You sure?\n"),
                 QMessageBox::Cancel | QMessageBox::No |
                 QMessageBox::Yes, QMessageBox::Yes);
    }
    if (resBtn == QMessageBox::Yes) 
   {
        QDialog::reject();
    }
}

[Giorgi]

Thank you for reply. I also used

this->setWindowFlags(Qt::WindowStaysOnTopHint);

and

QMainWindow::showFullScreen();

to stay my confirmation message on top. that was my goal.