now with window closing confirmation

mainwindow.cpp

@@ -8,6 +8,23 @@ MainWindow::MainWindow(QWidget *parent) :
     ui->setupUi(this);
 }
 
+void MainWindow::closeEvent(QCloseEvent *event)
+{
+    const QMessageBox::StandardButton ret
+        = QMessageBox::warning(this, tr("Application"),
+                               tr("something-something-close?"),
+                               QMessageBox::Yes | QMessageBox::No);
+    switch (ret) {
+    case QMessageBox::Yes:
+        event->accept();
+        break;
+    case QMessageBox::No:
+    default:
+        event->ignore();
+        break;
+    }
+}
+
 MainWindow::~MainWindow()
 {
     delete ui;