connect(ui->start_and_show_clock_btn, &QPushButton::clicked, this, &MainWindow::start_and_show_clock_clicked);
connect(ui->stop_clock_btn, &QPushButton::clicked, this, &MainWindow::stop_clock_clicked);
connect(ui->show_clock_btn, &QPushButton::clicked, this, &MainWindow::show_clock_clicked);
connect(ui->start_and_show_clock_btn, &QPushButton::clicked, this, &MainWindow::start_and_show_clock_clicked);
connect(ui->stop_clock_btn, &QPushButton::clicked, this, &MainWindow::stop_clock_clicked);
connect(ui->show_clock_btn, &QPushButton::clicked, this, &MainWindow::show_clock_clicked);