void MainWindow::painting(int mode) {
    if (mode == 1) {
        scene = new QGraphicsScene;
        //scene->setSceneRect();
        ui->graphicsView->setScene(scene);
        //scene->addLine(scene->width()/, 0, 100, 250, QPen(QBrush(Qt::black),1));
        int t_curr = 0, v_curr = -scene->height();
        int t2 = 0, v2 = -scene->height();
        while (t_curr < t_nagr/2 || v_curr < v_max) {
            int cnt = cnt_steps/2;
            int delta = 0;
            if (cnt % 2 == 1)
                v2 = v_curr + step_size;
            else
                t2 = t_curr + t_upd;
            scene->addLine(t_curr, v_curr - scene->height(), t2, v2 - scene->height(), QPen(QBrush(Qt::black),1));
            t_curr = t2;
            v_curr = v2;

        }