void MainWindow::convert()
{
    emit this->started();

    QtConcurrent::run([&]{
        QElapsedTimer t;
        t.start();
        Book currentBook;
        for(int i = 0; i < ui->listWidget->count(); ++i)
        {
            currentBook.setSource(ui->listWidget->item(i)->text());
            currentBook.convert();
            emit completed((i*100)/ui->listWidget->count());
        }
        qDebug()<<t.nsecsElapsed();
        emit this->finished();
    });

}