Problem with curl writefunction

[januszmk]

Hello.
I have little problem.
I have functions:

size_t WriteData(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written;
    written = fwrite(ptr, size, nmemb, stream);
    return written;
}
int MainWindow::progress_func(void* ptr, double TotalToDownload, double NowDownloaded, double TotalToUpload, double NowUploaded)
{
    ui->progressBar->setMaximum(TotalToDownload);
    ui->progressBar->setValue(NowDownloaded);
    double speed;
    curl_easy_getinfo(curl, CURLINFO_SPEED_DOWNLOAD, &speed);
    ui->label_2->setText(QString("Prędkość: %0").arg(speed));
    return NowDownloaded;
}
bool MainWindow::downloadFile(QString url, QString filename)
{
    FILE *fp;
    fp = fopen(filename.toStdString().c_str(), "wb");
    ui->label->setText(filename);
    ui->label_2->setText("Predkosc: 0 KB/s");
    curl = curl_easy_init();
    curl_easy_setopt(curl, CURLOPT_AUTOREFERER, 1);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "User-Agent: Mozilla/5.0 (compatible;)");
    curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "cookie");
    curl_easy_setopt(curl, CURLOPT_COOKIEJAR, "cookie");
    curl_easy_setopt(curl, CURLOPT_HEADER, 1);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteData);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
    curl_easy_setopt(curl, CURLOPT_HTTPGET, 1);
    curl_easy_setopt(curl, CURLOPT_URL, url.toStdString().c_str());
    curl_easy_setopt(curl, CURLOPT_NOPROGRESS, FALSE);
    curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, &MainWindow::progress_func);
    curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, this);
    status = curl_easy_perform(curl);
    if(status !=0)
        qDebug() << QString("curl_easy_perform() error: %0").arg(curl_easy_strerror(status));
    curl_easy_cleanup(curl);
    fclose(fp);
    return true;
}

size_t WriteData(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written;
    written = fwrite(ptr, size, nmemb, stream);
    return written;
}
int MainWindow::progress_func(void* ptr, double TotalToDownload, double NowDownloaded, double TotalToUpload, double NowUploaded)
{
    ui->progressBar->setMaximum(TotalToDownload);
    ui->progressBar->setValue(NowDownloaded);
    double speed;
    curl_easy_getinfo(curl, CURLINFO_SPEED_DOWNLOAD, &speed);
    ui->label_2->setText(QString("Prędkość: %0").arg(speed));
    return NowDownloaded;
}
bool MainWindow::downloadFile(QString url, QString filename)
{
    FILE *fp;
    fp = fopen(filename.toStdString().c_str(), "wb");
    ui->label->setText(filename);
    ui->label_2->setText("Predkosc: 0 KB/s");
    curl = curl_easy_init();
    curl_easy_setopt(curl, CURLOPT_AUTOREFERER, 1);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "User-Agent: Mozilla/5.0 (compatible;)");
    curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "cookie");
    curl_easy_setopt(curl, CURLOPT_COOKIEJAR, "cookie");
    curl_easy_setopt(curl, CURLOPT_HEADER, 1);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteData);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
    curl_easy_setopt(curl, CURLOPT_HTTPGET, 1);
    curl_easy_setopt(curl, CURLOPT_URL, url.toStdString().c_str());
    curl_easy_setopt(curl, CURLOPT_NOPROGRESS, FALSE);
    curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, &MainWindow::progress_func);
    curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, this);
    status = curl_easy_perform(curl);
    if(status !=0)
        qDebug() << QString("curl_easy_perform() error: %0").arg(curl_easy_strerror(status));
    curl_easy_cleanup(curl);
    fclose(fp);
    return true;
}

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When I try to download a file, window of my aplication is frozen(?) until downloading is not finished.
Could you suggest what could I do to make this work?
Sory for my bad english
Janusz