WaitOrbusyDialog not updating corrcetly even after process events

[anbu01]

Hi,
I did a sample test for learning thread.I have the follwoing code but for saome reson the wait or busy dialog does not run properly.I have attached a video where you can see dialog initialize hangs https://youtu.be/mjpnrLUx1VI.Here is the sample code:-

Main Window.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow),m_count(0)
{
    ui->setupUi(this);
 
    QThread* thread = new QThread;
    Worker* worker = new Worker();
    m_dialog = new WaitOrBusyDialog;         //A custom class to busy dialog
 
    worker->moveToThread(thread);
    connect(worker, SIGNAL(error(QString)), this, SLOT(errorString(QString)),Qt::QueuedConnection);
    connect(thread, SIGNAL(started()), worker, SLOT(process()),Qt::QueuedConnection);
    connect(worker,SIGNAL(showDialog()),this,SLOT(onDi  alog()),Qt::QueuedConnection);
    connect(worker, SIGNAL(finished()), thread, SLOT(quit()),Qt::QueuedConnection);
    connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()),Qt::QueuedConnection);
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()),Qt::QueuedConnection);
    thread->start();
 
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::onDialog()
{
    m_dialog->show();
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow),m_count(0)
{
    ui->setupUi(this);

    QThread* thread = new QThread;
    Worker* worker = new Worker();
    m_dialog = new WaitOrBusyDialog;         //A custom class to busy dialog

    worker->moveToThread(thread);
    connect(worker, SIGNAL(error(QString)), this, SLOT(errorString(QString)),Qt::QueuedConnection);
    connect(thread, SIGNAL(started()), worker, SLOT(process()),Qt::QueuedConnection);
    connect(worker,SIGNAL(showDialog()),this,SLOT(onDi  alog()),Qt::QueuedConnection);
    connect(worker, SIGNAL(finished()), thread, SLOT(quit()),Qt::QueuedConnection);
    connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()),Qt::QueuedConnection);
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()),Qt::QueuedConnection);
    thread->start();

}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::onDialog()
{
    m_dialog->show();
}

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WorkerThread.cpp

void Worker::process() {
    qApp->processEvents();
    int i=0;
    emit showDialog();
    while(i<10000)
    {
        qApp->processEvents();
        qDebug("Hello World!");
        i++;
    }
    emit finished();
}

void Worker::process() {
    qApp->processEvents();
    int i=0;
    emit showDialog();
    while(i<10000)
    {
        qApp->processEvents();
        qDebug("Hello World!");
        i++;
    }
    emit finished();
}

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This is just a sample code to know simultanoeusly backgroud (debug output) and ui foreground process.The problem is why initially dialog hangs.

[anda_skoa]

Don't call qApp->processEvents() in the worker.
It runs in a different thread than the main event loop.

There is also no need to call processEvent(), the main thread doesn't do anything other then event processing.

Cheers,
_

[anbu01]

@anda
After ignoring processevent still the dialog hangs.

[anda_skoa]

Maybe something else blocking the main thread.

Have you tried without starting the thread, e.g. just calling onDialog() using QTimer::singleShot()?

Cheers,
_