QProgressDialog在initializeGL期间不绘制

Question

I'm using a QProgressDialog to display the progress of my initializeGL() function but the little window show up unpainted... Here's the simplified code :

QProgressDialog barTest("Wait","Ok", 0, 100, this);

barTest.move(400,400);

barTest.show();

for(int i = 0; i < 100; i++)
{
    barTest.setValue(i);
    qDebug() << i;
}

I'm running Mac OS 10.8

Answer 1

The problem is that the paint event for the window is stuck in Qt's Event Loop as long as you are executing code (eg the for loop).

If you want the paint events to be processed, you can use QApplication::processEvents :

for(int i = 0; i < 100; i++)
{
    barTest.setValue(i);
    qDebug() << i;

    // handle repaints (but also any other event in the queue)
    QApplication::processEvents();
}

Dependent on the quickness of the loop you might find it sufficient to update only each 10% for instance:

for(int i = 0; i < 100; i++)
{
    barTest.setValue(i);
    qDebug() << i;

    // handle repaints (but also any other event in the queue)
    if(i % 10 == 0) QApplication::processEvents();
}