Question

The question is very simple. Is it possible to show QDialog or QMessageBox without creating a tab in the task bar for it? I tried using exec(), show(), changing value of modal, but the tab is always on.

Answer 1

You need to specify parent window for the QMessageBox:

QApplication a(argc, argv);
qt_test_dialog w;
w.show();
// with additional button
// QMessageBox box(QMessageBox::Information, "Title", "Hello there!", QMessageBox::Ok);

// without additional button!
QMessageBox box(QMessageBox::Information, "Title", "Hello there!", QMessageBox::Ok, &w);

Or simply:

QMessageBox box(&w);
box.setText("Hello");
box.exec();

Note that parent parameter can even be empty QWidget:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    // plain wrong (you will not be able to exit application) - but it demonstrates 
    // the case
    QMessageBox box(new QWidget());
    box.setText("Hello");
    box.exec();
    return a.exec();
}