QFileDialog::getFileName how to set default extension?

[Talei]

I get now what You want to do.
So You need to do an extra work to get this to work the way you want it to.
First:

QFileDialog *fileDialog = new QFileDialog;
   fileDialog->setFileMode( QFileDialog::AnyFile );
 
   fileDialog->open( this, SLOT(slotSel(QString)) );

QFileDialog *fileDialog = new QFileDialog;
   fileDialog->setFileMode( QFileDialog::AnyFile );

   fileDialog->open( this, SLOT(slotSel(QString)) );

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then declare slot i.e. slotSel(QString). This will bring a QT FileDialog, not the SYSTEM!.
When You type i.e. 1 full path will be returned in slot
i.e.:

void MainWindow::slotSel( QString fileNameAndPath)
{
    qDebug() << fileNameAndPath;
}

void MainWindow::slotSel( QString fileNameAndPath)
{
    qDebug() << fileNameAndPath;
}

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And here You can do whatever You want with the string path.