Restrict QFileDialog to one specific directory

[spikey]

Hi,
how can I restrict the Qt file dialog to only show the files in the given directory (/usr/app/images) and that navigating out of that directory is not possible? (I do not want the user to see any directory navigation possibilities)

const QString IMAGE_DIR="/usr/app/images";
...
QString fileName = QFileDialog::getOpenFileName(
			this,
			trUtf8("Choose a Picture"),
			IMAGE_DIR,
			trUtf8("Cool Picture (*.png)")
			);

const QString IMAGE_DIR="/usr/app/images";
...
QString fileName = QFileDialog::getOpenFileName(
			this,
			trUtf8("Choose a Picture"),
			IMAGE_DIR,
			trUtf8("Cool Picture (*.png)")
			);

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Thank you for a hint.

Spikey