Looked into this a bit. We could replace this use of urllib which is synchronous with a callback, with use of [QNetworkAccessManager ](https://doc.qt.io/qt-5/qnetworkaccessmanager.html) so it would be tied into the event loop.

Probably putting an async instance variable to SampleDataLogic that defaults to false would be the best for backwards compatibility. Probably the logic should also keep the QNetworkAccessManager as an instance variable so that users of the class could connect to its signals.

The original mantis issue calls out the TCIA browser, so maybe the best approach is not to do anything generic in SampleData where it would require a lot of logic changes and instead encourage the use of QNetworkAccessManager in places where networking and progress bars are needed.

Note it's also possible to use the qSlicerWebWidget to initiate the download and then get the signal for progress and when the download completes.