I have experience with Barcode reader and I must say that the barcode reader itself has nothing to do with Qt. Actually you should handle the events the barcode sends..the bardcode behaives just like the keyboard. So if u have QLineEdit object and put the focus in it, then plug the barcode in the computer and read some barcode, the code will be written in the QLineEdit object...then tell the LineEdit textChanged(const QString&) method what SLOT() to connect with...

Simple easy and cool

P.S.
The Barcode Reader is not OS depended, it should work even in the BIOS system...