Under C7 I used to have a handy bit of code that used my webcam to read barcodes and QR codes. It just generated the strings, I don’t think it passed them to Firefox, but I’m happy with that. I’ve looked at zbar, but it is version 0.10 and appears to have been unmaintained for over 10 years. I did have a go at running
./configure but after multiple complaints of missing packages that were there I’ve given up with it.