Barcodes are detected by catching keypresses. When a keypress is not
part of a barcode, it is 'released' by forging a keypress event.
For security reasons, a non-native keypress doesn't trigger the native
input mechanism. So in order to make both barcode-scanning and manual
keypresses work in a field, it is necessary to have a handler listen
to the 'false' keypresses and simulate the native input behaviour.
Arthur Maniet