We have here in Austria a RKSV means cash register security regulation, so we need to sign the whole slip with a signature card-reader (yes sounds complicated, IT IS)... make a string for example:
R1-AT1_KASSA2_4_2023-04-28T07:18:00_0,00_0,00_0,00_0,00_0,00_XUosycfuEbwJPw5woi2nkA==_79D71B3B_OE/hT831XQs=_AGBaEF40lOR07UWsvLlBxwcgibQdXzNNFW3Ckr5+J53+qns1JplTxlTnSXy90wgPGBmIftDU6KIhHzqNOG6z+w== store this as a QR-Code...
I found a help site of WinDev:
[
doc.windev.com]
Maybe this can help you?