xz already supports Progress man
any program you see <stdin> <stdout> shows correct progress
you probably made a mistake somewhere :/
xz is lzma2 and nothing else, how lzma normally supports stdout likewise xz does as well
Every feature that lzma1 has is inheritage to lzma2 as well ....
check your problem and post again
Edit: try packing a 10 GB game using srep and xz and NOTHING else, then run WPI progress bar will show normally
