I kinda wonder if it'd be possible to actually record data on the operations used, and then incrementally use that to inform future loading bars. I guess it'd have trouble if future runs are going to execute on different hardware, but at least on consoles, it could use some sort of learning algorithm to say "30 seconds of 40 finished".

To be fair, I just now realized there's issues like disk fragmentation if someone is on a PS4/XB1...

Is that It’s an asynchronous operation and you need to send messages in the form of events back to the UI thread. But it’s difficult to predict how much of the total percentage of progress you just finished in the small part it’s doing, since every part is doing something different or longer-taking. So it’ll jump and won’t be steady. Or, you make a fake one that goes steady and shows down at the end, or something similar. So, fake. :)

I’m sorry to burst your bubble 😅.

Rather than try to explain it myself, here’s a post from someone else that does a decent job: https://www.maketecheasier.com/how-progress-bars-work/

Consider this scenario: I ask you how long it would take you to go to the shops and buy a carton of milk.

You could probably give me a good estimate based on your previous experience going to the shop and buying a carton of milk, but to actually tell me how long it would take would need you to go do the thing then come back and tell me.

Even with your estimation, something could always go wrong and cause your trip to take longer than expected. Maybe there was a traffic jam, maybe the shops are sold out of milk, maybe you get mugged along the way.

Loading bars are the same thing. There’s no way to definitively say how long something will take without doing the thing and seeing how long it DID take. The best you can do it an estimation based on known factors (eg. how long does this thing usually take). So in that sense loading bars are fake