True! I know some of the people involved in the windows update bar. Since cpu and dusk are so different across devices it’s hard to know actual time it will take. Instead teams divided their packages into theoretical weights and the progress bar showed the percent of total “weights”. That’s why it can be choppy is packages with few subdivisions have little to interpolate.
With a process that happens on regular intervals like a Windows Update, I always wondered why the system doesn't store metrics on how long the process has historically taken on previous runs, and then just uses a weighted average of historical times as a time-based total estimate, converted into a divisor for work-based progress estimates (i.e. if previous runs took 60 minutes on average, then progress at 25% would say "45 minutes remaining", then if it suddenly jumped to 50% would immediately say "30 minutes remaining." Even if they're choppy, those time estimates would actually be correct if you sampled and averaged them.)
Not sure if anyone's mentioned this yet, but the old original Mac OSX boot screen had a progress bar that was based on the exact length of the previous boot time.
Progress indicators that moving perfectly and steadily are probably time based, but I'd have thought they've always been work based. Example: you know you have to copy 20GB across the network; update the progress bar with 'percent of data complete' periodically (on a timer, in the byte copying loop, whatever.)
I've seen dual progress bars: one for "overall progress" (each one of five tasks fills this bar 20%) and one for the current task (maybe downloading, maybe unpacking, maybe copying, maybe waiting for hardware to reply...)
I've written progress bars that combine all of the above. Each sub-task had a weight though, and adaptive interpolation was used to animate the progress bar between chunky updates from less granular tasks based on how far they usually increment over which time interval.
