[WorldMaker]

I played with the idea of using a singular circular progress bar for composite progress notification. The basic idea was that if you keep the tail chasing the head, and the head always moving clockwise, the progress bar never gives the impression that it "shrinks backwards", it is always forward motion, but in the worst case when the tail catches up with the head (you discover more sub-tasks) it basically becomes a spinner until the tail starts to lag the head again. Tuning the animation parameters for that provided a lot of options to get a good feeling progress bar that reported a heterogeneous source of various tasks, some of which discovered/added while in progress of the overall whole.

My demo has unfortunately fallen to web bit rot and needs to be updated, but the code is here to explore: https://github.com/worldmaker/compradprog