[thefaux]

I agree that this is not an easy problem. I have written a status bar for a fairly widely used open source build tool in java. I hijacked System.out and System.err globally and added all writes to a queue that I line buffered and interleaved progress bars at the bottom. There was no noticeable performance degradation relative to not having the progress bar since all the queue management was handled on a background thread. I would characterize the volume of output as medium. The tool is chatty compared to some, but we aren't talking about managing massive amounts of data coming in.

At some point though, I stopped working on this tool because it and the compiler it was primarily used for were way too slow and started focusing on compiler design. I am currently working on a compiler that is self hosted and compiles itself in 1 second but I expect to get that down to under 100ms.

You don't need progress bars when your build is that fast.

I was undeniably rude in my initial post, but I also want to challenge you to be even better as a programmer. I had to write many compilers before I figured out how to self host as quickly as I now can. That is the advantage of working in isolation. I have thrown out more working compilers than all but a handful of people have written. My language is not public because I am still iterating but I wrote the bootstrap compiler in about 10 days of 4-5 hours per day and the self-hosted compiler took about 3 more weeks on top of that. It is ~4200 lines of code in itself. The next version will likely be fewer.