Beware weaving progress bar code into computationally heavy routines. As soon as you want to start multithreading, it gets tricky. The worst is a ProgressBar si

Beware weaving progress bar code into computationally heavy routines. As soon as you want to start multithreading, it gets tricky. The worst is a ProgressBar singleton in a big C++ GUI program. If I'm going to bother using a library for progress bars, I want it to deal with all those work of combining multiple threads' progress, i.e. it has a queue, knows each thread's estimated share of the total work, and all the threads push progress messages on the queue.