Currently, the abort mechanism is designed to function only within a single thread when the abort flag is set by an observer of the progress event. This severely limits the usefulness of the functionality as evidenced by the fact that it is rarely used (which must be the case as it has many bugs that no one reports on). Our goal is to redesign how VTK algorithms are interrupted (aborted) in a way that is friendly to multi-threaded execution.
A more in-depth explanation of the design and an example are located here.
Please share your comments if you have any questions, concerns, and improvements about this design.