Hi Petr, yes this is a problem.

The way I have been planning to solve it is with:

4) Perform the fillet calculation in the background and automatically cancel it and start a new calculation if a new radius has been entered.

Which has the only problem that it is quite difficult to achieve... :) However, I have been planning on this since there really needs to be a way to cancel long operations in general anyway even separate from this particular issue.

I've tried really hard not to have things like "preview" buttons, I really prefer to just do the preview automatically.

- Michael