Hi Michael, I have been planning on doing something in this area for a while, I just haven't been able to quite get around to finishing it yet.

But I'm planning on doing something a lot more automatic - if it is taking too long to calculate a history update, I'll just cancel it automatically, except it will wait to finish the last one when you have completed an action (like let up on the mouse when dragging a control point).

I'll see if I can finish up this area.

- Michael