ReduceMesh: Pan and Zoom when calculating

Hi @piac

In R8, when calculating a reducing mesh, we were able to move the viewport, but in R9, you cannot pan/move while calculating.

Thanks

Thanks @RedAlert

I moved this to a new topic, your report definitely deserves it.

Also, making it a YT issue to hopefully fix very soon: RH-100173. Hopefully we can also keep the entire speed improvement.