Blender Git Loki

Solve context issues when tweaking operator settings from top-bar

E.g. editing settings after transforming in 3D View would print
warnings, or in Movie Clip Editor wouldn't work at all.

We now store the area & region an operator was executed in and restore
it temporarily when redoing.
Ideally operators wouldn't depend on screen context for event-less
execution (exec callback), but we're far from that.