I've run into one of those problems that might not be resolvable, but I'm giving it a shot here to see if anyone has some ideas on what to do.

Objective:
I want to construct my 2D game levels by piecing them together in a giant container, then reduce lag by updating the position of a scrollRect to achieve camera tracking and zoom. Specifically, I want to reduce as much lag as possible by making flash believe that the container is only as big as the scrollRect's surface area.

Problem:
Flash automatically expands the redraw regions to fit the actual size of the container if it extends beyond the scrollRect.

Approaches:
I have tried to use a scrollRect, then setMask, and finally both in tandem. No luck.

I have considered using BitmapData's draw function to force a snapshot of the region I need, but this would probably create more lag rather than less because I'd be storing each frame as an image instead of just rendering in one pass.

Is there any other way?