[cairo] How to test the gl backend?

[Clemens Eisserer]

> With one top-level X window for the whole tree of widgets, every time you
> scroll that area even by 1 pixel, you're forced to redraw a 400x600 pixel
> area. Is doable on a local system, but hopeless on a slower network.

Wouldn't it possible to do the scrolling with a  cheap (in terms of
traffix) XCopyArea call, and only re-draw the "uncovered" area?

- Clemens