scrollRect : easy 'masking'

Before Flash 8, if you wanted to create a window with scrollable content, you'd have to mask the content. I always felt a little uncomfortable using this approach.
In Flash 8 you can use the new movieclip.scrollRect property.
There is an easy copy/paste example in the help files, but this is what it comes down to :

import flash.geom.Rectangle;
var container:MovieClip = mclip;
var window:Rectangle = new Rectangle(100, 0, 200, 40);
container.scrollRect = window;

mclip in this example is my 'content' movieclip in my scene. By using .scrollRect, mclip will be 'masked' according to the Rectangle properties.

Nice and clean...