Flex :: Canvas - Change Scale Without Changing Size?

I'm developing a Zoom tool in my Flex App, so I'm using scaleX and scaleY property to simulate this behaviour.But when I scale my Canvas, its size change as well (obviously). The problem is that I have this Canvas inside another Canvas, so the first Canvas can't be smaller than the second one.Here is an image before and after apply zoom changing scale property in both axis:At the left, the original Canvas. At the right, Canvas after update its scale (red rectangle is the original size at 1:1, and green is after resize).I need to extend the Canvas to take up the red rectangle (not the green).