The interface for DemoSurface's that wish to animate.
Copyright (c) Xoetrope Ltd., 2001-2006, This software is licensed under
the GNU Public License (GPL), please see license.txt for more details. If
you make commercial use of this software you must purchase a commercial
license from Xoetrope.
Adjust the settings for the next step.
Parameters: w - the width Parameters: h - the height Parameters: at - the animation thread on which this object is running