delayed mask

package  {

    import flash.display.*;
    import flash.events.*;
    import flash.geom.Rectangle;
    import flash.geom.Matrix;


    public class DelayedMask extends MovieClip {

        var maskDisplay:Bitmap;
        var maskRenderers:Vector.<BitmapData>;
        var maskRenderIndex:uint;
        const maskRenderCount:uint=2;

        public var guy_mc:DisplayObject;
        public var content_mc:DisplayObject;

        public function DelayedMask() {
            maskRenderers=new Vector.<BitmapData>();

            for(var i:uint=0;i<maskRenderCount;++i) {
                var maskRenderer:BitmapData=new BitmapData(guy_mc.width,guy_mc.height,true);
                maskRenderers[i]=maskRenderer;
            }

            maskDisplay=new Bitmap();
            addChild(maskDisplay);

            //guy_mc.visible=false;
            maskDisplay.mask=guy_mc;

            stage.addEventListener(MouseEvent.MOUSE_MOVE,mMove);
            addEventListener(Event.EXIT_FRAME,updateMask);
        }

        private function mMove(e:MouseEvent):void {
            guy_mc.x=mouseX;
            guy_mc.y=mouseY;
        }

        private function updateMask(e:Event):void {

            var maskRenderer:BitmapData=maskRenderers[maskRenderIndex];

            maskRenderer.lock();
            maskRenderer.fillRect(new Rectangle(0,0,guy_mc.width,guy_mc.height),0x00FF00FF);

            var transform:Matrix=content_mc.transform.matrix;
            var transform2:Matrix=guy_mc.transform.matrix;
            transform2.invert();
            transform.concat(transform2);

            maskRenderer.draw(content_mc,transform);

            maskRenderer.unlock();


            maskRenderIndex=(maskRenderIndex+1)%maskRenderCount;

            maskDisplay.bitmapData=maskRenderers[maskRenderIndex];
            maskDisplay.x=guy_mc.x;
            maskDisplay.y=guy_mc.y;
        }
    }

}