package {
    import flash.display.Shape;
    import flash.events.*;
  
    public class @ax-actionscript-misc-Ellipse extends Shape {
      private var w:Number;
      private var h:Number;
      private var changed:Boolean;
      
      public function @ax-actionscript-misc-Ellipse (width:Number, height:Number) {
        // Register for notification when this 
        // object is added to, or removed from, the display list
        var stageDetector:StageDetector = new StageDetector(this);
        stageDetector.addEventListener(StageDetector.ADDED_TO_STAGE, 
                                       addedToStageListener);
        stageDetector.addEventListener(StageDetector.REMOVED_FROM_STAGE,
                                       removedFromStageListener);
  
        // Set the width and height
        w = width;
        h = height;
        
        // Note that the object has changed
        setChanged();
      }
  
      public function setWidth (newWidth:Number):void {
        w = newWidth;
        setChanged();
      }
  
      public function getWidth ():Number {
        return w;
      }
  
      public function setHeight (newHeight:Number):void {
        h = newHeight;
        setChanged();
      }
  
      public function getHeight ():Number {
        return h;
      }
  
      // Notes that something about this shape has changed
      private function setChanged ():void {
        changed = true;
        if (stage != null) {
          stage.invalidate();
        }
      }
  
      // Notes that the most recent changes have been rendered
      private function clearChanged ():void {
        changed = false;
      }
      
      // Indicates whether or not there are changes to this shape
      // that have not yet been rendered
      private function hasChanged ():Boolean {
        return changed;
      }
  
      // Event listener triggered when this shape is added to the display list
      private function addedToStageListener (e:Event):void {
        // Register to be notified of screen updates
        stage.addEventListener(Event.RENDER, renderListener);
  
        // If the object was changed while off the display list, 
        // draw those changes at the next render opportunity. But if the 
        // object hasn't changed since the last time it was on the display 
        // list, then there's no need to draw it.
        if (hasChanged()) {
          stage.invalidate();
        }
      }
  
      // Event listener triggered when this shape 
      // is removed from the display list
      private function removedFromStageListener (e:Event):void {
        // No need to receive screen-update events when the object isn't
        // on the display list
        stage.removeEventListener(Event.RENDER, renderListener);
      }
  
      // Event listener triggered when the screen is about to be updated and
      // stage.invalidate() has been called.
      private function renderListener (e:Event):void {
        // Call draw if there are unrendered changes to this shape.
        // If another object triggers a render event, but this object hasn't
        // changed, then this object won't be redrawn.
        if (hasChanged()) {
          draw();
        }
      }  
  
      private function draw ():void {
        graphics.clear();
        graphics.lineStyle(1);
        graphics.beginFill(0xFFFFFF, 1);
        graphics.draw@ax-actionscript-misc-Ellipse(0, 0, w, h);
      }
    }
  }