In flex, if you using Mouse move event to redraw anything .. You might have experienced very slow rendering . 
eg:
 this.addEventListener(MouseEvent.MOUSE_MOVE, redraw);
and
    public function redraw(anything:Object=null):void{
            //draw something here
                this.graphics.clear();
                this.graphics.lineStyle(3, 0x000000);
                this.graphics.moveTo(startPoint.x, startPoint.y);
                this.graphics.lineTo(endPoint.x, endPoint.y);
                this.scaleTextInput.x = centerPoint.x;
                this.scaleTextInput.y = centerPoint.y;
            
        }
The Above code results very slow rendering ... 
Solution:
Use Event.ENTER_FRAME event instead? Although more resource intensive than the mouse move event, you should receive considerably more updates per second, allowing the mouse to appear more responsive to the user:
Eg:
this.addEventListener(Event.ENTER_FRAME, redraw);   instead of 
this.addEventListener(MouseEvent.MOUSE_MOVE, redraw);
and You are good to go ..Happy Flexing