title: What is the invalidateProperties(), invalidateSize() and invalidateDisplayList() functions did while extending a component in adobe flex/air?
body: <p>What <code>invalidateProperties()</code>, <code>invalidateSize()</code> and <code>invalidateDisplayList()</code> methods are did when extending a component in adobe flex/air ?. </p>
  
  <p>And why these are necessary?</p>