title: Set height of combobox programmatically in Flex 4
body: <p>I'm working on a Flex 4 combo box which has a Tree ItemRenderer, and I want to set the height for this combo box programmatically based on data (i.e: based on xml data).</p>
  
  <p>Thank to Peter deHaan at <a href="http://blog.flexexamples.com/2008/07/04/creating-a-variable-row-height-item-renderer-on-a-combobox-control-in-flex/" rel="nofollow">http://blog.flexexamples.com/2008/07/04/creating-a-variable-row-height-item-renderer-on-a-combobox-control-in-flex/</a>, I can set height for Tree ItemRenderer and Combo box in normal case, but when horizontal scroll bar is shown, the layout will be not good. (I have to set horizontalScrollPolicy to 'auto' because as Tree ItemRenderer can be expanded when XML data having multiple level.)</p>
  
  <p>My question is: how to know whether horizontal scroll bar of Combo box is shown or not? </p>