Setting the pop up placement on a Spark DropDownList in Flex 4

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/16/setting-the-pop-up-placement-on-a-spark-dropdownlist-in-flex-gumbo/ -->
<s:Application name="Spark_DropDownList_PopUp_placement_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/halo">
 
    <s:DropDownList id="dropDownList"
            labelField="label"
            requireSelection="true"
            skinClass="skins.CustomDropDownListSkin"
            horizontalCenter="0"
            top="20">
        <s:dataProvider>
            <s:ArrayList>
                <fx:Object label="The" />
                <fx:Object label="Quick" />
                <fx:Object label="Brown" />
                <fx:Object label="Fox" />
                <fx:Object label="Jumps" />
                <fx:Object label="Over" />
                <fx:Object label="The" />
                <fx:Object label="Lazy" />
                <fx:Object label="Dog" />
            </s:ArrayList>
        </s:dataProvider>
    </s:DropDownList>
 
</s:Application>

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/16/setting-the-pop-up-placement-on-a-spark-dropdownlist-in-flex-gumbo/ -->
<s:Skin name="CustomDropDownListSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        alpha.disabled="0.5"> 
    <!-- states -->
    <s:states>
        <s:State name="normal" />
        <s:State name="open" />
        <s:State name="disabled" />
    </s:states>
 
    <!-- host component -->
    <fx:Metadata>
    <![CDATA[ 
        [HostComponent("spark.components.DropDownList")]
    ]]>
    </fx:Metadata> 
 
    <!--- The PopUpAnchor control that opens the drop-down list. -->
    <s:PopUpAnchor id="popUp"  displayPopUp.normal="false" displayPopUp.open="true" includeIn="open"
            left="0" right="0" top="0" bottom="0" itemDestructionPolicy="auto"
            popUpPosition="left" popUpWidthMatchesAnchorWidth="true">
        <!--- The drop down area of the skin. This includes borders, background colors, scrollers, and filters. -->
        <s:Group id="dropDown" maxHeight="134" minHeight="22" >
            <!-- drop shadow -->
            <s:RectangularDropShadow blurX="20" blurY="20" alpha="1.0" distance="5" 
                    angle="90" color="#000000" left="0" top="0" right="0" bottom="0"/>
            <!-- border -->
            <s:Rect left="0" right="0" top="0" bottom="0">
                <s:stroke>
                    <s:SolidColorStroke color="0x686868" weight="1"/>
                </s:stroke>
            </s:Rect>
 
            <!-- fill -->
            <!---  Defines the appearance of drop-down list's background fill. -->
            <s:Rect id="background" left="1" right="1" top="1" bottom="1" >
                <s:fill>
                    <!--- The color of the drop down's background fill. The default color is 0xFFFFFF. -->
                    <s:SolidColor id="bgFill" color="0xFFFFFF" />
                </s:fill>
            </s:Rect>
 
            <s:Scroller left="0" top="0" right="0" bottom="0" focusEnabled="false" minViewportInset="1">
                <!--- The container for the data items in the drop-down list. -->
                <s:DataGroup id="dataGroup" itemRenderer="spark.skins.spark.DefaultItemRenderer">
                    <s:layout>
                        <s:VerticalLayout gap="0" horizontalAlign="contentJustify"/>
                    </s:layout>
                </s:DataGroup>
            </s:Scroller>
        </s:Group>
    </s:PopUpAnchor>
 
    <!--- The anchor button used by the DropDownList. The default skin is DropDownListButtonSkin. -->
    <s:Button id="openButton" left="0" right="0" top="0" bottom="0" focusEnabled="false"
            skinClass="spark.skins.spark.DropDownListButtonSkin" />  
    <!--- The prompt area of the DropDownList. -->
    <s:Label id="labelDisplay" verticalAlign="middle" maxDisplayedLines="1"
            left="7" right="30" top="2" bottom="2" verticalCenter="1" /> 
 
</s:Skin>