Creating a repeating background fill on a Spark Panel container in Flex 4

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/03/28/creating-a-repeating-background-fill-on-an-fxpanel-container-in-flex-gumbo/ -->
<s:Application name="Spark_Panel_skinClass_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx">
 
    <s:Panel id="panel"
            title="Spark Panel title"
            skinClass="skins.CustomPanelSkin"
            left="20" right="20" top="20" bottom="20">
        <s:RichText id="rchTxt"
                text="The quick brown fox jumps over the lazy dog."
                fontSize="72"
                left="10" right="10"
                top="10" bottom="10" />
    </s:Panel>
 
</s:Application>

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/03/28/creating-a-repeating-background-fill-on-an-fxpanel-container-in-flex-gumbo/ -->
<s:SparkSkin name="CustomPanelSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:fb="http://ns.adobe.com/flashbuilder/2009"
        blendMode="normal"
        mouseEnabled="false"
        minWidth="131" minHeight="127"
        alpha.disabled="0.5" alpha.disabledWithControlBar="0.5">
    <!-- states -->
    <s:states>
        <s:State name="normal" />
        <s:State name="disabled" />
        <s:State name="normalWithControlBar" stateGroups="withControls" />
        <s:State name="disabledWithControlBar" stateGroups="withControls" />
    </s:states>
 
    <fx:Metadata>
        [HostComponent("spark.components.Panel")]
    </fx:Metadata>
 
    <fx:Script fb:purpose="styling">
        <![CDATA[
            /* Define the skin elements that should not be colorized.
            For panel, border and title background are skinned, but the content area and title text are not. */
            static private const exclusions:Array = ["background", "titleDisplay", "contentGroup", "controlBarGroup"];
 
            override public function get colorizeExclusions():Array {
                return exclusions;
            }
 
            override protected function initializationComplete():void {
                useChromeColor = true;
                super.initializationComplete();
            }
 
            override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
                if (getStyle("borderVisible") == true) {
                    border.visible = true;
                    background.left = background.top = background.right = background.bottom = 1;
                    contents.left = contents.top = contents.right = contents.bottom = 1;
                } else {
                    border.visible = false;
                    background.left = background.top = background.right = background.bottom = 0;
                    contents.left = contents.top = contents.right = contents.bottom = 0;
                }
 
                dropShadow.visible = getStyle("dropShadowVisible");
 
                var cr:Number = getStyle("cornerRadius");
                var withControls:Boolean = (currentState == "disabledWithControlBar" || currentState == "normalWithControlBar");
 
                if (cornerRadius != cr) {
                    cornerRadius = cr;
 
                    dropShadow.tlRadius = cornerRadius;
                    dropShadow.trRadius = cornerRadius;
                    dropShadow.blRadius = (withControls) ? cornerRadius : 0;
                    dropShadow.brRadius = (withControls) ? cornerRadius : 0;
 
                    setPartCornerRadii(topMaskRect, withControls);
                    setPartCornerRadii(border, withControls);
                    setPartCornerRadii(background, withControls);
                }
 
                if (bottomMaskRect) {
                    setPartCornerRadii(bottomMaskRect, withControls);
                }
 
                borderStroke.color = getStyle("borderColor");
                borderStroke.alpha = getStyle("borderAlpha");
 
                super.updateDisplayList(unscaledWidth, unscaledHeight);
            }
 
            private function setPartCornerRadii(target:Rect, includeBottom:Boolean):void {
                target.topLeftRadiusX = cornerRadius;
                target.topRightRadiusX = cornerRadius;
                target.bottomLeftRadiusX = includeBottom ? cornerRadius : 0;
                target.bottomRightRadiusX = includeBottom ? cornerRadius : 0;
            }
 
            private var cornerRadius:Number;
        ]]>
    </fx:Script>
 
    <!-- drop shadow can't be hittable so it stays sibling of other graphics -->
    <s:RectangularDropShadow id="dropShadow"
            blurX="20" blurY="20" alpha="0.32" distance="11"
            angle="90" color="#000000"
            left="0" top="0" right="0" bottom="0"/>
 
    <!-- drop shadow can't be hittable so all other graphics go in this group -->
    <s:Group left="0" right="0" top="0" bottom="0">
 
        <!-- top group mask -->
        <s:Group id="topGroupMask"
                left="1" top="1" right="1" bottom="1">
            <s:Rect id="topMaskRect"
                   left="0" top="0" right="0" bottom="0">
                <s:fill>
                    <s:SolidColor alpha="0"/>
                </s:fill>
            </s:Rect>
        </s:Group>
 
        <!-- bottom group mask -->
        <s:Group id="bottomGroupMask"
                left="1" top="1" right="1" bottom="1" 
                includeIn="normalWithControlBar, disabledWithControlBar">
            <s:Rect id="bottomMaskRect" left="0" top="0" right="0" bottom="0">
                <s:fill>
                    <s:SolidColor alpha="0"/>
                </s:fill>
            </s:Rect>
        </s:Group>
 
        <!-- layer 1: border -->
        <s:Rect id="border"
                left="0" right="0" top="0" bottom="0" >
            <s:stroke>
                <s:SolidColorStroke id="borderStroke" weight="1" />
            </s:stroke>
        </s:Rect>
 
        <!-- layer 2: background fill -->
        <!--- Defines the appearance of the PanelSkin class's background. -->
        <s:Rect id="background"
                left="1" top="1" right="1" bottom="1">
            <s:fill>
                <s:BitmapFill id="backgroundFill" source="@Embed('skins/pattern_149.gif')" fillMode="repeat" />
            </s:fill>
        </s:Rect>
 
        <!-- layer 3: contents -->
        <!--- Contains the vertical stack of titlebar content and controlbar. -->
        <s:Group id="contents"
                left="1" right="1" top="1" bottom="1">
            <s:layout>
                <s:VerticalLayout gap="0" horizontalAlign="justify" />
            </s:layout>
 
            <s:Group id="topGroup" mask="{topGroupMask}">
 
                <!-- layer 0: title bar fill -->
                <s:Rect id="tbFill"
                        left="0" right="0" top="0" bottom="1">
                    <s:fill>
                        <s:LinearGradient rotation="90">
                            <s:GradientEntry color="0xE2E2E2" />
                            <s:GradientEntry color="0xD9D9D9" />
                        </s:LinearGradient>
                    </s:fill>
                </s:Rect>
 
                <!-- layer 1: title bar highlight -->
                <s:Rect id="tbHilite"
                        left="0" right="0" top="0" bottom="0">
                    <s:stroke>
                        <s:LinearGradientStroke rotation="90" weight="1">
                            <s:GradientEntry color="0xEAEAEA" />
                            <s:GradientEntry color="0xD9D9D9" />
                        </s:LinearGradientStroke>
                    </s:stroke>
                </s:Rect>
 
                <!-- layer 2: title bar divider -->
                <s:Rect id="tbDiv"
                        left="0" right="0" height="1" bottom="0">
                    <s:fill>
                        <s:SolidColor color="0xC0C0C0" />
                    </s:fill>
                </s:Rect>
 
                <!-- layer 3: text -->
                <s:Label id="titleDisplay"
                        maxDisplayedLines="1"
                        left="9" right="3" top="1" bottom="0" minHeight="30"
                        verticalAlign="middle" fontWeight="bold">
                </s:Label>
            </s:Group>
 
            <!--
            Note: setting the minimum size to 0 here so that changes to the host component's
            size will not be thwarted by this skin part's minimum size.   This is a compromise,
            more about it here: http://bugs.adobe.com/jira/browse/SDK-21143
            -->
            <s:Group id="contentGroup"
                    width="100%" height="100%" minWidth="0" minHeight="0">
            </s:Group>
 
            <s:Group id="bottomGroup" minWidth="0" minHeight="0"
                     includeIn="normalWithControlBar, disabledWithControlBar" >
 
                <s:Group left="0" right="0" top="0" bottom="0" mask="{bottomGroupMask}">
 
                    <!-- layer 0: control bar divider line -->
                    <s:Rect left="0" right="0" top="0" height="1" alpha="0.22">
                        <s:fill>
                            <s:SolidColor color="0x000000" />
                        </s:fill>
                    </s:Rect>
 
                    <!-- layer 1: control bar highlight -->
                    <s:Rect left="0" right="0" top="1" bottom="0">
                        <s:stroke>
                            <s:LinearGradientStroke rotation="90" weight="1">
                                <s:GradientEntry color="0xE5E5E5" />
                                <s:GradientEntry color="0xD8D8D8" />
                            </s:LinearGradientStroke>
                        </s:stroke>
                    </s:Rect>
 
                    <!-- layer 2: control bar fill -->
                    <s:Rect left="1" right="1" top="2" bottom="1">
                        <s:fill>
                            <s:LinearGradient rotation="90">
                                <s:GradientEntry color="0xDADADA" />
                                <s:GradientEntry color="0xC5C5C5" />
                            </s:LinearGradient>
                        </s:fill>
                    </s:Rect>
                </s:Group>
                <!-- layer 3: control bar -->
                <s:Group id="controlBarGroup"
                         left="0" right="0" top="1" bottom="1" minWidth="0" minHeight="0">
                    <s:layout>
                        <s:HorizontalLayout paddingLeft="10" paddingRight="10" paddingTop="7" paddingBottom="7" gap="10" />
                    </s:layout>
                </s:Group>
            </s:Group>
        </s:Group>
    </s:Group>
</s:SparkSkin>