How can I draw a joined border around two components?

Before I tackled this myself, I thought I pick the minds of the SO community.

Let's assume I have an Image that's used a button. By default, the image has no border around it. Clicking on this Image will cause another component be displayed beneath it or next to it. When the second component is displayed, I want to draw a joined border around the Image and the second component.

The second component would not be visible by default. It would only be visible after clicking on the Image by using the popupManager, PopUpAnchor, setting the visible property, etc.

Example before clicking:

+---------开发者_如何学编程-----------------------+
|                                |
|   XXX  <-- My Image            |
|   XXX                          |
|                                |
|                                |
|                                |
|                                |
|                                |
|                                |
|                                |
+--------------------------------+

Example after clicking:

+--------------------------------+
|  +---+                         |
|  |XXX|  <-- My Image           |
|  |XXX|_______________          |
|  |                   |         |
|  |   My Second       |         |
|  |   Component       |         |
|  |                   |         |
|  |                   |         |
|  +-------------------+         |
|                                |
+--------------------------------+

How difficult would it be to create something like this?

If you are using flex4 / spark, then you should consider skinning (anyway, the borderSides style is available only in Halo).

here is a small sample to achieve the behavior shown at the images:

It uses a custom component with two states (collapsed and expanded).
The text is only attached in the expanded state, and so are the border skins.
For this you'll need two skin classes that will be applied to the image- and to the text component's parent.

The Application:

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009" 
    xmlns:s="library://ns.adobe.com/flex/spark" 
    xmlns:mx="library://ns.adobe.com/flex/mx" xmlns:my="*">
    <s:VGroup width="100%" height="100%" paddingLeft="20" paddingTop="20">
        <my:ExpandableImage id="component" width="300" />
        <s:Button label="{component.currentState}" click="component.changeState(event);" />
    </s:VGroup>
</s:WindowedApplication>

ExpandableImage.mxml //the custom component with two states

<?xml version="1.0" encoding="utf-8"?>
<mx:VBox xmlns:fx="http://ns.adobe.com/mxml/2009" 
    xmlns:s="library://ns.adobe.com/flex/spark" 
    xmlns:mx="library://ns.adobe.com/flex/mx" 
    verticalScrollPolicy="off" horizontalScrollPolicy="off"
    verticalGap="0" width="100%"
    currentState="collapsedState">
    <fx:Script>
        <![CDATA[

            public function changeState(event:MouseEvent):void
            {
                if (currentState == 'collapsedState')
                    currentState = 'expandedState';
                else
                    currentState = 'collapsedState';
            }

        ]]>
    </fx:Script>
    <mx:VBox id="imgHolder" borderSkin="MyImageSkin" 
        width="50" height="50" includeIn="collapsedState, expandedState" cornerRadius="5"
        backgroundAlpha="1" borderAlpha="0" backgroundColor="#FFFFFF" borderColor="#000000">
        <mx:Image id="img" source="{IMyConstants.MYLOGO}" 
            width="48" height="48"
            mouseEnabled="true" click="changeState(event)" />
    </mx:VBox>
    <mx:VBox id="txtHolder" borderSkin="MyDetailsSkin" 
        width="100%" height="100%" includeIn="expandedState" cornerRadius="5"
        backgroundAlpha="1" borderAlpha=".5" backgroundColor="#FFFFFF" borderColor="#000000">
        <mx:Text id="txt" text="{IMyConstants.LOREMIPSUM}" 
            width="100%" />
    </mx:VBox>
    <mx:states>
        <s:State name="collapsedState" />
        <s:State name="expandedState" />
    </mx:states>
    <mx:transitions>
        <mx:Transition fromState="collapsedState" toState="expandedState">
            <s:Parallel duration="500">
                <mx:Resize target="{this}" />
                <mx:SetStyleAction target="{imgHolder}" 
                    name="borderAlpha" value=".5" />
            </s:Parallel>
        </mx:Transition>
        <mx:Transition fromState="expandedState" toState="collapsedState">
            <s:Parallel duration="500">
                <mx:Resize target="{this}" />
                <mx:SetStyleAction target="{imgHolder}" 
                    name="borderAlpha" value="0" />
            </s:Parallel>
        </mx:Transition>
    </mx:transitions>
</mx:VBox>

MyImageSkin.as //the skin to be applied on the image component's parent

public class MyImageSkin extends RectangularBorder 
{
    override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void 
    {
        super.updateDisplayList(unscaledWidth, unscaledHeight);
        var cornerRadius:Number = getStyle("cornerRadius");
        var borderColor:int = getStyle("borderColor");
        var borderAlpha:Number = getStyle("borderAlpha");
        var backgroundColor:int = getStyle("backgroundColor");
        var backgroundAlpha:Number = getStyle("backgroundAlpha");
        graphics.clear();
        //border
        drawRoundRect(0, 0, unscaledWidth, unscaledHeight, 
            {tl: cornerRadius, tr:cornerRadius, bl: 0, br: 0}, 
            borderColor, borderAlpha);
        //content
        drawRoundRect(1, 1, unscaledWidth-2, unscaledHeight-1, 
            {tl: cornerRadius, tr:cornerRadius, bl: 0, br: 0}, 
            backgroundColor, backgroundAlpha);
    }
}

MyDetailsSkin.as //the skin to be applied on the text's parent

public class MyDetailsSkin extends RectangularBorder 
{
    override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void 
    {
        super.updateDisplayList(unscaledWidth, unscaledHeight);
        var cornerRadius:Number = getStyle("cornerRadius");
        var borderColor:int = getStyle("borderColor");
        var borderAlpha:Number = getStyle("borderAlpha");
        var backgroundColor:int = getStyle("backgroundColor");
        var backgroundAlpha:Number = getStyle("backgroundAlpha");
        graphics.clear();
        //border
        drawRoundRect(0, 0, unscaledWidth, unscaledHeight, 
            {tl: 0, tr:cornerRadius, bl: cornerRadius, br: cornerRadius}, 
            borderColor, borderAlpha);
        //content
        drawRoundRect(1, 1, unscaledWidth-2, unscaledHeight-2, 
            {tl: 0, tr:cornerRadius, bl: cornerRadius, br: cornerRadius}, 
            backgroundColor, backgroundAlpha);
        //clear separator
        drawRoundRect(1, 0, 49, 1, {tl: 0, tr:1, bl: 1, br: 1}, backgroundColor, 1);
    }
}

i really hope this helps

Pretty sure you can do this with styles
Add a third container i marked with ****
turn the top and right borders off on my new container(***)
turn the bottom border off on your image container
turn the top border off on your second component

+--------------------------------+
|  +---+****************         |
|  |XXX|  <-- My Image *         |
|  |XXX|_______________*         |
|  |                   |         |
|  |   My Second       |         |
|  |   Component       |         |
|  |                   |         |
|  |                   |         |
|  +-------------------+         |
|                                |
+--------------------------------+