wicket-user-guide/src/docs/guide/keepControl/keepControl_9.gdoc

Our data are rarely displayed alone without a caption or other graphic elements that make clear the meaning of their value. For example:

{code:html}
<label>Total amount: </label><span wicket:id="totalAmount"></span>
{code}

Wicket comes with a nice utility tag called @<wicket:enclosure>@ that automatically hides those decorating elements if the related data value is not visible. All we have to do is to put the involved markup inside this tag. Applying @<wicket:enclosure>@ to the previous example we get the following markup:

{code:html}
<wicket:enclosure> 
    <label>Total amount: </label><span wicket:id="totalAmount"></span>
</wicket:enclosure>
{code}

Now if component @totalAmount@ is not visible, its description (@Total amount:@) will be automatically hidden. If we have more than a Wicket component inside @<wicket:enclosure>@ we can use @child@ attribute to specify which component will control the overall visibility:

{code:html}
<wicket:enclosure child="totalAmount"> 
    <label>Total amount: </label><span wicket:id="totalAmount"></span><br/>
	<label>Expected delivery date: </label><span wicket:id="delivDate"></span>
</wicket:enclosure>
{code}

@child@ attribute supports also nested components with a colon-separated path: 

{code:html}
<wicket:enclosure child="totalAmountContainer:totalAmount"> 
    <div wicket:id="totalAmountContainer">
		<label>Total amount: </label><span wicket:id="totalAmount"></span>
    </div>
    <label>Expected delivery date: </label><span wicket:id="delivDate"></span>
</wicket:enclosure>
{code}