Richfaces笔记:a4j:outputPanel
a4j:outputPanel is rendered as a <span> html element if the 'layout' attribute is equal 'inline' (default value) or as a <div> html element if layout="block". You can use this component for a layout purpose even if the page has no Ajax functionality.
If Ajax functionality presents on the page, the component offers two additional features:
* Marking the area of the page as automatically re-rendered on each Ajax request event without any necessity to mentioned this area in the reRender attribute of Ajax component. Attribute ajaxRendered="true" turn on this feature. Note, that the effect of using ajaxRendered="true" still might be overridden with the limitToList attribute of the Ajax component or renderRegionOnly attribute of the a4j:region component.
* Marking the placeholder for any JSF component in case of it is not rendered due to rendered="false". This might be important when the component becomes rendered during the next Ajax response. As soon as the placeholder is unknown, the rendered component doesn't appear on a page. To turn on the feature for marking the placeholder, you need to have the attribute layout="none".
When layout="none", the span style="display:none" is rendered and assigns the id of the child component if the component is not rendered. Otherwise, it does not become rendered at all.
