This template outputs HTML class attribute values for elements that can be expanded and collapsed. It outputs the string ui-expander only if $node has a ui:expanded attribute and $hastitle is true. By default, $hastitle is true if $node has a title element. Set $hastitle explicitly when calling this template on elements that have an automatic default title.

This template also outputs ui-expander-preview if $node is an expander and it has the style hint ui-expander-preview. This is an alternative style that shows a scaled down preview of collapsed content.