When you click on that link, the corresponding Java file opens and the cursor lands at the start of the method that contains the corresponding Wicket identifier:
This feature is made possible by the HyperlinkProvider interface. From the perspective of the layer.xml file (which is the configuration file for NetBeans plug-in modules), this is what is needed (i.e., this functionality is provided for all HTML files):
<attr name="instanceClass" stringvalue="org.netbeans.modules.web.wicketsupport.hyperlink.WicketHTMLHyperlingProvider"/>
<attr name="instanceOf" stringvalue="org.netbeans.lib.editor.hyperlink.spi.HyperlinkProvider"/>
And, if you want to see the code itself (which is well documented, thanks Petr), here's the file that extends HyperlinkProvider:
One question: If you are a Wicket user, where would you want the cursor to be positioned in the corresponding Java file? Currently it is put at the start of the method containing the Wicket identifier. But maybe it should be placed at the start of the line that contains the Wicket identifier instead? Feedback on this would be appreciated.