The r:collapsiblePanel component is fully analogous to a simple r:panel component. Except that it can be collapsed, and expanded. In the collapsed state only the header is shown and in expanded state the complete panel.

As with most of switchable components it has three switch types for switching between states - ajax, server and client. See the r:togglePanel for details.

Note: In ajax and server modes the PanelToggleEvent is queued and can be handled using a Listener defined via the toggleListener attribute