Currently vdl doc for for f:event's listener attribute says:
javax.el.MethodExpression (signature must match public void
listener(javax.faces.event.ComponentSystemEvent event) throws
However, the Mojarra implementation allows the event parameter to be optionally omitted. This
matches the specified behavior for h:commandButton's actionListener attribute:
The expression must evaluate to a public method that takes an ActionEvent parameter, with a return
type of void, or to a public method that takes no arguments with a return type of void. In the latter
case, the method has no way of easily knowing where the event came from, but this can be useful in
cases where a notification is needed that "some action happened".
We should update the f:event documentation to match the behavior currently implemented by Mojarra
to be consistent across the f:event/h:commandButton cases.