With argument, actually select the window showing the cross
reference."

(interactive "e")
! (mouse-set-point ev)
! (reftex-view-crossref current-prefix-arg))
(defun reftex-view-crossref-when-idle ()
;; Display info about crossref at point in echo area or a window.
--- 231,239 ----
If there is no such macro at point, search forward to find one.

With argument, actually select the window showing the cross
reference."