I have the following in my .emacs file...
(setq ediff-window-setup-function 'ediff-setup-windows-plain)
and indeed ediff usually does it's work with split buffers (2 files and the Control Panel).
But if I type "R" (ediff-show-registry) in the Control Panel or M-x eregistry it pops up a new frame. If I am looking at a file that is not part of an ediff session then M-x eregistry uses the same frame.
Is there a way to prevent eregistry from creating a new frame?
GNU Emacs 23.3.50.1 (i386-apple-darwin9.8.0, NS apple-appkit-949.54) of 2011-08-04 on braeburn.aquamacs.org - Aquamacs Distribution 2.3a Ediff 2.81.4 of December 7, 2009
I don't know of a way. Consider filing an enhancement request, using
M-x report-emacs-bug
. (Yes, that is also for enhancement requests.)