expression to the list @code{same-window-regexps}. By default, these
variables are @code{nil}, so this step is skipped.
-@vindex display-buffer-reuse-frames
@item
Otherwise, if the buffer is already displayed in an existing window,
``reuse'' that window. Normally, only windows on the selected frame
are considered, but windows on other frames are also reusable if you
-change @code{display-buffer-reuse-frames} to @code{t}, or if you
change @code{pop-up-frames} (see below) to @code{t}.
@item