bug#67249: 30.0.50; `same-frame` equivalent for `display-buffer-alist`

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Package: Emacs
Version: 30.0.50


As `special-display-buffer-names` and friends are nearing the 10 years
of being declared obsolete, I noticed that I can't find any replacement
for the `same-frame` parameter in `display-buffer-alist`.

The patch below is just a "proof-of-concept" I tried to see if I could
get a similar behavior to the old `same-frame` with the new code.
I'm not sufficiently familiar with the set of `display-buffer-*`
functions to judge if it's a good approach overall.

I also noticed that `special-display-popup-frame` is only called from
`special-display-function` (which is declared obsolete since 24.3), so
maybe it should also be declared obsolete?


        Stefan


diff --git a/lisp/window.el b/lisp/window.el
index b6fe5996123..72cd9f5d85c 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -6795,6 +6795,7 @@ special-display-popup-frame
 If ARGS is a list whose car is a symbol, use (car ARGS) as a
 function to do the work.  Pass it BUFFER as first argument, and
 pass the elements of (cdr ARGS) as the remaining arguments."
+  (declare (obsolete "??" "30.1"))
   (if (and args (symbolp (car args)))
       (apply (car args) buffer (cdr args))
     (let ((window (get-buffer-window buffer 0)))
@@ -8014,6 +8015,7 @@ display-buffer-pop-up-frame
 	 (fun pop-up-frame-function)
 	 frame window)
     (when (and fun
+	       (not (alist-get 'same-frame alist))
 	       ;; Make BUFFER current so `make-frame' will use it as the
 	       ;; new frame's buffer (Bug#15133).
 	       (with-current-buffer buffer