Subject: bug#69983: Use category for display-buffer-alist

From: Juri Linkov <[email-masked]>
Date: Sun, 24 Mar 2024 19:19:16 +0200

'display-comint-buffer-action' and 'display-tex-shell-buffer-action'
are out of place in window.el, and they are redundant per se.

What these variables are trying to achieve is already possible
to do by using a 'category' in 'display-buffer-alist'.
Here is an already supported example:

#+begin_src emacs-lisp
(add-to-list 'display-buffer-alist
             `(,(lambda (_buffer-name action)
                  (eq (alist-get 'category action) 'comint))
               (display-buffer-in-direction)
	       (direction . top)))

(display-buffer (get-buffer-create "blablabla")
		'(nil (category . comint)))
#+end_src

The advantage of this approach is removing a need
of writing a complex regexp to match the buffer name.

Using this approach it's possible just to mark
all related callers with the same category, e.g.:

diff --git a/lisp/cmuscheme.el b/lisp/cmuscheme.el
index c84a1809322..ccd7f2f713f 100644
--- a/lisp/cmuscheme.el
+++ b/lisp/cmuscheme.el
@@ -238,7 +238,7 @@ run-scheme
 	(inferior-scheme-mode)))
   (setq scheme-program-name cmd)
   (setq scheme-buffer "*scheme*")
-  (pop-to-buffer "*scheme*" display-comint-buffer-action))
+  (pop-to-buffer "*scheme*" '(nil (category . comint))))

diff --git a/lisp/progmodes/inf-lisp.el b/lisp/progmodes/inf-lisp.el
index 141bd18cf1e..1aa3bbd4239 100644
--- a/lisp/progmodes/inf-lisp.el
+++ b/lisp/progmodes/inf-lisp.el
@@ -308,7 +308,7 @@ inferior-lisp
 			   "inferior-lisp" (car cmdlist) nil (cdr cmdlist)))
 	(inferior-lisp-mode)))
   (setq inferior-lisp-buffer "*inferior-lisp*")
-  (pop-to-buffer "*inferior-lisp*" display-comint-buffer-action))
+  (pop-to-buffer "*inferior-lisp*" '(nil (category . comint))))

Or we need to keep backward-compatibility?  Then the first step
to deprecate there variables would be something like this:

diff --git a/lisp/window.el b/lisp/window.el
index bea050e181c..fa417817d1d 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -8912,7 +8944,7 @@ pop-to-buffer-same-window
 another window."
   (pop-to-buffer buffer display-buffer--same-window-action norecord))
 
-(defcustom display-comint-buffer-action display-buffer--same-window-action
+(defcustom display-comint-buffer-action (append display-buffer--same-window-action '((category . comint)))
   "`display-buffer' action for displaying comint buffers."
   :type display-buffer--action-custom-type
   :risky t