Subject: bug#55412: 28.1; In Emacs 28.1, using ':eval' in 'frame-title-format' doesn't work properly

From: Christian Tanzer <[email-masked]>
Date: Sat, 14 May 2022 15:45:10 -0000

=============================================================================
;;; In Emacs 28.1, using ':eval' in 'frame-title-format' doesn't work like it
;;; used to in Emacs 27 and earlier. In fact, it is completely broken, if one
;;; uses a frame-parameter in ':eval'.
;;;
;;; The following elisp snippet demonstrates the problem in an Emacs 28.1
;;; instance started with 'emacs -Q'

(defun title-suffix ()
  (cdr (assoc 'title-suffix (frame-parameters (selected-frame)))))

(defvar title-prefix "Test")
(setq frame-title-format (list title-prefix '(:eval (title-suffix)) " %b"))

;;; The original frame should show a frame title of 'Test *scratch*'
(set-frame-parameter (selected-frame) 'title-suffix "")

;;; The next frame created should show a frame title of 'Test-xxx *scratch*'
(make-frame-command)
(set-frame-parameter (selected-frame) 'title-suffix "-xxx")

;;; The third frame created should show a frame title of 'Test-yyy *scratch*'
(make-frame-command)
(set-frame-parameter (selected-frame) 'title-suffix "-yyy")

;;; In Emacs 27 and earlier, that is exactly what happens. Selecting a
;;; different frame doesn't change the titles of all other frames.

;;; In Emacs 28.1, all frames show the same frame title, with the last one
;;; selected determining which one is shown for the bunch of them. Changing to
;;; a different frame changes the titles of all frames to the title of the
;;; newly selected one.
==========================================================================

In GNU Emacs 28.1 (build 1, aarch64-apple-darwin21.1.0, NS appkit-2113.00 Version 12.0.1 (Build 21A559))
 of 2022-04-04 built on armbob.lan
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.3.1

Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'

Configured features:
ACL GMP GNUTLS JSON LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER THREADS
TOOLKIT_SCROLL_BARS ZLIB

Important settings:
  value of $EMACSLOADPATH: /Users/tanzer/.emacs.lib::/Applications/Emacs.app/Contents/Resources/site-lisp:
  value of $LC_CTYPE: UTF-8
  value of $LC_MESSAGES: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
/Users/tanzer/.emacs.lib/custom hides /Applications/Emacs-28.1.app/Contents/Resources/lisp/custom
/Users/tanzer/.emacs.lib/iso-transl hides /Applications/Emacs-28.1.app/Contents/Resources/lisp/international/iso-transl

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/ns-win ns-win ucs-normalize
mule-util term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice button
loaddefs faces cus-face macroexp files window text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 51129 6052)
 (symbols 48 6554 1)
 (strings 32 18387 2569)
 (string-bytes 1 613674)
 (vectors 16 14168)
 (vector-slots 8 205987 11758)
 (floats 8 33 51)
 (intervals 56 234 0)
 (buffers 992 10))