bug#52761: 29.0.50; (--with-pgtk) poor point movement performance when global-flycheck-mode is called during start-up

[Simon Pugnet <simon@polaris64.net>]

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I've noticed a strange performance issue with Emacs when built
--with-pgtk, but only when global-flycheck-mode is called during Emacs
start-up.

To reproduce, download and extract the following packages: -

 - Flycheck: https://melpa.org/#/flycheck
 - Dash.el (dependency): https://elpa.gnu.org/packages/dash.html

Assuming these are at ~/flycheck and ~/dash, perform the following
steps: -

1. Create ~/init.el as follows: -

#+begin_src emacs-lisp
(add-to-list 'load-path (expand-file-name "~/flycheck"))
(add-to-list 'load-path (expand-file-name "~/dash"))
(require 'flycheck)
(global-flycheck-mode)
#+end_src

2. Run Emacs, loading this init.el file: "emacs -Q -l ~/init.el"

Now, when I use C-n/C-p to move around any buffer, there is a very
short but noticeable delay between key-presses and the point actually
moving. It's quite easy to notice when compared to the same Emacs run
as just "emacs -Q".

This only happens when Emacs is built --with-pgtk (and other features
as below). If I remove --with-pgtk, this delay disappears. Also, if I
do not call global-flycheck-mode during initialisation and instead
call it manually at some later stage, the delay also does not appear.
It only seems to happen when the global-flycheck-mode call is done
during initialisation.

Please let me know if there is any more information I can provide.

All the best and thanks in advance for your help,

Simon


In GNU Emacs 29.0.50 (build 4, x86_64-pc-linux-gnu, GTK+ Version
3.24.31, cairo version 1.17.4)
 of 2021-12-23 built on tikal
Repository revision: 2fa7feca336dd16c57ffef072e0f0da6fffe4c5f
Repository branch: master
Windowing system distributor 'System Description: Arch Linux

Configured using:
 'configure --with-native-compilation --with-modules --with-json
 --with-xinput2 --with-pgtk'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
JPEG
JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY
INOTIFY
PDUMPER PGTK PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XIM GTK3 ZLIB

Important settings:
  value of $LC_CTYPE: en_GB.UTF-8
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=ibus
  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:
/usr/local/share/emacs/29.0.50/lisp/emacs-lisp/eieio-compat hides
/usr/local/share/emacs/29.0.50/lisp/obsolete/eieio-compat

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media rmc puny
dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg
rfc6068 epg-config gnus-util text-property-search time-date seq gv
subr-x byte-opt 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/pgtk-win pgtk-win
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 keymap hashtable-print-readable backquote threads
dbusbind inotify dynamic-setting system-font-setting
font-render-setting
cairo move-toolbar gtk x-toolkit pgtk lcms2 multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 56008 9769)
 (symbols 48 5662 1)
 (strings 32 16131 1632)
 (string-bytes 1 536291)
 (vectors 16 11510)
 (vector-slots 8 261217 13969)
 (floats 8 26 26)
 (intervals 56 224 0)
 (buffers 992 11))

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