Emacs can freeze for seconds when scroll-down-line is called multiple 
times if the buffer contains a lot of text properties.

I noticed this when using lsp-mode for C++.

To reproduce the issue without lsp-mode, execute this elisp command with 
M-:, this will add a face to operators:

(font-lock-add-keywords 'c++-mode '(("[][~!^&\|<>:=,.\\+*/%-]" 0 'error)))

Also, bind scroll-down-line to a key, like shift-up:

(global-set-key (kbd "<S-up>") 'scroll-down-line)

Then, put the attached example.cpp into a c++ buffer, move the point to 
the bottom, then press and hold shift-up. Emacs will update the window 
for several scroll events, but after that it won't update the screen for 
a while. Even after shift-up is released, Emacs needs several seconds to 
be interactive again.


In GNU Emacs 29.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version
  3.24.36, cairo version 1.16.0) of 2023-03-21 built on okoska
Repository revision: 7a1272168af1a5b82979efa29451147c5d867981
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12101006
System Description: Debian GNU/Linux bookworm/sid

Configured using:
  'configure --with-native-compilation=aot --without-compress-install
  --with-json --with-xinput2 --with-xwidgets --with-tree-sitter
  --with-cairo'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG SECCOMP SOUND SQLITE3 THREADS
TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM
XWIDGETS GTK3 ZLIB

Important settings:
   value of $LC_ALL: C.UTF-8
   value of $LANG: en_US.UTF-8
   value of $XMODIFIERS: @im=none
   locale-coding-system: utf-8-unix

Major mode: C++//l

Minor modes in effect:
   tooltip-mode: t
   global-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
   line-number-mode: t
   indent-tabs-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   abbrev-mode: t

Load-path shadows:
/home/geza/.emacs.d/elpa/transient-20230304.1149/transient hides 
/usr/local/share/emacs/29.0.60/lisp/transient

Features:
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vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win
term/common-win x-dnd 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
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charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-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 xwidget-internal dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
xinput2 x multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 150387 10063)
  (symbols 48 11460 0)
  (strings 32 32439 3583)
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  (vectors 16 19041)
  (vector-slots 8 386441 14177)
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  (intervals 56 7894 0)
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