Setup: 1. install `ligature.el` from melpa. 2. start `emacs -Q` and execute the attached script or simply use the attached script as the `init.el`. 3. open the attached `init.el` file and execute `init-faces` or hit "C-#" to start randomizing the font faces, 4. eventually you will see some characters gets rendered with extra spaces (sample screenshots provided below), hit "C-!" to stop the randomization, 5. hitting "C-return" will randomize font once, which might be useful for you find debug, Expected behavior: the fonts are rendered consistently without extra spacing, Observed behavior: the fonts are rendered with extra spacing randomly, Related information: I previously reported this bug here: https://github.com/mickeynp/ligature.el/issues/56. In GNU Emacs 29.4 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.24.42, cairo version 1.18.0) of 2024-07-16 built on 27527c2e06f843c0962737354e0b3cf7 System Description: Fedora Linux 40 (Sway) Configured using: 'configure --build=x86_64-redhat-linux-gnu --host=x86_64-redhat-linux-gnu --program-prefix= --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64 --libexecdir=/usr/libexec --localstatedir=/var --runstatedir=/run --sharedstatedir=/var/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-cairo --with-dbus --with-gif --with-gpm=no --with-harfbuzz --with-jpeg --with-json --with-modules --with-native-compilation=aot --with-pgtk --with-png --with-rsvg --with-sqlite3 --with-tiff --with-tree-sitter --with-webp --with-xpm --with-xwidgets build_alias=x86_64-redhat-linux-gnu host_alias=x86_64-redhat-linux-gnu CC=gcc 'CFLAGS=-DMAIL_USE_LOCKF -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer ' LDFLAGS=-Wl,-z,relro PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig CXX=g++ 'CXXFLAGS=-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer '' Configured features: ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XIM XWIDGETS GTK3 ZLIB Important settings: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix Major mode: ELisp/l Minor modes in effect: global-ligature-mode: t ligature-mode: t 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 line-number-mode: t indent-tabs-mode: t transient-mark-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t Load-path shadows: None found. Features: (shadow sort mail-extr emacsbug message yank-media puny dired dired-loaddefs rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util text-property-search time-date mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils comp comp-cstr warnings icons rx ligature cl-extra help-mode use-package-core ligature-autoloads package browse-url url url-proxy url-privacy url-expand url-methods url-history url-cookie generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs password-cache json subr-x map byte-opt gv bytecomp byte-compile url-vars cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/pgtk-win pgtk-win term/common-win pgtk-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 frame minibuffer nadvice seq simple cl-generic indonesian philippine 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 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 dynamic-setting system-font-setting font-render-setting cairo gtk pgtk multi-tty make-network-process native-compile emacs) Memory information: ((conses 16 108675 14724) (symbols 48 8830 0) (strings 32 27784 2658) (string-bytes 1 906120) (vectors 16 22224) (vector-slots 8 441624 17378) (floats 8 45 30) (intervals 56 736 1) (buffers 984 12))