bug#26333: 26.0.50; Hang when displaying some special characters for the first time

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Steven Allen]

1. Start `emacs -Q` (GUI mode, GTK3).
2. Open a scratch buffer.
3. Insert a MATHMATICAL SANS-SERIF BOLD SMALL LAMBDA (0x1D77A): 𝝺

The first time this character is displayed, Emacs hangs for ~15 seconds
pegging the CPU at 100%. Unfortunately, the profiler doesn't seem to
notice/record this hang.

Note 1: displaying this character in other applications (GTK3 or
otherwise) does not exhibit the same issue.
Note 2: C-g doesn't interrupt this hang.

OS: Arch Linux
Fonts (packages):
  - artwiz-fonts
  - bdf-unifont
  - cantarell-fonts
  - gsfonts
  - montecarlo-font
  - office-code-pro
  - siji-git
  - terminus-font
  - ttf-bitstream-vera
  - ttf-dejavu
  - ttf-font-awesome
  - ttf-freefont
  - ttf-google-fonts-git
  - ttf-ms-fonts
  - ttf-symbola
  - xorg-font-util
  - xorg-fonts-alias
  - xorg-fonts-encodings
  - xorg-fonts-misc

In GNU Emacs 26.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.10)
 of 2017-03-30 built on bistromath
Repository revision: 3a11b3e330e88a42386ac3a635330ebd9c610827
Windowing system distributor 'The X.Org Foundation', version 11.0.11903000
Recent messages:
Starting new Ispell process /usr/bin/aspell with default dictionary...
Spacemacs is ready.
Loading /home/steb/.local/share/emacs/.cache/recentf...done
Open the quickhelp.
Skipping check for new version (reason: dotfile)
Quit
CPU profiler started
s-; is undefined
Quit
CPU profiler stopped

Configured using:
 'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --mandir=/usr/share/man --with-gameuser=:games
 --without-selinux --without-pop --without-tiff --with-sound=alsa
 --with-xft --with-modules --with-x-toolkit=gtk3 --without-gconf
 --with-gsettings 'CFLAGS=-march=native -mtune=native -O2 -pipe
 -fstack-protector-strong --param=ssp-buffer-size=4'
 CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,noexecstack,--hash-style=gnu'

Configured features:
XPM JPEG GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY ACL
GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11 MODULES LIBSYSTEMD

Important settings:
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix

Major mode: Text

Minor modes in effect:
  company-quickhelp-mode: t
  company-quickhelp-local-mode: t
  imagex-auto-adjust-mode: t
  flyspell-mode: t
  hl-todo-mode: t
  winum-mode: t
  winner-mode: t
  volatile-highlights-mode: t
  spaceline-info-mode: t
  save-place-mode: t
  savehist-mode: t
  popwin-mode: t
  persp-mode: t
  Info-breadcrumbs-in-mode-line-mode: t
  global-git-gutter+-mode: t
  flycheck-pos-tip-mode: t
  global-flycheck-mode: t
  flx-ido-mode: t
  eyebrowse-mode: t
  global-evil-surround-mode: t
  evil-surround-mode: t
  global-evil-search-highlight-persist: t
  evil-search-highlight-persist: t
  global-anzu-mode: t
  anzu-mode: t
  eval-sexp-fu-flash-mode: t
  counsel-mode: t
  ivy-mode: t
  clean-aindent-mode: t
  which-key-mode: t
  override-global-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  evil-mode: t
  evil-local-mode: t
  spacemacs-leader-override-mode: t
  global-spacemacs-leader-override-mode: t
  recentf-mode: t
  dired-omit-mode: t
  global-git-commit-mode: t
  diff-auto-refine-mode: t
  async-bytecomp-package-mode: t
  shell-dirtrack-mode: t
  global-hl-line-mode: t
  xterm-mouse-mode: t
  global-auto-revert-mode: t
  ido-vertical-mode: t
  global-page-break-lines-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  window-divider-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/home/steb/.local/share/emacs/elpa/org-bullets-20140918.1137/org-bullets hides /home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-bullets
/home/steb/.local/share/emacs/elpa/scala-mode-20170323.502/ob-scala hides /home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-scala
/home/steb/.local/share/emacs/elpa/ht-20161015.1945/ht hides /home/steb/.local/share/spacemacs/core/libs/ht
/home/steb/.local/share/emacs/elpa/cmake-mode-20160928.505/cmake-mode hides /usr/share/emacs/site-lisp/cmake-mode
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-lib hides /usr/share/emacs/site-lisp/notmuch-lib
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-compat hides /usr/share/emacs/site-lisp/notmuch-compat
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-parser hides /usr/share/emacs/site-lisp/notmuch-parser
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch hides /usr/share/emacs/site-lisp/notmuch
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-query hides /usr/share/emacs/site-lisp/notmuch-query
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-show hides /usr/share/emacs/site-lisp/notmuch-show
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-tree hides /usr/share/emacs/site-lisp/notmuch-tree
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-wash hides /usr/share/emacs/site-lisp/notmuch-wash
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-hello hides /usr/share/emacs/site-lisp/notmuch-hello
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-mua hides /usr/share/emacs/site-lisp/notmuch-mua
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-address hides /usr/share/emacs/site-lisp/notmuch-address
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-maildir-fcc hides /usr/share/emacs/site-lisp/notmuch-maildir-fcc
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-message hides /usr/share/emacs/site-lisp/notmuch-message
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-crypto hides /usr/share/emacs/site-lisp/notmuch-crypto
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-tag hides /usr/share/emacs/site-lisp/notmuch-tag
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/coolj hides /usr/share/emacs/site-lisp/coolj
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-print hides /usr/share/emacs/site-lisp/notmuch-print
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-jump hides /usr/share/emacs/site-lisp/notmuch-jump
/home/steb/.local/share/emacs/elpa/notmuch-20170313.1712/notmuch-company hides /usr/share/emacs/site-lisp/notmuch-company
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-texinfo hides /usr/share/emacs/26.0.50/lisp/org/ox-texinfo
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-odt hides /usr/share/emacs/26.0.50/lisp/org/ox-odt
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-publish hides /usr/share/emacs/26.0.50/lisp/org/ox-publish
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-org hides /usr/share/emacs/26.0.50/lisp/org/ox-org
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-md hides /usr/share/emacs/26.0.50/lisp/org/ox-md
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-latex hides /usr/share/emacs/26.0.50/lisp/org/ox-latex
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-man hides /usr/share/emacs/26.0.50/lisp/org/ox-man
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-icalendar hides /usr/share/emacs/26.0.50/lisp/org/ox-icalendar
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-html hides /usr/share/emacs/26.0.50/lisp/org/ox-html
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-beamer hides /usr/share/emacs/26.0.50/lisp/org/ox-beamer
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox hides /usr/share/emacs/26.0.50/lisp/org/ox
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ox-ascii hides /usr/share/emacs/26.0.50/lisp/org/ox-ascii
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-table hides /usr/share/emacs/26.0.50/lisp/org/org-table
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-w3m hides /usr/share/emacs/26.0.50/lisp/org/org-w3m
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-timer hides /usr/share/emacs/26.0.50/lisp/org/org-timer
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-rmail hides /usr/share/emacs/26.0.50/lisp/org/org-rmail
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-plot hides /usr/share/emacs/26.0.50/lisp/org/org-plot
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-src hides /usr/share/emacs/26.0.50/lisp/org/org-src
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-protocol hides /usr/share/emacs/26.0.50/lisp/org/org-protocol
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-mouse hides /usr/share/emacs/26.0.50/lisp/org/org-mouse
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-mobile hides /usr/share/emacs/26.0.50/lisp/org/org-mobile
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-mhe hides /usr/share/emacs/26.0.50/lisp/org/org-mhe
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-pcomplete hides /usr/share/emacs/26.0.50/lisp/org/org-pcomplete
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-list hides /usr/share/emacs/26.0.50/lisp/org/org-list
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-macs hides /usr/share/emacs/26.0.50/lisp/org/org-macs
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-macro hides /usr/share/emacs/26.0.50/lisp/org/org-macro
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-irc hides /usr/share/emacs/26.0.50/lisp/org/org-irc
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-inlinetask hides /usr/share/emacs/26.0.50/lisp/org/org-inlinetask
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-info hides /usr/share/emacs/26.0.50/lisp/org/org-info
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-indent hides /usr/share/emacs/26.0.50/lisp/org/org-indent
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-id hides /usr/share/emacs/26.0.50/lisp/org/org-id
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-habit hides /usr/share/emacs/26.0.50/lisp/org/org-habit
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org hides /usr/share/emacs/26.0.50/lisp/org/org
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-gnus hides /usr/share/emacs/26.0.50/lisp/org/org-gnus
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-feed hides /usr/share/emacs/26.0.50/lisp/org/org-feed
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-eshell hides /usr/share/emacs/26.0.50/lisp/org/org-eshell
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-footnote hides /usr/share/emacs/26.0.50/lisp/org/org-footnote
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-element hides /usr/share/emacs/26.0.50/lisp/org/org-element
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-faces hides /usr/share/emacs/26.0.50/lisp/org/org-faces
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-docview hides /usr/share/emacs/26.0.50/lisp/org/org-docview
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-entities hides /usr/share/emacs/26.0.50/lisp/org/org-entities
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-datetree hides /usr/share/emacs/26.0.50/lisp/org/org-datetree
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-ctags hides /usr/share/emacs/26.0.50/lisp/org/org-ctags
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-crypt hides /usr/share/emacs/26.0.50/lisp/org/org-crypt
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-colview hides /usr/share/emacs/26.0.50/lisp/org/org-colview
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-clock hides /usr/share/emacs/26.0.50/lisp/org/org-clock
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-capture hides /usr/share/emacs/26.0.50/lisp/org/org-capture
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-compat hides /usr/share/emacs/26.0.50/lisp/org/org-compat
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-bibtex hides /usr/share/emacs/26.0.50/lisp/org/org-bibtex
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-agenda hides /usr/share/emacs/26.0.50/lisp/org/org-agenda
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-attach hides /usr/share/emacs/26.0.50/lisp/org/org-attach
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-bbdb hides /usr/share/emacs/26.0.50/lisp/org/org-bbdb
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-archive hides /usr/share/emacs/26.0.50/lisp/org/org-archive
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-tangle hides /usr/share/emacs/26.0.50/lisp/org/ob-tangle
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-fortran hides /usr/share/emacs/26.0.50/lisp/org/ob-fortran
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-sqlite hides /usr/share/emacs/26.0.50/lisp/org/ob-sqlite
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-table hides /usr/share/emacs/26.0.50/lisp/org/ob-table
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-sql hides /usr/share/emacs/26.0.50/lisp/org/ob-sql
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-shen hides /usr/share/emacs/26.0.50/lisp/org/ob-shen
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-screen hides /usr/share/emacs/26.0.50/lisp/org/ob-screen
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-scheme hides /usr/share/emacs/26.0.50/lisp/org/ob-scheme
/home/steb/.local/share/emacs/elpa/scala-mode-20170323.502/ob-scala hides /usr/share/emacs/26.0.50/lisp/org/ob-scala
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-sass hides /usr/share/emacs/26.0.50/lisp/org/ob-sass
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-C hides /usr/share/emacs/26.0.50/lisp/org/ob-C
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-ruby hides /usr/share/emacs/26.0.50/lisp/org/ob-ruby
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-R hides /usr/share/emacs/26.0.50/lisp/org/ob-R
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-ref hides /usr/share/emacs/26.0.50/lisp/org/ob-ref
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-python hides /usr/share/emacs/26.0.50/lisp/org/ob-python
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-plantuml hides /usr/share/emacs/26.0.50/lisp/org/ob-plantuml
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-picolisp hides /usr/share/emacs/26.0.50/lisp/org/ob-picolisp
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-perl hides /usr/share/emacs/26.0.50/lisp/org/ob-perl
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-org hides /usr/share/emacs/26.0.50/lisp/org/ob-org
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-octave hides /usr/share/emacs/26.0.50/lisp/org/ob-octave
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-ocaml hides /usr/share/emacs/26.0.50/lisp/org/ob-ocaml
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-mscgen hides /usr/share/emacs/26.0.50/lisp/org/ob-mscgen
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-maxima hides /usr/share/emacs/26.0.50/lisp/org/ob-maxima
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-matlab hides /usr/share/emacs/26.0.50/lisp/org/ob-matlab
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-makefile hides /usr/share/emacs/26.0.50/lisp/org/ob-makefile
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-lob hides /usr/share/emacs/26.0.50/lisp/org/ob-lob
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-lisp hides /usr/share/emacs/26.0.50/lisp/org/ob-lisp
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-lilypond hides /usr/share/emacs/26.0.50/lisp/org/ob-lilypond
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-ledger hides /usr/share/emacs/26.0.50/lisp/org/ob-ledger
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-latex hides /usr/share/emacs/26.0.50/lisp/org/ob-latex
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-keys hides /usr/share/emacs/26.0.50/lisp/org/ob-keys
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-js hides /usr/share/emacs/26.0.50/lisp/org/ob-js
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-java hides /usr/share/emacs/26.0.50/lisp/org/ob-java
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-io hides /usr/share/emacs/26.0.50/lisp/org/ob-io
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-haskell hides /usr/share/emacs/26.0.50/lisp/org/ob-haskell
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-gnuplot hides /usr/share/emacs/26.0.50/lisp/org/ob-gnuplot
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-exp hides /usr/share/emacs/26.0.50/lisp/org/ob-exp
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-eval hides /usr/share/emacs/26.0.50/lisp/org/ob-eval
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-emacs-lisp hides /usr/share/emacs/26.0.50/lisp/org/ob-emacs-lisp
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob hides /usr/share/emacs/26.0.50/lisp/org/ob
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-dot hides /usr/share/emacs/26.0.50/lisp/org/ob-dot
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-ditaa hides /usr/share/emacs/26.0.50/lisp/org/ob-ditaa
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-css hides /usr/share/emacs/26.0.50/lisp/org/ob-css
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-core hides /usr/share/emacs/26.0.50/lisp/org/ob-core
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-clojure hides /usr/share/emacs/26.0.50/lisp/org/ob-clojure
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-comint hides /usr/share/emacs/26.0.50/lisp/org/ob-comint
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-calc hides /usr/share/emacs/26.0.50/lisp/org/ob-calc
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-awk hides /usr/share/emacs/26.0.50/lisp/org/ob-awk
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/ob-asymptote hides /usr/share/emacs/26.0.50/lisp/org/ob-asymptote
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-loaddefs hides /usr/share/emacs/26.0.50/lisp/org/org-loaddefs
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-version hides /usr/share/emacs/26.0.50/lisp/org/org-version
/home/steb/.local/share/emacs/elpa/org-plus-contrib-20170210/org-install hides /usr/share/emacs/26.0.50/lisp/org/org-install

Features:
(shadow sort company-oddmuse company-keywords company-etags
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cl-macs gv core-themes-support core-display-init core-jump
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easymenu cl-loaddefs cl-lib page-break-lines easy-mmode subr-x pcase
time-date mule-util xdg tooltip eldoc electric uniquify ediff-hook
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font-lock syntax facemenu font-core term/tty-colors frame cl-generic
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cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind inotify
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 986417 1002486)
 (symbols 48 70025 35)
 (miscs 40 284 1008)
 (strings 32 170233 319877)
 (string-bytes 1 5608065)
 (vectors 16 110815)
 (vector-slots 8 2569333 222112)
 (floats 8 460 902)
 (intervals 56 6174 560)
 (buffers 976 23))

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Eli Zaretskii]

> From: Steven Allen <steven@stebalien.com>
> Date: Sat, 01 Apr 2017 12:20:35 -0700
> 
> 
> 1. Start `emacs -Q` (GUI mode, GTK3).
> 2. Open a scratch buffer.
> 3. Insert a MATHMATICAL SANS-SERIF BOLD SMALL LAMBDA (0x1D77A): 𝝺
> 
> The first time this character is displayed, Emacs hangs for ~15 seconds
> pegging the CPU at 100%. Unfortunately, the profiler doesn't seem to
> notice/record this hang.

That's normal: Emacs is looking for a font that can display this
character.  If you install the Symbola font, I think the search will
be much faster.

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Steven Allen]

So, I could have sworn I tested this with emacs -Q when I first found
the bug (I've been sitting on it for a while) but I guess I didn't. I
apologize.

It only reproduces for certain fonts.

Known Bad: Source Code Pro, Office Code Pro, Fira Mono
Known Good: Symbola, DejaVu Sans Mono (the default on my system)

So, to reproduce, evaluate the following before pasting the special
character.

  (set-face-attribute 'default nil :font "Source Code Pro-10")

Eli Zaretskii <eliz@gnu.org> writes:
> That's normal:

Hardly. 15 seconds is a *long* time for a computer and every other
application displays the character in question instantly. Not even
regenerating my entire font cache (fc-cache) takes that long.

> If you install the Symbola font, I think the search will
> be much faster.

I do have Symbola installed and the character does display correctly
eventually.

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Andreas Politz]

Steven Allen <steven@stebalien.com> writes:

> It only reproduces for certain fonts. [...]

> So, to reproduce, evaluate the following before pasting the special
> character.
>
>   (set-face-attribute 'default nil :font "Source Code Pro-10")
>
> [...]

Takes less than a second here.  Looks like the behavior depends on more
than the default font.

-ap

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Eli Zaretskii]

> From: Steven Allen <steven@stebalien.com>
> Cc: 26333@debbugs.gnu.org
> Date: Sat, 01 Apr 2017 15:00:58 -0700
> 
> 
> So, I could have sworn I tested this with emacs -Q when I first found
> the bug (I've been sitting on it for a while) but I guess I didn't. I
> apologize.
> 
> It only reproduces for certain fonts.
> 
> Known Bad: Source Code Pro, Office Code Pro, Fira Mono
> Known Good: Symbola, DejaVu Sans Mono (the default on my system)
> 
> So, to reproduce, evaluate the following before pasting the special
> character.
> 
>   (set-face-attribute 'default nil :font "Source Code Pro-10")

Is this the only thing one has to do, in "emacs -Q", in order to
reproduce the problem with these fonts?  Or do you have other
font-related customizations on your init files?

> Eli Zaretskii <eliz@gnu.org> writes:
> > That's normal:
> 
> Hardly. 15 seconds is a *long* time for a computer and every other
> application displays the character in question instantly. Not even
> regenerating my entire font cache (fc-cache) takes that long.

I meant "normal" as in "Emacs is known to do that sometimes when
searching for a font".  I'm not sure comparison with other
applications is valid, as Emacs attempts to solve a more complex
problem, and its font-searching algorithms are biased in favor of
finding fonts which support scripts and languages, not symbols.

As for comparison with fc-cache, Emacs many times examines each font
several times with different options, so it could be slower.

> > If you install the Symbola font, I think the search will
> > be much faster.
> 
> I do have Symbola installed and the character does display correctly
> eventually.

Is it eventually displayed using Symbola or some other font?

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Steven Allen]

Eli Zaretskii <eliz@gnu.org> writes:
> Is this the only thing one has to do, in "emacs -Q", in order to
> reproduce the problem with these fonts?  Or do you have other
> font-related customizations on your init files?

That's the only thing I have to do. Evaluate that, paste the character
in question, and then wait.

Eli Zaretskii <eliz@gnu.org> writes:
> I meant "normal" as in "Emacs is known to do that sometimes when
> searching for a font".

Emacs is also known to sometimes crash. That doesn't make this behavior
"normal". I'd understand "expected behavior" but I'd disagree (15
seconds is a *really* long time to hang just to lookup a font).

Eli Zaretskii <eliz@gnu.org> writes:
> I'm not sure comparison with other applications is valid, as Emacs
> attempts to solve a more complex problem, and its font-searching
> algorithms are biased in favor of finding fonts which support scripts
> and languages, not symbols.

How are those any different? From a computer's perspective, they're all
just Unicode blocks.

Regardless, if this is the case, one could solve this problem by simply
stacking the algorithms: execute the normal (fast) search first and
fallback on Emacs' complex (slow) search.

However, I kind of doubt this is a fundamental limitation in the current
font search algorithm.

Eli Zaretskii <eliz@gnu.org> writes:
> Is it eventually displayed using Symbola or some other font?

Symbola. However, when the default font is DejaVu, it's displayed with
"DejaVu Math TeX Gyre" (a different font in a different file).

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Steven Allen]

A workaround is to manually specify that "DejaVu Maath TeX Gyre" should
be used:

   (defun font--configure (&optional frame)
     (let ((font (font-spec :name "DejaVu Math TeX Gyre")))
       (set-fontset-font t '(#x1D400 . #x1D7FF) font frame)))
   (add-hook 'after-make-frame-functions #'font--configure)
   (font--configure)

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Lars Ingebrigtsen]

Steven Allen <steven@stebalien.com> writes:

> 1. Start `emacs -Q` (GUI mode, GTK3).
> 2. Open a scratch buffer.
> 3. Insert a MATHMATICAL SANS-SERIF BOLD SMALL LAMBDA (0x1D77A): 𝝺
>
> The first time this character is displayed, Emacs hangs for ~15 seconds
> pegging the CPU at 100%. Unfortunately, the profiler doesn't seem to
> notice/record this hang.

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

I'm unable to reproduce this problem in Emacs 28, but then again, this
problem seems to rely on a particular set of fonts being installed.

Are you still seeing the problem in recent Emacs versions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Sun, 23 Jan 2022 17:17:15 +0100
> Cc: 26333@debbugs.gnu.org
> 
> Steven Allen <steven@stebalien.com> writes:
> 
> > 1. Start `emacs -Q` (GUI mode, GTK3).
> > 2. Open a scratch buffer.
> > 3. Insert a MATHMATICAL SANS-SERIF BOLD SMALL LAMBDA (0x1D77A): 𝝺
> >
> > The first time this character is displayed, Emacs hangs for ~15 seconds
> > pegging the CPU at 100%. Unfortunately, the profiler doesn't seem to
> > notice/record this hang.
> 
> (I'm going through old bug reports that unfortunately weren't resolved
> at the time.)
> 
> I'm unable to reproduce this problem in Emacs 28, but then again, this
> problem seems to rely on a particular set of fonts being installed.

It could be that those 15 sec is what Emacs needs to search the
available fonts before it finds the one that can display the
character.

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Eli Zaretskii]

> Date: Sun, 23 Jan 2022 18:44:59 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 26333@debbugs.gnu.org, steven@stebalien.com
> 
> It could be that those 15 sec is what Emacs needs to search the
> available fonts before it finds the one that can display the
> character.

Oops, I see that I already said that, and the OP didn't like it, to
say the least.

bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> I'm unable to reproduce this problem in Emacs 28, but then again, this
> problem seems to rely on a particular set of fonts being installed.
>
> Are you still seeing the problem in recent Emacs versions?

More information was requested, but no response was given within a
month, so I'm closing this bug report.  If the problem still exists,
please respond to this email and we'll reopen the bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no