bug#45557: 27.1; Incorrect rendering of COMBINING OVERLINE

[Stephen Eglen]

In brief: x̅ does not appear as x with an overline in the JuliaMono font.

emacs -Q

(set-face-attribute 'default nil :font "JuliaMono")

(insert 611 773 32 120 773)

ɣ̅ x̅

should generate a gamma and x, both with overline.

gamma is overlined, but not x.

Checking with JuliaMono author, this does not seem to be a font issue:

https://github.com/cormullion/juliamono/issues/87


This has been confirmed by a harfbuzz maintainer, where you can see
detailed discussion.  It was suggested there to report this as an Emacs
bug, which I am now doing.

https://github.com/harfbuzz/harfbuzz/discussions/2790

Thanks, Stephen

----------------------------------------------------------------------
In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.22, cairo 
version 1.17.3)
 of 2020-08-28 built on juergen
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Manjaro Linux


Configured using:
 'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft --with-wide-int
 --with-modules --with-cairo --with-harfbuzz 'CFLAGS=-march=x86-64
 -mtune=generic -O2 -pipe -fno-plt' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

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

Important settings:
  value of $LC_MONETARY: en_GB.UTF-8
  value of $LC_NUMERIC: en_GB.UTF-8
  value of $LC_TIME: en_GB.UTF-8
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Image[png]

Minor modes in effect:
  pdf-occur-global-minor-mode: t
  global-magit-file-mode: t
  magit-auto-revert-mode: t
  global-git-commit-mode: t
  async-bytecomp-package-mode: t
  global-edit-server-edit-mode: t
  csv-field-index-mode: t
  shell-dirtrack-mode: t
  recentf-mode: t
  show-paren-mode: t
  TeX-PDF-mode: t
  straight-use-package-mode: t
  straight-package-neutering-mode: t
  display-time-mode: t
  tooltip-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
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/home/stephen/.emacs.d/straight/build/csv-mode/csv-mode hides 
~/langs/emacs/elisp-ds/csv-mode
~/langs/emacs/elisp-ds/emaxima/maxima-font-lock hides 
~/langs/emacs/maxima-font-lock
~/langs/emacs/elisp-ds/emaxima/maxima hides ~/langs/emacs/maxima
~/langs/emacs/mspools hides /usr/share/emacs/27.1/lisp/mail/mspools
/home/stephen/.emacs.d/straight/build/let-alist/let-alist hides 
/usr/share/emacs/27.1/lisp/emacs-lisp/let-alist

Features:
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custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
cairo move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 760591 140616)
 (symbols 48 84280 1)
 (strings 32 297932 8875)
 (string-bytes 1 9266510)
 (vectors 16 106532)
 (vector-slots 8 2940584 207654)
 (floats 8 1223 536)
 (intervals 56 22449 4880)
 (buffers 1000 60))