Subject: 24.5; Font fallback doesn't work for the Emoji range

From: Vasilij Schneidermann <[email-masked]>
Date: Wed, 3 Jun 2015 19:22:42 +0200

I did install the Symbola font to be able to display glyphs for code
points in the Emoji range which works for applications like my browser,
however Emacs isn't able of displaying these glyphs despite that
measure.  To reproduce the issue on a Linux system, it's sufficient to
have the Symbola font installed and with a default font different from
it to insert a character like PILE OF POO with C-x 8 RET which yields a
rectangle with numbers in it.  Temporarily switching the default font
to Symbola with M-x set-frame-font is one possible workaround to display
the glyph, another one is modifying the default fontset to explicitly
make use of that font for the Emoji range:

    (set-fontset-font "fontset-default" nil "Symbola"
                      (selected-frame) 'append)

I find this behaviour sort of puzzling as inspection of a buffer as
produced with M-x view-hello-file and M-x describe-char on the various
scripts confirms that Emacs managed choosing suitable fallback fonts for
scripts not covered by my default font.  Can someone enlighten me to
what exactly is going on here?

In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.16.2)
 of 2015-04-20 on bitzer.hoetzel.info
Windowing system distributor `The X.Org Foundation', version 11.0.11701000
System Description: Arch Linux

Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong
 --param=ssp-buffer-size=4' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

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

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils time-date tooltip electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer 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 make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 70978 6876)
 (symbols 48 17559 0)
 (miscs 40 35 138)
 (strings 32 9044 4472)
 (string-bytes 1 248344)
 (vectors 16 8908)
 (vector-slots 8 383094 18351)
 (floats 8 63 213)
 (intervals 56 177 0)
 (buffers 960 11)
 (heap 1024 42438 899))