Some unicode symbols can't be displayed

Some unicode symbols can't be displayed

[Julien Cubizolles]

Some unicode symbol aren't properly displayed in gtk emacs -Q. I only get
a square block with the unicode number in it.

Here is an example (output of describe-char):

--8<---------------cut here---------------start------------->8---
             position: 15833 of 27566 (57%), column: 25
            character: 👍 (displayed as 👍) (codepoint 128077, #o372115, #x1f44d)
    preferred charset: unicode (Unicode (ISO10646))
code point in charset: 0x1F44D
               script: symbol
               syntax: w 	which means: word
             category: .:Base
             to input: type "C-x 8 RET 1f44d" or "C-x 8 RET THUMBS UP SIGN"
          buffer code: #xF0 #x9F #x91 #x8D
            file code: #xF0 #x9F #x91 #x8D (encoded by coding system utf-8-unix)
              display: no font available

Character code properties: customize what to show
  name: THUMBS UP SIGN
  general-category: So (Symbol, Other)
  decomposition: (128077) ('👍')

There are text properties here:
  fontified            t
--8<---------------cut here---------------end--------------->8---

What's even more confusing: it's correctly displayed as a thumbs up sign
in emacs -nw, and on another machine where I have basically the same
emacs setup.

I'm running GNU Emacs 26.0.50 (build 2, x86_64-pc-linux-gnu, GTK+
Version 3.20.9) of 2017-04-04

Julien.

Re: Some unicode symbols can't be displayed

[Julien Cubizolles]

Julien Cubizolles <j.cubizolles@free.fr> writes:

> Some unicode symbol aren't properly displayed in gtk emacs -Q. I only get
> a square block with the unicode number in it.

Note that some symbols are displayed properly, 
❤ for instance:

--8<---------------cut here---------------start------------->8---
             position: 519 of 667 (78%), restriction: <100-668>, column: 0
            character: ❤ (displayed as ❤) (codepoint 10084, #o23544, #x2764)
    preferred charset: unicode-bmp (Unicode Basic Multilingual Plane (U+0000..U+FFFF))
code point in charset: 0x2764
               script: symbol
               syntax: w 	which means: word
             category: .:Base
             to input: type "C-x 8 RET 2764" or "C-x 8 RET HEAVY BLACK HEART"
          buffer code: #xE2 #x9D #xA4
            file code: #xE2 #x9D #xA4 (encoded by coding system utf-8-emacs)
              display: by this font (glyph code)
    xft:-PfEd-DejaVu Sans Mono-normal-normal-normal-*-13-*-*-*-m-0-iso10646-1 (#xB43)

Character code properties: customize what to show
  name: HEAVY BLACK HEART
  general-category: So (Symbol, Other)
  decomposition: (10084) ('❤')

There are text properties here:
  fontified            t
--8<---------------cut here---------------end--------------->8---

Re: Some unicode symbols can't be displayed

[Eli Zaretskii]

> From: Julien Cubizolles <j.cubizolles@free.fr>
> Date: Thu, 06 Apr 2017 17:14:11 +0200
> 
> Some unicode symbol aren't properly displayed in gtk emacs -Q. I only get
> a square block with the unicode number in it.

This means you don't have a font installed that Emacs can use to
display this character.

> What's even more confusing: it's correctly displayed as a thumbs up sign
> in emacs -nw, and on another machine where I have basically the same
> emacs setup.

"emacs -nw" uses the font of the terminal emulator.

Bottom line: install a suitable font.  On my system, this character is
displayed in Emacs using the Symbola font.

Re: Some unicode symbols can't be displayed

[Julien Cubizolles]

Eli Zaretskii <eliz@gnu.org> writes:

> "emacs -nw" uses the font of the terminal emulator.

> Bottom line: install a suitable font.  On my system, this character is
> displayed in Emacs using the Symbola font.

Thanks, installing the Symbola font fixed it, even though Emacs is using
DejaVu Sans Mono. It must somehow fall back to Symbola. It's strange
however that the terminal emulator had a "better" fallback than Emacs.

Re: Some unicode symbols can't be displayed

[Eli Zaretskii]

> From: Julien Cubizolles <j.cubizolles@free.fr>
> Cc: help-gnu-emacs@gnu.org
> Date: Thu, 06 Apr 2017 22:41:11 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > "emacs -nw" uses the font of the terminal emulator.
> 
> > Bottom line: install a suitable font.  On my system, this character is
> > displayed in Emacs using the Symbola font.
> 
> Thanks, installing the Symbola font fixed it, even though Emacs is using
> DejaVu Sans Mono. It must somehow fall back to Symbola.

Yes, it falls back to Symbola (or other fonts, see fontset.el in the
Emacs sources) when the default font cannot display a character.

> It's strange however that the terminal emulator had a "better"
> fallback than Emacs.

Perhaps the terminal emulator used something other than DejaVu Sans
Mono as its default?  Or maybe it installs the fonts it needs as part
of its installation?  Emacs doesn't install fonts, and we don't want
to specify non-free fonts as fallbacks, so we have more limitations
than an arbitrary program out there.