bug#24560: 25.1; With `--font 7x13', wrong font is used for Unicode characters

[Eli Zaretskii <eliz@gnu.org>]

Ping!  Ping!

> Date: Sat, 15 Oct 2016 17:10:41 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 24560@debbugs.gnu.org, thecybershadow@gmail.com
> 
> Ping!  Ping!
> 
> Kenichi, could you please comment on this issue?
> 
> > Date: Sat, 08 Oct 2016 16:07:34 +0300
> > From: Eli Zaretskii <eliz@gnu.org>
> > Cc: 24560@debbugs.gnu.org, thecybershadow@gmail.com
> > 
> > Ping!
> > 
> > > Date: Thu, 29 Sep 2016 18:30:37 +0300
> > > From: Eli Zaretskii <eliz@gnu.org>
> > > Cc: 24560@debbugs.gnu.org
> > > 
> > > Adding Handa-san to this discussion, in the hope that he could shed
> > > some light on this issue.
> > > 
> > > > From: Vladimir Panteleev <thecybershadow@gmail.com>
> > > > Cc: 24560@debbugs.gnu.org
> > > > Date: Wed, 28 Sep 2016 21:58:20 +0000
> > > > 
> > > > On 2016-09-28 20:16, Eli Zaretskii wrote:
> > > > > Are you sure the 7x13 font installed on your system supports all those
> > > > > characters?  Emacs won't switch to a different font if the default
> > > > > font supports the character it needs to display.
> > > > 
> > > > As I mentioned in my bug report and as is visible in the screenshots,
> > > > the characters are indeed present in the font and are rendered correctly
> > > > in other applications. Only Emacs exhibits this problem.
> > > > 
> > > > > Or could it be that some customizations, either yours or site-wide,
> > > > > force Emacs to use other fonts for the above characters?
> > > > 
> > > > This problem is reproducible with "emacs -Q", without any
> > > > customizations, on all distributions I've tried.
> > > 
> > > Then I guess there's some factor at work here that I don't quite
> > > figure out.  Maybe the Emacs font selection algorithm doesn't like
> > > that font for some reason?
> > > 
> > > If you start Emacs with 12x13 font or 8x13, does Emacs display more
> > > characters than 7x13 before it switches to another font?
> > > 
> > > > Here is a complete recipe using a live CD, to remove any possibility of
> > > > user or site customization:
> > > > 
> > > > 1. Get the Antergos live ISO (
> > > > https://antergos.com/download/antergos-live-iso/ ) and boot from it
> > > > (e.g. in a VM).
> > > > 2. Choose "Start Antergos live".
> > > > 3. Choose "Try It".
> > > > 4. Install Emacs and urxvt (in a terminal, run "pacman -S emacs
> > > > rxvt-unicode").
> > > > 5. Run "emacs -Q --font 7x13".
> > > > 6. M-x view-hello-file
> > > > 7. Observe that Cyrillic characters are rendered in a 12x13 font.
> > > > 8. Run "urxvt -fn 7x13".
> > > > 9. Copy some Cyrillic characters from Emacs and paste them in urxvt.
> > > > 10. Observe that urxvt renders the Cyrillic characters correctly, in the
> > > > correct font.
> > > > 
> > > > This is not specific to Arch / Antegros: The problem is also
> > > > reproducible on Ubuntu and Fedora Workstation Live CDs, though you may
> > > > have to also install some font packages (xorg-x11-fonts-misc for
> > > > Fedora), and Emacs uses the 8x13 font for Cyrillic characters (so the
> > > > problem is less obvious). urxvt still uses the correct font there.
> > > > 
> > > > >> I have found that evaluating the Sexpr:
> > > > >>
> > > > >> (set-fontset-font "fontset-default" 'unicode "-misc-fixed-*-*-*--13-*-*-*-*-70-iso10646-1")
> > > > >>
> > > > > 
> > > > > Don't do that, this setting will cause all kinds of surprises.  To
> > > > > customize the fonts, use specific character codepoint ranges, and only
> > > > > specify font for a range if the font support most or all of that
> > > > > range.
> > > > 
> > > > Noted. However, immediately lacking a better concrete workaround, I
> > > > don't have a better option at my disposal.
> > > 
> > > Hopefully, Handa-san will have some advice here.
> > 
> > 
> > 
> > 
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