language-selector fontconfig overides language fonts for CJK

[Jens Petersen]

Binary package hint: language-selector

Description: Ubuntu 9.10
Release: 9.10
Package-version: language-selector-0.4.18

Ubuntu's language-selector fontconfig overide system seems to have
a problem with CJK: particularly with rendering Japanese on a Chinese
desktop and Chinese on a Japanese desktop (I am not talking about
Han Unification ambiguities, but text with lang tags).

close example:

1. set a Japanese environment with language-selector
2. start a new desktop session in Japanese
3. open firefox
4. go to http://zh.wikipedia.org/zh-cn/ for example

Results:
4. Chinese page is rendered mostly with Japanese glyphs
    with fallback to Chinese font for missing glyphs

Expected
4. Chinese page rendered in Chinese font

Notes
For comparison you can try in Fedora for example
where rendering will respect the xhtml lang tag of the page.

ProblemType: Bug
Architecture: amd64
Date: Wed Dec 2 10:29:30 2009
DistroRelease: Ubuntu 9.10
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Alpha amd64 (20091014.1)
Package: language-selector 0.4.18
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=ja_JP.UTF-8
 LANG=ja_JP.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: language-selector
Uname: Linux 2.6.31-14-generic x86_64
XsessionErrors:
 (gnome-settings-daemon:1348): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (gnome-settings-daemon:1348): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (nautilus:1409): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
 (polkit-gnome-authentication-agent-1:1429): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed

[Arne Goetje (arnegoetje)]

I tried to solve this by checking for lang tags, but didn't succeed so far. Fontconfig doesn't give me the desired results. Need to investigate more, maybe fontconfig itself is buggy, too.

[Sebastien Bacher (seb128)]

is that stil an issue in lucid?

[Jens Petersen (juhpetersen)]

Yes - (4) still applies. I just tested with a Lucid live image.

[Gunnar Hjalmarsson (gunnarhj)]

My belief is that the current (in 16.04) Noto Sans CJK fonts have, if not solved the reported issue 100%, at least improved the behavior significantly. Would appreciate comments from CJK users who can confirm or refute that.

[Yuan Chao (yuanchao)]

My understand is that Noto Sans is not the default fonts for Japanese locale yet. This problem
has been reported. Please refer to #1581160.

[Gunnar Hjalmarsson (gunnarhj)]

Right, that's true, Yuan Chao.. (I forgot the comment I made on bug #1581160; sorry.)

So, in other words, if you have a system with full Japanese language support, you currently use Takao fonts. And if they are partially used for rendering Chinese contents, the problem described in this bug report is still present. Is that the case?

At the same time I suppose that the opposite - i.e. Japanese contents on a system with full Chinese support - looks ok in 16.04, since Noto Sans CJK JP is present on all machines.

So far there hasn't been a lot of response to my question at bug #1581160. :(