[Bug 2063714] New: serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

Bug ID: 2063714
           Summary: serif:lang=ja falls back to Droid Sans instead of Noto
                    Sans CJK JP
           Product: Fedora
           Version: 36
            Status: NEW
         Component: fontconfig
          Assignee: [e-mail]
          Reporter: [e-mail]
        QA Contact: [e-mail]
                CC: [e-mail], [e-mail],
                    [e-mail],
                    [e-mail],
                    [e-mail], [e-mail],
                    [e-mail], [e-mail],
                    [e-mail], [e-mail],
                    [e-mail]
  Target Milestone: ---
    Classification: Fedora

Description of problem:
In Fedora 36 when google-noto-serif-cjk-ttc-fonts is not installed
fontconfig seems to fall back to google-droid-sans-fonts
rather than google-noto-sans-cjk-ttc-fonts.

This might be related to/caused by bug 517789?

How reproducible:
100%

Steps to Reproduce:
1. boot Fedora Live image
2. fc-match serif:lang=ja

Actual results:
2. DroidSansJapanese.ttf: "Droid Sans" "Regular"

Expected results:
2. NotoSansCJK-Regular.ttc: "Noto Sans CJK JP" "Regular"

Additional info:
I get the same result with your older copr repo applied F35 fwiw.

[Bug 2063714] serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

--- Comment #1 from Akira TAGOH  ---
First, no, this isn't related to Bug#517789. fontconfig is trying to estimate
the score from the various properties provided by font caches. what fonts are
the best font according to the request is depending on what a sort of fonts
installed. strictly speaking, it is reproducible but it isn't that easy to
predict which one it would be.
Usually we add a substitute rule to make it predictable. it is mostly obvious
from the order of the family names. However, in this case, if no serif fonts is
installed, it will be decided by other properties. thus, it doesn't care what
fonts are default for sans-serif, and it could says this behavior isn't a bug.

One thing we can make it better is to add sans-serif at the end of family name
list as a last resort. that may looks like (not tested):

<fontconfig>
  <match>
    <test name="family">
      <string>serif</string>
    </test>
    <edit name="family" mode="append_last">
      <string>sans-serif</string>
    </edit>
  </match>
</fontconfig>

Note the position of this config. it must be proceeded prior to other config
which interacts with "sans-serif". This would gives you Noto Sans related
family instead of DejaVu Sans. though adding different typefaces as a fallback
sounds not a good idea.

[Bug 2063714] serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

--- Comment #2 from Jens Petersen  ---
Thanks for the detailed analysis, Akira

[Bug 2063714] serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

Akira TAGOH  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|fontconfig                  |google-noto-fonts
                 CC|                            |[e-mail],
                   |                            |[e-mail],
                   |                            |[e-mail]
             Status|NEW                         |MODIFIED

--- Comment #3 from Akira TAGOH  ---
This should be fixed in google-noto-fonts-20201206^1.git0c78c8329-9.fc38

[Bug 2063714] serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

Jens Petersen  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
   Fixed In Version|                            |google-noto-fonts-20201206^
                   |                            |1.git0c78c8329-9.fc38

--- Comment #4 from Jens Petersen  ---
I tested the build and it LGTM now, thanks!

[Bug 2063714] serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

Jens Petersen  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|36                          |37

[Bug 2063714] serif:lang=ja falls back to Droid Sans instead of Noto Sans CJK JP

https://bugzilla.redhat.com/show_bug.cgi?id=2063714

Akira TAGOH  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |NEXTRELEASE
             Status|MODIFIED                    |CLOSED
        Last Closed|                            |2023-08-07 07:23:37

--- Comment #5 from Akira TAGOH  ---
Unfortunately there are no plans to backport this change for some reasons. This
has been fixed in f38 and f37 is going to be EOL. so closing this.