RFR: 8370719: [Linux] Use /etc/os-release values for font configuration file names

[Phil Race]

On Mon, 3 Nov 2025 21:16:42 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> The JBS issue has a long discussion and explanation but here's a short version.
>> Instead of having baked in names of distros in the code that figures out names for font configuration files for Linux
>> use the standard ID and VERSION_ID fields in /etc/os-release which is now standard.
>> even systemd doesn't work if it does not exist https://0pointer.de/blog/projects/os-release
>> And if it doesn't we just use "Linux" as the name.
>
> src/java.desktop/unix/classes/sun/font/FcFontConfiguration.java line 320:
> 
>> 318:         }
>> 319:         try {
>> 320:             File f = new File("/etc/os-release");
> 
> Don't we need to check "/usr/lib/os-release" as well?
> https://www.freedesktop.org/software/systemd/man/latest/os-release.html
>>The file /etc/os-release takes precedence over /usr/lib/os-release. Applications should check for the former, and exclusively use its data if it exists, and only fall back to /usr/lib/os-release if that is missing. Applications should not combine the data from both files. /usr/lib/os-release is the recommended place to store OS release information as part of vendor trees. /etc/os-release should be a relative symlink to /usr/lib/os-release, to provide compatibility with applications only looking at /etc/. A relative symlink instead of an absolute symlink is necessary to avoid breaking the link in a chroot or initrd environment.

I'd considered that. Taking the wording above,  which encourages apps to check /etc first, and that every system I've checked has an /etc/os-release, and that it isn't a big deal even if we fail to find it unless you are creating a custom fontconfig file, I saw no need.

> src/java.desktop/unix/classes/sun/font/FcFontConfiguration.java line 321:
> 
>> 319:         try {
>> 320:             File f = new File("/etc/os-release");
>> 321:             if (f.canRead()) {
> 
> Should we check whether this is a file and not a directory?

That would be a weird problem which likely would mean the system can't even boot.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28073#discussion_r2487966755
PR Review Comment: https://git.openjdk.org/jdk/pull/28073#discussion_r2487967931