[Fontconfig] [PATCH] Do not remove UUID file when a scanned directory is empty

[Keith Packard]

Akira TAGOH <akira at tagoh.org> writes:

> Not rare today. this has been made to improve flatpaks startup time
> because regenerating fontconfig caches always happened.

I'd like to find a solution which doesn't involve writing files into the
font directories themselves, but I'm having trouble thinking of how that
might work without involving changes in the flatpaks themselves. All we
really need is some way to compute the right cache file name given the
path found inside the flatpak.

Is the .fonts.conf file for the flatpak computed dynamically? Can we
adjust how that is built? What if that file contained an association
between the paths it uses and the paths used outside? We could then
construct the external path from the internal path and use that to
generate the right cache file name.

Would we need more than one mapping per <dir> element in the font
configuration?

Alternatively, a flat-pak using system could place a magic file in each
top-level font directory for fontconfig to use for this mapping. As that
would simply contain the name of the directory in the external
namespace, it would be easy to generate with a shell script even. At
least we wouldn't be creating and destroying these files each time
fc-cache runs, as we wouldn't need them in each new directory, only at
the top of each font tree.

-- 
-keith
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