bug#41174: Epiphany can't find fonts

[Leo Prikler]

Hi Guix,

After some discussion in IRC and testing, I found out that adding
$GUIX_PROFILE/share/fonts to the webkit sandbox (during initialization
via `webkit_web_context_add_path_to_sandbox') resolves this problem.  A
more general solution would be to iterate over $XDG_DATA_DIRS, append
`/fonts' to each item and add the resulting path to the sandbox (if it
is a directory).

As this is a problem related to the webkit sandbox, it probably affects
other packages, that make use of it, as well.  Looking even deeper
(i.e. diving into the webkitgtk source), it appears that there is
indeed a `bindFonts' procedure in the BubblewrapLauncher, but that only
considers $XDG_DATA_HOME/fonts, not all of $XDG_DATA_DIRS.  As this is
the root of the issue, it should probably be fixed there.

Regards,
Leo

Note for those looking for a workaround: Assuming you're installing
your fonts to $GUIX_PROFILE/share/fonts, making $XDG_CACHE_HOME/fonts
or $HOME/.fonts a symlink to that should work.