The UUID files would be placed in each font directory to provide the
unique cache name, independent of path, for that directory. The UUID
files are undesireable for a couple of reasons:
1) They must be placed in the font directories to be useful. This
requires modifying the font directories themselves, introducing
potential visible timestamp changes when running multiple
applications, and makes the cache processing inconsistent between
applications with permission to write to the font directories and
applications without such permission.
2) The UUID contents were generated randomly, which makes the font
cache not reproducible across multiple runs.
One proposed fix for 2) is to make the UUID dependent on the font
directory path, but once we do that, we can simply use the font
directory path itself as the key as the original MD5-based font cache
naming mechanism did.
The goal of the UUID file mechanism was to fix startup time of
flatpaks; as the font path names inside the flatpak did not match the
font path names in the base system, the font cache would need to be
reconstructed the first time the flatpak was launched.
The new mechanism for doing this is to allow each '<dir>' element in
the configuration include a 'map' attribute. When looking for a cache
file for a particular directory, if the directory name starts with the
contents of the <dir> element, that portion of the name will be
replaced with the value of the 'map' attribute.
Outside of the flatpak, nothing need change -- fontconfig will build
cache files using real directory names.
Inside the flatpak, the custom fonts.conf file will now include
mappings such as this:
<dir map="/usr/share/fonts">/run/host/fonts</dir>
When scanning the directory /run/host/fonts/ttf, fontconfig will
use the name /usr/share/fonts/ttf as the source for building the cache
file name.
The existing FC_FILE replacement code used for the UUID-based
implementation continues to correctly adapt font path names seen by
applications.
v2:
Leave FcDirCacheCreateUUID stub around to avoid removing
public API function.
Document 'map' attribute of <dir> element in
fontconfig-user.sgml
Suggested-by: Akira TAGOH <akira@tagoh.org>
Signed-off-by: Keith Packard <keithp@keithp.com>
All non trivial users of FontConfig must use FcConfigGetSysRoot to
resolve file properties in patterns. In order to support sysroot the
filename in the file property must be relative to the sysroot, but the
value of the file property in a pattern is directly exposed, making it
impossible for FontConfig to resolve the filename itself transparently.
Whilst working on the Reproducible Builds[0] effort, we noticed that
fontconfig generates unreproducible cache files.
This is due to fc-cache uses the modification timestamps of each
directory in the "checksum" and "checksum_nano" members of the _FcCache
struct. This is so that it can identify which cache files are valid
and/or require regeneration.
This patch changes the behaviour of the checksum calculations to prefer
the value of the SOURCE_DATE_EPOCH[1] environment variable over the
directory's own mtime. This variable can then be exported by build
systems to ensure reproducible output.
If SOURCE_DATE_EPOCH is not set or is newer than the mtime of the
directory, the existing behaviour is unchanged.
This work was sponsored by Tails[2].
[0] https://reproducible-builds.org/
[1] https://reproducible-builds.org/specs/source-date-epoch/
[2] https://tails.boum.org/
Trying to address what these configuration files really do.
This change allows to see the short description that mention
the purpose of the content in the config file and obtain
them through API.
This change also encourage one who want to make some UI for
the user-specific configuration management. it is the main
purpose of this change for me though.
Aside from that, I've also made programs translatable. so
we see more dependencies on the build time for gettext,
and itstool to generate PO from xml.
In 32ac7c75e8 the behavior of
FcConfigAppFontAddFile/Dir() were changed to return false
if not fonts were found. While this is welldefined and useful
for AddFile(), it's quite problematic for AddDir(). For example,
if the directory is empty, is that a failure or success? Worse,
the false value from AddDir() was being propagated all the way
to FcInit() returning false now. This only happened upon memory
allocation failure before, and some clients assert that FcInit()
is successful.
With this change, AddDir() is reverted back to what it was.
AddFont() change (which was actually in fcdir.c) from the original
commit is left in.
just setting FC_MATCH=3 shows a lot of information and hard to keep on track for informamtion
which is really necessary to see. to use this more effectively, added FC_DBG_MATCH_FILTER to
see for what one really want to see. it takes a comma-separated-list of object names.
If you want to see family name only, try like this:
FC_DBG_MATCH_FILTER=family FC_DEBUG=4096 fc-match
debugging output will be filtered out and see family only in the result.
Adds FC_SYMBOL.
This affects fonts having a cmap with platform 3 encoding 0.
We now map their glyphs from the PUA area to the Latin1 area.
See thread "Webdings and other MS symbol fonts don't display"
on the mailing list.
Test before/after with:
$ pango-view --markup --text='<span fallback="false">×</span>' --font=Wingdings
The SGML for these functions exists, and they are named as manpages,
but because they are not mentioned in fontconfig-devel.sgml, no
documentation is ever generated, and installation under --enable-docs
fails.
(The documentation I have written in fontconfig-devel.sgml is boilerplate
so I can get the manpages generated. It's probably wrong.)
Szunti
Akira TAGOH
Keith Packard
Ben Wagner
Chris Lamb
Tom Anderson
Behdad Esfahbod
Helmut Grohne
Alan Coopersmith
Nick Alcock