[Fontconfig] How can I store FC_MATRIX object to cache file?

Behdad Esfahbod behdad at behdad.org
Thu Sep 2 13:44:35 PDT 2010


Can you explain more why the PANOSE values are needed?  And, do we need to
allow users to query based on them, or just having them in the cache?


On 09/02/10 14:24, mpsuzuki at hiroshima-u.ac.jp wrote:
> Hi,
> How can I store FC_MATRIX object to cache file?
> --
> Now I'm trying to add some properties to fontconfig database,
> which are taken from OS/2 and PCLT tables in OpenType: like
> sFamilyClass (so-called IBM family classification), Panose etc.
> They are useful to guess whether typeface is typographic/scriptic,
> serif/sans-serif, proportional/fixed-pitch etc. My original
> motivation is an improvement of the font substitution in poppler.
> For detail, please find:
> 	https://bugs.freedesktop.org/show_bug.cgi?id=5168
> Panose in OpenType is a collection of 10 parameters, and
> all parameters are expressed by 8bit. 80bit is too large
> to pack into double integer, so I have to consider what is
> the best way to store such in FcPattern. I think there are
> 3 options:
> 1) Name all parameters and store separately, aslike,
> adding 10 types to FcObjectTypes: FC_OS2_PANOSE_0,
> FC_OS2_PANOSE_1, ...
> # The name of each byte is different from OpenType spec
> # and its reference, so I don't use OpenType spec name
> 2) ASCII-fy 10 parameters to NULL-terminated string,
> and use as a string type property.
> 3) Define new data type, a structure including 10 members
> and add "FcTypePanose" to FcType.
> --
> About 1), it's easy for me to write such patch and for
> users to use, but the addition of 10 objects may be too
> much, because current variety of the object type is 41.
> About 2), it's easy for me to write such patch but tricky
> for users to use, because it is requred to decode from
> ASCII string to original data.
> About 3), it's easiest for users. So I have to consider
> about this option.
> Checking the source code of fontconfig, FcMatrix data
> type looks similar (a structure with fixed length), but
> it seems that the data typed FcMatrix cannot be stored
> in cache file. I inserted FcMatrix object to FcPattern
> and tried to save it in cache file, but it seems that
> FcMatrix typed data cannot be saved (fc-cat can read
> object type but cannot read value).
> The code for FcString, FcCharSet and FcLangSet are
> variable length data and have many works. So I want to
> know how I can store FcMatrix typed data to cache file.
> Regards,
> mpsuzuki
> P.S.
> If option 1) or 2) are acceptable for fontconfig maintainers,
> I will do so.

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