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

[suzuki toshiya]

Hi,

Just I've filed my proposal to bugzilla, with my preliminary patch:
https://bugs.freedesktop.org/show_bug.cgi?id=30225

Also I found a similar discussion in August:
https://bugs.freedesktop.org/show_bug.cgi?id=29497
Unfortunately, it seems that the original submitter does not
raise the discussion in this list.

Regards,
mpsuzuki

Behdad Esfahbod wrote:
> Can you file a bug with reference to these details please?
>
> behdad
>
> On 09/03/10 03:50, mpsuzuki at hiroshima-u.ac.jp wrote:
>   
>> On Thu, 02 Sep 2010 16:44:35 -0400
>> Behdad Esfahbod <behdad at behdad.org> wrote:
>>     
>>> 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?
>>>       
>> In some popular document formats, like PDF, SVG, ODF and OOXML,
>> Panose values are embedded to give the hint for font substitution.
>> ==================================================================
>> PDF 
>> ---
>> PDF Reference 6th edition (for PDF version 1.7)
>> 5.7.2 Font Descriptors for CIDFonts
>>
>> 	see the description for "Style" entry which
>> 	includes 2 bytes from OS/2.sFamilyClass,
>> 	10 bytes from OS/2.Panose.
>>
>> SVG
>> ---
>> http://www.w3.org/TR/2003/REC-SVG11-20030114/fonts.html
>> 20.8.3 The `font-face' element
>>
>> 	there are many elements inherited from CSS2,
>> 	including Panose.
>>
>> ODF
>> ---
>> http://docs.oasis-open.org/office/v1.1/OS/OpenDocument-v1.1.pdf
>> 14.6.1 CSS2/SVG Font Descriptors
>>
>> 	ODF adopted the elements for the fonts from
>> 	CSS2 and SVG, so even the font is for the text
>> 	(not for embedded scalable graphics), it may
>> 	have Panose value in the svg:panose-1 attribute.
>> 	
>> OOXML
>> -----
>> ISO/IEC 29500-1:2008
>> 17.8.3.13 panose1 (Panose-1 Typeface Classification Number)
>>
>> 	OOXML have several font properties (GDI parameters,
>> 	Panose, and supported unicode range). In 17.8.2 Font
>> 	Substitution, there is a list of properties to be
>> 	used in the font substitution, and panose is described
>> 	as the highest priority.
>>
>> PCL
>> ---
>> "PCL 5e Technical Quick Reference Guide"
>>   http://h20000.www2.hp.com/bc/docs/support/SupportManual/bpl13205/bpl13205.pdf
>> "PCL5 Comparison Guide"
>>   http://h20000.www2.hp.com/bc/docs/support/SupportManual/bpl13206/bpl13206.pdf
>>
>> 	PCL5 selects the font by giving Panose parameters
>> 	sequentially and narrowing down the candidates,
>> 	see PCL 5e Technical Quick Reference Guide p 11-15.
>>
>> 	See table 1-1 "PCL5 Feature Support Matrix" in
>> 	page 1-12 PCL5 Comparison Guide, many PCL5
>> 	implementations support the feature to narrow
>> 	down by Panose parameters.
>>
>> 	Also PCL6 (PCL XL) supports the feature by
>> 	giving a string of PCL5 commands to PCLSelectFont
>> 	attribute.
>> ==================================================================
>> In addition, current fontconfig does not have easy element to
>> be related with CSS's 5 family classification (serif, sans-
>> serif, cursive, fantasy). I think getting FamilyClass & Panose
>> values from fontconfig cache may be helpful, because the
>> application don't have to open a face, load OS/2 table,
>> check FamilyClass/Panose values, close a face.
>>
>> The font selection by the matching of familynames & charsets
>> leaves a room for an improvement, because severeal documents
>> formats (and CSS) have these properties in the documents.
>>
>> --
>>
>> The query based on these properties is arguable. The algorithm
>> to evaluate "best matching" font by Panose is not specified
>> in Panose specification paper. If exactly same, it is ok - but if
>> different, it is arguable how the similarity should be evaluated.
>> Some people want to give the highest priority to serif/sans-serif
>> contrast, others want to give it to weight similarity. At present,
>> I don't have good idea that everybody think it as acceptable.
>>
>> Thus, I think just giving the APIs to provide these properties
>> (FamilyClass, Panose, etc) is appropriate starting point. It
>> is still convenient for fontconfig client applications because
>> they can reduce the costs to open/check/close many font files
>> by themselves.
>>
>> # In fact, in PCL5, the priority of each bytes in Panose is user
>> # controllable.
>>
>> Behdad, could I answer to your question? If I'm misunderstanding
>> what I was requested, please give me one more chance.
>>
>> Regards,
>> mpsuzuki
>>
>> P.S.
>> If putting so many data to fontconfig is bad idea, please let me
>> know.
>>
>>     
>>> 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
>>>> # like FC_OS2_PANOSE_FAMILYTYPE.
>>>>
>>>> 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.
>>>>
>>>>