[Fontconfig] Re: fontconfig support to exclude glyphs from fonts

[Nicolas Mailhot]

Le jeudi 29 juin 2006 à 05:03 +0200, Keith Packard a écrit :

> On Wed, 2006-06-28 at 16:15 -0700, Jay Hobson wrote:
> 
> >     The patch adds two new tags to supported XML tag list. The tags work 
> > in conjuction with other tags already present in the library. The tags 
> > require fonts.conf or its included counterparts to be amended, detailing 
> > languages to restrict in specified families. The first added tag "hide" 
> > documents which languages are restricted from use for the family. The 
> > second tag "only" documents which languages the family is allowed to 
> > support.
> 
> We've been discussing this here at Guadec and decided that what we
> really want to do is ban unicode codepoint sets from certain fonts. As
> fontconfig computes said ranges, it should be reasonably easy to add a
> match/edit phase to font scanning and edit the unicode codepoint set
> before creating the cache file. It means that changes to this would
> require manual regeneration of the cache, but it also means that the
> glyphs wouldn't ever be shown from those fonts as higher level libraries
> use that codepoint set to select fonts for each glyph.

While fine-tuning blacklisting by codepoint sets would be even better, I
think Jay's choice of doing it only in aliasing context with specific
langs should not be totally dropped :
- if a user specifically requests a glyph using an exact font name (not
an alias) who are we to refuse it? (in an alias context with all the
fallbacks of course the problem is different)
- also, due to some glyphs being shared by several cultural areas which
do not agree on their drawing, you need to take the lang used into
account when blacklisting (that is until libs like pango implement locl
and all fonts are changed to put the right variants in the same places)

However for my short-term needs any kind of blacklisting will work, so
please work help Jay modify his patch till it's ready for inclusion.

Regards,

-- 
Nicolas Mailhot
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