Re: Chinese Traditional appearance -- mixed weights?

[Behdad Esfahbod <behdad behdad org>]

On Sat, 2007-10-20 at 18:33 -0400, Owen Taylor wrote:
> On Fri, 2007-10-19 at 21:34 -0400, Behdad Esfahbod wrote:
> > Hi Owen,
> > 
> > I've had this message of yours from last September in my inbox for quite
> > a while, because I couldn't congest it the first time.  Tonight I gave
> > it another try and I still don't follow.  Do you mind clarifying what
> > the fontconfig change is about?  More inline.
> > 
> > On Sat, 2006-09-30 at 11:55 -0400, Owen Taylor wrote:
> > > 
> > > The font selection algorithm for older versions of fontconfig is:
> > > 
> > >  1) Explicitly specified non-generic fonts, in the order specified
> > >    (generic fonts being things like "sans-serif", "serif", "monospace")
> > > 
> > >  2) Fonts from the generic in use matching the language tag of the text 
> > >    sorted by the order that those fonts appear in the generic.
> > >    The generic in use is determined in  priority order:
> > > 
> > >      - If one was given explicitly, that generic
> > >      - If a explicitly specified font is recognized as belong to
> > >        a generic class, that generic. (So, Arial pulls in sans-serif,
> > >        Courier, serif)
> > >      - Otherwise, sans-serif
> > >        
> > >  3) Other fonts matching the language tag, in random order.
> > > 
> > >  4) Other fonts from the generic in use.
> > > 
> > >  5) Other fonts in random order.
> > 
> > Ok, these make sense.  And the final list is pruned, right?
> 
> Yes, I omitted that detail because it makes no user-visible difference.
> 
> > > If the language tag refinement scheme ended up with no language tag,
> > > then 2) and 3) are skipped... this is what is going on when your
> > > language is en-US.
> > > 
> > > The fix in the most recent versions of fontconfig referred to above
> > > is that 2) and 3) are replaced with:
> > > 
> > >  2') The best font that matches the language tag of the text chosen as
> > >      the first language-tag matching font of:
> > > 
> > >        - Fonts from the generic use, in the order specified 
> > >        - Other fonts in random order
> > 
> > I don't understand this one.
> > 
> > And which version of fontconfig was this introduced in?
> 
> commit 5cf8c5364f1b7a676f52b480fa55c571cadc6fda
> Author: Keith Packard <keithp keithp com>
> Date:   Tue Dec 14 00:12:25 2004 +0000
> 
>     I changed FcFontSetSort to respect the generic aliases better in
>     the face of language matching.
>     What I did was to ammend the strict sort order used by FcFontSort
>     so that it 'satisfies' the language specified in the pattern by
>     locating the  best matching font supporting each pattern language
>     and then ignores language in the remaining fonts for purposes of
>     matching.
> 
>     So, when asking for 'sans:lang=en', you'll get an English font
>     first, and then the remaining fonts sorted with respect to the
>     'sans' alias alone -- pushing Kochi fonts ahead of other
>     English-supporting Han fonts.
> 
>     reviewed by: Owen Taylor <otaylor redhat com>
> 
> I don't know what version of fontconfig that corresponds to.
> 
> > > The advantage of that is that once we know what font we prefer for,
> > > say, Greek, a language tag of Greek won't then won't reorder Russian
> > > fonts to prefer fonts that also happen to cover Greek.
> > 
> > And I don't get this either.  So, you are saying that if we ask for
> > fonts with lang=Greek but look for fonts supporting Russian in the
> > result it will work as good as doing the same with lang=Russian?
> 
> So, say we have three fonts:
> 
>  Nice font covering Russian
>  Nice font covering Greek
>  Ugly font covering Greek and Russian
> 
> Sorted in that order in the sans-serif alias in fonts.conf.
> 
> The way that fontconfig used to work, FcFontSort with lang=gr would
> have given us:
> 
>  Nice font covering Greek
>  Ugly font covering Greek and Russian
>  Nice font covering Russian
> 
> Because the Greek and Russian font was considered to be "better" than
> the Russian only font. This forced us to do language tag refinement.
> 
> But the observation is that once Greek has been "satisfied" by one font,
> there is no reason for fontconfig to reorder the rest of fonts, so newer
> versions of fontconfig will instead give us instead:
> 
>  Nice font covering Greek
>  Nice font covering Russian
>  Ugly font covering Greek and Russian
> 
> And we get reasonable results with the simple lang=gr language tag.

Ah Ok, makes a lot of sense now.  Thanks!

I still think the language tag refinement has its own merits, specially
with new Pango support for PANGO_LANGUAGES.


> - Owen

Regards,
-- 
behdad
http://behdad.org/

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