Re: Ligatures and Pango?



On Monday 14 November 2005 11:14, Owen Taylor wrote:
> On Thu, 2005-11-03 at 20:18 -0500, Behdad Esfahbod wrote:
> > On Thu, 3 Nov 2005, Han-Wen Nienhuys wrote:
> > > Behdad Esfahbod wrote:
> > > > The OpenType fonts declare which ligatures they have.  I think
> > > > it will be solved by the patch in this bug:
> > > >
> > > >   http://bugzilla.gnome.org/show_bug.cgi?id=101079
> > > >
> > > > I'll look into it soon.
> > >
> > > Does that include support for TTF files that have ligatures?
> >
> > No, I don't think so.
>
> I investigated this a while ago and it seemed to be quite
> non-standard how ligatures are mapped in TTF fonts. There are Unicode
> codepoints for some of the common ligatures, but fonts (as I recall)
> frequently mapped even those ligatures into the private-use area. And
> had other ligatures in the private use area as well.
>
> You'd need extra per-font supplemental data to do it well. Though
> maybe something simple is possible that will get ff/fi/ffi for a
> reasonable percentage of common fonts.

The information is in the GSUB table of the TTF font in question. 
And this is a standard AFAIK. So, the information is there, you just 
have to use it... :p

My CJK-Unifonts (www.cjkunifonts.info) also use PUA codepoints (Plane 15 
in my case) to provide Taiwanese POJ-ligatures for applications which 
cannot handle anchors for diacritics correctly (and hopefully can 
handle these ligatures instead).

Cheers
Arne
-- 
Arne Götje (高盛華) <arne linux org tw>
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