Re: [Silgraphite-devel] Re: Pango and SILGraphite was Re: Possible Pango 1.4 ideas

[Owen Taylor <otaylor redhat com>]

ftang netscape com (Yung-Fong Tang) writes:

> Owen:
> 
> Thanks for your prompt reply.
> 
> >The place where I would hope you could insert Graphite is at the
> >level of converting:
> >
> > Font + Character string  =>  Glyph string
> >
> >This is the:
> >
> >  void (*script_shape) (PangoFont        *font,
> >			const char       *text,
> >			int               length,
> >			PangoAnalysis    *analysis,
> >			PangoGlyphString *glyphs);
> >
> >....
> >  The ones I was referring to in my earlier mail are public and
> >supported API; the Pango interfaces comprise about 5 pieces:
> >
> > 1) Public high-level API (PangoLayout)
> > 2) Public low-level API  (What is used to implement PangoLayout)
> > 3) Shape-engine only API (What, e.g., the arabic-xft shaper uses)
> > 4) Backend-only API      (What is used to implement libpangoxft)
> > 5) Internal Pango API
> >
> >Headers are installed for 1-4), but 3) and 4) have lower levels
> > of compatibility degrees, and you need special #defines to use them.
> >
> >(PANGO_ENABLE_ENGINE, PANGO_ENABLE_BACKEND)
> >
> >Regards,
> >                                        Owen
> >
> So.... which pieces (1-5) is (*script_shape) ?
> 
> Which header file(s) I should look into?

(*script_shape) is part of 3). It's in pango/pango-engine.h.
 
> Does pango hard code the range of unicode it can support ? or depend
> on the TTF 'cmap' now? (in mozilla, we switch font depend on the
> 'cmap' value [erik/bstell also did some trick to skip over some
> character claims to be there but not really there])

Pango gets its font coverages from fontconfig (this means that Pango
doesn't have to load up a font to know what characters it covers.)

As I understand it, fontconfig has all the Mozilla magic; I think
it essentially computes:

 (Characters in cmap) - (Blank characters - Characters that are supposed to be blank)

Regards,
                                        Owen