Re: [ft-devel] WOFF2 support update and questions

[Nikhil Ramakrishnan]

Hi,

> > * For TTC fonts, the `Collection Directory' specifies the index of
> >   tables that are part of each font in the collection. The
> >   `face_index' parameter in `FT_New_Face' specifies which face to
> >   load, so does that mean I can use that to directly extract and
> >   load only those tables that belong to the font on that index?
>
> I think so, yes.
>
> >   Do I have to decompress each table and load the whole collection
> >   as an SFNT? I'm not sure...
>
> Me neither, sorry.  I have never worked with WOFF.  Please report any
> unclear issues to the WOFF2 standard team so that they can improve the
> documentation.

Alexei pointed out that all the tables are compressed as a single
stream, so it is now clear that the whole stream must be uncompressed.
I have another question, unrelated to WOFF2, but about TTCs in
general:

Let's say I want to load the nth font inside a TTC. Would it be
sufficient to write an SFNT stream starting with the Offset Table (and
not the TTC Header) along with only those tables that make up the nth
face?

To put this in context of WOFF2, I want to know whether I should pass
the SFNT stream of a WOFF2 compressed TTC font with a TTC header and
*all* its tables, or would it be correct/sufficient to write the
stream such that the fact that the WOFF2 is actually a collection, is
hidden from rest of the SFNT processing (they only see the requested
face in the stream). Do these `individual' streams function
identically to a full `TTC' stream?


-- 
Nikhil