Re: [ft] GSUB opentype

[Antoine Leca]

Willem de Vries wrote:
> Although I searched through the documentation and mailing archives, I
> could not get a clear picture about the GSUB support.
> Does freetype support GSUB tables?

No. It is a higher level than Freetype is. Freetype may provide some access
to the GSUB tables (the raw information), but it will not actually apply
them to the rendered bitmaps (doing the substitutions.)
[OK, that's the big picture.]


> Are there additional libs or modules needed?
> Are there apps that do implement GSUB support?

There are some.

OpenType/TrueType Open (of which GSUB is a subset, another important part
being codenamed GPOS) is a specification to store typographic informations
in the fonts, the original idea was to let to the end-user applications
(e.g. Word) the workload to actually use those informations.

Nowadays, there are libraries, like Cooltype from Adobe (which is an
important sponsor of Opentype) and to a lesser degree OTLS from Microsoft
(the other sponsor) for general use applications, but it is NOT a plug-in,
there is quite work to get this in the application!
And there are also specialized cases like the libraries to support complex
scripts, like is ICU's LayoutEngine, Uniscribe in Windows, PanGo/Cairo for
Gnome or the equivalent in KDE.

FreeType 1 contained (actually, still contains) a general use library to
access _and_ use the GSUB and GPOS tables to arbitrarily strings of glyphs,
but development was discontinued years ago. It may perhaps be still useful
to develop test tools.
It was the only part of FT1 that was not carried over to FT2.


Hope this helps,


Antoine