RE: [Freetype] Pango or Freetype and some other questions!!

[Turner, David]

Hello,

> Hello,
> 
> Pango uses Freetype for reading and storing OT tables. Does 
> Qt support OT
> and if yes is it also using freetype as font reader? 
> 
> Aamir
> 

Unfortunately, the situation is a bit more complex than that:

- FreeType 1.x contains some code to parse and process OpenType
  tables. This code never made it into FT2 for various reasons
  (detailed later)

- Pango did import the FT1 OpenType sources, and Owen Taylor
  modified them to fix a relatively important number of bugs
  in them, as well as enhance it.

- The QT developers also did import the FT1 OpenType sources
  into the QT sources (I believe it's in the "3rdparty"
  directory, or something like this). They also did produce
  a number of fixes an enhancements to the code

- From a technical point of view, Pango and QT both have their
  own OpenType parser/processor. Even if they share a common origin,
  their codes are now really different. For example, I believe that
  the fixes/enhancements in both source trees were done nearly
  completely independently

- Nearly none of the fixes have been backported to FT1, because
  we consider this source tree "dead", mainly because none of
  us have the time to work on it, and because nobody seems to
  be interested in doing this.

- the code hasn't been ported to the official FT2 tree for several
  reasons. Some of them are:

    - the code uses internal FT1 structures and APIs that have
      changed a lot in FT2, so it won't be a 1-day port

    - I believe it'd be much better to put this functionality
      into an independent library. FreeType would only be used
      to retrieve the tables from the font file.

  Unfortunately, nobody had the time to write this
  "independent library", so both Pango and QT continue using
  their own sources.

  On a related note however, we have created a branch, called "LAYOUT",
  of the "freetype2" CVS module, which incorporates implementations
  of OpenType and AAT/GX parsers/processors from RedHat Japan.

  however, we don't have much news about progress in this direction,
  so I don't think that the code here can be considered complete.


Hope this is clear,

- David Turner
- The FreeType Project  (www.freetype.org)


> -----Original Message-----
> From: Werner LEMBERG [mailto:address@hidden 
> Sent: Saturday, June 05, 2004 4:42 PM
> To: address@hidden; 786
> Cc: address@hidden; Aamir wali
> Subject: Re: [Freetype] Pango or Freetype and some other questions!!
> 
> 
> > " What about the new GSUB lookup type 8?  AFAIK, this is 
> specifically
> > for Urdu.  Have you added it to to PANGO?" (Note the capital PANGO)
> 
> I don't know.  FreeType 1 and the experimental ftlayout stuff for
> FreeType 2 doesn't have it yet.  It should be rather easy to add IMHO.
> Note that I don't have time currently to work on this -- do you
> volunteer?
> 
> > Well what I don't understand is why are we calling it Pango code?
> > Shouldn't it be freetype's code (ftxgsub.c in freetype package)?
> 
> Pango has started with FreeType 1's version of the OpenType stuff.  It
> has been ported to FreeType 2, and a lot of changes (mainly bug fixes
> and interface improvements) have been applied.  The differences are
> very substantial meanwhile, so it is correct IMHO to talk about `Pango
> code'.
> 
> > >> Have you added it to to PANGO?" 
> >
> > So shouldn't it be the freetype guys who should be thinking about
> > adding it?  And if it does have to be added then it's right in the
> > OT code in pango where other types are implemented.
> 
> Basically, FreeType 1 is unsupported today.  There is an ongoing
> effort to implement OpenType and GX support in FreeType 2 -- you
> should check out the freetype2 CVS module from the `TLAYOUT' branch.
> Any help in improving and testing this code is highly welcome.
> 
> > Another question: Say for the moment 'All the GSUB tables has been
> > implemented' is there a list of which features have so far been
> > implemented.
> 
> Be careful: `calt' is an OpenType *feature* which isn't handled by
> FreeType itself.
> 
> > Is calt implemented?
> 
> I don't know.  Looking into the OpenType specification I can see that
> Adobe recommends to use a GSUB lookup type 6 for implementation, and
> this is definitely supported by the current Pango code.
> 
> > I have pango-1.2.5 & Freetype-current, this does not?
> 
> Theoretically, it should, but it depends on the font: If `calt' is
> always activated in the font, Pango will apply this lookup.  If it is
> an optional feature it is possible that Pango doesn't activate it
> automatically.
> 
> > But there seems to be some problems; the calt rules listed in the
> > font do not seem to apply at some instances.  Now this could either
> > be the problem with my gedit/linux or with the lookuptype 6's
> > implementation.  Can Freetype's team allow me to please discuss this
> > problem with them offline?
> 
> I prefer discussion on the address@hidden list, since this problem
> might be of interest for others too.  Additionally, people from both
> Qt and Pango are reading this list (AFAIK).
> 
> BTW, you might compare the gedit output with results from fontforge.
> 
> 
>     Werner
> 
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