[ft-devel] RE: FreeType error reading CJKV font outlines.

[David Turner]

Hi,

On Wed, 24 Jan 2007 14:49:28 -0800, "Ivan Nincic" <address@hidden> said:
> 
> Please disregard my last email. I just realized that I was loading font
> outlines with FT_LOAD_NO_SCALE which implies FT_LOAD_NO_HINTING.
> 
> Is it possible to determine in advance that a font is 'tricky' and that
> hinting needs to be applied.
>
In theory, it's not possible to detect 100% of cases because it's equivalent
to running the bytecode programs for all glyphs at all possible sizes.

However, it is possible to find good heuristics by scanning bytecode programs
for some really annoying instructions (SFVTL, SPVTL, SDPVTL, DeltaP, etc...)
that may result in problems with the unpatented interpreter.

But, this scanning must be done for all glyphs (as well as the font program
and CVT program) when opening the font file, and this can take a very long
time, retrospectively. And all of this in order to detect "features" that are
present in less than 1% of fonts available.

So we prefer our quick hacks at the moment. Maybe we could provide a function
to "enforce" the scanning when the user requests it, this may turn useful for
special cases (e.g. font fragments coming from a PDF document)

Regards,

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



> Also I am not sure how to keep glyph outlines in font units after hinting is 
> applied?
> 
> -----Original Message-----
> From: Ivan Nincic [mailto:address@hidden 
> Sent: Wednesday, January 24, 2007 2:24 PM
> To: 'address@hidden'
> Cc: 'address@hidden'
> Subject: FreeType error reading CJKV font outlines.
> 
> Hello,
> 
> I noticed that FT 2.7 is supposed to `just work' with Asian fonts, like
> MingLiU, which cannot properly be  loaded without a bytecode interpreter. 
> 
> Attached are couple of subsetted Asian TTF fonts that do not render
> properly. These fonts were are extracted from a document. Also attached
> is
> the screenshot showing the problem (the first line of text is rendered
> using
> FreeType to get the outlines, whereas the second line is rendered using
> Acrobat Reader). 
> 
> Perhaps I missed to declare an extra option or a module? What can be done
> to
> render this type fonts properly?
>  
> Ian
> 
>