[Bf-committers] Arabic support in text editing

Majid AL-Dharrab majid at aldharrab.com
Wed Oct 26 12:26:33 CEST 2011

Actually, fribidi's shaper is very primitive and rudimentary and it has lots
of fundamental problems. It simply replaces letters with their Unicode
presentation forms depending on their position in a word. That is not a good
approach because it completely ignores ligatures and other OpenType
features, leading to broken support for most modern fonts that use OpenType
tables. That's why libass only uses a fribidi function that positions text
characters in the correct order, following rules from Unicode's bidi
algorithm (http://unicode.org/reports/tr9/#The_Paragraph_Level). Shaping is
then handled by HarfBuzz, which a great OpenType shaper.

Unfortunately, I'm not a developer, so I'm afraid I can't help any further
with this issue. But you can contact libass's developer if you face any
problems with either lib. His GSoC project was supporting complex and bidi
scripts, so he probably knows a couple of tricks that might help. Good luck.

On Wed, Oct 26, 2011 at 9:57 AM, Dalai Felinto <dfelinto at gmail.com> wrote:

> Thanks for the link.
> I looked at fribidi and found it interesting. Their standalone is
> doing the same as we are with the python scripts (they call it log2vis
> - to convert from logic to visual strings).
> Now, if we use this lib, do we still need harfbuzz? It seemed to me
> that truetype2 can handle most of the layout, no?
> --
> Dalai
> 2011/10/25 Majid AL-Dharrab <majid at aldharrab.com>:
> > I guess you can't go wrong with harfbuzz-ng on freetype2. After all, that
> is
> > what's used to render text in Firefox. libass, the SSA subtitle renderer
> > used in VLC and MPlayer, has recently started to support complex and bidi
> > scripts using harfbuzz and fribidi on top of freetype2. That resulted in
> > very sophisticated rendering of complex texts. Implementing that turned
> out
> > to be easier than the developer had thought.
> >
> >
> http://ssadev.blogspot.com/2011/05/getting-complex-text-layout-into-libass.html
> >
> > I hope his experience helps make the issue a bit easier for our Blender
> > devs. Good luck!
> > _______________________________________________
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> > Bf-committers at blender.org
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> >
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