Hello,
In short: You are supposed to ignore both Arabic Presentation
Forms blocks. They are not part of the Arabic model of Unicode
(except for Rls character of course).
Longer answer: Many (lazy) implementations, use the Presentation
Forms - B block as a glyph encoding to shape Arabic in the
Unicode namespace and pass the shaped string to the rendering
engine, which by definition, is the place that character to glyph
mapping should have been done. Fortunately with OpenType fonts,
you don't need to worry about shaping at all. They define their
supported glyphs and shapes all in the font itself.
About the joining algorithm, no, Unicode joining algorithm does
not support Presentation Forms all!
behdad
On Sat, 18 Sep 2004, Peyman wrote:
> Hi,
>
> I hope somebody in the forum answer my question ASAP:
>
> What is the use of "Arabic Presentation Forms - A" in Unicode
> (Range FB50-FDFF).
>
> I understand we may use some symbols like /Rial/ by a single
> code (FDFC) but what I don't understand is the ligatures. Do we
> need them all If we want to design a Persian editor? Or some of
> them?
>
> Basically, what is behind the joining algorithm? For example,
> we have the code 067E for /p/. Do we need to implement FB56,
> FB57, FB58, FB59 for initial, middle, final, and isolated forms
> of /p/ in the involved algorithm?
>
> Peyman
--behdad
behdad.org
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