[HarfBuzz] Unicode vs glyphs

[Khaled Hosny]

On Tue, Jun 14, 2011 at 09:02:25PM +0530, Shriramana Sharma wrote:
> On 14-06-2011 20:59, Khaled Hosny wrote:
> >All the mentioned scripts can have fonts with glyphs that are not
> >assigned Unicode code points, you were lucky to not encounter them until
> >now, but in the era of "smart fonts" it is becoming more and more
> >common practice especially in high quality fonts.
> >
> >Regards,
> >  Khaled
> 
> Khaled, if I am correct to presume (from your name) that you know
> Arabic script, can you tell us whether you nowadays use the
> separately encoded compatibility presentation forms or you use smart
> font technologies to display those presentation forms?

Most fonts do both; put the glyphs in the presentation forms block(s)
(for the odd application that requires this) and map them using OpenType
lookups.

For more complex fonts where the presentation forms does not cover all
the used glyphs I drop it altogether and rely on OpenType solely.

OpenType also provide more control over glyph positioning (important for
diacritical marks) which is not possible otherwise (even apples AAT does
not support mark anchors AFAIK).

> If I am not
> mistaken, Arabic has different written forms for characters in
> initial, middle, final and isolate positions (or am I thinking of
> Mongolian)?

Both do (Mongolian is very close to Arabic in this regard, having
descended from the same script, though rotated 90 degrees to resemble
neighbouring vertical scripts.)

Regards,
 Khaled

-- 
 Khaled Hosny
 Egyptian
 Arab