[xep-support] XEP with Arabic Typesetting font

[Chris Lilley]

On Friday, February 20, 2004, 3:03:40 PM, Nikolai wrote:

NG> Mete,

>> Is XEP capable of rendering a Lam-Alef ligature 
>> with a hamza and possibly also a fatha on top of it?

NG> Treatment of hamza, fatha  and similar diacritical 
NG> signs is indeed a hard issue for XEP in its current shape.

NG> XEP process combining diacritics as if the were 
NG> ordinary symbols. Therefore, to get an Alef+hamza,
NG>  you should use a separate glyph for it (&#x623).
NG> This glyph will be correctly shaped to isolated/initial
NG> or medial/final form, and if there is a Lam preceding 
NG> it in the text, it will produce a correct Lam+Alef+hamza 
NG> ligature.

Am I correct to infer from this that XEP has support for only
precombined characters in general, so that for example a latin letter
'e' followed by a combining acute accent will not render as an
'e-acute'?

NG> For fatha, the situation is more difficult: there is no 
NG> Unicode point to cover its combinations with Alef
NG> or Alef+hamza.

Since Unicode has a policy of not adding new precomposed characters
unless really necessary (because of the multiplicative explosion of
code points), there is unlikely to be such a codepoint in the future
either. Nor is it needed, there are already Unicode points for fatha,
damma, kasra etc and these are, naturally, combining characters.

Unlike the acute accent (in French) but like the accents and tone
marks in Vietnamese, these characters also need to stack.


NG> Rather than adding such an API, we would better prefer to refine
NG> our own engine to cover complex cases like these :-).

A worthy goal, although coverage of basic newspaper Arabic is
probably a better first target before moving on the the complexities
of Quranic typesetting.

Does anyone have short examples of these sorts of more complex script
renderings (plus images of correct renderings), which could be used
for test cases? I am thinking of XSL FO test cases of course, though
also interested in their use for SVG test cases.

-- 
 Chris Lilley                    mailto:chris at w3.org
 Chair, W3C SVG Working Group
 Member, W3C Technical Architecture Group

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