[xep-support] Another Arabic problem (diacritics)

[Alexei Gagarinov]

Hi Peter,

>> I have found another old post talking about diacritics:
>> http://services.renderx.com/lists/xep-support/1812.html
>> In this post it is suggested to use special characters. For example for 
>> alef+hamza one should use &#x623. But I can not find any special character 
>> for this combination.
> 
> I did the same search on your behalf and came to the same conclusion.

Arabic diacritics behavior is the same as described in that post.

> A while back I had a problem with XEP not dealing with Farsi numbers
> correctly - it ordered them RtoL instead of LtoR.

I guess, this is an issue with the using of BIDI algorithm;
I don't remember any compliance about Farsi numbers. :)

> Taking this further would mean to me that you could use unused parts of
> unicode (which exist for such purposes) and put customised glyphs in
> your font on those places, bypassing in this way the rendering/glyph
> shaping attempts by XEP.
> 
> This would be an ugly hack and probably very tedious if it applied to
> more than a few glyphs, but it should work fine. The numbering worked
> for me.

If you're considering such a hack as an alternative I can suggest an 
optimization.
XEP places glyphs according their dimensions. So you may change required 
  glyph's bounding boxes. Set a negative value for the left side and 
zero for the width. It should be enough for Arabic diacritics.
And this approach makes the editing more easy (with GUI font tools).



OpenType Specification added new features for advanced typographic 
extensions.
These features include font tables for the placement of complex glyphs 
(shifts, in the both directions, for certain sequences of glyphs and so on).
I believe this would be enough for the correct rendering of alef+hamza 
and similar glyphs (if you use OpenType fonts with the correct advanced 
typographic tables, of course).

The only point here is that XEP does not support these advanced OpenType 
features.

Are you using OpenType or another type of fonts for Arabic?

Best regards,
   Alexei Gagarinov
RenderX
---
www.renderx.com
www.renderx.net

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